Design method of bending detonation combustion chamber with V-shaped passivated front edge

Abstract

The invention discloses a design method of a bending detonation combustion chamber with a V-shaped passivated front edge, and belongs to the field of hypersonic velocity detonation engines of aircrafts. The oblique detonation engine aims at solving the problems of an existing oblique detonation engine in the aspects of detonation, standing, mixing and the like. According to the method, by determining the temperature increasing amplitude of the V-shaped front edge, the distance and flow parameters of a detached shock wave are determined by using a two-dimensional detached shock wave theory, the geometrical shape and interference type of a bent shock wave are determined based on a bent shock wave theory, and the crotch shape of the passivated V-shaped front edge is determined. And finally, constructing a geometric model and a combustion chamber geometric model according to the passivation angle and curvature of the V-shaped front edge. According to the method, the length of the engine can be effectively shortened, the formation and stability of detonation waves are improved, effective standing of the detonation waves is achieved, and normal work of the engine is guaranteed. The combustion chamber has the advantages of saving space, being easy to detonate, compact in structure and the like, and is suitable for a propelling system of a hypersonic aircraft.

Description

Technical Field

[0001] The invention belongs to the field of hypersonic detonation engines for aircraft, relates to detonation engines, and in particular to a design method for a curved detonation combustion chamber with a V-shaped blunt leading edge. Background Art

[0002] A detonation engine refers to a new type of power device based on the detonation combustion mechanism. Its working principle is that the oblique detonation engine injects fuel in the inlet duct in advance, pre-mixes it with air to a certain degree before entering the combustion chamber, and induces the generation of oblique detonation waves that can be stationary in the hypersonic airflow through devices such as oblique splitting, completes the mixed gas combustion and heat release within a short distance, and the high-temperature and high-pressure combustion products expand through the nozzle and accelerate to generate thrust.

[0003] Detonation engines mainly include pulse detonation engines, rotating detonation engines and oblique detonation engines. Among them, pulse detonation engines need ignition for each detonation, while rotating detonation engines only need one detonation. At the same time, they use less fuel but can produce greater thrust. Oblique detonation engines can have higher speeds than the first two and can be better adapted to hypersonic vehicles, so they have received widespread international attention.

[0004] However, during flight, conventional oblique detonation engines often face poor performance parameters or even fail to detonate successfully due to problems such as excessive back pressure in the combustion chamber, excessive low-energy flow, and insufficient fuel mixing due to a short isolation section.

[0005] Domestic and foreign scholars have carried out a lot of work on the problem of oblique detonation engine failure to detonate, mainly focusing on exploring the influence of incoming flow parameters and combustion chamber geometric parameters on the detonation mechanism. The mechanism and law of flow characteristics such as the disturbance effect of unsteady and non-uniform incoming flow, the disturbance effect of temperature, the influence of pressure, and the influence of the inclined plane angle are analyzed in detail. In addition, in order to improve the impact of the above problems on engine detonation, scholars have proposed many ideas in recent years, such as improving the oblique detonation engine by changing the detonation wedge angle ([1] Xue Rui, Du Peng, Ding Guoyu, et al. Research progress of oblique detonation combustion and oblique detonation engine [J]. Journal of Applied Mechanics, 2024, 41(02): 241-259.); and improving the oblique detonation engine by changing the wall temperature ([2] Du Lei, Sun Bo, Dai Chunliang, et al. Numerical study on the influence of wall temperature on the flow characteristics of the inlet duct of the oblique detonation engine [J]. Propulsion Technology, 2021, 42(04): 95 0-960.) and accelerated detonation through chemical non-equilibrium effect ([3] Dai Chunliang, Sun Bo, Zhuo Changfei, et al. Influence of leading edge passivation and chemical non-equilibrium effect on the inlet characteristics of oblique detonation engine [J]. Propulsion Technology, 2022, 43(01): 109-120.); In addition, some scholars have proposed a method of bending shock wave induced detonation, which improves the performance of the engine to a certain extent ([4] Xiong Haochen, Qiu Ruofan, Han Xin, et al. A new detonation method for bending shock wave induced detonation [J / OL]. Acta Aeronautica Sinica, 1-13[2024-09-10].).

[0006] The above research method mainly achieves detonation by shock wave reflection in the isolation section and increasing the initial detonation angle, but it faces the problems of difficulty in settling after detonation and long mixing distance. In order to better shorten the engine length and consider engineering reality, it is necessary to develop a local detonation method that takes passivation into consideration. Summary of the invention

[0007] The purpose of the present invention is to provide a design method for a curved detonation combustion chamber with a V-shaped blunt leading edge to address the problems of the prior art such as the difficulty in detonation, unstable stationing, and excessive engine length of the oblique detonation engine. The method induces detonation by locally configuring shock wave interference, and combines the design of the V-shaped blunt leading edge and the curved shock wave to effectively shorten the engine length, improve the detonation efficiency and stability, and achieve a compact structure.

[0008] The present invention adopts the following technical solution:

[0009] 1) Determine the temperature increase of the V-shaped leading edge based on the given inlet outlet parameters and detonation temperature.

[0010] 2) According to the incoming flow conditions (Mach number, temperature, pressure, etc.) and the size of the straight leading edge angle β, the two-dimensional detached shock wave theory is used to determine the detached shock wave distance and flow parameters, providing the incoming flow input for solving the crotch bending shock wave.

[0011] 3) Based on the detonation amplitude and the flow parameters in front of the bending shock wave, the geometric shape of the bending shock wave is determined according to the bending shock wave theory and the interference type of the primary shock wave is configured through design.

[0012] 4) Determine the crotch shape after the V-shaped leading edge is blunted for a given shock wave interference type and intensity.

[0013] 5) The geometric model is constructed according to the angle and curvature of the V-shaped leading edge blunting, and the combustion chamber geometric model is constructed by stretching according to the airflow turning angle.

[0014] In step 1), the temperature increase amplitude of the V-shaped leading edge is achieved by adjusting the angle and length of the V-shaped passivation to enhance the formation and stability of the detonation wave.

[0015] In step 2), the flow parameters including velocity, pressure and temperature distribution calculated using the two-dimensional detached shock wave theory provide input conditions for the subsequent bending shock wave solution.

[0016] In step 3), the geometry of the bending shock wave is obtained through numerical simulation or experimental methods to ensure that it can effectively induce the generation of detonation waves.

[0017] In step 4), the crotch shape after the V-shaped leading edge is blunted is determined by an optimization algorithm to achieve the best detonation wave stationary effect and combustion efficiency.

[0018] In step 5), the angle and length of the leading edge V-shape can be increased or decreased according to the thrust performance to meet the actual needs of the project.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] 1. Effectively shorten the engine length: Through the design of the V-shaped blunt leading edge and the induction effect of the curved shock wave, the present invention can achieve stable detonation and stationary detonation waves within a shorter distance. Compared with the traditional oblique detonation engine, the local configuration of the shock wave interference induction detonation method of the present invention can effectively shorten the engine length, significantly shorten the combustion chamber length, and help save space in the aircraft and improve overall performance.

[0021] 2. Improve detonation efficiency and stability: The V-shaped passivation leading edge can enhance the formation and stability of the detonation wave. By adjusting the angle and length of the V-shaped passivation, the induction effect of the detonation wave can be optimized. The design of the curved shock wave enables the detonation wave to reach a stable state in a shorter time, improving the detonation efficiency. The design of the concave surface behind the combustion chamber entrance further enhances the stationary effect of the detonation wave and ensures the normal operation of the engine.

[0022] 3. Compact structure and easy to manufacture: The combustion chamber design of the present invention is relatively simple, with a small number of parts, which is conducive to reducing manufacturing difficulty and cost. Most parts can be made of lightweight materials such as high-strength and lightweight aluminum alloys to further reduce the weight of the device. The design of the V-shaped passivated leading edge and the curved shock wave are easy to achieve through modern processing technology, improving manufacturing accuracy and efficiency. The design of the concave surface behind the combustion chamber inlet can effectively stop the detonation and ensure the normal operation of the engine.

[0023] 4. Strong adaptability: The method of the present invention can be adjusted and optimized according to different incoming flow conditions and detonation requirements to meet the needs of different application scenarios. By changing the blunting angle and length of the V-shaped leading edge, the geometric shape of the curved shock wave and other parameters, the detonation wave induction effect can be finely controlled.

[0024] 5. Improve combustion efficiency: The V-shaped blunt leading edge and curved shock wave design help optimize the mixing effect of fuel and air and improve combustion efficiency. The high temperature and high pressure environment in the combustion chamber is conducive to the full combustion of the fuel, further improving the thrust performance of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of a design method for a curved detonation combustion chamber with V-shaped blunting of the leading edge of a curved detonation engine according to the present invention.

[0026] Figure 2 Detailed view of the V-shaped blunt leading edge near the symmetry plane.

[0027] Figure 3 A top view of the V-shaped leading edge.

[0028] Figure 4 It is a front view of the V-shaped leading edge.

[0029] Figure 5 A half-section view of the V-shaped blunt leading edge.

[0030] The marks in the figure are: 1 represents a blunt body with a V-shaped blunt straight leading edge, 2 represents a V-shaped blunt curved leading edge, 3 represents an inclined surface generated by the upward extension of the curved leading edge, 4 represents a detached shock wave generated by the leading edge, 5 represents a Mach rod in the primary shock interference zone, 6 represents a shear layer formed by the incoming flow in the rounded area, 7 represents a transmitted shock wave in the secondary shock interference zone formed by the curved shock wave 10 and the transmitted shock wave 12 near the wall, 8 represents a leading edge profile in the supersonic-subsonic mixing zone, 9 represents a leading edge profile in the supersonic zone, 10 represents a curved shock wave formed by continuous compression of the supersonic airflow by the rounded curved wall, 11 represents a Mach rod in the secondary shock interference zone formed by the curved shock wave 12 and the transmitted shock wave 12 near the wall, 12 represents a transmitted shock wave in the primary shock interference zone near the wall, 13 represents the intersection of three shock waves in the primary shock interference zone in the Mach reflection structure flow field, and 14 represents the symmetric center point of the leading edge. DETAILED DESCRIPTION

[0031] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings. It should be noted that since the present invention is a planar symmetrical structure, the following description only marks and describes part of the structure, and the same symmetrical part design method is applied.

[0032] like Figures 1 to 5 As shown, the method for designing a leading edge V-shaped passivation profile according to an embodiment of the present invention mainly comprises the following steps:

[0033] 1) Provide the basic design mechanism in the design method. Figure 1 The simplified basic model of the V-shaped leading edge configuration shown in FIG. 1 is composed of a V-shaped blunt straight leading edge blunt body 1 and a V-shaped blunt curved leading edge 2, wherein the geometric properties of the V-shaped blunt curved leading edge 2 are represented by the curved leading edge radius R. When constructing the model, it should be ensured that the entire V-shaped leading edge configuration is symmetrical about the leading edge symmetry center point 14 to ensure the uniformity and stability of the flow field. According to the incoming flow components (hydrogen, kerosene, etc.), the pressure and temperature required for detonation are determined, and the size of the straight leading edge angle β and the amplification temperature of the V-shaped leading edge are determined according to the detonation pressure.

[0034] 2) Given the incoming flow Mach number Ma and the straight leading edge angle β, Figure 5The straight leading edge of the V-shaped leading edge model shown is essentially a section of swept cylinder. In the hypersonic flow field, the airflow and the straight leading edge first generate a detached shock wave 4, which will gradually develop along the flow direction and eventually reach full development and meet the Mach rod 5 in the primary shock wave interference area to form a Mach reflection structure. The primary shock wave interference area transmission shock wave 12 and the shear layer 6 formed by the incoming flow in the rounded area are emitted from the three shock wave intersection 13 in the primary shock wave interference area, and form a supersonic jet surrounded by the shear layer on both sides of the rounded area. In this process, the leading edge profile of the supersonic airflow and subsonic airflow mixing area is the leading edge profile 8 of the supersonic-subsonic mixing area, and the leading edge profile of the pure supersonic airflow area is the leading edge profile 9 of the supersonic area; the final shock wave detachment height reaches a constant value. According to the detached shock wave distance and flow parameters, the incoming flow input is provided for the solution of the crotch bending shock wave.

[0035] 3) According to the pressure and temperature required for detonation and the post-detachment shock wave parameters (detachment shock wave height, etc.), the shape of the corresponding curved shock wave 10 formed by the continuous compression of the rounded area wall and the supersonic airflow by the rounded curved wall is solved according to the curved shock wave theory and the curved streamline characteristic line method, and the interference type of the primary shock wave is configured.

[0036] 4) The supersonic airflow after the detached shock wave 4 generated at the leading edge is continuously compressed by the curved wall to form a curved shock wave 10 formed by the continuous compression of the supersonic airflow by the rounded curved wall. The curved shock wave 10 and the transmitted shock wave 12 in the primary shock wave interference zone have secondary shock wave interference near the wall, forming secondary Mach reflection, generating Mach rod 11 in the secondary shock wave interference zone and transmitted shock wave 7 in the secondary shock wave interference zone. The transmitted shock wave 7 in the secondary shock wave interference zone enters the wall, resulting in a small-scale separation shock wave / boundary layer interference in the boundary layer, which greatly increases the wall load on both sides of the flow field and forms a thermal / mechanical load peak. By controlling the shock wave interference structure, the airflow pressure and temperature near the lip wall can be effectively increased. For a given shock wave interference type and intensity, the crotch shape after the V-shaped leading edge is passivated is determined to meet the detonation requirements.

[0037] 5) According to the given inlet pressure ratio, determine the parameters such as the slope angle and curvature, so as to stretch the model out of the slope 3 generated by the upward extension of the curved leading edge. When generating the three-dimensional model, pay attention to the design of the lip leading edge section and the lip blunting radius, and ensure that the entire V-shaped leading edge configuration (including the straight leading edge, the curved leading edge and the transition area between them) maintains symmetry about the leading edge center point 14; this symmetry is conducive to optimizing the flow field characteristics, improving the detonation efficiency and ensuring the overall performance of the inlet; according to the lip leading edge section and the lip blunting radius, a complete three-dimensional V-shaped blunted lip of the inward-turning inlet is generated by the sweeping method. In this process, ensure that the leading edge profile 8 of the supersonic-subsonic mixing area and the leading edge profile 9 of the supersonic area are coordinated with the overall design to meet the flow field characteristics and detonation requirements.

[0038] Compared with the common ordinary type, the V-shaped passivated detonation combustion chamber of the present invention can effectively shorten the engine length by locally configuring the shock wave interference to induce detonation. This makes the combustion chamber proposed in this article have the advantages of saving space, easy detonation, and compact structure. In addition, the design of the concave curved surface behind the combustion chamber entrance can effectively stop the detonation and ensure the normal operation of the engine.

[0039] The above embodiments are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A design method for a curved detonation combustion chamber with a V-shaped leading edge passivation, characterized in that The following steps are involved: 1) According to the given inlet outlet parameters and detonation temperature, determine the temperature increase amplitude of the V-shaped leading edge and the size of the straight leading edge angle β; 2) According to the incoming flow conditions and the size of the straight leading edge angle β determined in step 1), the distance and flow parameters of the detached shock wave are determined using the two-dimensional detached shock wave theory to provide incoming flow input for solving the crotch bending shock wave; the incoming flow conditions include Mach number, temperature, and pressure; 3) Based on the pressure and temperature required for detonation and the post-shock wave parameters, the geometric shape of the curved shock wave is determined according to the curved shock wave theory and the curved streamline characteristic line method, and the interference type of the primary shock wave is designed and configured; 4) For a given shock wave interference type and intensity, the crotch shape after the V-shaped leading edge is blunted is determined by controlling the shock wave interference structure to meet the detonation requirements; 5) A geometric model is constructed according to the angle and curvature of the V-shaped leading edge blunting, and stretched according to the airflow turning angle to construct a complete geometric model of the curved detonation combustion chamber with V-shaped blunting of the leading edge.

2. The design method according to claim 1, characterized in that: In step 1), the temperature increase amplitude of the V-shaped leading edge is achieved by adjusting the angle and length of the V-shaped blunting to enhance the formation and stability of the detonation wave.

3. The design method of a curved detonation combustion chamber with V-shaped blunt leading edge according to claim 1, characterized in that: In step 2), the flow parameters including velocity, pressure and temperature distribution calculated using the two-dimensional detached shock wave theory provide input conditions for the subsequent bending shock wave solution.

4. The design method of a curved detonation combustion chamber with V-shaped blunt leading edge according to claim 1, characterized in that: In step 3), the geometric shape of the bending shock wave is obtained through numerical simulation or experimental methods to ensure that it can effectively induce the generation of detonation waves.

5. The design method of a curved detonation combustion chamber with V-shaped blunt leading edge according to claim 1, characterized in that: In step 4), the crotch shape after the V-shaped leading edge is blunted is determined by an optimization algorithm to achieve the best detonation wave stationary effect and combustion efficiency.

6. The design method of a curved detonation combustion chamber with V-shaped blunt leading edge according to claim 1, characterized in that: In step 5), the angle and length of the leading edge V-shape are increased or decreased according to the thrust performance to meet the actual needs of the project.

7. The design method of a curved detonation combustion chamber with V-shaped blunt leading edge according to claim 1, characterized in that: In step 5), the constructed geometric model includes a V-shaped blunt straight leading edge blunt body and a V-shaped blunt curved leading edge, and the geometric properties of the V-shaped blunt curved leading edge are represented by the curved leading edge radius.

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