Air injection-concave cavity combined oblique detonation engine and detonation control method thereof

Abstract

The invention provides an air injection-concave cavity combined oblique detonation engine and a detonation control method thereof, and belongs to the technical field of air suction type hypersonic propulsion. Comprising a body; the air inlet channel is arranged at one end of the extending direction of the body and used for generating oblique shock waves through induction to compress the hypersonic incoming flow; the exhaust nozzle is arranged at the other end of the extending direction of the body and is used for spraying out combusted fuel gas and generating thrust; the fairing is located on the outer side of the body, spaced from the body and used for adjusting external airflow; the mixing section is located between the body and the fairing and communicates with the air inlet channel and the exhaust nozzle; the injector is arranged at one end, close to the air inlet channel, of the mixing section and is used for injecting fuel into the mixing section, so that the fuel and the air are fully mixed in the mixing section; the inner surface of the end, close to the exhaust nozzle, of the fairing is provided with a concave cavity-air injection combined wedge face used for oblique detonation wave detonation control, and the detonation length is shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air-breathing hypersonic propulsion, in particular to a jet-cavity combined oblique detonation engine and an ignition control method thereof. BACKGROUND

[0002] Detonation combustion is a supersonic combustion mode with high thermal cycle efficiency, and has the characteristics of small time and space scale and self-pressurization. These characteristics make it have great potential in the application of aircraft propulsion systems. Existing detonation propulsion systems mainly include pulse detonation engines, rotating detonation engines and oblique detonation engines. The oblique detonation engine (ODE) based on oblique detonation wave generates thrust through the oblique detonation wave standing in the combustion chamber, and has the characteristics of simple structure, small volume and high specific impulse. Previous studies have shown that oblique detonation waves can achieve stable combustion at high Mach numbers, and are considered to have greater application potential above 9 Mach. A series of numerical and experimental studies have verified the feasibility of ODE. However, solving the ignition problem is still the key to the application of ODE. The ignition length of oblique detonation wave is very sensitive to the incoming flow parameters, and the change of engine working conditions often causes significant changes in ignition length. However, due to size constraints, the length of the wedge surface in the combustion chamber must be limited. In addition, a too long wedge surface will also bring about great resistance and higher difficulty in thermal protection. Therefore, it is of great significance for the development of oblique detonation engine to control the ignition of oblique detonation wave on a shorter wedge surface and achieve stable combustion.

[0003] The Chinese invention patent with publication number CN117418965A provides an oblique detonation engine and an ignition method thereof, which includes a fairing, a difficult fuel injector, an easy fuel injector, an inlet, a combustion chamber and a tail nozzle. By combining the easy fuel and the difficult fuel, the easy fuel is located in the lower sub-incoming flow, thereby shortening the ignition length and solving the problem of difficult ignition of the difficult fuel. However, the ignition length of this method still depends on the ignition characteristics of the easy fuel on the traditional wedge surface, and this method needs to introduce multiple fuels, which increases the system complexity.

[0004] Therefore, it is necessary to provide a jet-cavity combined oblique detonation engine and an ignition control method thereof, which controls the ignition of oblique detonation wave by configuring a cavity-jet combination, shortens the ignition length of oblique detonation wave, reduces the wedge surface resistance and thermal protection difficulty, and reduces the consumption of gas. SUMMARY

[0005] Therefore, it is necessary to provide a jet-cavity combined oblique detonation engine and an ignition control method thereof, which controls the ignition of oblique detonation wave by configuring a cavity-jet combination, shortens the ignition length of oblique detonation wave, reduces the wedge surface resistance and thermal protection difficulty, and reduces the consumption of gas.

[0006] In one aspect, the application provides a combined ramp-injection and cavity oblique detonation engine, comprising: a body; an inlet channel arranged at one end of the body in the direction of extension of the body, for compressing a hypersonic incoming flow by inducing a ramp shock wave; a nozzle arranged at the other end of the body in the direction of extension of the body, for ejecting the combusted gas and generating thrust; a fairing arranged outside the body and spaced apart from the body, for adjusting the external airflow; a mixing section arranged between the body and the fairing and in communication with the inlet channel and the nozzle respectively; an injector arranged at one end of the mixing section close to the inlet channel, for injecting fuel into the mixing section, so that the fuel and air are fully mixed in the mixing section; wherein the inner surface of the fairing close to the nozzle is provided with a combined cavity-injection wedge surface for oblique detonation wave initiation control and shortening of the initiation length.

[0007] In the above technical solution, preferably, the combined cavity-injection wedge surface comprises a front wedge surface and a rear wedge surface, the front wedge surface and the rear wedge surface are used for inducing and maintaining the ramp shock wave; a cavity is arranged between the front wedge surface and the rear wedge surface, the cavity is used for enhancing the oblique detonation wave initiation and stabilizing the position of the oblique detonation wave; an openable injection hole is arranged on the rear wedge surface, the injection hole is used for jet flow forced initiation.

[0008] Preferably, the profile of the cavity is trapezoidal.

[0009] Preferably, the cavity comprises a front wall surface, a rear wall surface and a bottom surface, the front wall surface is arranged perpendicularly to the front wedge surface, the rear wall surface is arranged at an angle to the rear wedge surface; the distance between the front wall surface and the rear wall surface is 3-5 times the depth of the bottom surface and the opening part of the cavity.

[0010] Preferably, the diameter of the injection hole is d , the distance from the edge of the rear wall surface to the injection hole is 2 d -4 d , and the injection direction of the injection hole is perpendicular to the rear wedge surface.

[0011] Preferably, the gas fuel used by the injection hole is the same as that used by the injector.

[0012] In the above technical solution, preferably, the inlet channel is a one-stage or multi-stage compression inlet channel.

[0013] In the above technical solution, preferably, the injector is a combination of at least one of a branch plate injection, a cantilever injection and a wall surface injection.

[0014] In another aspect, the present application provides a method for initiating control of a jet-cavity combined oblique detonation engine, comprising the following steps: S1: configuring the jet-cavity combined oblique detonation engine as described above; S2: after the aircraft in which the oblique detonation engine is located reaches a set flight speed at a specified height, the incoming flow enters the mixing section after being compressed by the inlet, the injector injects fuel into the mixing section, and fuel-incoming flow mixing is performed; S3: the jet holes at the cavity-jet combined wedge surface selectively inject fuel transversely into the flow field, so as to initiate and maintain the oblique detonation wave.

[0015] Preferably, in step S3, for the case that the jet holes are not opened and the oblique detonation wave is successfully induced at the cavity-jet combined wedge surface, the jet holes do not need to be opened, and the current working condition is maintained unchanged; For the case that the oblique detonation wave cannot be successfully induced at the cavity-jet combined wedge surface, the jet holes are temporarily opened to induce the oblique detonation wave, and if the working condition of initiating detonation is maintained at the front or rear wedge surface of the cavity after the jet holes are closed, the current working condition is maintained unchanged, and if the working condition of initiating detonation cannot be maintained at the front or rear wedge surface of the cavity after the jet holes are closed, the jet holes are continuously opened to maintain the oblique detonation wave.

[0016] The jet-cavity combined oblique detonation engine and the initiation control method thereof provided by the present application have the following beneficial effects compared with the prior art: (1) The cavity-jet combined wedge surface structure is adopted in the present application, compared with the traditional wedge initiation, the introduction of the cavity and the jet greatly shortens the initiation length of the oblique detonation wave, reduces the wedge resistance and the difficulty of thermal protection, and the combination of the cavity and the jet makes the present application more flexible than other single passive initiation control technologies, and can be applied to a wider range of working conditions. (2) Compared with the method of actively initiating control by using a single jet, the present application only needs to introduce the jet at the initial stage of initiation within a certain range of working conditions, and the jet holes do not consume gas after being closed, which greatly reduces the consumption of gas / fuel. (3) The gas fuel used by the jet holes and the injector is the same, and there is no need to introduce multiple fuels, so the system complexity is lower. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0018] Figure 1 Figure 1 is a schematic diagram of an engine according to the present application; Figure 2 Figure 2 is a schematic diagram of a wedge surface of a cavity-jet combination according to the present application; Figure 3 Figure 3 is a flow chart of a method according to the present application; Figure 4 Figure 4 is a schematic diagram of a failed detonation wave according to the present application; Figure 5 Figure 5 is a schematic diagram of a quasi-stable detonation wave according to the present application.

[0019] Figure 6 is a schematic diagram of an engine according to the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0021] The detonation length of the oblique detonation wave is very sensitive to the flow parameters, and the change of the engine working condition often causes a significant change in the detonation length. However, due to the size limitation, the length of the wedge surface in the combustion chamber is necessarily limited. In view of this, the present application provides a jet-cavity combined oblique detonation engine, as shown in Figure 1 The jet-cavity combined oblique detonation engine comprises: a body 10, i.e. the main part of the engine; an air inlet 1 arranged at one end of the extension direction of the body 10, used for compressing the hypersonic flow by inducing an oblique shock wave; in the present embodiment, the air inlet 1 is a one-stage or multi-stage compression air inlet 1, and preferably, an air inlet 1 with two 8° deflection angle compressions is selected; a tail nozzle 4 arranged at the other end of the extension direction of the body 10, used for ejecting the burned gas and generating thrust; a fairing 2 located outside the body 10 and arranged in a spaced manner with the body 10, used for adjusting the external airflow; The mixing section 3 is located between the body 10 and the fairing 2, and is connected with the air inlet 1 and the nozzle 4 respectively; The injector 5 is arranged at one end of the mixing section 3 close to the air inlet 1, and is used for fuel injection into the mixing section 3, so that the fuel and the air are fully mixed in the mixing section 3; in the embodiment, the injector 5 can adopt any one of the branch plate injection, the cantilever injection and the wall surface injection, or a combination of two or more different types of injectors 5. The inner surface of the fairing 2 close to one end of the nozzle 4 is provided with a cavity-jet combined wedge surface 6, which is used for oblique detonation wave initiation control and shortens the initiation length. The combination of the cavity and the jet makes the present application more flexible than other single passive initiation control technologies, and can be applied to a wider range of working conditions.

[0022] As shown in Figure 1 Combining Figure 2 It is shown that the cavity-jet combined wedge surface 6 includes a front end wedge surface 61 and a rear end wedge surface 64, and the front end wedge surface 61 and the rear end wedge surface 64 are used to induce and maintain the oblique shock wave; a cavity 62 is arranged between the front end wedge surface 61 and the rear end wedge surface 64, and the cavity 62 is used to strengthen the oblique detonation wave initiation and stabilize the oblique detonation wave position; an openable jet hole 63 is arranged on the rear end wedge surface 64, and the jet hole 63 is used for jet forced initiation. The front end wedge surface 61 and the rear end wedge surface 64 are both located at the end of the mixing section 3, and the distance from the body 10 gradually decreases.

[0023] As shown in Figure 2 The profile of the cavity 62 is trapezoidal, specifically, the cavity 62 includes a front wall surface, a rear wall surface and a bottom surface, the front wall surface is arranged vertically with the front end wedge surface 61, and the rear wall surface is arranged at an angle with the rear end wedge surface 64; the distance between the front wall surface and the rear wall surface is 3-5 times the depth of the bottom surface and the opening part of the cavity 62. Figure 2 The profile of the cavity 62 shown is a right trapezoid.

[0024] The diameter of the jet hole 63 is d , and the distance from the jet hole 63 to the edge of the rear wall surface is 2 d -4 d The jet direction of the jet hole 63 is perpendicular to the rear end wedge surface 64. By limiting the size and position of the jet hole 63, the oblique detonation wave initiation can be better realized.

[0025] In the embodiment, the jet hole 63 and the injector 5 use the same gaseous fuel, such as hydrogen fuel. Compared with the case of using different fuels, the system complexity can be reduced due to the use of the same fuel.

[0026] In addition, the present application provides an initiation control method of the oblique detonation engine with the jet-cavity combination, which includes the following steps: S1: configure the oblique detonation engine with the above-mentioned jet-cavity combination; S2: when the aircraft with the oblique detonation engine reaches the set flight speed at the specified height, the flow through the inlet 1 is compressed and enters the mixing section 3, the injector 5 injects fuel into the mixing section 3 to mix the fuel with the flow; in this embodiment, the oblique detonation engine flies at Mach 8 at an altitude of 30 km, the flow through the two 8° deflection angles of the inlet 1 is compressed and enters the mixing section 3, and is mixed with the hydrogen fuel provided by the injector 5. After mixing, the gas parameters are: pressure P = 20535.967 Pa, temperature T = 535.14 K, and velocity V = 2268 m / s. The mixed gas parameters serve as the given flow parameters in front of the cavity 62-jet combination wedge 6.

[0027] S3: the jet holes 63 at the cavity-jet combination wedge 6 selectively inject fuel transversely into the flow field to initiate and maintain the oblique detonation wave.

[0028] As shown in Figure 3 , step S3 corresponds to three different situations: 1) for the situation that the jet holes are not opened and the oblique detonation wave is successfully induced at the cavity-jet combination wedge, the jet holes do not need to be opened, and the current working condition is maintained unchanged; 2) for the situation that the oblique detonation wave cannot be successfully induced at the cavity-jet combination wedge, the jet holes are temporarily opened to induce the oblique detonation wave, and if the detonation initiation condition is maintained on the front or rear wedge of the cavity after the jet holes are closed, the current working condition is maintained unchanged; 3) for the situation that the oblique detonation wave cannot be successfully induced at the cavity-jet combination wedge, the jet holes are temporarily opened to induce the oblique detonation wave, and if the detonation initiation condition cannot be maintained on the front or rear wedge of the cavity after the jet holes are closed, the jet holes are continuously opened to maintain the oblique detonation wave.

[0029] In this embodiment, the fuel used by the injector and the jet hole is hydrogen, and of course it can also be other fuels. If it is replaced, the fuel used by the injector and the jet hole needs to be consistent. The use of hydrogen in the embodiment is not considered as a limitation of the present application.

[0030] In this embodiment, the jet-cavity 62 combination with the Figure 2 structure is used to inject hydrogen fuel into the mixing section 3 through the jet hole 63, the total pressure of the injection is 600 kPa, the static pressure is 300 kPa, and the total temperature is 300 K.

[0031] Figure 4 The flow field temperature cloud map at a moment when the oblique detonation wave (ODW) is successfully initiated and propagates after the jet hole is opened can be seen that there is a blue low-temperature area at the bottom of the rear wedge, which is hydrogen fuel. Figure 5is Figure 4 The moment when the jet hole is closed after successful initiation, the oblique detonation wave slowly retreats and finally maintains a state. It can be seen that the oblique detonation wave retreats obviously Figure 4 The bottom of the rear wedge surface has no low-temperature area because the jet hole has been closed at this time. It corresponds to the second case described above.

[0032] The above only describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A jet-cavity combined oblique detonation engine, characterized in that, include: ontology; The air intake, located at one end in the extension direction of the main body, is used to compress the hypersonic incoming flow by inducing the generation of oblique shock waves; The tail nozzle, located at the other end of the body extension direction, is used to spray out the combusted gas and generate thrust. The fairing, located on the outside of the main body and spaced apart from it, is used to adjust the external airflow; The mixing section is located between the main body and the fairing, and is interconnected with the air intake and the tail nozzle, respectively. The injector is located at one end of the mixing section near the intake manifold and is used to inject fuel into the mixing section so that the fuel and air are fully mixed in the mixing section. The inner surface of the fairing near the tail nozzle end is provided with a cavity-jet combination wedge surface, which is used for oblique detonation wave initiation control and shortening the initiation length.

2. The jet-cavity combined oblique detonation engine according to claim 1, characterized in that, The cavity-jet combined wedge surface includes a front wedge surface and a rear wedge surface, which are used to induce and maintain oblique shock waves. A cavity is disposed between the front wedge surface and the rear wedge surface, which is used to enhance the initiation of oblique detonation shock waves and stabilize the position of oblique detonation shock waves. An openable jet hole is provided on the rear wedge surface, which is used for forced jet initiation.

3. The jet-cavity combined oblique detonation engine according to claim 2, characterized in that, The cavity has a trapezoidal outline.

4. The jet-cavity combined oblique detonation engine according to claim 3, characterized in that, The cavity includes a front wall, a rear wall, and a bottom surface. The front wall is perpendicular to the front wedge surface, and the rear wall is at an angle to the rear wedge surface. The distance between the front and rear walls is 3-5 times the depth between the bottom surface and the opening of the cavity.

5. The jet-cavity combined oblique detonation engine according to claim 4, characterized in that, The diameter of the jet nozzle is d The distance from the jet nozzle to the edge of the rear wall is 2. d -4 d The jet direction of the jet nozzle is perpendicular to the rear wedge surface.

6. The jet-cavity combined oblique detonation engine according to claim 2, characterized in that, The jet nozzle uses the same gaseous fuel as the injector.

7. The jet-cavity combined oblique detonation engine according to claim 1, characterized in that, The air intake is a single-stage or multi-stage compression air intake.

8. The jet-cavity combined oblique detonation engine according to claim 1, characterized in that, The injector is a combination of at least one of the following: plate injector, cantilever injector, and wall injector.

9. A method for initiation control of a jet-cavity combined oblique detonation engine, characterized in that, Includes the following steps: S1: A slant detonation engine configured with a jet-cavity combination as described in any one of claims 3-8; S2; When the aircraft containing the oblique detonation engine reaches the set flight speed at the designated altitude, the incoming flow is compressed through the air intake and enters the mixing section. The injector injects fuel into the mixing section to mix the fuel flow. S3: The jet orifice at the wedge of the concave-jet combination will selectively inject fuel laterally into the flow field, causing the oblique detonation shock wave to ignite and sustain.

10. The detonation control method for a jet-cavity combined oblique detonation engine according to claim 9, characterized in that, In step S3, if the jet hole is not opened and oblique detonation shock wave is successfully induced at the concave cavity-jet combination wedge surface, then it is not necessary to open the jet hole and the current working state remains unchanged. If the oblique detonation shock wave cannot be successfully induced at the wedge surface of the cavity-jet combination, the jet hole is briefly opened to induce the oblique detonation shock wave. If the detonation condition is maintained on the front or rear wedge surface of the cavity after the jet hole is closed, the current condition is maintained. If the detonation condition cannot be maintained on the front or rear wedge surface of the cavity after the jet hole is closed, the jet hole is continuously opened to jet gas and maintain the oblique detonation shock wave.

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