United Engine Corporation (UEC) intends to soon start creating new aircraft and rocket engines that will use detonation technologies.
Detonation subsonic and supersonic engine technology demonstrators have already been created. In tests, they showed 30-50% better specific thrust and fuel consumption compared to conventional power plants, RIA Novosti reported with reference to the corporation's data.
The Experimental Design Bureau im. Cradles. The Bureau proposed the development of a family of such propulsion systems that could be used on unmanned aerial vehicles, cruise missiles, aerospace aircraft and rockets.
Detonation engines are different:
- combustion of the fuel mixture, accompanied by the passage of a shock wave through it, which is formed due to supersonic propagation of the combustion front along the fuel mixture;
- a wide range of speeds - from subsonic to hypersonic, which can help in the creation of hypersonic missiles, the design of which is actively being carried out in Russia in last years.
In 2013, the Experimental Design Bureau. Lyulki tested a prototype reduced sample of a pulsating resonator detonation engine with a two-stage combustion of a kerosene-air mixture. During the tests, the average measured thrust power plant amounted to about one hundred kilograms, and the duration continuous work- more than ten minutes. During the experiments, the new engine was switched on and off repeatedly, as well as traction control.
According to the design bureau, detonation engines will increase the thrust-to-weight ratio of aircraft by 1.5–2 times. Work on the creation of pulsating detonation engines has been carried out in Russia since 2011.
In addition to Russia, several companies in the world are developing detonation engines at once: the French company SNECMA and the American General Electric and Pratt & Whitney.
BASICS OF THE DETONATING ENGINE
If specific consumption fuel did not grow with increasing flight speed, then applying modern solutions to improve external aerodynamics, by increasing the flight altitude, at supersonic speeds, it would be possible to achieve the same range characteristics as that of a subsonic mainline aircraft. But the internal aerodynamics of supersonic aircraft has an unrecoverable drawback - at supersonic speeds, the specific fuel consumption of a traditional power plant increases monotonously with increasing speed at any flight altitudes. The way out is seen in the use of engines based on other principles than the traditional Brayton thermodynamic cycle of fuel combustion at constant pressure. The latter include pulse jet and detonation engines. The article discusses the advantages of using detonation combustion in turbojet and rocket engines.
One of the best in terms of thermodynamics is a detonation engine. Due to the fact that it burns fuel in shock waves about 100 times faster than with conventional slow combustion (deflagration), this type of engine is theoretically distinguished by a record power taken per unit volume compared to all other types of heat engines.
The question of using detonation combustion in power engineering and jet engines was first raised by Ya.B. Zeldovich back in 1940. According to his estimates, ramjet engines using detonation combustion of fuel should have the highest possible thermodynamic efficiency.
DIRECTIONS OF WORK ON PULSED DETONATION ENGINES
Direction #1 - Classic Pulse Detonation Engine
The combustion chamber of a typical jet engine consists of nozzles for mixing fuel with an oxidizer, a device for igniting the fuel mixture, and the flame tube itself, in which redox reactions (combustion) take place. The flame tube ends with a nozzle. As a rule, this is a Laval nozzle, which has a tapering part, a minimum critical section in which the velocity of the combustion products is equal to the local speed of sound, an expanding part in which the static pressure of the combustion products is reduced to a pressure of environment, as much as possible. Very roughly, one can estimate the thrust of an engine as the area of the critical section of the nozzle, multiplied by the pressure difference in the combustion chamber and the environment. Therefore, the thrust is higher, the higher the pressure in the combustion chamber.
The thrust of a pulse detonation engine is determined by other factors - the transfer of an impulse by a detonation wave to the thrust wall. Nozzle in this case is not needed at all. Pulse detonation engines have their own niche - cheap and disposable aircraft. In this niche, they are successfully developing in the direction of increasing the pulse repetition rate.
Traditional impulse detonation engines are long tubes through which shock waves travel at low frequency. The system of compression and rarefaction waves automatically regulates the supply of fuel and oxidizer. Due to the low repetition rate of shock waves (units of Hz), the time during which fuel combustion occurs is short compared to the characteristic cycle time. As a result, despite high efficiency actually detonation combustion (20-25% more than engines with the Brayton cycle), the overall efficiency of such designs is low.
The main task in this area at the present stage is the development of engines with high frequency following shock waves in the combustion chamber or creating an engine with continuous detonation(CDE).
The classic appearance of the IDD is a cylindrical combustion chamber, which has a flat or specially profiled wall, called the "draft wall". The simplicity of the IDD device is its undeniable advantage. Despite the variety of proposed schemes of PDE, all of them are characterized by the use of detonation tubes of considerable length as resonant devices and the use of valves that provide periodic supply of the working fluid.
It should be noted that the PDE, created on the basis of traditional detonation tubes, despite the high thermodynamic efficiency in a single pulsation, has the disadvantages characteristic of classical pulsating air-blasts. jet engines, namely:
– low frequency (up to 10 Hz) of pulsations, which determines the relatively low level of average traction efficiency;
– high thermal and vibration loads.
Direction No. 2 - Multipipe IDD
The main trend in the development of IDD is the transition to a multi-pipe scheme. In such engines, the frequency of operation of a single tube remains low, but due to the alternation of pulses in different tubes, the developers hope to obtain acceptable specific characteristics. Such a scheme seems to be quite workable if the problem of vibrations and asymmetry of thrust, as well as the problem of bottom pressure, in particular, possible low-frequency oscillations in the bottom area between the pipes, are solved.
Direction No. 3 - PDD with a high-frequency resonator
The traction module of the IDD of the proposed scheme consists of a reactor and a resonator. The reactor serves to prepare fuel-air mixture to detonation combustion, decomposing molecules combustible mixture into reactive constituents.
Interacting with the bottom surface of the resonator as with an obstacle, the detonation wave in the process of collision transfers to it an impulse from the overpressure forces.
IDD with high-frequency resonators have the right to success. In particular, they can claim to modernize afterburners and refine simple turbojet engines, again designed for cheap UAVs. As an example, attempts at MAI and CIAM to modernize the MD-120 turbojet engine in this way by replacing the combustion chamber with a fuel mixture activation reactor and installing traction modules with high-frequency resonators behind the turbine. So far, it has not been possible to create a workable design, because. when profiling resonators, the authors use the linear theory of compression waves, i.e. calculations are carried out in the acoustic approximation. The dynamics of detonation waves and compression waves is described by a completely different mathematical apparatus.
The use of standard numerical packages for the calculation of high-frequency resonators has a fundamental limitation. All modern models turbulences are based on averaging the Navier-Stokes equations (the basic equations of gas dynamics) over time. In addition, Boussinesq's assumption is introduced that the turbulent friction stress tensor is proportional to the velocity gradient. Both assumptions are not satisfied in turbulent flows with shock waves if the characteristic frequencies are comparable with the frequency of turbulent pulsation. Unfortunately, we are dealing with just such a case, so here it is necessary either to build a model more high level, or direct numerical simulation based on the complete Navier-Stokes equations without using turbulence models (a task that is too heavy at the present stage).
From the schemes presented above, it can be seen that the PDE schemes being studied today are single-mode engines with a very limited control range, so their direct use as the only power plant on an aircraft is impractical. Another thing - rocket engine.
1The problem of development of rotary detonation engines is considered. The main types of such engines are presented: the Nichols rotary detonation engine, the Wojciechowski engine. The main directions and trends in the development of the design of detonation engines are considered. It is shown that modern concepts of a rotary detonation engine cannot, in principle, lead to the creation of a workable design that surpasses the existing jet engines in terms of its characteristics. The reason is the desire of designers to combine wave generation, fuel combustion, and fuel and oxidizer ejection into one mechanism. As a result of self-organization of shock-wave structures, detonation combustion is carried out in a minimum rather than maximum volume. The result actually achieved today is detonation combustion in a volume not exceeding 15% of the volume of the combustion chamber. The way out is seen in a different approach - first, an optimal configuration of shock waves is created, and only then fuel components are fed into this system and optimal detonation combustion is organized in a large volume.
detonation engine
rotary detonation engine
Wojciechowski engine
circular detonation
spin detonation
impulse detonation engine
1. B. V. Voitsekhovsky, V. V. Mitrofanov, and M. E. Topchiyan, Structure of the detonation front in gases. - Novosibirsk: Publishing House of the USSR Academy of Sciences, 1963.
2. Uskov V.N., Bulat P.V. On the problem of designing an ideal diffuser for compressing a supersonic flow // Basic Research. - 2012. - No. 6 (part 1). - S. 178-184.
3. Uskov V.N., Bulat P.V., Prodan N.V. The history of the study of irregular reflection of the shock wave from the symmetry axis of a supersonic jet with the formation of a Mach disk // Fundamental research. - 2012. - No. 9 (part 2). - S. 414-420.
4. Uskov V.N., Bulat P.V., Prodan N.V. Justification of the application of the stationary Mach configuration model to the calculation of the Mach disk in a supersonic jet // Fundamental research. - 2012. - No. 11 (part 1). – S. 168–175.
5. Shchelkin K.I. Instability of combustion and detonation of gases // Uspekhi fizicheskikh nauk. - 1965. - T. 87, no. 2.– S. 273–302.
6. Nichols J.A., Wilkmson H.R., Morrison R.B. Intermittent Detonation as a Trust-Producing Mechanism // Jet Propulsion. - 1957. - No. 21. - P. 534–541.
Rotary detonation engines
All types of rotary detonation engines (RDE) have in common that the fuel supply system is combined with the fuel combustion system in the detonation wave, but then everything works like in a conventional jet engine - a flame tube and a nozzle. It was this fact that initiated such activity in the field of modernization of gas turbine engines (GTE). It seems attractive to replace only the mixing head and the mixture ignition system in the gas turbine engine. To do this, it is necessary to ensure the continuity of detonation combustion, for example, by launching a detonation wave in a circle. Nichols was one of the first to propose such a scheme in 1957, and then developed it and conducted a series of experiments with a rotating detonation wave in the mid-1960s (Fig. 1).
By adjusting the diameter of the chamber and the thickness of the annular gap, for each type of fuel mixture, it is possible to choose such a geometry that detonation will be stable. In practice, the relationship between the gap and the diameter of the engine turns out to be unacceptable, and it is necessary to control the speed of wave propagation by controlling the fuel supply, as discussed below.
As with pulse detonation engines, the circular detonation wave is capable of ejecting oxidizer, allowing RDE to be used at zero speeds. This fact led to a flurry of experimental and computational studies of RDE with an annular combustion chamber and spontaneous ejection of the fuel-air mixture, which it makes no sense to list here. All of them are built approximately according to the same scheme (Fig. 2), reminiscent of the Nichols engine scheme (Fig. 1).
Rice. 1. Scheme of organization of continuous circular detonation in the annular gap: 1 - detonation wave; 2 - a layer of "fresh" fuel mixture; 3 - contact gap; 4 - an oblique shock wave propagating downstream; D is the direction of the detonation wave
Rice. 2. Typical Circuit RDE: V - free flow velocity; V4 - flow rate at the outlet of the nozzle; a - fresh fuel assemblies, b - detonation wave front; c - attached oblique shock wave; d - combustion products; p(r) - pressure distribution on the channel wall
A reasonable alternative to the Nichols scheme could be the installation of a plurality of fuel-oxidation injectors that would inject a fuel-air mixture into the region immediately before the detonation wave according to a certain law with a given pressure (Fig. 3). By adjusting the pressure and the rate of fuel supply to the combustion region behind the detonation wave, it is possible to influence the rate of its propagation upstream. This direction is promising, but the main problem in the design of such RDEs is that the widely used simplified model of the flow in the detonation combustion front does not correspond to reality at all.
Rice. 3. RDE with controlled fuel supply to the combustion area. Wojciechowski rotary engine
The main hopes in the world are associated with detonation engines operating according to the Wojciechowski rotary engine scheme. In 1963 B.V. Voitsekhovsky, by analogy with spin detonation, developed a scheme for continuous combustion of gas behind a triple configuration of shock waves circulating in an annular channel (Fig. 4).
Rice. Fig. 4. Scheme of the Wojciechowski continuous combustion of gas behind a triple configuration of shock waves circulating in the annular channel: 1 - fresh mixture; 2 - doubly compressed mixture behind a triple configuration of shock waves, detonation area
IN this case the stationary hydrodynamic process with gas combustion behind the shock wave differs from the detonation scheme of Chapman-Jouguet and Zel'dovich-Neumann. Such a process is quite stable, its duration is determined by the reserve of the fuel mixture and, in well-known experiments, is several tens of seconds.
Wojciechowski's detonation engine scheme served as a prototype numerous studies̆ rotational and spin detonation engines̆ initiated in the last 5 years. This scheme accounts for more than 85% of all studies. All of them have one organic drawback - the detonation zone occupies too little of the total combustion zone, usually no more than 15%. As a result, the specific performance of engines is worse than that of engines of traditional design.
On the causes of failures with the implementation of the Wojciechowski scheme
Most of the work on engines with continuous detonation is associated with the development of the Wojciechowski concept. Despite the more than 40-year history of research, the results actually remained at the level of 1964. The share of detonation combustion does not exceed 15% of the volume of the combustion chamber. The rest is slow combustion under conditions that are far from optimal.
One of the reasons for this state of affairs is the lack of a workable calculation methodology. Since the flow is three-dimensional, and the calculation takes into account only the laws of conservation of momentum on the shock wave in the direction perpendicular to the model detonation front, the results of calculating the inclination of shock waves to the flow of combustion products differ from those observed experimentally by more than 30%. The consequence is that, despite many years of research on various fuel supply systems and experiments on changing the ratio of fuel components, all that has been done is to create models in which detonation combustion occurs and is maintained for 10–15 s. There is no talk of increasing efficiency, or of advantages over existing liquid-propellant and gas-turbine engines.
The analysis of the available RDE schemes carried out by the authors of the project showed that all the RDE schemes offered today are inoperative in principle. Detonation combustion occurs and is successfully maintained, but only to a limited extent. In the rest of the volume, we are dealing with the usual slow combustion, moreover, behind a non-optimal system of shock waves, which leads to significant losses full pressure. In addition, the pressure is also several times lower than necessary for ideal combustion conditions with a stoichiometric ratio of the fuel mixture components. As a result, the specific fuel consumption per unit of thrust is 30-40% higher than that of conventional engines.
But the main problem is the very principle of organizing continuous detonation. As shown by studies of continuous circular detonation, carried out back in the 60s, the detonation combustion front is a complex shock wave structure consisting of at least two triple configurations (about triple configurations of shock waves. Such a structure with an attached detonation zone, like any thermodynamic system with feedback, left alone, tends to take a position corresponding to the minimum level of energy. As a result, the triple configurations and the area of detonation combustion are adjusted to each other so that the detonation front moves along the annular gap with the minimum possible volume of detonation combustion for this. This is directly opposite to the goal that engine designers set for detonation combustion.
For creating efficient engine RDE needs to solve the problem of creating an optimal triple configuration of shock waves and organizing a detonation combustion zone in it. Optimal shock-wave structures must be able to create in a variety of technical devices, for example, in optimal diffusers of supersonic air intakes. The main task is the maximum possible increase in the share of detonation combustion in the volume of the combustion chamber from today's unacceptable 15% to at least 85%. Existing engine designs based on the schemes of Nichols and Wojciechowski cannot provide this task.
Reviewers:Uskov V.N., Doctor of Technical Sciences, Professor of the Department of Hydroaeromechanics of St. Petersburg State University, Faculty of Mathematics and Mechanics, St. Petersburg;
Emelyanov V.N., Doctor of Technical Sciences, Professor, Head of the Department of Plasma Gas Dynamics and Heat Engineering, BSTU "VOENMEH" named after A.I. D.F. Ustinov, St. Petersburg.
The work was received by the editors on October 14, 2013.
Bibliographic link
Bulat P.V., Prodan N.V. REVIEW OF PROJECTS OF DETONATING ENGINES. ROTARY DETONATING ENGINES // Fundamental Research. - 2013. - No. 10-8. - S. 1672-1675;URL: http://fundamental-research.ru/ru/article/view?id=32642 (date of access: 03/14/2019). We bring to your attention the journals published by the publishing house "Academy of Natural History"
What's Really Behind Reports of the World's First Detonation Rocket Engine 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-propellant rocket engine (LRE) using detonation combustion of fuel was launched. 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 detonation combustion”, published in the Journal of Technical Physics back in 1940. Since then, research and experiments on the practical implementation of promising technology have been going on all over the world. 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 recent years, our country has not often been able to boast of something like this.
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 goes so fast that detonation is often confused with an explosion, especially since so much energy is released at the same time that, for example, an automobile engine, when this phenomenon occurs in its cylinders, 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 the crisis of rocket engine building. 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. Screw and motor internal combustion have exhausted their potential, and only the advent of jet engines made it possible to reach a qualitatively new level altitude, speed and range.
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 difficult and expensive unit in the LRE is not a chamber with a nozzle, which is in plain sight, but a fuel turbopump unit (TNA), hidden in the depths of the 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. Alternatives Russian engines not yet in the US.
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 update fuel mixture, and then launch 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. Specific characteristics of PUVRD due to intermittent mode the average work was low, and after the designers by the end of the 1940s coped with the difficulties of creating compressors, pumps and turbines, turbojet engines and LRE became the kings of the sky, and 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 well as in the USA, work on a rotary detonation engine has 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 no longer carried out at the molecular, 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 fade, 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 turbines 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 nothing is reported about its real characteristics. 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%.
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.
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.
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 the new engine so good? 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 allocation of such a large number 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 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, there is no stabilization of the flame front in it, for each pulsation the mixture is updated 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.
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 (LPRE) using detonation combustion of fuel was launched -. 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 on the practical implementation of promising technology have been going on all over the world. 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 recent years, our country has not often been able to boast of something like this.
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, the energy that is released when fuel is burned is used. 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 the jet thrust.
Detonation is also combustion, but it occurs 100 times faster than with conventional fuel combustion. This process goes so fast that detonation is often confused with an explosion, especially since so much energy is released at the same time that, for example, an automobile engine, when this phenomenon occurs in its cylinders, 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 the crisis of rocket engine building. 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 of altitudes, speeds and flight ranges.
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 the help of nuclear engines stumbled upon 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 it has to work in an environment of liquid oxygen, where the slightest not even a spark, but 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 the Russian company to sell its engines for installation on American Atlas V and Antares launch vehicles today. 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 that confronted the engineers was 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 application of pulsating jet engines that they tried to find an alternative to piston engines in the 1930s. Simplicity again attracted: unlike an aviation turbine, a pulsed air-jet engine (PuVRD) did not need a compressor rotating at a speed of 40,000 rpm to force air into the insatiable womb of the combustion chamber, nor operating at a gas temperature above 1000 ° C turbine. In the PuVRD, the pressure in the combustion chamber created pulsations in the combustion of the fuel.
The first patents for a pulsating jet engine were obtained independently 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 well as in the USA, work on a rotary detonation engine has 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 no longer carried out at the molecular, 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 fade, 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 turbines for the fleet. The US Navy uses 430 gas turbine units on 129 ships, consuming $3 billion worth of fuel 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 the necessary funds for the creation in 2014 of a specialized laboratory "Detonation LRE". 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. A special role in this success was played by the creation of mathematical models and fuel injectors, which made it possible to obtain a mixture of the consistency necessary for the onset 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 nothing is reported about its real characteristics. According to NPO Energomash, a detonation rocket engine will increase thrust by 10% while burning the same amount of fuel as in a 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, there is still a long way to go before using this technology in real aircraft. Another important aspect is that another world priority in the field of high technologies is now 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
Overall rating of the material: 5
SIMILAR MATERIALS (BY MARKS):
Graphene transparent, magnetic and filtering water Father of the video Alexander Poniatov and AMPEX
