Do-it-yourself metal rocket furnace. What is a rocket furnace: design options, diagrams and principle of operation. Device from a pipe with a water circuit, diagram

This unusual type of heating system is not familiar to ordinary developers. Many professional stove-makers have never come across such designs either. This is not surprising, since the idea of ​​a rocket furnace came to us relatively recently from America, and today enthusiasts are trying to convey it to the mass consciousness of citizens.

Due to the simplicity and low cost of construction, thermal comfort and high efficiency, rocket furnaces deserve a separate article, which we decided to devote to them.

How does a rocket oven work?

Despite the loud space name, this heating structure has nothing to do with rocket systems. The only external effect that gives some similarity is a jet of flame that bursts out of a vertical pipe near the travel version of the rocket stove.

The work of this hearth is based on two basic principles:

1. Direct combustion - the free flow of fuel gases through the furnace channels without being impelled by the draft created by the chimney.
2. Afterburning of flue gases emitted during wood burning (pyrolysis).

The simplest jet furnace works on the principle of direct combustion. Its design does not allow achieving thermal decomposition of wood (pyrolysis). To do this, it is necessary to perform a powerful heat-accumulating coating of the outer casing and high-quality thermal insulation of the inner pipe.

Regardless, portable rocket ovens perform well. They do not require a lot of power. The generated heat is sufficient for cooking and heating in the tent.

Rocket furnace designs

You should start acquaintance with any design with its simplest options. Therefore, we give a diagram of the operation of a mobile rocket stove (Fig. 1). It clearly shows that the firebox and combustion chamber are combined in one piece of steel pipe, bent upwards.

For laying firewood, a plate is welded in the lower part of the pipe, under which there is an air hole. Ash, which plays the role of a heat insulator, helps to enhance heat transfer in the cooking area. It is poured into the lower part of the outer casing.

The secondary chamber (casing) can be made from a metal barrel, bucket or old gas cylinder.

In addition to metal, the simplest rocket furnace can be built from several dozen bricks even without using mortar. A firebox and a vertical chamber are laid out of them. The dishes are placed on its walls so that there is a gap under the bottom for the exit of flue gases (Fig. 2).

A prerequisite for the good work of such a design is a "warm pipe", as the stove-makers say. In practice, this means that before laying firewood, the rocket stove must be warmed up for a few minutes, burning wood chips and paper in it. After the pipe is warmed up, the wood is put into the firebox and set on fire, a powerful ascending stream of hot gases arises in the stove channel.

Fuel filling in simple designs of rocket furnaces is horizontal. This is not very convenient, since it forces you to periodically push the wood into the firebox as it burns out. Therefore, in stationary systems, vertical filling is used, and air is supplied from below through a special blower (Fig. 3).

Burning out, the firewood is lowered into the oven by itself, saving the owner from manual feeding.

Basic dimensions

A visual representation of the configuration of a stationary long-burning rocket furnace is given by drawing No. 1.

Anyone who wants to build a stationary rocket furnace, without being distracted by simplified modifications, should know its basic dimensions. All dimensions of this design are tied to the diameter (D) of the bell (drum) covering the vertical part of the flame tube (riser). The second dimension required for calculations is the cross-sectional area (S) of the hood.

Based on the two indicated values, the remaining dimensions of the furnace structure are calculated:

1. The height of the hood H is between 1.5 and 2D.
2. The height of its clay coating is 2 / 3H.
3. The thickness of the coating is 1 / 3D.
4. The cross-sectional area of ​​the flame tube is 5-6% of the area of ​​the bell (S).
5. The size of the gap between the bell lid and the upper edge of the flame tube should not be less than 7 cm.
6. The length of the horizontal section of the flame tube must be equal to the height of the vertical one. Their cross-sectional areas are the same.
7. The area of ​​the blower must be 50% of the cross-sectional area of ​​the flame tube. To ensure a stable operating mode of the furnace, experts recommend making a flame channel from a rectangular metal pipe with an aspect ratio of 1: 2. She is laid flat.
8. The volume of the ash pan at the exit from the furnace into the external horizontal smoke channel must be at least 5% of the volume of the bell (drum).
9. The external flue must have a cross-sectional area of ​​1.5 to 2S.
10. The thickness of the adobe insulating cushion, which is made under the external chimney, is chosen in the range from 50 to 70 mm.
11. The thickness of the adobe coating of the bed is chosen equal to 0.25D (for a drum with a diameter of 600 mm) and 0.5D for a hood with a diameter of 300 mm.
12. The external chimney must be at least 4 meters high.
13. The length of the flue in the bed depends on the diameter of the hood. If it is made from a 200-liter barrel (diameter 60 cm), then you can make a stove bench up to 6 meters long. If the cap is made of a gas cylinder (diameter 30 cm), then the bed should not be longer than 4 meters.

When building a stationary rocket furnace, special attention should be paid to the quality of the lining of the vertical section of the flame tube (riser). To do this, you can use refractory bricks of the SHL brand (light chamotte) or washed river sand. To protect the lining from flue gases, it is made in a metal shell, using old buckets or galvanized sheet for this.

Sand filling is carried out in layers. Each layer is compacted and lightly sprayed with water. Having made 5-6 layers, they are given a week to dry. It is easier to make thermal protection from chamotte, but the space between the outer shell and the brick will also have to be covered with sand so that there are no empty cavities (Fig. 4).

Figure No. 4 of the scheme of the lining of the flame channels of rocket furnaces

After the backfill has dried, the upper edge of the lining is coated with clay and only after that the installation of the rocket-rocket furnace is continued.

Advantages and Disadvantages of Rocket Furnaces

An important advantage of a correctly constructed structure is omnivorousness. Such a stove can be fired with any type of solid fuel and wood waste. Moreover, the moisture content of the wood does not play a special role here. If someone claims that such a stove can only work on well-dried wood, then this means that gross mistakes were made during its construction.

The heat output of a rocket furnace, which is based on a drum from a barrel, is quite impressive and reaches 18 kW. A gas cylinder stove is capable of developing a thermal power of up to 10 kW. This is quite enough for heating a room with an area of ​​16-20 m2. Note also that the power of the rocket furnaces is controlled only by changing the volume of the loaded fuel. It is impossible to change the heat transfer by supplying air. The blower adjustment is used only to bring the furnace into operation.

Since the amount of heat generated by the rocket stove is very large, it is not a sin to use it for such household needs as heating food (on the drum lid). But it is impossible to use such a hearth to heat the water used in the radiator heating system. Any introduction of coils and registers into the furnace design negatively affects its operation, worsening or stopping the pyrolysis process.

Helpful Hint: Before you start building a stationary jet furnace, make a simplified camp structure out of metal or clay. This will help you practice the basic assembly techniques and gain a rewarding experience.

The disadvantages of rocket furnaces include the impossibility of their use in baths and garages. They are designed for energy storage and long-term heating. Therefore, it cannot provide much heat in a short period of time, as is necessary in a steam room. For garages that store fuels and lubricants, an open flame oven is also not the best option.

Do-it-yourself rocket oven assembly

The easiest way is to assemble a camping-garden version of a reactive furnace. To do this, you do not have to purchase masonry materials and prepare adobe for coating.

Several metal buckets, a stainless steel pipe for the flue duct and fine gravel for filling - that's all you need in order to make a rocket furnace with your own hands.

First step- cutting with metal scissors a hole in the lower bucket for the passage of the flame tube. It must be done at such a height that there is room under the pipe for crushed stone filling.

Second step- installation in the lower bucket of a flame tube, consisting of two elbows: a short boot and a long one for the outlet of gases.

Third step- cutting a hole in the bottom of the upper bucket, which is put on the lower one. The head of the frying pipe is inserted into it so that its cut is 3-4 cm above the bottom.

Fourth- backfilling of fine gravel into the lower bucket at half its height. It is needed for heat accumulation and thermal insulation of the fire channel.

Last step- manufacture of dish stands. It can be welded from round fittings with a diameter of 8-10 mm.

A more complex, but at the same time durable, powerful and aesthetic version of the rocket stove requires the use of a gas cylinder and a thick steel rectangular pipe.

This does not change the assembly scheme. The exhaust of gases is organized here at the side, and not at the top. To prepare food, the upper part with a valve is cut off from the cylinder and a flat round plate 4-5 mm thick is welded in its place.

A rocket stove is a type of wood-fired cooking stove. Stationary models of stoves are also used for heating.

It got its name from the hum that is heard at the beginning of the fire. With the correct combustion mode, it dies down. The shape of the structure also resembles a rocket - vertical cylinder... The oven is also called reactive.

A similar principle was used in Korea and China for heating homes in winter. Travelers in the old days noted that much less firewood was spent than in a traditional Russian village.

Reactive furnaces, product drawings

Rocket stoves are subdivided into portable and stationary... The first devices are smaller and simpler in design. She reminds inverted letter "G"... Fuel is placed in the lower bar. Thanks to the vertical shape of the main body, natural draft occurs.

Photo 1. A drawing and a finished version of a metal rocket furnace with an indication of the dimensions, left and top view.

As the temperature rises, the device works more efficiently. It has enough power to quickly heat water for cooking for several people. To prevent the wood from burning out too quickly, you need to regulate the draft in the stove. To do this, cover or close completely the fuel door.

Portable jet furnaces serially produced... Most popular models "Robinson" and "Ognivo"... Due to the simplicity of the design, you can make them yourself.

Stationary devices are somewhat more complicated. In the hood, the air ducts are made in such a way that the heated air rises upwards first. Transferring heat to the inner walls, it gradually goes down. Then it goes into the chimney located at the bottom.

Photo 2. Drawing of a rocket furnace made of bricks and a metal barrel. Arrows indicate parts of the device.

Such an oven is quite economical to use, since it burns not only firewood, but also pyrolysis gases. The flue duct of the furnace is sometimes not taken out of the room immediately, but is carried out inside a bed made of brick and / or clay. This bed heats the room to a comfortable temperature. The design itself is made from large diameter pipes, barrels or bricks.

Important! The device needs in preheating before the firebox... First, they light paper, newspaper, or something else that quickly ignites. And only in the warmed-up firebox firewood is stacked.

Long burning brick rocket stove

Since bricks accumulate heat, such devices are well suited for heating rooms. Taking into account the duration of burning, one tab of fuel is enough to maintain a comfortable temperature for 6-8 hours.

Sometimes the stove is made entirely of brick. Only fittings (doors) need steel or cast iron. In other cases, the outer part of the furnace hood is made from a barrel or wide tube.

Attention! Brick oven requires a separate foundation not related to the one being built for the building itself. It is advisable to plan its location before starting construction.

Device from a pipe with a water circuit, diagram

The furnace structure is welded from iron pipes of different diameters.

If it is supposed to heat a small room, the stove cover can be made from waste gas bottle.

In a house of a more impressive size, for these purposes, it is suitable iron barrel.

If you install a water circuit on the chimney of the stove, you can get a long-burning boiler that will heat the room well.

The water circuit is usually made from gas cylinders.

"Robinson"

This is a simple and reliable camping stove. She is capable of quite quickly (in 10 minutes) boil a liter water. In this case, you do not need to add firewood.

The design was developed in the last century, but due to its advantages it is still used today. "Robinson" is mass-produced, but it is easy to assemble it yourself.

You may also be interested in:

"Flint"

This oven is similar to the previous version. But the combustion chamber in it shorter and more obtuse in relation to the chimney. Such a stove resembles an inverted letter "G" in shape.

How to make a rocket stove with your own hands

He has several stages- selection of a suitable design; selection of materials and tools; directly manufacturing.

Project selection

When choosing a suitable project, consider the following factors:

1. The purpose of the oven is whether it only requires cooking or also heating the room.
2. Available materials.
3. Approximate wattage. It depends on it how many servings of food or how much room the device will be enough for.

Materials (edit)

For a brick structure you will need:

• fireclay (refractory) brick;
• refractory mortar for masonry;
• concrete mortar (for the base);
• mineral wool;
• asbestos;
• a whole barrel or an empty gas cylinder for the cap (optional);
• oven doors - combustion chamber and ash pan;
• if the hood is brick - thick stainless steel sheet according to the size of its section.

For finishing the furnace are used:

• refractory paint;
• clay;
• stones;
• etc.

For metal, take:

1. Round metal pipe diameter about 150 mm and length no more than 90 mm(it is better about 60 mm).
2. Profiled (rectangular) pipe with a cross section 100-120 mm and length about a third round.
3. Instead of a rectangular pipe, you can take a sheet of steel with a thickness 3 mm.
4. 3 nuts.
5. Steel rods, plates or long leg bolts.

Reference. For better traction, take the profiled pipe with the side no more than the diameter of the round.

Instrument preparation

Useful for manufacturing:

• Master OK;
• level;
• welding machine;
• bayonet shovel;
• metal brush;
• level;
• Bulgarian.

Manufacturing, dimensions of devices

There are many variations on this theme. Consider making two fundamentally different types of jet stove. This is a brick stove with a stove bench, which is used indoors, and a camp stove, assembled from metal. Changes are made if necessary, combinations of methods are possible (for example, a heating and cooking device, but made of pipes covered with clay or stones).

How to make a brick stove with a stove bench

First stage- foundation device. A rectangular depression is dug under it, which is then filled with concrete.

For strength, it is better to pre-install the reinforcement. The base must be strictly horizontal.

After the concrete solution has hardened brick laying begins... The outer walls are located around the perimeter of the concrete site. A combustion chamber is formed. On one side of it there is a combustion chamber with an opening for loading firewood. On the other hand, there are air ducts.

Important! Each row of bricks is also level tested. This is done in both planes - horizontal and vertical.

The combustion chamber also leave a hole for ash cleaning, which is closed by a door. When this camera is ready, a metal barrel is put on it. The gaps are filled with insulation, for example, mineral wool.

If the barrel is not used, it is installed on top cooking stove... An asbestos insulation is placed under it.

The chimney is connected to the air duct and out into the street.

Then finished the device is decorated. For example, it is coated with clay and covered with paint. Another option is to leave the brickwork.

Reactive Hiking Stove

It consists of two compartments connected to each other. To assemble it, first cut the pipes at an angle of 45 °... If instead of the second pipe you took a metal sheet, cut it into the following parts:

• two with sides 300 mm vs 150 mm;
• two - 300 mm vs 100 mm;
• and one 150 and 100 mm.

Photo 3. Ready-made jet stove for hiking. The device is made of metal pipes.

Then weld them together. You will also need one more plate for dividing the fuel compartment, its dimensions 200 mm and 100 mm.

All fragments are welded together according to the diagram. The round pipe is fixed at the bottom of the rectangular and in the middle with respect to the lateral sides.

From rebar scraps are welded grate... It is convenient to make it retractable in order to lay firewood and then push it inside the firebox.

Saw off from the pipe 4 rings. They are attached from the top so that the dishes do not block the draft hole.

Collapsible legs are installed... Nuts are welded from below, into which long bolts are then screwed. There is another way. The rods or cuttings of the steel sheet are welded to the bottom. It is less convenient to transport, but there is no need for assembly.

When the structure is ready, it needs to be painted... Only refractory paint is used. This will protect against corrosion and also cover the traces of soldering.

Possible difficulties

When laying bricks, it is not easy to accurately calculate the size of the holes for the furnace and ash doors. So you can lay out a row with a door without mortar, "Dry", and figure out how best to arrange it. And then lay out the bricks, fastening with mortar.

When making a furnace from pipes, it is difficult to calculate the place of their connection. Therefore, at first, a round fragment is sawed off and attached to a rectangular one in the right place. Around a line is drawn with a marker, along which the cut is made. If the fuel part is collected from separate plates, it will be more convenient to cut a hole before welding them between themselves.

Useful video

Watch a video that demonstrates the process of kindling a camping rocket stove, tells about the characteristics of the device.

Pros of using a rocket oven

Reactive furnaces quite economical to use. But for ultra-efficient operation, it is important that the fuel is dry, otherwise secondary combustion of gases will not occur.

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Rocket oven not suitable for installation in a bath. The fact is that for the desired effect, it is required that the walls of the room first heat up. And with the mode created by this furnace, it is the air that heats up.

As a heating device in a house for permanent residence, such a device is not always convenient.

Simple oven options for heating a room, heating food and water are always popular, especially among home craftsmen who seek to make such units on their own. Such structures include a rocket stove, which runs on wood, and perfectly copes with the tasks assigned to it, while it does not require complex materials for manufacturing. Today we will dwell in more detail on the design of such an interesting heater, as well as provide drawings and videos in order to make a rocket furnace with our own hands.

Principle of operation

Before proceeding with the manufacture of the unit, you should consider in detail the principle of its operation. I would like to clarify right away that a rocket stove for a home has nothing to do with a jet engine and space flights. A similar name was given to the stove by the people due to its unusual appearance: the unit is very similar to an inverted rocket and emits a characteristic buzz during operation.

The buzzing appears in the stove only in a certain operating mode, when too much oxygen is supplied to the firebox. Please note that if your oven hums too loudly or makes an unusual roar, this indicates improper, uneconomical and ineffective operation. The correct operation of the rocket furnace is accompanied by a barely audible rustle.

A portable rocket oven is very often taken with you on a hike to warm up food

Heating units of this type, depending on the scope of application, can be divided into:

• Portable;
• Stationary.

The former are mainly used in field conditions, they are mobile, easy to transport and do not take up much free space. The second type of construction is more capital. It is used for indoor installations, for heating a room or for heating food.

The principle of operation of a rocket furnace is easiest to show on the example of the simplest tourist firebox "Robinson". The design is an inverted tube in the shape of the letter "L".

Solid fuel (wood, wood chips) is loaded into that part of the pipe, which is in a horizontal position relative to the surface of the earth, then the fuel is ignited from the side of the vertical part of the pipe.

In the transition channel, a thrust is created, which increases as the fuel warms up, and therefore, for effective operation, it is necessary to shut off the air supply from the outside. If the air supply is not limited, the wood will burn out and no heat energy will be produced in the end.

Even the simplest rocket furnace is capable of heating water in a large container in a matter of minutes. If the upper part of the pipe is properly insulated, the device can burn thick logs and heat a large room.

Types of rocket furnaces

Depending on the type of construction, rocket furnaces are divided into:

• Rocket furnace with a water circuit (with proper arrangement, it can replace a full-fledged solid fuel boiler);
• Rocket furnace from a gas cylinder;
• Rocket furnace "Ognivo - Boss";
• A simple brick rocket stove with a stove bench;
• Hiking options from metal pipes.

General view of a rocket furnace made from a gas cylinder

Advantages and disadvantages

The advantages of a rocket-type furnace include:

• High heat transfer rate, which in some cases reaches 18 kW;
• High efficiency;
• Super-efficient work, which is characterized by the complete burnout of firewood, coal and soot loaded inside;
• To ensure combustion, even waste from the woodworking industry (chips, leaves, twigs, twigs, leaves, regardless of the degree of moisture) are suitable;
• Economical combustion and low wood consumption;
• High temperature conditions at the outlet (heating of a large container with water is carried out in a few minutes).

Along with the advantages, the following disadvantages are distinguished in furnaces of this type:

• Installing a water heating coil reduces the thermal efficiency of the furnace;
• The continuous combustion cycle makes it impossible to install a rocket stove in garages and saunas;
• The small size of the firebox does not allow a large amount of fuel to be loaded at once; to ensure long-term burning, a constant lining of firewood is made.

How to make a rocket oven with your own hands

Many people decide to install a rocket furnace due to the possibility of making it from improvised means. Such a stove does not require expensive materials and components, while it stands out among other wood-burning stoves with an original design.

To make a stove, it is enough to understand at least a little in the drawings and be able to work with your hands. Especially for home craftsmen, we will consider several options for making a rocket stove.

Camping from a profile pipe

This design stands out for its maximum simplicity, therefore, it is from it that you can begin work on mastering the technology of building rocket furnaces. With the right approach, the entire production process will take no more than 3-4 hours.

The manufactured stove will have small overall dimensions and weight, which is why it is convenient to take it with you on hikes and fishing.

We will consider a slightly complicated version of the rocket furnace; due to the additional detail, the process of further use of the unit will be greatly facilitated. It is a small metal plate with a grate that can be removed for easy loading of firewood.

To make a stove, you need to prepare the following elements:

• Two pieces of a square pipe measuring 15 by 15 cm (metal thickness - 3 mm). The length of one pipe is 45 cm, the other is 30 cm;
• 4 strips of steel with a thickness of 3 mm and dimensions of 30 by 5 cm;
• 2 steel strips 3 mm thick and measuring 14 x 5 cm.
• A metal lattice with dimensions of 30 x 14 cm. If a lattice of suitable dimensions could not be purchased, you can make it yourself from steel bars.

Camping rocket furnace is made in the form of a bent pipe segment

Furnace production includes the following steps:

1. We mark two pipes for further cutting with a grinder at an angle of 45 degrees;
2. We connect the pipes to each other with the cut sides and weld;
3. At the top of the vertical pipe we make 4 cuts at the corners, insert prepared steel strips into them to form a cross, weld the structure;
4. We make a frame for a sliding lattice from the remaining steel strips, put a lattice on the frame and weld it on;
5. We check the oven for performance;
6. When the unit has completely cooled down, paint it with heat-resistant paint to give it an attractive appearance.

The design can be slightly improved by welding a handle to the sliding grid.

Some craftsmen make a rocket oven right in the field from two soda cans. Such an oven provides the minimum amount of heat, but it will be enough to heat up a dinner or a glass of water.

From a gas cylinder

To make a rocket furnace from a gas cylinder, the diagram of which is shown in the figure, you will need:

• 80 cm steel pipe with a diameter of 158 mm and a metal thickness of 4 mm;
• 150 cm steel pipe with a diameter of 127 mm and a wall thickness of 3.4 mm;
• Profile pipe 100 cm long, 12 by 12 cm in size and 4 mm thick;
• 2 empty gas cylinders;
• Sheet metal;
• Steel bars;
• Thermal insulation material;
• Metal pipe with a diameter of 12 cm for the chimney.

Diagram of a gas cylinder furnace with dimensions

The production process includes the following stages:

1. We cut the profile pipe into two parts. One should have a length of 30 cm, the second - 35 cm. In the second pipe we cut a hole for the firebox and under the vertical pipe of the future stove;
2. We cut the remaining piece of the profile pipe lengthwise, weld it to the firebox (it will serve as a hole for air supply);
3. We weld the firebox to the vertical pipe;
4. We make doors for the firebox and ash pan;
5. We check the performance of the manufactured structure (primary chamber), wait for it to cool;
6. With the help of a grinder, we cut out a hole for the firebox in the lower gas cylinder. We weld a pipe with a diameter of 120 mm, which will act as a chimney, in the lower part of the pipe we make a hole for cleaning the chimney;
7. We weld a piece of pipe of a slightly larger diameter to the chimney, we weld the firebox to the cylinder;
8. Pour perlite into the space formed in the cylinder between the pipe and the surface of the cylinder, which acts as a thermal insulator;
9. At the second cylinder we cut off the bottom with a grinder, weld a hole near the valve, the structure will act as a container for igniting gases;
10. We connect all parts of the stove together.

A more detailed process for making a rocket furnace from a gas cylinder is discussed in the video.

Video: rocket furnace from a gas cylinder

Of bricks

The diagram of the simplest rocket furnace is shown in the figure.

The simplest design assumes the presence of 21 bricks

To build an improved structure, you will need about 20-30 bricks and dry clay.

We fold the structure out of bricks, as in the picture. In appearance, it resembles a rocket that is preparing for launch.

Clay is used to give the structure strength and stability

We check the oven for operability, wait until the bricks cool down, and coat them with prepared clay. The manufacturing process is complete. Once the clay is completely dry, the oven can be used.

Video: rocket oven from twenty bricks

Long burning design

The best option for a long-burning stove is a stove with a stove bench. This design is perfect for heating a small room.

A long-burning rocket stove is an excellent option for heating a home.

The manufacturing process includes the following steps:

1. The place where the firebox will subsequently be located is deepened into the ground by 10 cm, a refractory stone is placed in the formed depression;
2. A formwork is installed along the perimeter of the masonry, a reinforcing mesh is laid on the bottom;
3. The lower part of the future working chamber is laid on the same level with the installed formwork, the structure is poured with concrete;
4. The constructed part is left for a day until the concrete has completely solidified, then the base of the furnace and the combustion chamber are formed;
5. The walls of the future furnace gradually rise along the perimeter;
6. The lower channel of the rocket furnace is laid;
7. The constructed structure is sheathed with bricks, except for the places where the firebox and raiser will be located;
8. A metal container (an iron barrel or a gas cylinder is suitable) is cut off with a grinder on both sides, covered with a primer and painted with heat-resistant paint, a pipe is cut into the lower part;
9. A branch is welded to the chimney pipe, which will play the role of an ash pan;
10. A fire tube is laid out of bricks in the form of a square;
11. Heat-insulating material is poured into the formed gap between the metal container and the masonry;
12. The body of the future furnace is being formed, all brick surfaces are cleaned with clay, the future contour of the stove-bench is laid;
13. The operability of the furnace is checked;
14. All gaps are compacted, the shape of the bed is formed, adobe is covered on top.

How to properly heat the stove

If no special preparation is required for the firebox of mobile rocket furnaces, then in order for the long-burning furnace to work at the limit of its capabilities, it is imperative to preheat. Such an event also helps to reduce the degree of pollution of the chimney.

It is most convenient to warm up the oven with paper sheets, wood chips and sawdust. The degree of warming up is assessed by the hum that occurs in the channel. Initially, the hum will be strong, this indicates a high draft and low temperature, according to the degree of noise reduction, we can talk about an increase in the temperature in the furnace.

It is best to use small chips and sawdust to warm up the rocket furnace.

As soon as the noise starts to decrease, the main fuel is loaded into the furnace. After 15 minutes, the damper begins to gradually close. The gap must be adjusted so that a barely audible rustle is heard from the oven.

There are plenty of successful designs for rocket furnaces on the web, and the authors are often guided more by intuition than technical calculations. The main thing is to adhere to the "L-shaped" type of construction, and then everything depends only on your imagination.

Be sure to check the operation of the oven at the preliminary stage.

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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, as in 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 a 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 the utter speculation is 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 carefully, 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 screens of the world: the Soviet fantastic parody of the whole 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 gullible to the source code: how is it that a skilled 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 wood log. 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 flame 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 self-regulating to some extent; 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:

1. Drum height H - 1.5-2D.
2. 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.
3. Drum coating thickness - 1 / 3D.
4. The cross-sectional area of ​​the riser is 4.5-6.5% of S; it is better to keep within 5-6% of S.
5. 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.
6. The length of the flame tube is equal to the height of the riser.
7. 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.
8. 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.
9. 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.
10. The cross-sectional area of ​​the external chimney is 1.5-2s, where s is the cross-sectional area of ​​the riser.
11. 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.
12. 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.
13. The height of the outer chimney is from 4 m.
14. 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 marked 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 design 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:

1. For the manufacture of a mixture of the main heat-insulating layer (5b), crushed stone from chamotte brand ShL is used.
2. 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.
3. For cladding, mineral cardboard, tongue-and-groove boards are used.
4. Wooden blanks are pre-treated with impregnation with biocidal additives.
5. The area under the main part of the structure is covered with a metal sheet.
6. After placing the structure at the planned place, formwork is installed, adobe is poured.
7. A drum is made of a gas cylinder of a suitable size.
8. To create reliable welded joints, electrodes with a diameter of 2 mm, direct current of 60-70A are used.
9. The sealing seal is created from an asbestos cord and fixed with heat-resistant glue.
10. A riser is assembled from the prepared steel blanks.
11. Install the bottom layer of insulation; plywood (20 mm) or boards are used for formwork.
12. 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.
13. Install the firebox, controlling the accuracy of the vertical position.
14. Part of the blower will protrude outward, therefore, at the final stage, the wall is leveled with adobe.
15. 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).
16. Install an ash pan made of steel sheet 0.8-1 mm thick.
17. The drum tube is mounted with the formation in the inner part of the wedge-shaped slope towards the outlet (mixture 5b).
18. A lining with layer-by-layer filling (5g) is created, the plug is made of clay.
19. The assembly is continued according to the scheme, the corrugation, drum and ash pan covers are installed.
20. 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.