At the end of January, there were reports of new advances in Russian science and technology. From official sources it became known that one of the domestic projects of a promising detonation-type jet engine has already passed the testing stage. This brings closer the moment of complete completion of all the required work, according to the results of which space or military missiles of Russian design will be able to obtain new power plants with increased characteristics. Moreover, the new principles of engine operation can find application not only in the field of missiles, but also in other areas.
In late January, Deputy Prime Minister Dmitry Rogozin told the domestic press about the latest successes of research organizations. Among other topics, he touched on the process of creating jet engines using new operating principles. A promising engine with detonation combustion has already been brought to testing. According to the Deputy Prime Minister, the application of new principles of operation of the power plant allows a significant increase in performance. In comparison with structures of traditional architecture, an increase in thrust of about 30% is observed.
Detonation rocket engine diagram
Modern rocket engines of different classes and types, operated in various fields, use the so-called. isobaric cycle or deflagration combustion. Their combustion chambers maintain a constant pressure at which the fuel burns slowly. An engine based on deflagration principles does not need particularly durable units, however, it is limited in maximum performance. Increasing the basic characteristics, starting from a certain level, turns out to be unreasonably difficult.
An alternative to an engine with an isobaric cycle in the context of improving performance is a system with the so-called. detonation combustion. In this case, the oxidation reaction of the fuel occurs behind the shock wave moving at a high speed through the combustion chamber. This places special demands on the engine design, but at the same time offers obvious advantages. In terms of fuel combustion efficiency, detonation combustion is 25% better than deflagration. It also differs from combustion with constant pressure by the increased power of heat release per unit surface area of the reaction front. In theory, it is possible to increase this parameter by three to four orders of magnitude. As a consequence, the speed of the reactive gases can be increased 20-25 times.
Thus, the detonation engine, with its increased efficiency, is able to develop more thrust with less fuel consumption. Its advantages over traditional designs are obvious, but until recently, progress in this area left much to be desired. The principles of a detonation jet engine were formulated back in 1940 by the Soviet physicist Ya. B. Zeldovich, but finished products of this kind have not yet reached exploitation. The main reasons for the lack of real success are the problems with creating a sufficiently strong structure, as well as the difficulty of launching and then maintaining the shock wave using existing fuels.
One of the latest domestic projects in the field of detonation rocket engines was launched in 2014 and is being developed at NPO Energomash named after Academician V. P. Glushko. According to the available data, the goal of the project with the code "Ifrit" was to study the basic principles of new technology with the subsequent creation of a liquid-propellant rocket engine using kerosene and gaseous oxygen. The new engine, named after the fire demons from Arabic folklore, was based on the principle of spin detonation combustion. Thus, in accordance with the main idea of the project, the shock wave must continuously move in a circle inside the combustion chamber.
The head developer of the new project was NPO Energomash, or rather a special laboratory created on its basis. In addition, several other research and design organizations were involved in the work. The program received support from the Advanced Research Foundation. By joint efforts, all participants of the Ifrit project were able to form an optimal look for a promising engine, as well as create a model combustion chamber with new operating principles.
To study the prospects of the entire direction and new ideas, a so-called. model detonation combustion chamber that meets the requirements of the project. Such an experienced engine with a reduced configuration was supposed to use liquid kerosene as fuel. Oxygen gas was suggested as an oxidizing agent. In August 2016, testing of a prototype camera began. It is important that for the first time in history, a project of this kind was brought to the stage of bench tests. Earlier, domestic and foreign detonation rocket engines were developed, but not tested.
During the tests of the model sample, very interesting results were obtained, showing the correctness of the approaches used. So, due to the use of the right materials and technologies, it turned out to bring the pressure inside the combustion chamber to 40 atmospheres. The thrust of the experimental product reached 2 tons.
Model chamber on a test bench
Certain results were obtained within the framework of the Ifrit project, but the domestic liquid-fueled detonation engine is still far from full-fledged practical application. Before the introduction of such equipment into new projects of technology, designers and scientists have to solve a number of the most serious problems. Only then will the rocket and space industry or the defense industry be able to start realizing the potential of the new technology in practice.
In mid-January, Rossiyskaya Gazeta published an interview with the chief designer of NPO Energomash, Pyotr Lyovochkin, on the current state of affairs and prospects for detonation engines. The representative of the developer company recalled the main provisions of the project, and also touched upon the topic of the successes achieved. In addition, he spoke about the possible areas of application of "Ifrit" and similar structures.
For example, detonation engines can be used in hypersonic aircraft. P. Lyovochkin recalled that the engines now proposed for use on such equipment use subsonic combustion. At the hypersonic speed of the flight apparatus, the air entering the engine must be decelerated to the sound mode. However, the braking energy must lead to additional thermal loads on the airframe. In detonation engines, the fuel burning rate reaches at least M = 2, 5. This makes it possible to increase the flight speed of the aircraft. Such a machine with a detonation type engine will be able to accelerate to speeds eight times the speed of sound.
However, the real prospects for detonation-type rocket engines are not yet very great. According to P. Lyovochkin, we "just opened the door to the area of detonation combustion." Scientists and designers will have to study many issues, and only after that it will be possible to create structures with practical potential. Because of this, the space industry will have to use traditional liquid-propellant engines for a long time, which, however, does not negate the possibility of their further improvement.
An interesting fact is that the detonation principle of combustion is used not only in the field of rocket engines. There is already a domestic project for an aviation system with a detonation-type combustion chamber operating on a pulse principle. A prototype of this kind was brought to the test, and in the future it can give a start to a new direction. New engines with knock combustion can find application in a wide variety of areas and partially replace traditional gas turbine or turbojet engines.
The domestic project of a detonation aircraft engine is being developed at the OKB im. A. M. Cradle. Information about this project was first presented at last year's international military-technical forum "Army-2017". At the stand of the company-developer there were materials on various engines, both serial and under development. Among the latter was a promising detonation sample.
The essence of the new proposal is to use a non-standard combustion chamber capable of pulsed detonation combustion of fuel in an air atmosphere. In this case, the frequency of "explosions" inside the engine must reach 15-20 kHz. In the future, it is possible to further increase this parameter, as a result of which the engine noise will go beyond the range perceived by the human ear. Such engine features may be of some interest.
First launch of the experimental product "Ifrit"
However, the main advantages of the new power plant are associated with improved performance. Bench tests of prototypes have shown that they exceed traditional gas turbine engines by about 30% in specific indicators. By the time of the first public demonstration of materials on the engine OKB im. A. M. The cradles were able to get quite high performance characteristics. An experienced engine of a new type was able to work for 10 minutes without interruption. The total operating time of this product at the stand at that time exceeded 100 hours.
Representatives of the developer indicated that already now it is possible to create a new detonation engine with a thrust of 2-2.5 tons, suitable for installation on light aircraft or unmanned aerial vehicles. In the design of such an engine, it is proposed to use the so-called. resonator devices responsible for the correct course of fuel combustion. An important advantage of the new project is the fundamental possibility of installing such devices anywhere in the airframe.
Experts of the OKB them. A. M. The cradles have been working on aircraft engines with impulse detonation combustion for more than three decades, but so far the project has not left the research stage and has no real prospects. The main reason is the lack of an order and the necessary funding. If the project receives the necessary support, then in the foreseeable future a sample engine can be created, suitable for use on various equipment.
To date, Russian scientists and designers have managed to show very remarkable results in the field of jet engines using new operating principles. There are several projects at once, suitable for use in the rocket-space and hypersonic areas. In addition, the new engines can be used in "traditional" aviation. Some projects are still in early stages and are not yet ready for inspections and other work, while in other areas the most remarkable results have already been obtained.
Investigating the topic of detonation combustion jet engines, Russian specialists were able to create a bench model model of a combustion chamber with the desired characteristics. The experimental product "Ifrit" has already passed tests, during which a large amount of various information was collected. With the help of the data obtained, the development of the direction will continue.
Mastering a new direction and translating ideas into a practically applicable form will take a lot of time, and for this reason, in the foreseeable future, space and army rockets in the foreseeable future will be equipped with only traditional liquid-propellant engines. Nevertheless, the work has already left the purely theoretical stage, and now each test launch of an experimental engine brings closer the moment of building full-fledged missiles with new power plants.
