A rocket or jet stove is a heating and cooking device that uses wood products as fuel. The popularity of such equipment is due to several factors. One of the most important - ease of manufacture and small investments. In addition, the rocket furnace is in demand due to its optimal technical characteristics, but we will talk about this a little later.
Some interesting features
The jet furnace appeared a long time ago. During this time, a huge number of myths have developed about such equipment. The most interesting thing is that the rocket furnace uses the same principle of operation as in the jet engine of the MIG-25 aircraft. Someone even said that such heating equipment works on reverse reactive thrust, but this is not so.
All these myths and fictions are associated more with the name than with the principle of the device. But rocket-type furnaces were so named only because when they were improperly burned, they make a whistling sound, similar to the one made by a rocket during flight. If the stove was folded correctly, then it will work quietly, with a slight rustle. It can be done, though quickly, but not always as simple as we would like. That is why before proceeding with the assembly, it is necessary to learn in more detail the principle of operation, characteristics, consider a couple of diagrams and drawings.
Long burning rocket furnace
The main requirement put forward to jet furnaces, and to any other devices of long burning, is high heat transfer. Moreover, it is desirable that it was possible to load fuel without stopping the combustion process. If such heating equipment will burn for 6-7 hours without "refueling", then it can safely be called suitable.
In general, any long-burning rocket furnace is based on the afterburning of pyrolysis gases. As you know, pyrolysis is the process of decomposition of solid fuel into volatile gases, which occurs under conditions of insufficient oxygen in the furnace, which slows down the combustion process and makes the fuel smolder. All this allows a relatively small amount of wood fuel to heat the room for a rather long time.
Operating principle
Almost all furnaces of this type have a vertical load. The fuel that gets into the furnace burns down, and gradually settles to the bottom. The main part of the oxygen enters through the blower, due to which an excess of air is achieved, which should be enough for afterburning. But its quantity is recommended to be limited, since cold streams can cool the heated mixture.
If the load is vertical, then the main regulator is a flame that displaces air. Usually, to maintain the pyrolysis process, that is, to keep the temperature at the proper level, there is a flame tube. The longer it is, the better the traction. But along the entire length of the pipe we have a significant temperature difference.
Quite an important point is the heat transfer after the furnace. For more efficient heat generation, a small amount (within 5-10%) is removed to the outside. So the room heats up faster, and it becomes possible to reduce the heat loss of the riser (battery). Almost all rocket stoves with their own hands are made in such a way that the riser is covered with a thin layer of metal, which will retain heat. We continue to consider the device.
DIY rocket stove: drawings
In order for heating equipment to work as efficiently as possible, it is necessary to be guided by drawings during assembly. You can find them in this article and use them during assembly.
Let's talk about how to create a mini rocket furnace. It is needed for heating and cooking in the warm season. Heats up to 400 degrees Celsius. In this case, the furnace must be portable. The furnace can be made open. The main structural difference from the classic jet furnace is that the furnace is made with a combined blower. As a result, the volume of incoming secondary air is reduced, therefore, oxygen cannot cool the pyrolysis gas.
The made hole in the hopper lid allows you to adjust the temperature, although not very accurately, but it’s enough for cooking. Now let's take a closer look at the build process.
First stage of assembly
To begin with, we need a regular bend in good condition. Its sizes may vary. It all depends on how big the oven you want to get. Two pipes (usually with a diameter of 150 mm) are welded at an angle of no more than 90 degrees. As a result, we get a firebox with a pipe. It must be remembered that the short section of the pipe must be horizontal, and the long - vertical. Accordingly, the flame from the horizontal pipe will be drawn into the vertical channel.
The most primitive way of organizing the supply of secondary air from the point of view of complexity is that a sheet of metal is attached to the brackets in the furnace. It turns out that the hearth will be separated from the chimney. Passing air will move to the corner of the knee, which is what was required to be achieved. Please note that a do-it-yourself rocket stove (drawings, see this article) manufactured must have legs. It is desirable to weld them. A grill can be placed on the vertical part of the pipe to cook.
Second stage: manufacturing a rocket stove
As a basis, we take the design obtained a little earlier. It is necessary to add an additional element to it, as a result of which we get a kind of potbelly stove. We need to make a horizontal channel. A rectangular section of the channel is more preferable, as it allows to improve the operational properties of the unit. As for the duct, it can be made horizontal. The most important thing is that air flows through it. The most appropriate solution is to install a plate with ribs on the bottom wall.
As for the chimney, it is connected to the knee. The material used is a steel pipe of suitable diameter. Often such an oven is assembled from what is at hand. But the most important requirement is to organize a high-quality firebox and exhaust. In this case, it is undesirable to use too thin metal, on which the corrosion process will be noticeable.
Vertical heat exchanger furnace
The idea itself is quite simple to implement. It consists in the fact that a thick-walled steel heat exchanger is mounted on the path of the passage of hot flows. In this case, the construction described above is used, and an additional element is added to it. But here it is advisable to slightly increase the size of the furnace and change the vertical pipe to a container for dry heat transfer. It could be an empty gas bottle that fits perfectly. True, it is necessary to perform the chimney channel coaxially with the horizontal pipe (furnace).
The furnace can be made in various designs. The most popular are the pipe, duct and furnace body. If the firebox has not too small dimensions, it can act as a primary heat exchanger. Therefore, if you want to achieve continuous burning, say, one that has an Apostle rocket furnace, then the fuel compartment must be expanded. Usually it is made high, about 50-60 cm. Therefore, vertically loaded logs light up from below and completely burn out under their own weight.
Injector mounting
At the stage of afterburning of fuel for a better process, establish a separate channel for oxygen supply. For these purposes, it is desirable to use a steel pipe having a diameter of not more than 18 mm, and curved. One end of the pipe must be plugged, drilled in it about five to six holes of small diameter. This side goes through the whole system. In this case, the end with drilled holes should reach the flame. The free side is diverted into the environment, where there will be access to air. Heating the metal leads to traction in the tube, and oxygen enters for afterburning. In principle, a Gabriel Apostle rocket furnace of this type is very efficient and has a high heat dissipation.
Useful addition
If you have a desire, then at the final stage you can organize a turbocharger. For this, an air pump must be connected to the injector. An old vacuum cleaner or a powerful compressor is suitable. In this case, pay attention to the fact that the injector has a good throughput.
The system operates as follows. After turning on the pump, excess pressure is created in it. In proportion to the increase in power, the thrust increases. Gradually the temperature of the heat exchanger will increase. This is similar to the blacksmith furs that have been used since ancient times. Such a rocket furnace on sawdust, wood and other low-grade fuel will work very efficiently. Investments are practically not required, since it is possible to assemble equipment from improvised tools and materials.