Detonation engine tests
FPI_RUSSIA / Vimeo
The specialized laboratory "Detonation LRE" of the Energomash Research and Production Association tested the world's first full-size detonation liquid-propellant rocket engine technology demonstrators. According to TASS, the new power plants run on an oxygen-kerosene fuel pair.
The new engine, unlike other power plants operating on the principle internal combustion, operates due to the detonation of the fuel. Detonation is the supersonic combustion of a substance, in this case a fuel mixture. In this case, a shock wave propagates through the mixture, followed by a chemical reaction with the release of a large number heat.
The study of the principles of operation and the development of detonation engines has been carried out in some countries of the world for more than 70 years. The first such work began in Germany in the 1940s. True, the researchers failed to create a working prototype of a detonation engine at that time, but pulsating jet engines were developed and mass-produced. They were placed on V-1 rockets.
In pulsating jet engines, fuel burned at subsonic speeds. This combustion is called deflagration. The engine is called pulsating because fuel and oxidizer were fed into its combustion chamber in small portions at regular intervals.
Pressure map in the combustion chamber of a rotary detonation engine. A - detonation wave; B - trailing front of the shock wave; C - mixing zone of fresh and old combustion products; D - fuel mixture filling area; E is the region of the non-knocking burnt fuel mixture; F - expansion zone with detonated burnt fuel mixture
Detonation engines today are divided into two main types: impulse and rotary. The latter are also called spin. The principle of operation of impulse engines is similar to that of pulsating air jet engines. The main difference lies in the detonation combustion of the fuel mixture in the combustion chamber.
Rotary detonation engines use an annular combustion chamber in which fuel mixture is fed sequentially through radial valves. In such power plants, detonation does not fade - the detonation wave “runs around” the annular combustion chamber, the fuel mixture behind it has time to be updated. The rotary engine was first studied in the USSR in the 1950s.
Detonation engines are capable of operating in a wide range of flight speeds - from zero to five Mach numbers (0-6.2 thousand kilometers per hour). It is believed that such power plants can produce more power, consuming less fuel than conventional jet engines. At the same time, the design of detonation engines is relatively simple: they lack a compressor and many moving parts.
All detonation engines tested so far have been developed for experimental aircraft. Tested in Russia, such a power plant is the first to be installed on a rocket. What type of detonation engine was tested is not specified.
At the end of January, there were reports of new successes in Russian science and technology. It became known from official sources that one of the domestic projects of a promising detonation-type jet engine has already passed the testing stage. This brings the moment of complete completion of all the required work, as a result of which space or military rockets Russian development will be able to get new power plants with improved performance. Moreover, the new principles of engine operation can be applied not only in the field of rockets, but also in other areas.
In the last days of January, Deputy Prime Minister Dmitry Rogozin told the domestic press about the latest successes of research organizations. Among other topics, he touched upon the process of creating jet engines using new operating principles. A promising engine with detonation combustion has already been brought to the test. According to the Deputy Prime Minister, the application of new principles of work power plant allows you to get a significant increase in performance. In comparison with the designs of traditional architecture, there is an increase in thrust of about 30%.
Diagram of a detonation rocket engine
Modern rocket engines different classes and types operated in various areas use the so-called. isobaric cycle or deflagration combustion. In their combustion chambers, a constant pressure is maintained, at which the fuel burns slowly. An engine based on deflagration principles does not need particularly strong units, but is limited in maximum performance. Increasing the main characteristics, starting from a certain level, turns out to be unreasonably difficult.
An alternative to an isobaric cycle engine in the context of performance enhancement is a system with a so-called. detonation combustion. In this case, the fuel oxidation reaction occurs behind the shock wave moving at high speed through the combustion chamber. This places special demands on the design of the engine, but at the same time offers obvious advantages. In terms of fuel combustion efficiency, detonation combustion is 25% better than deflagration combustion. It also differs from combustion with constant pressure by an increased heat release rate per unit surface area of the reaction front. In theory, it is possible to increase this parameter by three to four orders of magnitude. Consequently, the speed of reactive gases can be increased by 20-25 times.
Thus, the detonation engine, characterized by an increased coefficient useful action, capable of developing 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 as early as 1940 by the Soviet physicist Ya.B. Zeldovich, but finished products of this kind have not yet reached operation. The main reasons for the lack of real success are problems with creating a sufficiently strong structure, as well as the difficulty of launching and subsequently maintaining a 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 V.I. Academician V.P. Glushko. According to the available data, the purpose of the project with the Ifrit cipher was to study the basic principles new technology with the subsequent creation of a liquid rocket engine using kerosene and gaseous oxygen. The new engine, named after the fire demons from Arab 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 lead 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 image promising engine, as well as to create a model combustion chamber with new principles of operation.
To study the prospects of the whole direction and new ideas, a so-called. model detonation chamber combustion, corresponding to the requirements of the project. Such an experimental engine with a reduced configuration was supposed to use liquid kerosene as a fuel. Gaseous hydrogen was proposed as the oxidizing agent. In August 2016, testing of the experimental chamber began. Important, that for the first time in history, a project of this kind was brought to the stage of bench tests. Previously, domestic and foreign detonation rocket engines were developed, but not tested.
During the tests of the model sample, it was possible to obtain very interesting results showing the correctness of the approaches used. So, by using the right materials and technologies turned out to bring the pressure inside the combustion chamber to 40 atmospheres. The thrust of the experimental product reached 2 tons.
Model camera on the test bench
Within the framework of the Ifrit project, certain results were obtained, but the domestic liquid-fuel detonation engine is still far from full-fledged practical application. Before introducing such equipment into new technology projects, designers and scientists will have to decide whole line the most serious tasks. Only after that, the rocket and space industry or the defense industry will be able to start realizing the potential of new technology in practice.
In the middle of January Russian newspaper”published an interview with the chief designer of NPO Energomash, Petr Levochkin, the topic of which was the current state of affairs and the prospects for detonation engines. The representative of the enterprise-developer 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.
Eg, detonation engines can be used in hypersonic aircraft. P. Levochkin recalled that the engines now proposed for use in such equipment use subsonic combustion. At the hypersonic speed of the flight apparatus, the air entering the engine must be slowed down to 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 would be able to accelerate to speeds eight times the speed of sound.
However, the real prospects for detonation-type rocket engines are not too great yet. According to P. Levochkin, we "have 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 detonation principle combustion finds application not only in the field of rocket engines. Already exists domestic project aviation system with a detonation-type combustion chamber operating on the impulse principle. A prototype of this kind was brought to the test, and in the future it may give rise to a new direction. New engines with detonation combustion can find application in the most different areas and partially replace gas turbine or turbojet engines traditional designs.
The domestic project of a detonation aircraft engine is being developed at the OKB. A.M. Cradles. Information about this project was first presented at last year's international military-technical forum "Army-2017". At the stand of the enterprise-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 the use of a non-standard combustion chamber capable of carrying out pulsed detonation combustion of fuel in an air atmosphere. In this case, the frequency of "explosions" inside the engine should reach 15-20 kHz. In the future, an additional increase in this parameter is possible, as a result of which the engine noise will go beyond the range perceived by the human ear. Such features of the engine may be of particular interest.
The first launch of the Ifrit prototype
However, the main advantages of the new power plant are associated with improved performance. Bench tests of experimental products showed that they are about 30% superior to traditional gas turbine engines in terms of specific performance. By the time of the first public demonstration of materials on the OKB engine. A.M. Cradles could get and quite high performance characteristics. An experimental 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 it is already 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. resonators responsible for right move fuel combustion. An important advantage new project is the fundamental possibility of installing such devices anywhere in the airframe.
Specialists of OKB im. A.M. The cradles are working on aircraft engines with pulsed detonation combustion for more than three decades, but so far the project has not left the research stage and has no real prospects. main reason– lack of order and necessary financing. If the project receives the necessary support, then in the foreseeable future a sample engine suitable for use on various vehicles can be created.
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 fields. In addition, new engines can be used in "traditional" aviation. Some projects are still in their early stages and not yet ready for inspections and other work, while in other areas the most remarkable results have already been obtained.
Exploring the subject of jet engines with detonation combustion, Russian specialists were able to create a bench model of a combustion chamber with the desired characteristics. The Ifrit prototype has already been tested, during which a large amount of various information was collected. With the help of the received data, 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 only with traditional liquid engines. Nevertheless, the work has already left the purely theoretical stage, and now each test run of an experimental engine brings closer the moment of building full-fledged missiles with new power plants.
According to the websites:
http://engine.space/
http://fpi.gov.ru/
https://rg.ru/
https://utro.ru/
http://tass.ru/
http://svpressa.ru/
Detonation engines are called engines in the normal mode of which detonation combustion of fuel is used. The engine itself can be (theoretically) anything - internal combustion engine, jet, or even steam. In theory. However, until now, all known commercially acceptable engines of such fuel combustion modes, commonly referred to as "explosion", have not been used due to their ... mmm .... commercial unacceptability ..
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What is the use of detonation combustion in engines? Grossly simplifying and generalizing, something like this:
Advantages
1. Replacing conventional combustion with detonation due to the peculiarities of the gas dynamics of the shock wave front increases the theoretical maximum achievable completeness of combustion of the mixture, which makes it possible to increase Engine efficiency, and reduce consumption by about 5-20%. This is true for all types of engines, both internal combustion engines and jet engines.
2. The combustion rate of a portion of the fuel mixture increases by about 10-100 times, which means that it is theoretically possible to increase the liter power for an internal combustion engine (or specific thrust per kilogram of mass for jet engines) by about the same number of times. This factor is also relevant for all types of engines.
3. The factor is relevant only for jet engines of all types: since the combustion processes take place in the combustion chamber at supersonic speeds, and the temperatures and pressures in the combustion chamber increase many times, there is an excellent theoretical opportunity to multiply the jet flow rate from the nozzle. Which in turn leads to a proportional increase in thrust, specific impulse, efficiency, and / or a decrease in engine mass and required fuel.
All these three factors are very important, but they are not revolutionary, but, so to speak, evolutionary in nature. Revolutionary is the fourth and fifth factor, and it applies only to jet engines:
4. Only the use of detonation technologies makes it possible to create a direct-flow (and, therefore, on an atmospheric oxidizer!) universal jet engine of acceptable weight, size and thrust, for the practical and large-scale development of the range of up to, super-, and hypersonic speeds of 0-20 Mach.
5. Only detonation technologies make it possible to squeeze out of chemical rocket engines (fuel-oxidizer steam) speed parameters required for them wide application in interplanetary flights.
Items 4 and 5. theoretically reveal to us a) cheap road into near space, and b) the road to manned launches to the nearest planets, without the need to make monstrous super-heavy launch vehicles weighing over 3500 tons.
The disadvantages of detonation engines stem from their advantages:
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1. The burning rate is so high that most often these engines can be made to work only cyclically: inlet-burn-out. Which at least three times reduces the maximum achievable liter power and / or thrust, sometimes depriving the idea itself of meaning.
2. Temperatures, pressures, and rates of their rise in the combustion chamber of detonation engines are such that they exclude the direct use of most of the materials known to us. All of them are too weak to build a simple, cheap and efficient engine. Either a whole family of fundamentally new materials is required, or the use of design tricks that have not yet been worked out. We do not have materials, and the complication of the design, again, often makes the whole idea meaningless.
However, there is an area in which detonation engines are indispensable. This is an economically viable atmospheric hypersound with a speed range of 2-20 Max. Therefore, the battle is on three fronts:
1. Create an engine diagram with continuous detonation in the combustion chamber. Which requires supercomputers and non-trivial theoretical approaches to calculate their hemodynamics. In this area, the damned quilted jackets, as always, took the lead, and for the first time in the world they theoretically showed that a continuous delegation is generally possible. Invention, discovery, patent - all things. And they began to make a practical structure from rusty pipes and kerosene.
2. Creation constructive solutions making possible applications classic materials. Curse the quilted jackets with drunken bears, and here they were the first to come up with and make a laboratory multi-chamber engine that has already been working for an arbitrarily long time. The thrust is like that of the Su27 engine, and the weight is such that 1 (one!) grandfather holds it in his hands. But since the vodka was scorched, the engine turned out to be pulsating for the time being. On the other hand, the bastard works so cleanly that it can even be turned on in the kitchen (where the quilted jackets actually washed it down between vodka and balalaika)
3. Creation of supermaterials for future engines. This area is the tightest and most secret. I have no information about breakthroughs in it.
Based on the above, consider the prospects for detonation, piston internal combustion engine. As you know, the increase in pressure in the combustion chamber of classical dimensions, during detonation in the internal combustion engine, faster speed sound. Remaining in the same design, there is no way to make a mechanical piston, and even with significant bound masses, move in a cylinder with approximately the same speeds. The timing of the classic layout also cannot operate at such speeds. Therefore, a direct conversion of a classic ICE to a detonation one is meaningless from a practical point of view. The engine needs to be redesigned. But as soon as we start doing this, it turns out that the piston in this design is simply extra detail. Therefore, IMHO, a piston detonation ICE is an anachronism.
What is really behind the reports of the world's first detonation rocket engine being tested in Russia?
At the end of August 2016, the news spread around the world news agencies: at one of the stands of NPO Energomash in Khimki near Moscow, the world's first full-size liquid rocket engine(LRE) using detonation combustion of fuel -. Domestic science and technology has been going to this event for 70 years. The idea of a detonation engine was proposed by the Soviet physicist Ya. B. Zeldovich in the article “On the Energy Use of Detonation Combustion”, published in the Journal of Technical Physics back in 1940. Since then, research and experiments have been carried out around the world on the practical implementation of promising technology. In this race of minds, Germany, then the USA, then the USSR pulled ahead. And now Russia secured an important priority in the world history of technology. IN last years something like our country can not boast often.
On the crest of a wave
Detonation liquid-propellant rocket engine test
What are the advantages of a detonation engine? In traditional rocket engines, as, indeed, in conventional piston or turbojet aircraft engines uses the energy that is released when the fuel is burned. In this case, a stationary flame front is formed in the LRE combustion chamber, combustion in which occurs at a constant pressure. This process of normal combustion is called deflagration. As a result of the interaction of the fuel and the oxidizer, the temperature of the gas mixture rises sharply and a fiery column of combustion products escapes from the nozzle, which form jet thrust.
Detonation is also combustion, but it occurs 100 times faster than with conventional fuel combustion. This process is so fast that detonation is often confused with an explosion, especially since so much energy is released in this case that, for example, car motor when this phenomenon occurs in its cylinders, it can actually collapse. However, detonation is not an explosion, but a type of burning so rapid that the reaction products do not even have time to expand, so this process, unlike deflagration, takes place at a constant volume and a sharply increasing pressure.
In practice, it looks like this: instead of a stationary flame front in the fuel mixture inside the combustion chamber, a detonation wave is formed, which moves at supersonic speed. In this compression wave, the detonation of the mixture of fuel and oxidizer occurs, and from a thermodynamic point of view, this process is much more efficient than conventional fuel combustion. The efficiency of detonation combustion is 25–30% higher, i.e., when the same amount of fuel is burned, more thrust is obtained, and due to the compactness of the combustion zone, the detonation engine in terms of power removed per unit volume theoretically exceeds conventional rocket engines by an order of magnitude.
This alone was enough to draw the closest attention of specialists to this idea. After all, the stagnation that has now arisen in the development of world cosmonautics, which has been stuck in near-Earth orbit for half a century, is primarily associated with a crisis rocket engine. By the way, aviation is also in crisis, unable to cross the threshold of three speeds of sound. This crisis can be compared to the situation in piston aviation in the late 1930s. The propeller and the internal combustion engine have exhausted their potential, and only the advent of jet engines made it possible to reach a qualitatively new level altitude, speed and range.
Detonation rocket engine
The designs of classical rocket engines over the past decades have been licked to perfection and have practically come to the limit of their capabilities. It is possible to increase their specific characteristics in the future only within very small limits - by a few percent. Therefore, world cosmonautics is forced to follow an extensive path of development: for manned flights to the Moon, giant launch vehicles have to be built, and this is very difficult and insanely expensive, at least for Russia. An attempt to overcome the crisis with nuclear engines ran into environmental problems. It may be too early to compare the appearance of detonation rocket engines with the transition of aviation to jet propulsion, but they are quite capable of accelerating the process of space exploration. Moreover, this type of jet engines has another very important advantage.
GRES in miniature
An ordinary LRE is, in principle, a large burner. To increase its thrust and specific characteristics, it is necessary to raise the pressure in the combustion chamber. In this case, the fuel that is injected into the chamber through the nozzles must be supplied at a higher pressure than is realized during the combustion process, otherwise the fuel jet simply cannot penetrate into the chamber. Therefore, the most complex and expensive unit in a rocket engine is not at all a chamber with a nozzle, which is in full view, but a fuel turbopump unit (TPU), hidden in the depths of a rocket among the intricacies of pipelines.
For example, the most powerful RD-170 liquid-propellant rocket engine in the world, created for the first stage of the Soviet super-heavy launch vehicle Energia by the same NPO Energia, has a pressure in the combustion chamber of 250 atmospheres. This is a lot. But the pressure at the outlet of the oxygen pump pumping the oxidizer into the combustion chamber reaches 600 atm. This pump is powered by a 189 MW turbine! Just imagine this: a turbine wheel with a diameter of 0.4 m develops four times more power than the nuclear icebreaker Arktika with two nuclear reactors! At the same time, TNA is a complex mechanical device, the shaft of which makes 230 revolutions per second, and he has to work in an environment of liquid oxygen, where the slightest spark, not even a grain of sand in the pipeline, leads to an explosion. The technology for creating such a TNA is the main know-how of Energomash, the possession of which allows Russian company and today to sell their engines for installation on American launch vehicles Atlas V and Antares. There are no alternatives to Russian engines in the USA yet.
For a detonation engine, such difficulties are not needed, since detonation itself provides pressure for more efficient combustion, which is a compression wave running in the fuel mixture. During detonation, the pressure increases by 18–20 times without any TNA.
In order to obtain conditions in the combustion chamber of a detonation engine equivalent, for example, to the conditions in the combustion chamber of an LRE of the American Shuttle (200 atm), it is enough to supply fuel at a pressure of ... 10 atm. The unit required for this, in comparison with the TNA of a classic rocket engine, is like a bicycle pump near the Sayano-Shushenskaya State District Power Plant.
That is, a detonation engine will not only be more powerful and more economical than a conventional rocket engine, but also an order of magnitude simpler and cheaper. So why was this simplicity not given to designers for 70 years?
Pulse of progress
the main problem, which faced the engineers - how to cope with the detonation wave. The point is not only to make the engine stronger so that it can withstand increased loads. Detonation is not just a blast wave, but something more subtle. The blast wave propagates at the speed of sound, and the detonation wave propagates at supersonic speed - up to 2500 m/s. It does not form a stable flame front, so the operation of such an engine is pulsating: after each detonation, it is necessary to renew the fuel mixture, and then start a new wave in it.
Attempts to create a pulsating jet engine were made long before the idea of \u200b\u200bdetonation. It was in the use of pulsating jet engines that they tried to find an alternative piston engines in the 1930s. Simplicity again attracted: in contrast to aviation turbine for a pulse jet engine (PUJE) neither a compressor rotating at a speed of 40,000 revolutions per minute was needed to force air into the insatiable belly of the combustion chamber, nor a turbine operating at a gas temperature of over 1000 ° C. In the PuVRD, the pressure in the combustion chamber created pulsations in the combustion of the fuel.
The first patents for pulsating jet engine were obtained independently of each other in 1865 by Charles de Louvrier (France) and in 1867 by Nikolai Afanasyevich Teleshov (Russia). The first workable design of the PuVRD was patented in 1906 by the Russian engineer V.V. Karavodin, who built a model plant a year later. Due to a number of shortcomings, the Karavodin installation has not found application in practice. The first PUVRD to operate on a real aircraft was the German Argus As 014, based on a 1931 patent by the Munich inventor Paul Schmidt. Argus was created for the "weapon of retaliation" - the V-1 winged bomb. A similar development was created in 1942 by the Soviet designer Vladimir Chelomey for the first Soviet 10X cruise missile.
Of course, these engines were not yet detonation engines, since they used conventional combustion pulses. The frequency of these pulsations was low, which gave rise to a characteristic machine-gun sound during operation. The specific characteristics of the PuVRD due to the intermittent operation were on average low, and after the designers coped with the difficulties of creating compressors, pumps and turbines by the end of the 1940s, turbojet engines and LRE became the kings of the sky, and the PuVRD remained on the periphery of technical progress .
It is curious that the German and Soviet designers created the first PuVRD independently of each other. By the way, the idea of a detonation engine in 1940 came to mind not only to Zeldovich. At the same time, the same thoughts were expressed by Von Neumann (USA) and Werner Döring (Germany), so that in international science The model for using detonation combustion was called ZND.
The idea to combine a PUVRD with detonation combustion was very tempting. But the front of an ordinary flame propagates at a speed of 60–100 m/s, and the frequency of its pulsations in a PUVRD does not exceed 250 per second. And the detonation front moves at a speed of 1500‒2500 m/s, so the frequency of pulsations should be thousands per second. It was difficult to implement such a rate of mixture renewal and detonation initiation in practice.
Nevertheless, attempts to create workable pulsating detonation engines continued. The work of the US Air Force specialists in this direction culminated in the creation of a demonstrator engine, which on January 31, 2008 for the first time took to the skies on an experimental Long-EZ aircraft. In a historic flight, the engine worked for ... 10 seconds at a height of 30 meters. Nevertheless, the priority in this case remained with the United States, and the aircraft rightfully took its place in the National Museum of the US Air Force.
Meanwhile, another, much more promising scheme for a detonation engine was invented long ago.
Like a squirrel in a wheel
The idea to loop the detonation wave and make it run in the combustion chamber like a squirrel in a wheel was born by scientists in the early 1960s. The phenomenon of spin (rotating) detonation was theoretically predicted by the Soviet physicist from Novosibirsk B. V. Voitsekhovsky in 1960. Almost simultaneously with him, in 1961, the same idea was expressed by the American J. Nicholls from the University of Michigan.
Rotary, or spin, detonation engine is structurally an annular combustion chamber, fuel is supplied to which by means of radially arranged nozzles. The detonation wave inside the chamber does not move in an axial direction, as in a PuVRD, but in a circle, compressing and burning the fuel mixture in front of it and, in the end, pushing the combustion products out of the nozzle in the same way as a meat grinder screw pushes minced meat out. Instead of the pulsation frequency, we get the frequency of rotation of the detonation wave, which can reach several thousand per second, that is, in practice, the engine does not operate as a pulsating engine, but as a conventional liquid-propellant rocket engine with stationary combustion, but much more efficiently, since in fact it detonates the fuel mixture .
In the USSR, as in the USA, work on a rotary detonation engine have been going on since the beginning of the 1960s, but again, despite the seeming simplicity of the idea, its implementation required the solution of puzzling theoretical issues. How to organize the process so that the wave does not die out? It was necessary to understand the most complex physical and chemical processes occurring in a gaseous medium. Here the calculation was carried out not at the molecular level, but at the atomic level, at the junction of chemistry and quantum physics. These processes are more complex than those that occur during the generation of a laser beam. That is why the laser has been working for a long time, but the detonation engine has not. To understand these processes, it was necessary to create a new fundamental science - physicochemical kinetics, which did not exist 50 years ago. And for the practical calculation of the conditions under which the detonation wave will not die out, but will become self-sustaining, powerful computers were required, which appeared only in recent years. This is the foundation that had to be laid in the basis of practical success in taming detonation.
Active work in this direction is being carried out in the United States. These studies are carried out by Pratt & Whitney, General Electric NASA. For example, the US Naval Research Laboratory is developing spin detonation gas turbine units for the fleet. The US Navy uses 430 gas turbine plants on 129 ships, they consume fuel worth three billion dollars a year. The introduction of more economical detonation gas turbine engines (GTE) will save huge amounts of money.
In Russia, dozens of research institutes and design bureaus have worked and continue to work on detonation engines. Among them is NPO Energomash, the leading engine-building company in the Russian space industry, with many of whose enterprises VTB Bank cooperates. The development of a detonation rocket engine was carried out for more than one year, but in order for the tip of the iceberg of this work to sparkle under the sun in the form of a successful test, it took the organizational and financial participation of the notorious Advanced Research Foundation (FPI). It was the FPI that allocated necessary funds to create in 2014 a specialized laboratory "Detonation rocket engines". After all, despite 70 years of research, this technology is still “too promising” in Russia to be funded by customers like the Ministry of Defense, who, as a rule, need a guaranteed practical result. And it's still very far away.
The Taming of the Shrew
I would like to believe that after all that has been said above, the titanic work that peeps between the lines of a brief message about the tests that took place at Energomash in Khimki in July - August 2016 becomes clear: “For the first time in the world, a steady state mode of continuous spin detonation of transverse detonation waves with a frequency of about 20 kHz (wave rotation frequency - 8 thousand revolutions per second) on the fuel pair "oxygen - kerosene". It was possible to obtain several detonation waves that balanced the vibration and shock loads of each other. Heat-shielding coatings specially developed at the Keldysh Center helped to cope with high temperature loads. The engine withstood several starts under conditions of extreme vibration loads and ultra-high temperatures in the absence of cooling of the near-wall layer. The creation of mathematical models And fuel injectors, which made it possible to obtain a mixture of the consistency necessary for the occurrence of detonation.
Of course, the significance of the success achieved should not be exaggerated. Only a demonstrator engine was created, which worked for a relatively short time, and about it real characteristics nothing is reported. According to NPO Energomash, a detonation rocket engine will increase thrust by 10% while burning the same amount of fuel as in conventional engine, and the specific thrust impulse should increase by 10–15%.
The creation of the world's first full-size detonation rocket engine secured for Russia an important priority in the world history of science and technology.
But the main result is that the possibility of organizing detonation combustion in a liquid-propellant rocket engine has been practically confirmed. However, the way to use this technology as part of real aircraft there is still a long way to go. Another important aspect is that another global priority for high technology from now on, it is assigned to our country: for the first time in the world, a full-size detonation rocket engine was launched in Russia, and this fact will remain in the history of science and technology.
For the practical implementation of the idea of a detonation rocket engine, it took 70 years of hard work of scientists and designers.
Photo: Foundation for Advanced Study
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In reality, instead of a constant frontal flame in the combustion zone, a detonation wave is formed, rushing at supersonic speed. In such a compression wave, fuel and oxidizer are detonated, this process, from the point of view of thermodynamics, increases the efficiency of the engine by an order of magnitude, due to the compactness of the combustion zone.
Interestingly, back in 1940, the Soviet physicist Ya.B. Zel'dovich proposed the idea of a detonation engine in the article "On the Energy Use of Detonation Combustion". Since then, many scientists from different countries, then the United States, then Germany, then our compatriots came forward.
In the summer, in August 2016, Russian scientists managed to create the world's first full-size liquid-propellant jet engine operating on the principle of detonation combustion of fuel. Our country has finally established a world priority in the development of the latest technology for many post-perestroika years.
Why is it so good new engine? A jet engine uses the energy released by burning a mixture at constant pressure and a constant flame front. During combustion, the gas mixture of fuel and oxidizer sharply increases the temperature and the flame column escaping from the nozzle creates jet thrust.
During detonation combustion, the reaction products do not have time to collapse, because this process is 100 times faster than deflagration and the pressure increases rapidly, while the volume remains unchanged. The release of such a large amount of energy can actually destroy a car engine, which is why such a process is often associated with an explosion.
In reality, instead of a constant frontal flame in the combustion zone, a detonation wave is formed, rushing at supersonic speed. In such a compression wave, fuel and oxidizer are detonated, this process, from the point of view of thermodynamics increases engine efficiency by an order of magnitude, due to the compactness of the combustion zone. Therefore, experts so zealously set about developing this idea. In a conventional rocket engine, which is essentially a large burner, the main thing is not the combustion chamber and nozzle, but the fuel turbopump unit (TNA), which creates such pressure that fuel penetrates into the chamber. For example, in the Russian RD-170 rocket engine for Energia launch vehicles, the pressure in the combustion chamber is 250 atm and the pump that supplies the oxidizer to the combustion zone has to create a pressure of 600 atm.
In a detonation engine, pressure is created by detonation itself, which represents a traveling compression wave in the fuel mixture, in which the pressure without any TNA is already 20 times greater and turbopump units are superfluous. To make it clear, the American Shuttle has a pressure in the combustion chamber of 200 atm, and the detonation engine in such conditions needs only 10 atm to supply the mixture - this is like a bicycle pump and the Sayano-Shushenskaya hydroelectric power station.
In this case, a detonation-based engine is not only simpler and cheaper by an order of magnitude, but much more powerful and economical than a conventional liquid-propellant rocket engine. The problem of co-control with a detonation wave arose on the way to implementing the detonation engine project. This phenomenon is not just a blast wave, which has the speed of sound, but a detonation wave propagating at a speed of 2500 m/s, it does not have flame front stabilization, the mixture is renewed for each pulsation and the wave starts again.
Previously, Russian and French engineers developed and built pulsating jet engines, but not on the principle of detonation, but on the basis of ordinary combustion pulsation. The characteristics of such PUVRDs were low, and when engine builders developed pumps, turbines and compressors, the age of jet engines and LREs came, and pulsating ones remained on the sidelines of progress. The bright heads of science tried to combine detonation combustion with a PUVRD, but the frequency of pulsations of a conventional combustion front is no more than 250 per second, and the detonation front has a speed of up to 2500 m/s and its pulsation frequency reaches several thousand per second. It seemed impossible to put into practice such a rate of mixture renewal and at the same time initiate detonation.
In the USA, it was possible to build such a detonation pulsating engine and test it in the air, however, it worked for only 10 seconds, but the priority remained with the American designers. But already in the 60s of the last century, the Soviet scientist B.V. Voitsekhovsky and, almost at the same time, an American from the University of Michigan, J. Nichols, came up with the idea to loop a detonation wave in the combustion chamber.
How a detonation rocket engine works
Such rotary engine consisted of an annular combustion chamber with nozzles placed along its radius to supply fuel. The detonation wave runs like a squirrel in a wheel around the circumference, the fuel mixture is compressed and burned out, pushing the combustion products through the nozzle. In a spin engine, we obtain a wave rotation frequency of several thousand per second, its operation is similar to the working process in a rocket engine, only more efficiently, due to the detonation of the fuel mixture.
In the USSR and the USA, and later in Russia, work is underway to create a rotary detonation engine with a continuous wave, to understand the processes occurring inside, for which a whole science of physical and chemical kinetics was created. To calculate the conditions of an undamped wave, powerful computers were needed, which were created only recently.
In Russia, many research institutes and design bureaus are working on the project of such a spin engine, including the engine-building company of the space industry NPO Energomash. The Advanced Research Foundation came to help in the development of such an engine, because it is impossible to obtain funding from the Ministry of Defense - they only need a guaranteed result.
Nevertheless, during tests in Khimki at Energomash, a steady state of continuous spin detonation was recorded - 8 thousand revolutions per second on an oxygen-kerosene mixture. At the same time, detonation waves balanced vibration waves, and heat-shielding coatings withstood high temperatures.
But do not flatter yourself, because this is only a demonstrator engine that has worked for a very short time and nothing has yet been said about its characteristics. But the main thing is that the possibility of creating detonation combustion has been proven and a full-size spin engine it is in Russia that will remain in the history of science forever.
