Heating rocket stove master blueprints. What is a rocket furnace: design options, diagrams and principle of operation

Let's say right away: rocket stove - a simple and convenient wood-fired heating and cooking device with good, but not exceptional parameters. Its popularity is explained not only by its catchy name, but more so by the fact that neither a stove-maker nor even a bricklayer can make it with their own hands; if necessary - literally in 15-20 minutes. And also by the fact that, having invested a little more work, you can get an excellent couch in the house without resorting to building a complex, expensive and cumbersome or. Moreover, the very principle of the rocket furnace gives great freedom to design and the manifestation of creativity, see fig.

But the "jet furnace" is perhaps more remarkable for the huge number of associated, at times completely absurd inventions. For example, here are a few pearls snatched at random:

"The operating principle of the furnace is the same as that of the MIG-25 ramjet engine." Yes, the MIG-25 and its descendant MIG-31, as they say, did not sit down in the bushes near the ramjet engine (ramjet). On the 25th and 31st there are by-pass turbojet engines (turbojet engines), the four of which then pulled the Tu-144 and still pulls other machines. And any furnace with any jet engine (RD) is technical antipodes, see below.
Reverse jet furnace. Is the stove flying tail first, or what?
"How can she blow such a pipe?" The naturally aspirated stove does not blow into the pipe. On the contrary, the chimney pulls from it, on natural draft. The higher the pipe, the better it pulls.
"The rocket stove is a combination of a Dutch bell-type stove (sic!) With a Russian stove bench." First, there is a contradiction in the definition: a Dutch stove is a channel stove, and any bell stove is anything but a Dutch stove. Secondly, the bed of the Russian stove warms up in a completely different way than the rocket stove.

Note: in fact, the rocket stove was so nicknamed because in the wrong mode of the furnace (which will be discussed later), it emits a loud whistling rumble. A properly tuned rocket furnace whispers or rustles.

These and similar inconsistencies, of course, are confusing and prevent you from making a rocket furnace properly. So let's figure out what the truth is about the rocket stove, and how to use this truth correctly so that this really good stove shows all its merits.

Stove or rocket?

For complete clarity, we still need to figure out why a furnace cannot be a rocket, and a rocket cannot be a furnace. Any RD is the same internal combustion engine, only the outflowing gases act as pistons, connecting rods with a crank and transmission. In a piston internal combustion engine, already at the moment of combustion, the high temperature of the working fluid creates a lot of pressure, which pushes the piston, and it already moves the entire mechanics. The movement of the piston is active, the working fluid pushes it where it itself seeks to expand.

When fuel is burned in the combustion chamber of a jet engine, the thermal potential energy of the working fluid is immediately converted into kinetic energy, like that of a load falling from a height: since the incandescent gases have an outlet to the nozzle, they rush there. In the taxiway, the pressure plays a subordinate role and nowhere exceeds the first tens of atmospheres, this, for any conceivable nozzle section, is not enough to accelerate the flashlight to 2.5M or launch a satellite into orbit. According to the law of conservation of momentum (momentum), an aircraft with a taxiway receives a push in the opposite direction (recoil momentum), this is jet thrust, i.e. thrust from recoil, reaction. In a turbojet engine, the second circuit creates an invisible air envelope around the jet stream. As a result, the recoil momentum seems to be pulled in the direction of the thrust vector, therefore turbojet engine is much more economical than a simple turbojet engine.

In the furnace, there is no transformation of types of energy into each other, therefore it is not an engine. The stove simply distributes the potential heat energy appropriately in space and time. From the point of view of the furnace, an ideal RD has an efficiency of 0%, since it only pulls at the expense of fuel. From the point of view of the jet engine, the furnace has an efficiency of 0%, it only dissipates heat and does not pull at all. On the contrary, if the pressure in the chimney rises to or above atmospheric (and without this, where will the jet thrust or active effort come from?), The stove will at least smoke, or even poison the residents or start a fire. Chimney draft without pressurization, i.e. without energy consumption from the outside, it is provided due to the temperature difference along its height. Potential energy is here again, it is not transformed into any other.

Note: in a rocket taxiway, fuel and oxidizer are fed into the combustion chamber from the tanks, or they are immediately refueled into it if the taxiway is on solid fuel. In a turbojet engine (TJE), the oxidizer - atmospheric air - is pumped into the combustion chamber by a compressor driven by a turbine in the exhaust gas stream, the rotation of which consumes a certain fraction of the energy of the jet stream. In a turboprop engine (TVD), the turbine is calculated so that it takes 80-90% of the power of the jet, which is transmitted to the propeller and compressor. In a ramjet engine (ramjet engine), air supply to the combustion chamber is provided by a high-speed hypersonic pressure. There have been many experiments in the ramjet, but there were no serial aircraft with it, and is not expected, the ramjet is too capricious and unreliable.

Kan or not kan?

Among the myths about the rocket furnace, there are some that are not entirely absurd, and even somewhat substantiated. One such misconception is the identification of the "racket" with the Chinese Kan.

As a child, the author had a chance to visit the Amur region in winter, in the Blagoveshchensk region. There were many Chinese people living there in the villages, and then they scampered in all directions from the Cultural Revolution of the Great Chairman Mao and his completely frostbitten Red Guards.

Winter in those parts is not Moscow's; frost at -40 is a common thing. And what amazed and aroused interest in stoves in general was how Chinese fanzas were heated by kangs. Firewood is being carried to Russian villages in carts, smoke from chimneys is a pillar of smoke. And all the same, in the hut of logs, not in a child's girth, by morning the corners from the inside froze over. And the fanza is built like a country house (see fig.), The windows are covered with a fish bubble or even rice paper, bunches of chips or twigs are placed in the canal, but the room is always warm.

However, there are no subtle heat engineering wisdom in the cana. This is an ordinary, only small, kitchen stove with a lower outlet to the chimney, and most of the chimney itself is a long horizontal channel, a hog, on which the bed is arranged. Chimney, for the sake of fire safety - outside the building.

The effectiveness of the kan is determined, first of all, by the heat curtain it creates: the bed goes around, if not the entire perimeter from the inside, except for the door, then 3 walls for sure. Which once again confirms: the design and parameters of the furnace should be linked to those of the heated room.

Note: The Korean Ondol stove operates on the principle of a warm floor - a very low bed takes up almost the entire area of the room.

Secondly, in the very cold, the Kans were drowned with argal - the dried droppings of ruminants, domestic and wild. Its calorific value is quite high, but argal burns slowly. In fact, the argal fire is already a long-burning furnace.

It is not in the Russian custom to stick twigs into the oven every now and then, and our peasants disdained to cook food on animal feces. But travelers of the past highly valued argal as fuel, collected it along the way and carried a supply with them, carefully protecting it from getting wet. N.M. Przhevalsky in one of his letters asserted that without argal he would not have been able to carry out his expeditions across Central Asia without losses. And the Englishmen, who disdained argal, returned to the base 1 / 3-1 / 4 of the personnel of the detachments. True, he was recruited from sepoys, Indian soldiers in the British service, and pandits - spies recruited from the local population. One way or another, but the highlight of the rocket stove is not at all in the stove bench on the hog. To get to it, you will have to learn to think in American: all the primary sources on the rocket furnace are from there, and utter speculations are generated only and only by misunderstanding.

How to deal with missiles?

From our point of view, it is necessary to study the original technical documentation of rocket furnaces with caution, but not at all because of inches-millimeters, liter-gallons and the subtleties of American technical jargon. Although they also mean a lot.

Note: a textbook example - "Naked conductor runs under the carriage". Literary translation - a naked conductor runs under the carriage. And in the original article from the Petroleum Engineer, it meant "Bare wire runs under the crane trolley."

The rocket furnace was invented by members of the survival societies- people with a peculiar way of thinking, even by American standards. In addition, they were not bound by any standards and norms, but, like all Americans, mechanically everything was always converted into money, taking into account their own benefit; a person with a different outlook in America simply will not get along. And instinctive self-interest inevitably gives rise to egocentrism. He by no means excludes good deeds, but not out of emotional impulse, but on the basis of dividends. Not in this life, so in that one.

Note: just how much the average inhabitant of the greatest empire in history fears everything, you can only understand long enough with them. And the sociopsychologists there go out of their way, convincing that living languishing in fear is normal and even cool. The rationale is clear: the intimidated biomass is easily predictable and manageable.

Without heating and cooking, of course, you cannot survive. What is the stove for? For the time being, the survivors were content with camping stoves. But then, according to the confessions of the Americans themselves, in 1985-86. they were greatly impressed by two films that were released with a short interval and triumphantly bypassed all the screens of the world: the Soviet fantastic parody of the entire human race "Kin-dza-dza" and Hollywood's "The Day After", about the global nuclear war.

The survivors realized that after the nuclear winter there would be no extreme romance, but there would be the planet Plyuk in the Kin-dza-dza galaxy. The newly-minted plukans will have to be satisfied with "ka-tse" in small quantities, bad, expensive and difficult to obtain. Yes, all of a sudden someone hasn't watched "Kin-dza-dza" - ka-tse, in Plukan, a match, a measure of wealth, prestige and power. It was necessary to invent their own furnace, none of the existing ones was designed for a post-nuclear pluck.

Americans are very often endowed with a sharp mind, but a deep one is the rarest exception. A completely normal and with an IQ higher than the average US citizen may sincerely not understand how it does not reach the other what he himself has already "caught up" and how someone else may not like what suits him.

If the American has already grasped the essence of the idea, then he brings the product according to it to possible perfection - what if there is a buyer, you cannot sell raw iron. But technical documentation, seemingly beautiful and neat, can be drawn up in essence extremely carelessly, or even deliberately distorted. And what's wrong with that, it's my know-how. Maybe I'll sell it to someone. Pluck will be, or not, but for now the know-how costs money. In America, such an attitude to business is considered quite honest and dignified, but there a clinical alcoholic at work will never miss a stoper and will not pull a couple of bolts home to the farm. On that, in general, all America is.

And the Russian broad-mindedness is also a double-edged sword. Our master most often just from the sketch immediately understands how this thing works, but in the little things he turns out to be careless and overly trusting of the source code: how is it that a craftsman's bro deceives his own. If something is not, well, it is not necessary. It seems clear how everything is spinning there - even your hands are itching. And there, perhaps, while it comes to the hammer, chisel and accompanying literature, still count and count. Moreover, important points can be omitted, veiled or deliberately incorrect.

Note: An American acquaintance once asked the author of this article - how is it that we, really stupid ones, chose the very smart Reagan as president? And you, really smart, tolerate a slobbering senile with dyed eyebrows in the Kremlin? True, then in America, no one would even dream in a bad dream that in the next century a black citizen with a Muslim name would settle in the Oval Office, and his first lady would dig a vegetable garden near the White House and start growing turnips there. Times is changing, as Bob Dylan once sang on a completely different occasion ...

Sources of misunderstanding

There is such a thing in technology - the law of the square-cube. Simply, when the size of something changes, its surface area changes in a square, and its volume in a cube. Most often this means that the overall dimensions of the product must be changed according to the principle of geometric similarity, i.e. just keeping the proportions is impossible. With regard to solid fuel stoves, the square-cube law is doubly valid, since fuel also obeys it: it emits heat from the surface, and its supply is contained in the volume.

Note: a consequence of the square-cube law - any specific furnace design has a certain permissible fork of its size and power, within which the specified parameters are provided.

Why, for example, cannot be made the size of a refrigerator and with a capacity of somewhere around 50-60 kilowatts? Because the potbelly stove, in order for it to somehow warm up, must be heated inside itself to at least 400-450 degrees. And in order to warm up to such a temperature the volume of the refrigerator with a given heat transfer, firewood or coal is needed as much as it does not fit into it. There will be no sense from a mini-stove either: the heat will escape through the outer surface of the stove, which has grown relative to its volume, and the fuel will not give up more than it can.

The square-cube law acts threefold on the rocket furnace, because she is "licked" in an American professional manner. It is better to stay away from her with our nashensky kondachkom. For example, here in fig. American development, which, judging by its relevance, many of our craftsmen take as a prototype.

With the fact that the exact grade of fire clay is not indicated here, ours will still figure it out. But, to be honest, who noticed that, judging by the absence of an external chimney and the presence of carrying pipes, this stove is mobile with an open firebox? Most importantly, the fact that a 20-gallon keg with a diameter of 17 inches (431 mm with small change) went to her drum?

Judging by the constructions from the Runet - no one at all. They take this stuff and fit it on the outside according to the principle of geometric similarity to a domestic 200-liter barrel with a diameter of 590 mm. Many people guess to arrange a blower, but the bunker is left open. Vermiculite / perlite proportions not specified for riser lining and core molding? We make the lining homogeneous, although it will be clear from what follows that it should consist of insulating and accumulating parts. As a result, the stove roars, the fuel eats only dry, and a lot, and even before the end of the season, it grows inside with fumes.

How was the rocket oven born?

So, already without fiction with futurology, the survivors needed high efficiency home heating stove with low quality random wood fuel: wet wood chips, twigs, bark. Which, in addition, will need to be reloaded without stopping the furnace. And most likely it will not be possible to dry it in a firewood. Heat transfer after heating takes at least 6 hours to get enough sleep; getting fired up in a dream on Plyuk is no better than in America. Additional conditions: the design of the furnace should not contain complex metal products, non-metallic materials and assemblies that require production equipment for the manufacture, and the furnace itself should be available for construction by an unskilled worker without the use of power tools and complex technologies. Of course, no pressurization, electronics and other volatility.

They immediately took a couch from the kan, but what about the fuel? For a bell furnace, it needs high quality. Long-burning furnaces operate at least on sawdust, but only dry, and do not allow stopping with additional loading. They were nevertheless taken as a basis, very attracted by the high efficiency achieved by simple methods. But in attempts to make the "long stoves" work on poor fuel, one more circumstance emerged.

What is wood gas?

High efficiency is achieved largely due to the afterburning of pyrolysis gases. Pyrolysis is the thermal decomposition of a solid fuel into volatile combustible substances. As it turned out (and the survivors have their own research centers with highly qualified specialists), the pyrolysis of wood fuel, especially wet, continues for a long time in the gas phase, i.e. The pyrolysis gases that have just escaped from the tree still need a lot of heat to form a mixture that can burn out completely. This mixture was called wood gas, woodgas.

Note: in runet woodgas has created more confusion, tk. in American vernacular gas can mean any fuel, cf. ex. gas station - gas station, gas station. When translating the original sources without knowing the American technical, it turned out that woodgas is just wood fuel.

Before that, no one had seen wood gas: in ordinary stoves, it is formed immediately in the furnace, due to the excess energy of fiery combustion. The designers of long-burning furnaces came to the conclusion that the primary air must be heated, and the exhaust gases must be retained in a significant volume over a large mass of fuel, simply by trial and error, so they overlooked wood gas.

It turned out not so when heating with bundles of twigs: here the primary pyrolysis gases were immediately dragged into the chimney by the draft. Wood gas could have formed in it at some distance from the firebox, but by that time the primary mixture had cooled down, pyrolysis stopped, and heavy radicals from the gas settled on the walls of the chimney as carbon deposits. Which quickly tightened the channel completely; this phenomenon is well known to amateurs who build rocket furnaces at random. But the survivors eventually figured out what it was, and still made the right oven.

Who are you, the Rocket Stove?

There is an unspoken rule in technology: if it seems that it is impossible to create a device according to the given requirements, then read, smart guy, school textbooks. That is, go to the basics. In this case, to the basics of thermodynamics. Survivors do not suffer from sick vanity, they turned to the basics. And they found the main principle of operation of their oven, which has no analogues in others: slow adiabatic afterburning of pyrolysis gases in a weak flow. In long-burning furnaces, afterburning is equilibrium isothermal, requiring a large buffer volume, subject to the square-cube law, and a supply of energy in it. In pyrolysis gases in the afterburner, they expand almost adiabatically, but practically into a free volume. And now - we are learning to think in the American way.

How does a rocket oven work?

The scheme of the final fruit of the labors of the survivors is shown on the left side of Fig. The fuel is loaded vertically into the hopper (Fuel Magazine) and burns, gradually settling down. Air enters the combustion zone through a blower (Air Intake). The blower must provide an excess of air so that it is enough for afterburning. But not excessive, so that the cold air does not cool the primary mixture. With vertical loading of fuel and a blank bunker lid, the regulator, however, is not very effective, the flame itself acts: if it is too hot, it pushes the air away.

Then things begin that are already non-trivial. We need to warm up, and with good efficiency, a large oven. The square-cube law does not allow: the scanty heat will immediately dissipate so much that the pyrolysis will not reach the end, and the thermal gradient from the inside to the outside will not be enough for heat transfer into the room; everything will whistle into the pipe. This law is harmful, you cannot break through it. Okay, let's see in the basics, if there is anything that is beyond his control.

But of course, there is. The same adiabatic process, i.e. thermodynamic without heat exchange with the environment. There is no heat exchange - the squares are resting, and the cubes can be reduced even to a thimble, even to a skyscraper.

Imagine a volume of gas completely isolated from the whole. Let's say energy is released in it. Then the temperature and pressure will begin to rise until the energy release stops and solidify at a new level. Great, we burned the fuel completely, hot flue gases can be released into a heat exchanger or heat accumulator. But how can you do this without technical difficulties? And most importantly - how, without breaking the adiabat, to supply air for afterburning?

And we will make the adiabatic process non-equilibrium. How? Let the primary gases go directly from the combustion source into a pipe covered with high-quality insulation with a low intrinsic heat capacity (Insulation). Let's call this pipe for ourselves a fire or a combustion tunnel (Burn Tunnel), but we will not sign it (know-how! not accused of "opacity", let us designate it with a flame.

Along the length of the flame tube, the adiabatic index changes (this is a nonequilibrium process): the temperature will first drop slightly (wood gas is formed), then it will rise sharply, the gas will burn out. You can release it into the storage, but we have forgotten - and what will pull the gases through the fire tube? Aspiration means volatility, and there will be no exact adiabat, but something mixed with isobar, i.e. efficiency will drop.

Then we will lengthen the pipe twice, preserving the insulation, so that the heat does not go away in vain. Bend the "blank" half upwards, making the insulation on it weaker; how to keep the heat seeping through it, we will think about a little later. A temperature difference in height will appear in the vertical pipe, and, therefore, draft. And good: the thrust force depends on the temperature difference, and with an average temperature in the fire tube of about 1000 degrees, it is not difficult to achieve a difference of 100 at an altitude of about 1 m. So, while we have made a small economical stove-stove, now we need to think about how to use it warmly.

Yes, it doesn’t interfere with additional encryption. If we call the vertical part of the fire tube the primary or internal chimney (Primary or Internal Vent), then they will guess the main idea, we are not the smartest in the world. Well ... let's call the primary chimney the most common technical term for vertical pipes with an upward current - riser (riser). Purely American: correct and incomprehensible.

Now let's remember about heat transfer after heating. Those. we need a cheap, always available and very capacious heat accumulator. There is nothing to invent here, adobe (Thermal Mass) was invented by primitives. But it is not fire-resistant, it does not hold more than 250 degrees, and we have about 900 at the mouth of the riser.

It is not difficult to convert high-grade heat into medium-grade heat without losses: you need to give the gas the opportunity to expand in an isolated volume. But, if you leave the expansion adiabatic, then the volume will be too large. This means that it is material and labor-intensive.

I had to again bow to the basics: immediately after leaving the riser, let the gases expand at constant pressure, isobaric. This requires the removal of heat to the outside, about 5-10% of the thermal power, but it will not disappear and will even be useful for quickly warming up the room during the morning firebox. And further along the course of gases - isochoric cooling (in constant volume); this way, almost all the heat will go to the battery.

How to do it technically? We will cover the riser with a thin-walled iron drum (Steel Drum), it will also prevent heat loss from the riser. "Drum" turns out to be too high (the riser sticks up strongly), but it doesn't matter: we will coat it 2/3 of the height with the same adobe. We attach a stove bench with a sealed chimney (Airtight Duct), an external chimney (Exhaust Vent), and the stove is almost ready.

Note: the riser and the drum covering it look like an oven hood over an upward-stretched high. But thermodynamics here, as we see, is completely different. It is useless to try to improve the bell-type stove by building on the hailo - only the extra material and work will go away, and the stove will not get better.

It remains to solve the problem of cleaning the channel in the bed. For this, the Chinese have to break the kan from time to time and mutate it again, but we are not in the 1st century. BC. we live when the kan was invented. We will arrange a Secondary Airtight Ash Pit immediately after the drum with a sealed cleaning door. Due to the sharp expansion and cooling of flue gases in it, everything in them that has not burned out immediately condenses and settles. The cleanliness of the external chimney is guaranteed by this for years.

Note: the secondary cleaning will have to be opened once or twice a year, so that you can not be fooled with the hinges-latches. Let's just make a cover from a metal sheet on screws with a mineral cardboard gasket.

Small rocket

The next task of the designers was to create, on the same principle, a small continuous combustion oven for cooking in the warm season. During the heating season, the Optional Cooking Surface of a large oven is suitable for cooking, it heats up to about 400 degrees. The small rocket furnace was supposed to be portable, but it was permissible to make it with an open firebox, because when it's warm, you can cook outdoors or under a canopy.

Here the designers took revenge on the square-cube law, forcing it to work for themselves: they combined the fuel bunker with the blower, see Fig. at the beginning of the section on the right. It is impossible to do this in a large furnace; accurate adjustment of the furnace mode as the fuel settles (see below) will be impossible.

Here, the volume of the incoming primary air (Primary Air) turns out to be small relative to the heat release area and the air can no longer cool the primary mixture until the pyrolysis stops. Its supply is regulated by a slot in the cover of the hopper (Cover Lid). The hopper, inclined at 45 degrees, optimizes the automatic adjustment of the oven power for standard culinary procedures, but makes it more difficult.

Secondary air for afterburning wood gas in a small furnace enters through additional holes in the riser mouth or simply leaks under the burner if there is a cooking pot on it. If a small furnace is close to the size limit (about 450 mm in diameter), then an optional Secondary Woodgas Frame may be needed for complete afterburning.

Note: it is impossible to supply secondary air to the riser mouth of a large furnace through the holes in the drum (which would increase the efficiency of the furnace). Although the pressure in the entire flue gas duct is lower than atmospheric pressure, as it should be in the furnace, due to strong turbulence, flue gases will be thrown into the room. Here their kinetic energy, harmful to the furnace, affects; this is, perhaps, the only thing that makes a rocket oven with a jet engine in common.

The small rocket stove revolutionized the class of camp stoves, especially tourist stoves. A wood chip stove (a Bond stove in the West) will help to cook a stew or wait out a blizzard in a one-two-person tent, but a group caught in a spring hike by a belated storm will not save them. And the small rocket furnace is only slightly larger, it can be quickly made from nowhere from nothing, but it is capable of developing power up to 7-8 kW. However, we will talk further about rocket stoves from just about anything.

Also, the small rocket furnace has spawned many improvements. For example, Gabriel the Apostle provided her with a separate blower and a wide bunker. The result is a stove suitable for a compact and rather powerful water heater, see the video below. The large rocket furnace has also been modified, we will talk about this a little at the end, but for now we will dwell on more significant things.

Video: a water heater based on a rocket furnace designed by Gabriel Apostol

How to sink a rocket?

A rocket furnace with long burning ovens has a common property: you only need to run them on a warm pipe. For a small one, this is insignificant, but a large one on a cold chimney will only burn fuel in vain. Therefore, a large rocket furnace before loading the standard fuel into the bunker after a long break in the furnace and kindling requires acceleration - firing with paper, straw, dry shavings, etc., they are placed in an open blower. The end of the acceleration is judged by a change in the tone of the hum of the furnace or its decay. Then you can load the fuel into the bunker, and its ignition will happen by itself from the accelerating fuel.

The rocket stove, unfortunately, does not apply to stoves that are completely self-adjusting to the quality of the fuel and external conditions. At the beginning of the combustion of standard fuel, the blower door or the bunker cover in a small furnace is opened completely. When the stove hums strongly, cover it up "to a whisper." Further, during the heating process, it is necessary to gradually cover the air access, focusing on the sound of the stove. Suddenly the air damper slammed shut for 3-5 minutes - it's okay, if you open it, the stove will ignite again.

Why such difficulties? In the process of burning out the fuel, the flow of air into the combustion zone increases. When there is too much air, the furnace explodes, but do not rejoice: now the excess air cools the primary gas mixture, and the sound is amplified because the stable vortex in the riser is knotted into a disorderly lump. The gas phase pyrolysis is interrupted, no wood gases are generated, the furnace consumes too much fuel, and a bituminous soot-cemented soot settles in the riser. This, firstly, is fire hazardous, but most likely it will not come to a fire, the riser channel will quickly be completely overgrown with carbon deposits. But how to clean it if you have a non-removable drum cover?

In a large furnace, a spontaneous change of mode occurs abruptly, when the top of the sticks drops to the lower edge of the bunker, and in a small furnace - gradually, as the fuel mass settles. Since the experienced hostess does not leave her for a long time when cooking on the stove, the designers considered it possible, for the sake of compactness, to combine a bunker with a blower in it.

With a large furnace, such a trick will not work: a high riser pulls very strongly, and the air gap is needed so thin (and it also needs to be regulated) that it is impossible to achieve a stable furnace mode. It is easier with a separate blower: it is easier for air to flow around a mass of fuel, rounded in cross-section, from the sides, an overly flared flame squeezes it out there. The stove turns out to be somewhat self-regulating; however, within very small limits, so you still have to manipulate the blower door from time to time.

Note: it is impossible to make a bunker of a large furnace for the sake of simplicity without a tight lid, as they often do. Due to the unregulated additional air flow through the fuel mass, it will hardly be possible to achieve a stable operation of the furnace.

Materials, sizes and proportions, lining

Now let's see what a homemade rocket stove should be from the materials available to us. Here, too, we need to look back: not everything that is at hand in America is with us, and vice versa.

Of what?

For a large stove oven with a stove bench, more or less reliable experimental data is available for products with a drum from a 55-gallon barrel with a diameter of 24 inches. 55 gallons is 208 with a small change, and 24 inches is almost exactly 607 mm, so our 200-liter will do just fine. Keeping the parameters of the furnace, the diameter of the drum can be reduced by half, to 300 mm, which makes it possible to make it from 400-450 mm of tin buckets or a household gas cylinder.

Pipes of different sizes will go to the blower, bunker, firebox and riser, see below, round or shaped. So it will be possible to make the insulating lining of the furnace part from a mixture of equal shares of furnace clay and chamotte crushed stone, without resorting to brickwork; we'll talk more about the riser lining below. Combustion in a rocket furnace is weak, therefore, the thermochemistry of gases is gentle and the thickness of the steel of all metal parts, except for the gas pipeline in the stove bench, is from 2 mm; the latter can be made of thin-walled metal corrugated metal, here the flue gases have already completely exhausted both in terms of chemistry and temperature.

For external coating, the best heat accumulator is adobe. If the dimensions indicated below are observed, the heat transfer of a rocket furnace in adobe after heating can reach 12 hours or more. The rest of the parts (doors, covers) are made of galvanized metal, aluminum, etc., with sealing gaskets made of mineral cardboard. Ordinary stove fittings are not very suitable, it is difficult to ensure its tightness, and the slotted rocket stove will not work properly.

Note: it is advisable to equip the rocket furnace with a view in the outer chimney. Although the gas view in the high riser locks the common flue gas duct tightly, strong winds outside can draw heat out of the bed prematurely.

Dimensions and proportions

The basic calculated values, to which the rest are tied, are the drum diameter D and its cross-sectional area along the inside S. Everything else, based on the size of the available gland, is determined as follows:

Drum height H - 1.5-2D.
Drum coating height - 2 / 3H; for the sake of design, the edging of the design can be made oblique curvilinear, then 2 / 3H must be sustained on average.
Drum coating thickness - 1 / 3D.
The cross-sectional area of the riser is 4.5-6.5% of S; it is better to keep within 5-6% of S.
Height of the riser - the more, the better, but the gap between its edge and the drum cover must be at least 70 mm; its minimum value is determined by the viscosity of the flue gases.
The length of the flame tube is equal to the height of the riser.
The cross-sectional area of the flame tube (fire conduit) is equal to that of the riser. It is better to make a fire conduit from a square professional pipe, so the oven mode will be more stable.
The sectional area of the blower is 0.5 from its own firebox and riser. A more stable oven mode and its smooth adjustment will give a rectangular professional pipe with sides 2: 1, laid flat.
The volume of the secondary ash pan is from 5% of the initial volume of the drum (excluding the volume of the riser) for the furnace from the barrel to 10% of the same for the furnace from the cylinder. Interpolation for intermediate drum dimensions is linear.
The cross-sectional area of the external chimney is 1.5-2s, where s is the cross-sectional area of the riser.
The thickness of the adobe cushion under the external chimney is 50-70 mm; if the channel is round, it is considered from its lowest point. If the bed is on wooden floors, the pillow under the chimney can be cut in half.
The height of the bed over the external chimney is from 0.25D for a 600 mm drum to 0.5D for a 300 mm one. Less is possible, but then the heat transfer after heating will be shorter.
The height of the outer chimney is from 4 m.
The permissible length of the gas duct in the bed - see next. sect.

The limiting thermal power of the rocket furnace from the barrel is about 25 kW, the furnace from the gas cylinder is about 15 kW. Power adjustment - only by the size of the fuel load. By supplying air, the oven is put into operation, and nothing more!

Note: In the original survival furnaces, the riser cross-section was taken at 10-15% S, calculated on a completely wet fuel. Then in the same place, in America, there were rocket stoves with a stove bench for bungalows, designed for air-dry fuel and more economical. In them, the riser section is reduced to the recommended ones and here 5-6% S.

Riser lining

The efficiency of the rocket furnace largely depends on the thermal insulation of the riser. But, alas, American lining materials are not available to us. In terms of reserves of high-quality refractories, the United States has no equal, where they are considered a strategic raw material and are even sold to trusted allies with caution.

From our available materials for heating engineering, they can be replaced with light fireclay bricks of the SHL brand and ordinary self-excavated river sand with a large admixture of alumina, correctly laid, see below. However, these materials are porous; in the oven, they will quickly become saturated with carbon deposits. Then the stove will start roaring with any supply of air, with everything that comes out. Therefore, we need to surround the riser lining with a metal shell, and the end of the lining must be covered with oven clay.

Lining schemes for 3 types of furnaces are shown in Fig. The bottom line is that with a decrease in the size of the drum, the proportion of its direct heat transfer through the bottom and the non-lined part increases according to the square-cube law. Therefore, while maintaining the desired thermal gradient in the riser, the lining power can be reduced. This makes it possible to correspondingly increase the relative cross-section of the annular lowering of the flue gases in the drum.

What for? Firstly, the requirements for an external chimney are reduced, because the external link pulls better now. And since it pulls better, then the permissible length of the hog in the bed falls more slowly than the dimensions of the oven. As a result, if a stove from a barrel heats up a stove bench with a hog up to 6 m long, then half the size of a cylinder is 4 m.

How to lining with sand?

If the lining of the riser is chamotte, then the residual cavities are simply covered with construction sand. A self-dug river lining entirely of sand does not need to be thoroughly prepared for lining, it is enough to select large debris. But it is poured in layers, in 5-7 layers. Each layer is tamped and sprayed until a crust forms. Then the entire backfill is dried for a week, the upper edge is covered with clay, as already mentioned, and the construction of the furnace continues.

Balloon rocket

From the above, it is clear that it is more profitable to make a rocket stove: less work, fewer unsightly parts in sight, and the stove bench heats up almost the same. A heat curtain or underfloor heating in Siberian frost will heat a room of 50 sq. m and more, so here, too, a balloon rocket turns out to be more profitable, a large barrel will rarely have to be launched at full power with maximum efficiency.

The craftsmen, apparently, understood this too; at least some. For example, here in fig. - drawings of a balloon rocket furnace. On the right is the original; the author, it seems, was wisely versed in the original developments and in general everything turned out right for him. On the left - the necessary improvements, taking into account the use of air-dry fuel and warming up the bed.

A fruitful idea is a separate supply of heated secondary air. The oven will be more economical and the flame tube can be made shorter. The cross-sectional area of its duct is about 10% of the riser cross-section. The furnace always works with a fully open secondary. Initially, the mode is set by the primary valve; precisely adjusted by the hopper cover. At the end of the firebox, the stove explodes, but here it is not so scary, for cleaning the riser the author of the design provides a removable drum cover. She, of course, should be sealed.

Rockets from anywhere

Canning

Tourists, hunters, and fishermen (many of them members of survival societies) soon adapted the small rocket furnace to be used as a camping stove made from empty cans. It was possible to minimize the influence of the square-cube by using a horizontal fuel supply, see the diagram on the right. True, at the cost of some inconvenience: the sticks, as they burn out, need to be pushed inward. But the mode of the furnace began to be held firmly. How? Due to the automatic redistribution of air flows through the blower and above / through the fuel. The power of the canned rocket furnace is in the range of 0.5-5 kW, depending on the size of the furnace and is regulated by about three times the amount of fuel loading. The basic proportions are also simple:

The combustion chamber diameter is 60-120 mm.
The height of the combustion chamber is 3-5 diameters.
The blower section is 0.5 from its own combustion chamber.
The thickness of the thermal insulation layer is not less than the diameter of the combustion chamber.

These proportions are very approximate: changing them by half does not prevent the furnace from working, and the efficiency during the campaign is not so important. If the insulation is made of wet sandy loam, as described above, the joints of the parts can simply be coated with clay (left position in the figure below). Then the stove after 1-2 fireboxes will acquire strength, allowing it to be transported without special precautions. But in general, any of the available non-combustible materials will be used for insulation, trace. two pos. A burner of any design must provide a free flow of air, 3rd pos. A rocket furnace welded from a steel sheet (right position) with sand insulation is twice lighter and more economical than a stove of the same power.

Brick

We will not dwell on large stationary rocket furnaces: in them all the original thermodynamics is sprayed, and they are deprived of one of the main advantages of the original furnace - the simplicity of construction. We will tell you a little about rocket furnaces made of bricks, clay or stone fragments, which can be made in 5-20 minutes, when there are no cans at hand.

Here, for example (see the video below), a rocket-oven of 16 bricks laid on a dry basis is quite complete in thermodynamics. The voice acting is English, but everything is clear there even without words. A similar one can be folded from fragments of bricks (see fig.), Cobblestones, molded from clay. For 1 time, a stove made of greasy earth is enough. All of them are not very economical, the height of the combustion chamber is too small, but enough for pilaf or urgent heating.

Video: rocket oven made of 16 bricks (eng)

New material

Of the domestic developments, the Shirokov-Khramtsov rocket-furnace deserves attention (see the figure on the right). The authors, not caring about survival in the pluck, used a modern material - heat-resistant concrete, adjusting all thermodynamics to it. The components of refractory concrete are not cheap; a concrete mixer is needed for mixing. But its thermal conductivity is much lower than that of most other refractories. The new rocket furnace became more stable, and it became possible to release some of the heat outside in the form of infrared radiation through heat-resistant glass. The result is a rocket stove - a fireplace.

Do rockets fly in the bath?

Isn't a rocket stove suitable for a bath? It seems that a stove can be arranged on the drum cover. Or flowing instead of a couch.

Unfortunately, the rocket stove is not suitable for the bath.... To get light steam, you must immediately warm up the walls with thermal (IR) radiation, and immediately, or a little later - the air, by convection. For this, the oven must be a compact IR source and a convection center. The convection from the rocket furnace is distributed, and it gives little IR at all, the very principle of its design excludes significant radiation losses.

In conclusion: rocket stove-makers

In successful designs of rocket furnaces, there is still more intuition than accurate calculation. And therefore - good luck to you! - the rocket oven is a fertile field for craftsmen with a creative streak.

When choosing the main functional component of a solid fuel heating system, in addition to efficiency, attention is paid to the duration of operating cycles and ease of maintenance. To implement the plan, taking into account the noted details, a rocket furnace is suitable. The simplicity of the design implies the absence of excessive difficulties in the independent performance of working operations.

Varieties of rocket furnaces

Reactive furnace diagram

The specific name is explained by the characteristic hum, which resembles the roar of a rocket launching engines. In more advanced designs, with the correct setting of the operating mode, the noise is reduced to a minimum level.

The classic diagram demonstrates the features of a reactive stove. In this design, the fuel is loaded vertically. The flame is formed in a horizontal section. With a sufficiently strong supply of air, the jet of heated gases quickly unfolds by the wall of the main chamber. This provokes a vortex effect in the center (riser), increasing thrust. The walls are heated in the side channels. Residual heat is accumulated in the lining of the outlet pipe connected to the chimney. This part is traditionally created in the form of a couch.

The rocket furnace has the following advantageous characteristics:

high efficiency;
the possibility of using wood waste, cones, other types of solid fuel;
prompt loading without interrupting the combustion process;
lack of complex elements;
minimal waste (high temperature).

Reactive ovens cannot heat a large room

For objectivity, it should be noted the disadvantages of the rocket stove:

the use of a water heat exchanger impairs the characteristics of the operating mode;
in certain situations, it is possible for carbon monoxide to enter the room;
the capacity of the structure is not enough to fully heat a large property.

Not everyone likes the appearance of such a structure. However, this parameter largely depends on individual tastes. With the correct finishing, it is not difficult to ensure harmonious compliance with a specific interior style.

The reactive furnace in various modifications was used by the population of Japan, China, Korea and other countries. Modern counterparts, while maintaining the basic principles, differ:

a variety of designs;
the use of new materials;
accurate engineering calculation.

Some stove-makers mention the Chinese Kan as an example. However, this design is similar only to a long chimney, which was often installed under several couches along the walls. In the corresponding version, this part performed the functions of a modern "warm floor" system. The firebox was created in a standard scheme with the obligatory device of a stove for cooking.

Russian stove

When simplified as much as possible, you can get the desired result:

pipes are connected at right angles;
a shelf for fuel is installed in the horizontal part - 60% of the diameter lower from the upper edge;
the lower part of the hole forms an unregulated blower;
the device is equipped with supports for fixation on a horizontal surface in a working position.

Gas cylinder oven

A factory product made of quality metal is a good basis for creating a homemade structure. In addition to reliable welded joints, the gas cylinder is suitable for wall thickness.

Furnace and design diagram from a gas cylinder

When choosing accessories, use sheet metal with a thickness of at least 5-6 mm. The diameter of the main part of the structure is more than 30 cm. The door in the opening for fuel loading can be used to regulate the intensity of the air supply. This addition will prevent carbon monoxide from entering the room. If you intend to use the oven for cooking, cut off exactly the top of the cylinder along with the valve. The hole is closed with a steel plate with a thickness of more than 5 mm, which is attached to the main body by welding.

In the version without a lounger, the residual heat is not accumulated, therefore the efficiency is lower compared to the “classic” version of the stove.

It is recommended to insulate the inner chamber. Thick enough walls will help ensure the temperature rises to + 950C ° and above. This is necessary for high-quality reproduction of the technological process. With such heating, complete combustion of the fuel with a minimum amount of ash is ensured.

Shirokov-Khramtsov furnace

This Russian modification is an improved version of the classic scheme. The main components of the Shirokov-Khramtsov furnace are created from an expensive type of concrete that is resistant to high temperatures. Accurate calculation significantly improved the stability of performance, which made it possible to place heat-resistant glass in the hopper area for partial release of infrared radiation towards the room. An improvised fireplace heats the room and serves as a spectacular decor element.

Rocket furnace from a profile tube

A marching version of a factory-made rocket furnace "Robinson"

For a hike, equipping a summer cottage, solving other "temporary" problems, a mobile version of heating equipment is suitable. The Robinson oven can be used as a pertinent example. The fuel and air supply is organized through a profile element (rectangular section 150 x 100 mm). The combustion zone is made of a pipe. The divider at the outlet is used as a rack for warming dishes.

Other models

A functional do-it-yourself rocket furnace can be made from 20 whole bricks and two halves. Such a structure is assembled in literally ten minutes on a prepared flat site. Careful calculations and drawings are not needed. Working operations are carried out without welding equipment and building mixtures. Fuel consumption is approximately 3-6 times less than firewood compared to "stove". It is permissible to use raw firewood, branches, fragments of old furniture.

Simple brick oven

Unlike a campfire, this structure retains heat for a long time. Cookware can be placed in the narrow opening. For convenience, a specialized support is used - a lattice made of steel rods or cast iron. Even in this simplest version, a high temperature is created in the working area, which contributes to the complete combustion of fuel with minimal smoke emission.

Principle of operation

An ordinary fire does not provide a rational use of fuel resources. A significant part of the energy is uselessly dissipated into the surrounding space. There are no convection processes, heat accumulators. Precise regulation of the combustion process is not possible. Oxygen access is unlimited.

With the use of a chimney and a closed working area, the noted disadvantages are eliminated. However, a jet furnace is more efficient than a typical "potbelly stove". The main difference is the chimney located inside the main structure. An increase in the gas escape path is accompanied by a gradual decrease in temperature in different areas (for example, the values are given in C °):

central mine (riser): 700-1100;
the gap between the walls: 250-380;
area under the bed: 30-90.

Improved thrust in jet furnace design

The illustrations show design features that provide sufficient thrust while extending the fume extraction path. Another advantage is the high-temperature decomposition of organic matter with a limited supply of oxygen (pyrolysis).

If a do-it-yourself rocket oven is created correctly, favorable conditions are provided for the formation of low-molecular-weight hydrocarbon compounds. Heating devices of this type are capable of providing an efficiency of more than 90%. Similar solutions are used in the design of household solid fuel boilers for long-term burning.

Homemade construction

In the absence of experience, you can choose a simplified design of several bricks, a bent pipe. If you have the skills to handle a welding machine, create a furnace from a square profile and sheet metal.

Furnace drawing and dimensions

The presented option can be adjusted taking into account the volume of the room, other personal requirements and preferences. The developers recommend setting the riser bore diameter between 65 and 105 mm. Resize the shell accordingly.

Legendary drawing for assembly

For the accumulation of thermal energy, adobe was chosen. This material is not heat resistant, so the temperature must be reduced to a safe level. Additional recommendations:

the drum can be made from a standard 50-liter cylinder;
ensure perfect tightness of the smoke exhaust system to prevent the penetration of soot into the porous adobe;
to remove the residues of mechanical impurities, a second ash pan is installed.

Step-by-step instruction

Homemade wood burning stove rocket

A do-it-yourself reactive wood-fired oven can be created according to the following algorithm:

For the manufacture of a mixture of the main heat-insulating layer (5b), crushed stone from chamotte brand ShL is used.
The support frame for the stove is assembled from wooden logs (100 x 100) with cells of no more than 600 mm, the distance under the lounger can be increased.
For cladding, mineral cardboard, tongue-and-groove boards are used.
Wooden blanks are pre-treated with impregnation with biocidal additives.
The area under the main part of the structure is covered with a metal sheet.
After placing the structure at the planned place, formwork is installed, adobe is poured.
A drum is made of a gas cylinder of a suitable size.
To create reliable welded joints, electrodes with a diameter of 2 mm, direct current of 60-70A are used.
The sealing seal is created from an asbestos cord and fixed with heat-resistant glue.
A riser is assembled from the prepared steel blanks.
Install the bottom layer of insulation; plywood (20 mm) or boards are used for formwork.
Filling with mortar is performed up to level B according to the drawing. It takes 1-2 days for this part to dry completely at room temperature.
Install the firebox, controlling the accuracy of the vertical position.
Part of the blower will protrude outward, therefore, at the final stage, the wall is leveled with adobe.
After filling with the mixture to level G, it is recommended to accelerate the drying with a conventional 60-75 W incandescent lamp (placed under the riser).
Install an ash pan made of steel sheet 0.8-1 mm thick.
The drum tube is mounted with the formation in the inner part of the wedge-shaped slope towards the outlet (mixture 5b).
A lining with layer-by-layer filling (5g) is created, the plug is made of clay.
The assembly is continued according to the scheme, the corrugation, drum and ash pan covers are installed.
After completion of drying (2-25 weeks), the formwork is removed, the surface is formed, the visible metal parts are painted.

Explanations for the composition of building mixtures (5):

a - adobe made of clay and straw, the consistency of thick dough;
b - clay of medium fat content with chamotte crushed stone;
c - chamotte sand with clay in proportions one to one;
d - river sand without washing with a fixed granule size (2.5-3 mm);
e - furnace clay of medium fat content.

They purchase in advance the tools and consumables necessary to carry out work operations. The list of purchases is made on the basis of the prepared project documentation.

How to heat a rocket stove

Taking into account the long path of the smoke exhaust system in a stationary structure, it is clear that it is necessary to start the operating mode after preheating. When working with "Robinson" and other compact analogs, this rule does not need to be followed. But a large oven is first heated with dry shavings, paper, and other suitable consumables. A blower with an open door is used for loading. The degree of readiness is assessed by the characteristic decay of the noise. At this stage, a normal charge of fuel is used in the corresponding part of the furnace.

Imagine a situation: to heat the room at home or cook food, you need to quickly build a simple wood-burning stove. Fuel quality and consumption are secondary. A suitable option is a homemade rocket furnace made from scrap materials. We suggest that you familiarize yourself with the heater device and the assembly process at home.

Design and principle of operation

The rocket stove shown in the diagram consists of the following main elements:

a bunker for laying firewood of a vertical or inclined structure;
horizontally located combustion chamber;
a lined pipe - an afterburner (the second common name is a riser);
a metal cap that plays the role of an air heat exchanger;
blew;
chimney channel.

In operation, the furnace uses 2 principles: the occurrence of natural draft within the vertical section and the combustion of wood (pyrolysis) gases. The first is realized by heating the firebox and waste products of combustion, striving to rise through the afterburner channel. In it, the emitted pyrolysis gases burn out.

Reference. The name rocket or jet furnace is connected precisely with the principle of operation - a powerful natural draft arises in the vertical channel, causing intense combustion in the furnace and the release of heat.

The operation algorithm of the stove is as follows:

The firewood loaded into the bunker is ignited from below. The air supply is provided through the blower hatch.
In the process of combustion, flue gases warm up the insulated walls of the afterburner and rush under a hood made of thin metal, where they give off most of the heat to the air in the room.
With a sufficient amount of secondary air, the pyrolysis gases have time to burn inside the riser, releasing additional heat.
Combustion products are discharged directly into the chimney or first sent to the chimney of the bed.

Robinson Portable Stoves

In a simplified travel version, the stove is made without a cap and insulation. Accordingly, the secondary gases do not burn completely, since they have time to escape into the pipe. The small-sized portable heater, named "Robinson", is designed for quick cooking on fuel of any quality and degree of humidity.

Requirements for the dimensions of the elements

The main heat-exchange element of the rocket stove is a metal cap, the intensity of heating a room in a house depends on its size. In stationary brick-built structures, a 200-liter barrel with a diameter of 60 cm is usually used. Portable versions are made from standard gas cylinders Ø300 mm.

Scheme of a rocket heater with a stove bench

Accordingly, the rest of the dimensions dance from the dimensions of the barrel - the diameter and cross-sectional area:

the height of the cap is provided for 1.5-2 times the diameter;
the cross-sectional area of the afterburner is 5-6.5% of the barrel diameter;
the length of the riser is made such that a minimum gap of 7 cm remains between the upper cut of the pipe and the cover;
the internal size of the firebox is equal to the cross-section of the afterburner, the blower channel is twice as small;
chimney diameter - 1.5-2 times more than the afterburner section, height - at least 4 m.

To make it easier for you to calculate the diameters of pipes and lining, we present a drawing for various options for rocket furnaces - from a cylinder, a barrel and old buckets (the riser is made of a round or shaped pipe).

We make a furnace - a rocket

The easiest way to make a light camp stove, shown in the drawing, by finding the following materials in the household:

round steel pipe with a diameter of 133-150 mm and a length of 0.5 m;
profile pipe 14 x 20 cm, length 0.4 m;
metal sheet 2-3 mm thick on the grate;
rod Ø8-10 mm for legs;
scraps of iron on a stand.

The vertical round pipe is welded to the profile pipe at an angle of 45 °, then the lugs for the legs are attached to the body (they should be easily removed). A grate is placed inside the inclined firebox, and a cover is attached outside. For the convenience of cleaning ash, it is advisable to install a second door at the bottom.

Advice. Be sure to weld a stand to the upper cut of the firing channel - gases must penetrate between the bottom of the dish and the body, otherwise there will be no “rocket” thrust.

Drawing of the improved version of the portable oven

The design of the furnace can be improved by supplying secondary air to the inside of the flame tube. The modernization will increase the efficiency and duration of the firewood burning. Drill holes on both sides on both sides, covering them with rocket nozzles as shown in the drawing. How this stove functions is demonstrated in the video:

From a gas cylinder

The following materials will be used to make a furnace - rockets with their own hands:

round pipes with cross-sectional dimensions of 70 and 150 mm; with a wall thickness of 4 mm;
square pipe 150-200 mm in diameter;
chimney pipe Ø10-15 cm;
low-carbon steel (grade St20) sheet;
dense basalt wool (80-120 kg / m3) or bulk fire-resistant materials, for example, vermiculite or perlite gravel.

First, cut the rolled metal into blanks in accordance with the drawing. Then you need to saw off the cover from the propane cylinder, after unscrewing the valve and filling the tank to the top with water. The tool is an ordinary grinder with a metal circle.

Further assembly technology is as follows:

The master will tell in detail about the manufacture of a rocket stove from a cylinder in a video:

Brick

The simplest rocket stove for cooking can be folded out of bricks without the use of mortar, as shown in the ordering diagram. Such a structure is not difficult to disassemble and move if necessary.

A rocket stove with a stove bench must be laid on a foundation made of concrete or rubble stone. Material - ceramic or refractory bricks, sandy-clay or fireclay mortar, respectively. The finished base is covered with roofing material for the purpose of waterproofing, then a continuous first row of bricks is laid. The further order of work looks like this:

Important. The construction is carried out in compliance with the rules of the stove masonry, painted.

The length of the smoke channels inside the bed is limited by the draft in the rocket furnace and the external chimney. It is better to maintain the total length of the flue pipes within 4 m. To prevent the heater from smoking back into the room, raise the top of the chimney to a height of 5 m, counting from the grate. How to build a brick stove - a rocket without a barrel, look at the video:

In conclusion - the pros and cons of the stove

Such structures are really made quickly, and the performer does not need to be highly qualified. The first and main advantage of rocket-type furnaces is their simplicity and low demands on materials. In addition, they take a variety of fuels well - raw firewood, branches, brushwood, and so on.

Now on the negative points:

For the above reasons, a rocket heater is extremely inconvenient for a garage, where you need to heat the room quite quickly. But the hiking option is indispensable in nature at any time of the year.

Design engineer with over 8 years of experience in construction.
Graduated from the East Ukrainian National University. Vladimir Dahl with a degree in Electronic Industry Equipment in 2011.

Related entries:

The simple and cheap design of the rocket furnace began its march around the world from North America, where it is still very popular in the countryside to this day. They know her on all continents, including distant Australia. For amateur enthusiasts, the heating unit wins over with its simplicity and energy efficiency, which, combined with its low cost, makes it extremely attractive for making at home. Of course, a large house cannot be heated with a jet stove, but in a country house or in a small garden house it will be more than appropriate. Surprisingly, but a fact - only a few people know about this amazing design. And this is in a country where cold weather lasts longer than six months! Today we will fill this gap and tell you everything that we know about a warm and cozy "rocket", including the smallest details of its manufacture with our own hands and the subtleties of operation.

Reactive furnace - what is it

Household heat that comes from a jet oven will not be provided by any modern heater.

The jet, or, as it is also called, the rocket furnace, in fact, has nothing to do with modern technology. The only thing that makes this heating unit look like a space transport is an intense flow of flame and a hum associated with an incorrect operating mode. Nevertheless, it cannot be said that the rocket oven is a very technically backward device. Despite its simple design, it uses the most advanced solid fuel combustion methods:

pyrolytic combustion of gases released during dry distillation of solid fuel;
movement of gaseous products through the channels of the furnace, which does not require forced ejection due to thrust.

This is what the simplest jet-powered furnace looks like.

The simplest "rocket" is a curved section of large diameter pipe. Firewood or other fuel is placed in a short horizontal section and set on fire. At first, the heater works like an ordinary potbelly stove, but this is only until the temperature of the longer vertical part, which acts as a chimney, rises. Red-hot metal contributes to the re-ignition of combustible substances and the appearance of a vacuum at the top of the chimney. Due to the increased traction, the air flow to the wood increases, which significantly increases the intensity of combustion. In order to achieve even greater efficiency from this original device, the furnace opening is equipped with a door. With a decrease in the cross-section of the air channel, the supply of oxygen to the wood stops and their pyrolytic decomposition into gaseous hydrocarbons begins. But they will not completely burn in such a simple installation - for this it will be necessary to equip a separate zone for afterburning the flue gases. By the way, this, as well as the thermal insulation of the chimney, allows more complex "rockets" to successfully compete with other solid-fuel units. As for the simplest design we are considering, it is often used for cooking or heating food. All that is required for this is to equip a convenient platform for a kettle or kettle on the vertical section of the stove.

Geography of application of rocket heating units

Being a simple and convenient heating and cooking unit, the rocket oven is widely used both in mobile and stationary versions. Most often it is used:

for heating living quarters;
as equipment for drying fruits;
for heating greenhouses;
to ensure normal working conditions in workshops or garages;
to maintain a positive temperature in warehouses, in utility blocks, etc.

Due to its simplicity, unpretentiousness and reliability, the jet heating device enjoys well-deserved respect among fishermen and hunters, fans of motor rallies and survivalists. There is even a special performance, the purpose of which is indicated by the name - "Robinson".

Advantages and disadvantages of the rocket furnace

Despite the uncomplicated design, the rocket furnace has a lot of advantages:

efficiency at the level of the best examples of modern solid fuel heating equipment;
profitability - to achieve the required temperature, the jet unit will consume four times less firewood than a traditional stove;
heating temperature above 1000 ° С;
the ability to use any type of solid fuel, including dry plant waste, cones, pine needles and shavings;
complete combustion and environmental friendliness - during operation, the flame temperature rises so much that soot ignites. The smoke of a rocket furnace is composed primarily of water vapor and carbon dioxide;
the possibility of additional loading of fuel for continuous operation of the heater;
simplicity and reliability;
availability of portable structures designed for mobile use.

The heating unit is not devoid of disadvantages. The use of the device is associated with the risk of carbon monoxide entering the home. The stove cannot be used to heat a large house, and attempts to install a water heat exchanger in the combustion zone lead to a decrease in thermal power and disruption of normal operation. The disadvantages include the low aesthetic value of the structure, which, however, is a very ambiguous statement, since for fans of ethno-style, the design of the stove is a real find.

Types of jet heaters. Choosing a design for self-production

Craftsmen have developed several designs of rocket furnaces suitable for mobile or stationary use:

portable units made of metal pipes, cans or buckets;
jet heaters from a gas cylinder;
furnaces built of fireclay bricks and metal containers;
heating heat generators with a stove bench.

The most difficult to manufacture are structures, the construction of which requires the skills of a bricklayer. Nevertheless, in the presence of detailed schemes of ordinal layouts, even a novice home craftsman can cope with this work.

Portable rocket oven

Portable rocket furnaces are mass-produced by the industry

Camping options are represented by the simplest designs, which are based on the same pipe bent or welded from separate sections. The improvements concerned only the installation of a partition for arranging an ash pan, in which a slot is made for air suction. Often, the lower part of the loading chamber is equipped with a grate to supply air directly to the combustion zone. The opening for laying firewood is equipped with a door, which subsequently regulates the air supply.

The requirements for a mobile structure also apply to convenience during cooking, so the upper cut of the chimney must be equipped with a support for metal dishes.

Unit from a gas cylinder

The use of a gas cylinder is the next step in the development of jet heaters. A more complex design allows a significant increase in the heat output and efficiency of the furnace. All that is required for the manufacture of the installation is a household gas cylinder or a barrel of fuels and lubricants, pieces of thick-walled steel pipes and a metal sheet 3-5 mm thick.

The rocket stove from a gas cylinder can be used to heat small utility rooms

If you have a piece of steel pipe with thick walls and a diameter of more than 30 cm, a rocket furnace can be made from it. This option will avoid time-consuming operations associated with disassembling the factory gas tank.

How this design works can be seen in the diagram below. The firewood loaded into the firebox burns out due to the air flow through the loading window. Afterburning of combustible gases occurs in a pipe installed inside the cylinder due to the supply of secondary air. To enhance the effect, the inner chamber is insulated, which makes it possible to raise the temperature inside above 1000 ° C. In the course of movement, hot gases hit the bell and enter the outer chamber, the walls of which act as a heat exchanger. Having given up their energy, the combustion products are removed through a chimney cut into the lower part on the back of the cylinder.

To create the thrust necessary for the stable operation of the rocket furnace, the top of the chimney is raised at least 4 m relative to the loading window.

Combined brick and metal barrel rocket kiln

The use of fireclay bricks for arranging a firebox and internal chambers of a jet heater translates the "rocket" into the category of stationary structures. The high heat capacity of the materials used makes it possible to accumulate heat and give it away for several hours, therefore, such units are often installed in residential premises.

Furnace construction with refractory lining of the working area

Reactive stove with stove bench

Like other solid fuel stoves, the "rocket" has the disadvantage that most of the heat is emitted through the chimney. Despite this, some of the advantages of its design make it easy to get rid of this disadvantage. The thing is that the unit was called reactive for a reason, but because of the high rate of excision of burning gases. It is this feature of it that can be turned for good by significantly increasing the length of the smoke exhaust ducts.

Diagram of a jet furnace with a stove bench

This idea has found its realization in massive stationary structures with a couch or bed-shaped couch. It is successfully made from brick or rubble stone, decorated with a plastic mass of clay and sawdust. Due to the high heat capacity of the materials used, the stove can retain heat throughout the night, which, combined with high efficiency, makes the heating unit very attractive for installation in residential premises.

When choosing a structure for making at home, one must take into account the peculiarities of its operation. As a traveling option, a mobile unit is chosen - it will be enough to keep warm, dry clothes and cook dinner. In order to heat small technical rooms from time to time, a portable design from a gas cylinder is used. If you need to heat a small country house or cottage, then there is simply no better option than a jet heating unit with a stove bench.

We build a rocket oven with our own hands

The design proposed for self-production is the elite of rocket heaters. After construction, it will delight the owner for a long time with comfort and cozy warmth even in the most severe frost. As you might have guessed, we are talking about a unit with a stove bench. Despite the fact that such a design is the most complex, the schemes, instructions and descriptions presented by us will allow you to build a furnace in just 2-3 days.

Device and principle of operation

The rocket furnace consists of several chambers and channels. The bunker for loading firewood is made of fireclay bricks and is supplied in the lower part with an opening for air supply. It has a refractory lining and a channel that connects the firebox with a vertical gas duct (flame tube or riser). A metal barrel is used as a casing for a rocket furnace, inside which an afterburner is laid out with magnesite or fireclay bricks. The heat exchanger of the heating unit is not only a steel container, but also long horizontal channels of the bed, made of galvanized steel pipes or bricks.

The processes taking place inside a stationary jet furnace resemble the work of pyrolysis heating units.

There is no need to use refractory materials for the arrangement of heat exchange channels. A well-fired red brick is enough.

The body of the stove and trestle bed are formed from sandbags, stone or brick debris and coated with a clay composition. The good heat storage capacity of finishing materials allows the structure to give off heat for several hours after the firewood has completely burned out. To remove combustion products, a high chimney is used, which can pass both indoors and outdoors.

The high performance of the "rocket" is explained by the method of fuel combustion, which tends not so much to direct-flow heating units as to pyrolysis boilers. The operation of the furnace is accompanied by the active release of gas components, which are burned out in the riser. The hood helps to reduce the flow rate of incandescent gases, otherwise they simply would not have time to oxidize. By the way, the heating of the upper part of the flame tube creates a vacuum at its end, due to which active combustion of the fuel occurs. This creates such a high temperature in the riser that even soot is ignited. Nevertheless, experts recommend installing an ash pan at the point of transition from a vertical channel to a horizontal heat exchanger, equipping its chamber with a small door for the possibility of periodic maintenance.

Calculation of basic parameters, drawing

There is no need to give the exact dimensions of a rocket stove with a stove bench - its dimensions and configuration completely depend on the characteristics of the room. The presented method for calculating the parameters based on the use of the proportions of all parts of the rocket furnace will be quite enough to design a high-performance, efficient unit.

To carry out the calculation, it is sufficient to know the diameter D and the height H of the external heat exchanger shell (drum).

The flame tube height is at least 1.3H.
The clearance between the riser and the bonnet is 0.1–0.15H.
External clay coating is performed no higher than 1 / 3H.
The thickness of the heat storage layer should be no more than 1 / 3D.
The section of the flame tube is 0.25–0.3D.
The height of the ash pan is up to 10% of the vertical dimension of the casing.
The blower section should be 50% less than the riser area.
The thickness of the adobe cushion above the heat exchanger is at least 1 / 4D.
Chimney height - more than 4 m.
The length of the horizontal heat exchanger is calculated based on the volume of the drum. In the case of using a standard barrel from under fuels and lubricants, it can reach 6–8 m.

As you can see, it is not difficult to determine the dimensions of all elements of the furnace, especially since its design allows some liberties in terms of dimensions and configuration.

For perfectionists and those who are afraid to experiment, here is a drawing of a heating unit, made to scale on a marked sheet of paper. If necessary, it will not be difficult to remove the exact dimensions from it.

Stationary reactive heating plant drawing

Materials and tools

The construction of a jet furnace does not require any specific fixtures. From the power tool in the process of work, you will only need a welding machine and a grinder, and even then literally for a few minutes - to separate the barrel lid and configure the heat exchanger pipes. Everything else can also be found in any owner:

trowel (trowel);
bushhammer;
building level and plumb line;
roulette;
container for solution preparation;
bayonet shovel;
rammer;
buckets;
concrete trowel.

Although the design of the "rocket" and undemanding to materials, still some of them will have to be bought. Here is a list of what will be required during the construction process:

refractory bricks of any type;
metal barrel for the manufacture of the casing;
pipe Ø30–40 cm, which will hold the heat-insulating sprinkling of the vertical channel. You can use a case from an old water heater, a suitable capacity of an industrial receiver or hydraulic accumulator;
galvanized steel pipes with a diameter of more than 25 cm, which will be needed as a heat exchanger;
a steel pipe for arranging a chimney with a diameter of 150 mm and an elbow for its 90 ° outlet;
ash pan hatch;
blower door;
a special heat-resistant mixture for preparing a solution (can be replaced with sand and clay);
perlite for riser insulation;
Red brick;
rubble stone or brick waste;
sawdust or chaff.

Since the barrel will only be partially embedded in the oven, it will have to be painted to increase the aesthetic value of the unit. To do this, you will additionally need a metal brush, a solvent to degrease the metal surface, a primer and any heat-resistant paint.

Site selection and other preparatory activities

When determining the construction site, one should take into account the requirements that apply to all designs of solid fuel furnaces with an open flame:

the area of the room in which it is planned to install a jet heater with a lounger must be at least 16 m 2;
the absence of lags (floor beams) under the furnace body will greatly simplify installation;
there should be no wooden rafters and ceilings above the hearth;
if part of the chimney passes through the ceiling, then the stove is installed closer to the central part of the house. In this case, the pipe can be fixed near the ridge;
you should not install a heating structure close to the outer contour of the building - precious heat will go out into the street. It is better to attach the unit to one of the inner walls;
it is not recommended to erect a jet device near wooden walls and partitions. In this case, a stand-alone placement is chosen.

It is also important how convenient it will be to light up the rocket stove and throw firewood into it. For this, the firebox is placed in the direction of the entrance, providing at least 1m of free space in front of it.

One of the many options for installing the stove in the middle of the room

In a small room, it is convenient to place the rocket oven in the corner, orienting the loading hopper to one side and the sunbed to the other.

Having chosen a place, they begin to prepare it for future construction. If the room has a wooden floor, then that part of it that will be located under the stove is removed. After that, a shallow pit is dug, the bottom of which is compacted with a rammer.

In addition, it is necessary to prepare a metal barrel for installation. To do this, cut off its cover along the contour. In this case, part of the thickening in the form of a metal hoop is left to ensure the rigidity of the base of the casing. Most likely, the container from under the fuels and lubricants will be dirty and rusty, so it is better to clean it before installation.

The last thing to do before starting construction is to prepare the mortar. It is best to use a special heat-resistant composition, which can be bought in hardware stores, but you can do with a simple mixture of sand and clay in a ratio of 1: 1 or 1: 2, depending on the fat content of the latter. Water will be needed up to ¼ of the volume of dry components - the output should be a composition resembling thick sour cream.

Workflow instructions

As already mentioned, making a rocket stove with a stove bench will take much more effort and time than making a metal assembly. Step-by-step instructions with illustrations of all stages of construction will help to facilitate the task and reduce time.

The place where the firebox will be formed is deepened by 10 cm and laid out with refractory bricks, after which formwork is installed along the contour of the furnace. To strengthen the foundation, it is necessary to install reinforcement made of construction mesh, reinforcement Ø10–20 mm or scrap metal pipes and corners.
Formwork arrangement
The base of the working chamber is laid out according to the level.
The base of the loading chamber is laid out with refractory bricks
The structure is poured with concrete. Further work can be started immediately after the mortar has set. As a rule, one day is enough for this.
Pouring the foundation
From refractory bricks, laid in a continuous order, form the base of the reactive furnace and the combustion chamber.
Rocket furnace base
The side walls of the structure are raised in several rows of masonry.
The walls are formed using fireclay bricks installed on the edge
Equip the lower channel of the heat-generating rocket.
The combustion chamber is covered with a row of bricks, laid across in such a way as to leave open two openings - the firebox and the riser (vertical channel).
Method of overlapping the horizontal part of the working chamber
An old body from a storage-type boiler is prepared for installation. For this, the device is cut on both sides to obtain a large diameter pipe.
Furnace parts prepared for installation
The lower part of the tank from under the fuels and lubricants is equipped with a flange into which the horizontal heat exchanger pipe will enter. Weld seams must be continuous in order to ensure tightness and, accordingly, the safety of the structure.
Installation of the lower branch pipe is carried out by welding
After the outlet pipe is cut into the barrel, it is cleaned of rust, covered with a primer and several layers of heat-resistant paint.
A side outlet is welded to the horizontal chimney, which acts as an ash pan. To clean it, the channel is equipped with a sealed flange.
A fire tube is laid out of fireclay bricks. The shape of its inner channel is a square with a side of 18 cm. During operation, the vertical position of the structure must be controlled using a plumb line or a building level.
The height of the vertical channel depends on the dimensions of the outer drum
A casing is installed on the fire tube, after which the gaps between the metal container and the walls of the vertical channel are filled with perlite. To avoid spillage of thermal insulation on the floor, the lower part of the riser is carefully sealed with a clay mixture.
Riser Insulation Method
A firebox cap is made. It can be used as a cut-off part of the water heater, providing it with a convenient handle.
With the help of brick or masonry, the body of the furnace is formed. For this purpose, you can also use sandbags placed at the base of the vertical channel.
The furnace body can be laid out with sandbags

An unassuming outdoor look is hidden with adobe coating. For its manufacture, up to 50% of large sawdust or chaff (chaff) is introduced into the clay solution.

Furnace body coating

The additives in the clay mixture perform the same role as the crushed stone in concrete. They are needed so that during drying and subsequent work with variable heat loads, the surface of the furnace does not crack.
The perlite backfill on top must also be sealed with a coating.
The front of the oven is formed. To do this, in any suitable way (brick or masonry, sandbags, adobe) lay out the outline of the furnace. The inside is filled with rubble, and the top is given the desired shape using an adobe mixture.
An external casing made of a metal barrel is installed on the prepared base, orienting the container with the lower pipe towards the bed. The lower part of the container is sealed with clay.
Installing the casing - metal drum
Using a corrugated pipe, a channel is led to the firebox, which connects the firebox with the external atmosphere. If it is not installed, the stove will consume warm air from the room, which will be replaced by cold masses coming from outside. From the side of the firebox, the channel will need to be closed as soon as the firewood is completely burned out. This will prevent outside air from entering the heat exchange channels.
Air duct outside the building
To check the operation of the rocket furnace, the first kindling is carried out, during which they make sure that the gases freely escape into the horizontal chimney.
Heat exchanger pipes are connected to the lower branch pipe, which are installed on a base formed of red brick.
The chimney is being installed. All joints of the parts of the horizontal and vertical channels are sealed with an asbestos cord and refractory coating.
Using the same method as in the manufacture of the furnace body, they give the required configuration to the stove bench.
Fully formed stove with stove bench
The barrel can be completely covered with adobe, leaving only a horizontal platform open, which is convenient for heating food.
The chimney brought out to the outside is equipped with a condensate and tar trap, and the upper cut is protected from precipitation by means of a cap.
The outer part of the chimney is supplied with a trap for liquid substances

Tests of the rocket furnace are carried out only after the adobe coating has completely dried. Otherwise, the decorative coating may crack.

View of the finished rocket oven with a stove bench

For the safe operation of the rocket furnace, the room must be equipped with carbon monoxide sensors.

Modernization of the rocket heat generator

To expand the field of application of jet heating furnaces, they are being finalized, increasing the convenience and versatility of the design. A platform for cooking food in mobile structures is often replaced with a full-fledged stove. It is convenient to use such a hob in your own backyard for household purposes - for preparing food for pets or during the preservation period of blanks for the winter. A feature of this type of rocket furnace is a wide and flat horizontal channel into which hot gases are directed from the nozzle. Passing under the surface of the stove, they heat it red-hot, after which they go into the vertical chimney. Comfortable legs give the structure stability, and the original shape allows the unit to be used as a stand or table when it is not being used for its intended purpose.

Reactive stove with a stove - a must-have item in a suburban area

A liquid heat exchanger cannot be installed in the flame tube of a jet furnace, but this does not mean that it cannot be used as a heat generator for a water heating system. To do this, the "rocket" is equipped with a kind of contour of radiator plates, which create a kind of labyrinth in the afterburning zone. Due to their heating, heat is removed from the afterburner to the water jacket. The efficiency of the unit depends on the area and heat capacity of the plates; therefore, they are made in the form of massive metal strips with an area of up to ¾ of the section of the fire channel. I must say that such a heat exchanger is best used to obtain hot water using the rocket oven itself in the traditional way.

Diagram of a rocket unit equipped with a water circuit

The rocket oven with a convector has an original design. To increase heat transfer, vertical tubes are mounted on the surface of the outer casing, which perform the same role as the Buleryan air channels. Cold air is entrained at the bottom of the tubular heat exchangers and heats up as it travels up. This ensures forced convection, which further increases the thermal efficiency of the installation.

Rocket heat generator casing equipped with a convector

Features of the use of jet furnaces

Being a long burning system, the rocket furnace requires preliminary heating before starting operation. As a rule, no one observes this requirement in mobile installations - they consume a little fuel, and the stove itself is most often used according to the principle “it works, but okay”. In stationary structures, it is extremely important to warm up the furnace before starting it up, since with a cold flame tube, there can be no question of afterburning. The firewood will burn without giving off heat, and the chimney will very quickly be covered with soot, tar and creosote.

The furnace is heated with wood chips, paper or shavings, which are loaded into the firebox and ignited. The output to the operating mode is judged by the buzzing in the fire channel. A strong sound indicates that the unit is not operating efficiently. As soon as the hum starts to subside, you need to start laying the main fuel. The blower should be completely open for the first 10-15 minutes. Then the air supply is reduced, focusing on the sound of the furnace - it should "rustle" or "whisper". After the firewood burns out, the air channel of the firebox is covered to prevent heat leakage from the room. Ash is removed every 2-3 days, for which they use a metal scoop and a poker.

The reactive furnace is serviced no more than once a season. To do this, open the ash pan door, through which the soot residues are removed. If necessary, clean the smoke channel using the hatch of its trap. I must say that the correct operation of a jet heater never leads to smoke in the room. All that is required of the owner for this is to follow the recommendations for using the "rocket" and not neglect the safety rules.

Do-it-yourself rocket furnace: the subtleties and nuances of construction (video)

Unique technical characteristics, almost zero cost and availability of materials for construction cover all the disadvantages of a jet furnace. If you wish, you can build a full-fledged heater over the weekend, including arranging a comfortable couch. "Raketa" is also convenient in that it does not require high qualifications of a stove-maker, and in its external design it allows the realization of even the most unusual design idea.

Boilers, homemade stoves and heating equipment topics are always popular at FORUMHOUSE. No wonder. Indeed, due to the constant rise in energy prices, difficulties and high cost of connecting to the main gas, many are thinking about finding an alternative to "blue fuel".

Despite the large selection of prefabricated products, our enthusiasts create their own designs of heating systems. Of particular interest is the solid fuel boiler, built by the user of our portal with the nickname Perelesnik... It attracted a lot of attention because its operation is based on the principle of operation of a rocket furnace. In this article, we will talk about the main stages of boiler development, prior to its construction.

How it all started

Before moving on to the technical features of the boiler, it is worth focusing on the background of its construction.

Perelesnik FOUMHOUSE user

Gas has been brought into my house, but I periodically thought about switching to solid fuel. The only thing that stopped them was that gas heating was profitable, and the transition to firewood was not profitable. I heated the house with a 7 kW electrode boiler, working in conjunction with an air conditioner, which was operated "for heating". In severe frosts, the house was additionally heated by a gas-fired boiler. And now the gas has risen in price ...

It was the increase in the price of gas that was the event that led to the development of the rocket boiler.

Before you go and immediately buy "something" called "solid fuel boiler", Perelesnik began to study the subject. He got acquainted with the list of equipment offered in stores, looked at how boilers work at neighbors, understood what the most common problems arise, and studied reviews on the Internet.

After the brainstorming session, a list of requirements appeared that the device must meet - in terms of Perelesnik:

Possibility of stable operation at power from 2 to 20 kW. This is due to the peculiarities of the climate in the region where the member of the forum lives. In winter, the temperature can stay around 0 ° C for a month, and then drop sharply for a week to -25 ... 30 ° C. In the autumn-spring period, the temperature is in the range of + 5 ... + 10 ° C. Because the house also needs to be heated in the off-season, but maximum power is not required from the boiler, a “flexibly” adjustable device is needed.
The boiler must be "omnivorous", i.e. everything that can burn in the firebox should burn - firewood, fuel briquettes, coal, waste, etc., including wet fuel.
The design of the boiler should provide for laying logs with a diameter of up to 20 cm. This will reduce the need for chopping wood.
It should work from night to morning on one tab of fuel. In severe frost, the number of full fuel fillings should not exceed three.
Complete non-volatility. The device should work without the need to connect it to the mains. In the event of a wire break or a power outage, the operation of the circulation pump (it must pump the coolant) is provided by a backup power system.

The heating system is selected depending on the climatic conditions of residence, heat loss at home, the availability of a particular type of fuel, energy prices in your region.

Also, among the main requirements for the boiler were listed:

high efficiency, simple and inexpensive chimney design;
small formation of soot and deposits (which means that there is no need for frequent cleaning of the boiler and the efficiency of its operation increases);
safety of boiler operation under any operating conditions, heat resistance of units;
the possibility of additional loading of firewood during operating mode;
ease of use of the boiler when installed in a residential area;
light weight and dimensions.

The most interesting thing is that it was planned to “fit” all these requirements into the budget, not exceeding 500 dollars, excluding the cost of work.

It is enough to just superficially familiarize yourself with the requirements in order to understand that finding a solid fuel boiler that meets all the items on the list is not an easy task. That's why Perelesnik decided to go in two ways:

Try to find a finished factory product.
In case of failure, copy the design of the finished boiler and make it yourself.

In the course of searches and further study of information, both options disappeared. Due to technical features: “capriciousness” of work on “wet” wood, impossibility to work at low power, etc. pyrolysis boilers of long burning did not fit. Also not satisfied with the "homemade products" found in the vastness of the "world wide web". The third option remained - on the basis of their knowledge and experience gained, to develop the design of a solid fuel boiler "for yourself".

Rocket boiler - theory

In the course of his search Perelesnik stumbled upon a rocket furnace, and this structure "hooked" him.

Perelesnik

The rocket stove attracted me by the fact that its operation does not require any special chimney, we can say that it is not needed at all. The rocket furnace has excellent thrust, and without the use of any fans. Its design provides high-temperature afterburning of furnace gases. It is not demanding on the quality of fuel, it works effectively at different capacities.

The only thing left was to make a boiler out of the stove. Looking ahead, let's say that almost a year has passed from the idea to the implementation of the furnace “into metal”. This included several months in search of the optimal design, calculations, experiments. It took three months to make the boiler itself, but the result was worth it.

We managed to make a device that met almost all the requirements of the list (except that you can add fuel only when the previous batch has burned out to the state of coal). Moreover, it was possible meet the planned budget, although stainless steel and homemade heat-resistant ceramics were used for the construction of the internal parts and parts of the boiler.

Perelesnik developed a diagram that clearly shows the principle of operation of his boiler.

To understand why the rocket furnace was chosen as the basis for the boiler, it is worth focusing on the theoretical part.

Rocket furnaces are well known. They are built by enthusiasts and DIYers all over the world. The simplicity of their design, the ability to do without the use of expensive materials, and the great variability of such furnaces captivate us. A rocket stove can be as small as a camp stove (they cook food on them), made from pieces of metal pipes and cans.

And also a large, heating one, with a massive heat accumulator and a built-in stove bench. This "rocket" fits perfectly into the design of a modern cottage.

According to Perelesnik, great help in the development of his boiler was provided by the book by American authors "Rocket Stoves". It clearly, and most importantly - simply and intelligibly - explains the basic principles of independent construction of rocket furnaces. The main dimensions and proportions of the "heart" of the rocket cauldron, the so-called "heart", were also borrowed from this book. "J-pipes".

Perelesnik

Excellent combustion conditions are created in the "rocket". Fuel and furnace gases are burned out completely. The resulting heat is not "taken away" until all reactions have been completed, and only then is it used.

The advantages and benefits of the "rocket" are derived from the features of its design. At the rocket furnace, at the expense long vertical and an additionally insulated channel, the length of the path that the furnace gases pass through increases.

The gases, during their passage through the elongated channel, mix with the already heated air and acquire a temperature that best promotes all combustion processes. Carbon is also burned, which, if underburned, is deposited in the form of soot.

The high efficiency of the "rocket" is ensured due to the fact that wood is burned, which is released during the thermal decomposition of solid fuel (so-called pyrolysis).

Due to the large temperature difference that occurs at the inlet and outlet of the vertical pipe channel, a powerful natural draft arises. Accordingly, there will be no need to build a high chimney, which provides draft in conventional stoves.

It should be noted that the gases entering the flue gas duct are at a high temperature. To prevent the energy generated by the stove from being thrown into the chimney, some of this heat must be taken away. To do this, a bed is attached to the rocket furnace, where flue gases are launched through horizontally laid brick channels. It turns out a heat accumulator. The second option - the oven is complemented by a jacket. From here it is already a stone's throw to a solid fuel boiler.

Pushing off from this base, Perelesnik decided - it is necessary to make a boiler operating on the principle of the operation of a rocket furnace.