Composite cavity combustion chamber and scramjet

Abstract

The present application relates to a kind of composite cavity combustion chamber and hypersonic ramjet engine, wherein, composite cavity combustion chamber, comprising: combustion chamber main body (1) and the cavity structure (2) installed on the combustion chamber main body (1);The cavity structure (2) includes: first cavity portion (21) and second cavity portion (22);The first cavity portion (21) first cavity less than the second cavity that the second cavity portion (22) is surrounded;Along the width direction perpendicular to the direction of incoming flow of combustion chamber, the second cavity portion (22) with the first cavity portion (21) is connected and is arranged in the opposite side of the first cavity portion (21), and the first cavity is communicated with the second cavity;The opening side of the first cavity portion (21) is connected with the opening side of the second cavity portion (22) on the combustion chamber main body (1).

Description

Technical Field

[0001] This invention relates to the aerospace field, and more particularly to a composite concave combustion chamber and a scramjet engine. Background Technology

[0002] The scramjet engine is the core of hypersonic vehicles. The cavity, as a flame stabilizing device in the combustion chamber of the scramjet engine, integrates functions such as fuel injection, mixing, ignition, flame stabilization, and combustion, and has been widely used.

[0003] The concave flame stabilizers commonly used in supersonic combustion chambers are mostly trapezoidal in shape, see reference [1]. When the high-speed airflow passes through the concave cavity, a low-speed recirculation zone is formed inside the cavity. Through the concave cavity shear layer, mass, momentum and energy are exchanged with the fuel injected upstream and the upstream air. At the same time, it serves as a new ignition source to continuously ignite the fuel-air mixture coming from upstream.

[0004] Unlike aero engines that use compressors to compress the incoming airflow, scramjet engines utilize the ram effect of high-speed airflow to compress the incoming airflow. Therefore, the inlet airflow of the combustion chamber is significantly affected by flight conditions (Mach number, speed, altitude, angle of attack, etc.). Existing concave flame stabilizers are mainly designed and optimized for a specific fixed incoming airflow condition, focusing on structural form, injection scheme, and combustion organization, thus limiting the applicable range of incoming airflow Mach numbers.

[0005] Currently, to achieve good operation over a wide range of flight Mach numbers with a fixed combustion chamber configuration, a combination of multiple concave cavities is generally adopted. These can be categorized into parallel and series configurations based on their specific distribution. Parallel concave cavities typically use two concave cavities of the same size, one above the other (as in reference [2]). Compared to a single concave cavity, the applicable range of incoming Mach numbers is only slightly wider. Series concave cavities are generally arranged front and rear (as in reference [3]). The applicable range of incoming Mach numbers can be effectively widened by dynamically adjusting the position of the heat release area. However, this results in a large total pressure loss, high internal resistance, and also increases the structural length of the engine.

[0006] In addition, reference document [4] proposes a three-dimensional wall groove to address the problem of large aerodynamic drag generated by the wall cavity. It achieves the effect of reducing aerodynamic drag through a "dovetail" shaped cavity, but still limits its applicability in a wide Mach number range.

[0007] References

[0008] [1] Chinese Patent Authorization Announcement No. CN102966974B, Patent Name: Supersonic Combustion Chamber Wall Cavity Structure and Engine Combustion Chamber Including Thereof, Authorization Announcement Date: 2015.01.21;

[0009] [2] Chinese Patent Authorization Announcement No. CN105180212B, Patent Name: Combustion Chamber of Scramjet Engine, Authorization Announcement Date: 2017.06.16;

[0010] [3] Chinese Patent Authorization Announcement No. CN110319456B, Patent Name: A Solid Rocket Scramjet Engine with Multi-Stage Combustion Enhancement Device, Authorization Announcement Date: 2020.08.18;

[0011] [4] Chinese Patent Publication No. CN101245921A, Patent Title: A Wall Groove for a Supersonic Combustion Chamber, Publication Date: 2008.08.20. Summary of the Invention

[0012] The purpose of this invention is to provide a composite concave combustion chamber and a scramjet engine that are suitable for operation over a wide Mach number range.

[0013] To achieve the above-mentioned objectives, the present invention provides a composite concave cavity combustion chamber, comprising: a combustion chamber body and a concave cavity structure mounted on the combustion chamber body;

[0014] The cavity structure includes: a first cavity portion and a second cavity portion;

[0015] The first concave cavity formed by the first concave portion is smaller than the second concave cavity formed by the second concave portion;

[0016] Along the width direction perpendicular to the combustion chamber flow direction, the second recessed cavity portion is connected to the first recessed cavity portion and is disposed on opposite sides of the first recessed cavity portion, and the first recessed cavity and the second recessed cavity are connected.

[0017] The opening side of the first concave cavity portion is flush with the opening side of the second concave cavity portion and connected to the combustion chamber body.

[0018] According to one aspect of the invention, along the flow direction of the combustion chamber, the length of the first recess is less than the length of the second recess;

[0019] Along the height direction perpendicular to the combustion chamber flow direction, the depth of the first cavity is less than the depth of the second cavity.

[0020] According to one aspect of the present invention, if the length of the first cavity is L21 and the depth is D21, then it satisfies: L21 / D21<10;

[0021] The length of the second cavity is L22, which satisfies: L22>L21+n*D21, 2.1≥n≥1.9;

[0022] The depth of the second cavity is D22, which satisfies: D22>m*D21, 1.3≥m≥1.1.

[0023] According to one aspect of the invention, the first cavity is a trapezoidal cavity or a semi-circular cavity;

[0024] If the first cavity is a trapezoidal cavity, then the first cavity portion includes: a first front wall, a first bottom wall, a first rear wall, and a connecting side wall;

[0025] Along the flow direction of the combustion chamber, the first front wall and the first rear wall are respectively provided at the front and rear ends of the first bottom wall, and the first front wall and the first rear wall are provided on the same side of the first bottom wall;

[0026] Along the width direction perpendicular to the combustion chamber flow direction, the connecting sidewalls are respectively provided on both sides of the first concave cavity portion, and the connecting sidewalls are used to connect the first concave cavity portion and the second concave cavity portion.

[0027] According to one aspect of the invention, the second cavity is a trapezoidal cavity or a semi-circular cavity;

[0028] If the second cavity is a trapezoidal cavity, then the second cavity portion includes: a second front wall, a second bottom wall, and a second rear wall;

[0029] Along the flow direction of the combustion chamber, the second front wall and the second rear wall are respectively provided at the front and rear ends of the second bottom wall, and the second front wall and the second rear wall are provided on the same side of the second bottom wall;

[0030] Along the width direction perpendicular to the combustion chamber flow direction, one side edge of the second recessed cavity portion is connected to the edge of the connecting sidewall.

[0031] According to one aspect of the present invention, if the first cavity is a semi-circular cavity, then the first front wall, the first bottom wall, and the first rear wall form a continuous semi-circular structure, and the semi-circular radius R21 of the first cavity satisfies D21. <R21<L21;

[0032] If the second cavity is a semi-circular cavity, then the second front wall, the second bottom wall, and the second rear wall form a continuous semi-circular structure, and the semi-circular radius R22 of the second cavity satisfies D22. <R22<L22。

[0033] According to one aspect of the present invention, if the first cavity is a semi-circular cavity, the semi-circular radius R21 of the first cavity can be set as R21=(2*D21+L21) / 2;

[0034] If the second cavity is a semi-circular cavity, then the semi-circular radius R22 of the second cavity can be set as R22=(2*D22+L22) / 2.

[0035] According to one aspect of the invention, the connecting sidewall is vertically disposed between the first cavity portion and the second cavity portion; or,

[0036] The connecting sidewall is inclined between the first cavity portion and the second cavity portion;

[0037] Along the width direction perpendicular to the combustion chamber flow direction, the two connecting sidewalls are inclined in a direction that keeps them away from each other; or,

[0038] Between the first cavity portion and the second cavity portion, the connecting sidewall is provided in a stepped shape; wherein, the connecting sidewall has at least one stepped portion;

[0039] In the stepped section, the width of the stepped section is greater than or equal to the height;

[0040] If the connecting sidewall has multiple stepped sections, then the height of the multiple stepped sections is the same.

[0041] According to one aspect of the invention, the positions where the first front wall, the first bottom wall, and the first rear wall connect to the connecting side wall are respectively transitioned by a circular arc structure; and / or,

[0042] The second front wall, the second bottom wall, and the second rear wall are connected to the connecting side wall using a rounded transition structure.

[0043] The radius R24 of the arc structure satisfies: R24>(D22-D21) / 2.

[0044] To achieve the above-mentioned objectives, the present invention provides a scramjet engine employing the aforementioned composite concave cavity combustion chamber, comprising: an intake duct isolation section and a composite concave cavity combustion chamber connected sequentially from front to back along the combustion chamber inflow direction;

[0045] The intake duct isolation section is connected to and fixed to the main body of the composite cavity combustion chamber.

[0046] According to one aspect of the present invention, the composite cavity combustion chamber of the present invention is no longer a traditional two-dimensional configuration, but rather a three-dimensional composite cavity configuration is formed by combining two-dimensional cavities with different configurations (depth, aspect ratio, trailing edge depth, etc.) as sub-cavities in the third dimension. That is, the present invention efficiently combines traditional series or parallel cavities into one cavity, thereby effectively combining the advantages of different cavity configurations that are suitable for different incoming Mach numbers.

[0047] According to one aspect of the present invention, the composite cavity combustion chamber of the present invention efficiently integrates the advantages of different cavity configurations (depth, aspect ratio, trailing edge depth, etc.) for different incoming flow Mach numbers, significantly improving the applicable range of incoming flow Mach numbers.

[0048] According to one aspect of the present invention, in the composite concave combustion chamber of the present invention, vortex motion is induced between sub-concave cavities of different configurations, which significantly enhances the exchange of mass, momentum and energy between the sub-concave cavities, thereby improving the fuel mixing efficiency of the entire composite concave cavity and the mass, momentum and energy exchange capacity inside and outside the concave cavity, which is more conducive to ignition and combustion.

[0049] According to one aspect of the present invention, the composite concave cavity combustion chamber of the present invention has lower flow loss and shorter combustion chamber length compared to the traditional series concave cavity; compared to the traditional parallel concave cavity, its applicability over a wide Mach number range is significantly enhanced. Attached Figure Description

[0050] Figure 1 This is a structural diagram of a composite concave cavity combustion chamber according to an embodiment of the present invention;

[0051] Figure 2 This is a diagram showing the connection structure between the connecting sidewall and the first cavity portion and the second cavity portion according to an embodiment of the present invention.

[0052] Figure 3 This is a side view of a composite concave cavity combustion chamber according to an embodiment of the present invention;

[0053] Figure 4 This is a side view of a composite concave cavity combustion chamber according to another embodiment of the present invention;

[0054] Figure 5 This is a diagram showing the connection structure between the connecting sidewall and the first cavity portion and the second cavity portion according to another embodiment of the present invention.

[0055] Figure 6 This is a diagram showing the connection structure between the connecting sidewall and the first cavity portion and the second cavity portion according to another embodiment of the present invention.

[0056] Figure 7 This is a diagram showing the connection structure between the connecting sidewall and the first cavity portion and the second cavity portion, respectively, according to another embodiment of the present invention. Detailed Implementation

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0058] In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" express orientations or positional relationships based on the orientations or positional relationships shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on the present invention.

[0059] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, a composite concave-cavity combustion chamber includes: a combustion chamber body 1 and a concave-cavity structure 2 mounted on the combustion chamber body 1; in this embodiment, the concave-cavity structure 2 includes: a first concave-cavity portion 21 and a second concave-cavity portion 22; wherein the first concave cavity enclosed by the first concave-cavity portion 21 is smaller than the second concave cavity enclosed by the second concave-cavity portion 22. In this embodiment, along the width direction perpendicular to the combustion chamber flow direction, the second concave-cavity portion 22 is disposed on opposite sides of the first concave-cavity portion 21 and connected to it, and the first concave cavity and the second concave cavity are in communication. In this embodiment, the opening side of the first concave-cavity portion 21 and the opening side of the second concave-cavity portion 22 are flush with each other and connected to the combustion chamber body 1.

[0060] With the above configuration, since the second cavity formed by the second cavity portion 22 is small, the interconnected first cavity portion 21 and second cavity portion 22 achieve a stepped arrangement of the cavities, which can effectively combine the functions of different cavity configurations to achieve the advantage of excellent applicability under different incoming Mach number states.

[0061] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, along the combustion chamber flow direction, the length of the first cavity is less than the length of the second cavity; along the height direction perpendicular to the combustion chamber flow direction, the depth of the first cavity is less than the depth of the second cavity.

[0062] The above configuration ensures that each position in the first and second concave cavities has a certain height difference, resulting in a continuous step.

[0063] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the shapes of the first cavity and the second cavity can be set to be identical, differing only in size. Furthermore, the edges of the first cavity and the second cavity are arranged parallel to each other. By ensuring the parallel arrangement of the edges of the first cavity and the second cavity, the flow can be evenly distributed on both sides of the first cavity portion 21, effectively guaranteeing the operational stability of the present invention.

[0064] Combination Figure 1 , Figure 2 and Figure 3 As shown, according to one embodiment of the present invention, the length of the first cavity is L21 and the depth is D21, then it satisfies: L21 / D21<10; the length of the second cavity is L22, then it satisfies: L22>L21+n*D21, 2.1≥n≥1.9, preferably, L22>L21+2*D21; the depth of the second cavity is D22, then it satisfies: D22>m*D21, 1.3≥m≥1.1, preferably, D22>1.2*D21.

[0065] By setting the dimensions of the first and second concave cavities within the aforementioned range, it is possible to ensure that both cavities are open concave cavity structures, thereby reducing the aerodynamic drag of the concave cavities. Furthermore, it allows for a reasonable allocation and arrangement of the length, depth, and width between the interconnected first concave cavity portion 21 and the second concave cavity portion 22, with the difference in dimensions being on the same order of magnitude or equivalent to the size of the concave cavity itself. On the one hand, this can form a sufficiently strong composite concave cavity combustion chamber pressure and velocity gradient change, thereby inducing a sufficiently strong and large-scale flow field structure such as directional vortices and lateral velocities. On the other hand, it can more effectively integrate the effects of concave cavities with different configurations to achieve the advantage of excellent applicability under different incoming Mach number states.

[0066] Combination Figure 1 , Figure 2 and Figure 3 As shown, according to one embodiment of the present invention, the first cavity is a trapezoidal cavity, wherein the first cavity portion 21 includes: a first front wall 211, a first bottom wall 212, a first rear wall 213, and a connecting side wall 214. In this embodiment, along the combustion chamber flow direction, the first front wall 211 and the first rear wall 213 are respectively disposed at the front and rear ends of the first bottom wall 212, and the first front wall 211 and the first rear wall 213 are disposed on the same side of the first bottom wall 212. In this embodiment, along the width direction perpendicular to the combustion chamber flow direction, the connecting side wall 214 is respectively disposed on both sides of the first cavity portion 21, and the connecting side wall 214 is used to connect the first cavity portion 21 and the second cavity portion 22.

[0067] In this embodiment, the connection angles between the first front wall 211 and the first rear wall 213 and the first bottom wall 212 are different. The first front wall 211 is perpendicular to the first bottom wall 212, while the first rear wall 213 is inclined to the first bottom wall 212. Moreover, the inclined first rear wall 213 makes the length of the opening side of the first cavity greater than the length of the first bottom wall 212.

[0068] Combination Figure 1 , Figure 2 and Figure 3 As shown, according to one embodiment of the present invention, the second cavity is a trapezoidal cavity, wherein the second cavity portion 22 includes: a second front wall 221, a second bottom wall 222, and a second rear wall 223. In this embodiment, along the combustion chamber flow direction, the second front wall 221 and the second rear wall 223 are respectively disposed at the front and rear ends of the second bottom wall 222, and the second front wall 221 and the second rear wall 223 are disposed on the same side of the second bottom wall 222; in this embodiment, along the width direction perpendicular to the combustion chamber flow direction, one edge of the second cavity portion 22 is connected to the edge of the connecting side wall 214.

[0069] In this embodiment, the connection angles between the second front wall 221 and the second rear wall 223 and the second bottom wall 222 are different. The second front wall 221 and the second bottom wall 222 are arranged perpendicularly, while the second rear wall 223 and the second bottom wall 222 are connected at an incline. Moreover, the inclined second rear wall 223 makes the length of the second cavity opening side greater than the length of the second bottom wall 222.

[0070] In this embodiment, since the shapes of the first cavity and the second cavity are consistent, the included angle between the first rear wall 213 and the first bottom wall 212 and the included angle between the second rear wall 223 and the second bottom wall 222 are consistent.

[0071] like Figure 1 As shown, according to another embodiment of the present invention, when both the first cavity and the second cavity are trapezoidal cavities, the shapes of the first cavity and the second cavity can also be set to be different. The difference between the shapes of the first cavity and the second cavity can be achieved by adjusting the tilt angle of the first rear wall 213 and / or the second rear wall 223; or, the difference between the shapes of the first cavity and the second cavity can be achieved by changing the tilt angle of the first front wall 211 and / or the second front wall 221.

[0072] Combination Figure 1 , Figure 2 and Figure 4As shown, according to another embodiment of the present invention, the first cavity can be configured as a semi-circular cavity, and the first front wall 211, the first bottom wall 212, and the first rear wall 213 are configured as continuous arcs; wherein, when the first cavity is configured as a semi-circular cavity, the second cavity can be configured as a trapezoidal cavity or a semi-circular cavity. In this embodiment, if the first cavity is a semi-circular cavity, then the semi-circular radius R21 of the first cavity satisfies D21. <R21<L21。

[0073] More preferably, if the first cavity is a semi-circular cavity, then the semi-circular radius R21 of the first cavity can be set as R21=(2*D21+L21) / 2.

[0074] Combination Figure 1 , Figure 2 and Figure 4 As shown, according to another embodiment of the present invention, the second concave cavity can be configured as a semi-circular concave cavity, and the second front wall 221, the second bottom wall 222, and the second rear wall 223 are configured as continuous arcs; wherein, when the second concave cavity is configured as a semi-circular concave cavity, the first concave cavity can be configured as a trapezoidal concave cavity or a semi-circular concave cavity. In this embodiment, if the second concave cavity is a semi-circular concave cavity, then the semi-circular radius R22 of the second concave cavity satisfies D22. <R22<L22。

[0075] More preferably, if the second cavity is a semi-circular cavity, then the semi-circular radius R22 of the second cavity can be set as R22=(2*D22+L22) / 2.

[0076] By selectively configuring the first and / or second concave cavities as semi-circular cavities, the problems of high temperature and high heat flux density in the bottom corner area of ​​the trapezoidal concave cavity can be effectively alleviated, thus improving structural reliability. Furthermore, trapezoidal and semi-circular concave cavities have different flame stabilization capabilities and mechanisms. If the first and second concave cavities are trapezoidal and semi-circular, respectively, the composite concave cavity combustion chamber of this invention can better integrate the functions of different types of concave cavities to achieve excellent applicability under different incoming Mach number conditions.

[0077] Combination Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, a connecting sidewall 214 is vertically disposed between the first cavity portion 21 and the second cavity portion 22.

[0078] Combination Figure 1 and Figure 5 As shown, according to another embodiment of the present invention, a connecting sidewall 214 is inclined between the first cavity portion 21 and the second cavity portion 22. In this embodiment, the two connecting sidewalls 214 are inclined in a direction away from each other along the width direction perpendicular to the combustion chamber flow direction.

[0079] Combination Figure 1 and Figure 6 As shown, according to another embodiment of the present invention, a connecting sidewall 214 is provided in a stepped shape between the first cavity portion 21 and the second cavity portion 22; wherein the connecting sidewall 214 has at least one stepped portion; in this embodiment, the width of the stepped portion is greater than or equal to its height. If the connecting sidewall 214 has multiple stepped portions, the heights of the multiple stepped portions are the same.

[0080] With the above configuration, the position connected to the connecting sidewall 214 is set as a stepped structure, which adds an additional stepped cavity between the first cavity portion 21 and the second cavity portion 22, effectively combining more than three cavities, further improving the applicable flow Mach number range and flame stability capability of the composite cavity.

[0081] Combination Figure 1 and Figure 7 As shown, according to one embodiment of the present invention, the positions where the first front wall 211, the first bottom wall 212, the first rear wall 213 are connected to the connecting side wall 214 are respectively transitioned by a circular arc structure; and / or, the positions where the second front wall 221, the second bottom wall 222, the second rear wall 223 are connected to the connecting side wall 214 are respectively transitioned by a circular arc structure.

[0082] In this embodiment, the radius R24 of the arc structure satisfies: R24>(D22-D21) / 2.

[0083] By setting the above configuration, the position connected to the connecting sidewall 214 is set as an arc structure, making the edge of the stepped structure formed between the first cavity portion 21 and the second cavity portion 22 smoother. This can reduce flow loss and heat flux density at the edge, reduce cavity resistance, and improve the structural reliability of the present invention.

[0084] According to one embodiment of the present invention, the present invention provides a scramjet engine employing the aforementioned composite cavity combustion chamber, comprising: an intake duct isolation section and a composite cavity combustion chamber connected sequentially from front to back along the combustion chamber inflow direction; wherein the intake duct isolation section is connected to and fixed to the combustion chamber body 1 of the composite cavity combustion chamber.

[0085] The above description is merely an example of a specific solution of the present invention. For any devices and structures not described in detail herein, it should be understood that they are implemented using common devices and methods already available in the art.

[0086] The above description is merely one embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite concave cavity combustion chamber, characterized in that, include: Combustion chamber body (1) and cavity structure (2) installed on the combustion chamber body (1); The cavity structure (2) includes: a first cavity portion (21) and a second cavity portion (22); The first cavity formed by the first concave portion (21) is smaller than the second concave cavity formed by the second concave portion (22); Along the width direction perpendicular to the combustion chamber flow direction, the second cavity portion (22) is connected to the first cavity portion (21) and is disposed on opposite sides of the first cavity portion (21), and the first cavity and the second cavity are connected. The opening side of the first concave cavity portion (21) is flush with the opening side of the second concave cavity portion (22) and connected to the combustion chamber body (1); Along the flow direction of the combustion chamber, the length of the first concave cavity is less than the length of the second concave cavity; Along the height direction perpendicular to the combustion chamber flow direction, the depth of the first cavity is less than the depth of the second cavity; The length of the first cavity is L21 and the depth is D21, then it satisfies: L21 / D21<10; If the length of the second cavity is L22, then it satisfies: L22 > L21 + n D21, 2.1≥n≥1.9; If the depth of the second cavity is D22, then it satisfies: D22>m D21, 1.3≥m≥1.1; The first cavity is a trapezoidal cavity or a semi-circular cavity; If the first cavity is a trapezoidal cavity, then the first cavity portion (21) includes: a first front wall (211), a first bottom wall (212), a first rear wall (213), and a connecting side wall (214). Along the flow direction of the combustion chamber, the first front wall (211) and the first rear wall (213) are respectively provided at the front and rear ends of the first bottom wall (212), and the first front wall (211) and the first rear wall (213) are provided on the same side of the first bottom wall (212); Along the width direction perpendicular to the combustion chamber flow direction, the connecting sidewall (214) is respectively provided on both sides of the first cavity portion (21), and the connecting sidewall (214) is used to connect the first cavity portion (21) and the second cavity portion (22). The second cavity is a trapezoidal cavity or a semi-circular cavity; If the second cavity is a trapezoidal cavity, then the second cavity portion (22) includes: a second front wall (221), a second bottom wall (222), and a second rear wall (223). Along the flow direction of the combustion chamber, the second front wall (221) and the second rear wall (223) are respectively provided at the front and rear ends of the second bottom wall (222), and the second front wall (221) and the second rear wall (223) are provided on the same side of the second bottom wall (222); Along the width direction perpendicular to the combustion chamber flow direction, one side edge of the second cavity portion (22) is connected to the edge of the connecting sidewall (214).

2. The composite concave cavity combustion chamber according to claim 1, characterized in that, If the first cavity is a semi-circular cavity, then the first front wall (211), the first bottom wall (212), and the first rear wall (213) form a continuous semi-circular structure, and the semi-circular radius R21 of the first cavity satisfies D21. <R21<L21; If the second cavity is a semi-circular cavity, then the second front wall (221), the second bottom wall (222), and the second rear wall (223) form a continuous semi-circular structure, and the semi-circular radius R22 of the second cavity satisfies D22. <R22<L22。 3. The composite concave cavity combustion chamber according to claim 2, characterized in that, If the first cavity is a semi-circular cavity, then the semi-circular radius R21 of the first cavity is set to R21 = (2 D21+L21) / 2; If the second cavity is a semi-circular cavity, then the semi-circular radius R22 of the second cavity is set to R22 = (2 D22+L22) / 2.

4. The composite concave cavity combustion chamber according to claim 3, characterized in that, Between the first recessed portion (21) and the second recessed portion (22), the connecting sidewall (214) is vertically disposed; or, The connecting sidewall (214) is inclined between the first cavity portion (21) and the second cavity portion (22); Along the width direction perpendicular to the combustion chamber flow direction, the two connecting sidewalls (214) are inclined in a direction away from each other; or, Between the first cavity portion (21) and the second cavity portion (22), the connecting sidewall (214) is provided in a stepped manner; wherein, the connecting sidewall (214) has at least one stepped portion; In the stepped section, the width of the stepped section is greater than or equal to the height; If the connecting sidewall (214) has multiple stepped sections, then the height of the multiple stepped sections is the same.

5. The composite concave cavity combustion chamber according to claim 4, characterized in that, The first front wall (211), the first bottom wall (212), the first rear wall (213), and the connecting side wall (214) are connected by a rounded transition structure; and / or, The second front wall (221), the second bottom wall (222), the second rear wall (223) and the connecting side wall (214) are respectively connected by a rounded transition structure; The radius R24 of the arc structure satisfies: R24>(D22-D21) / 2.

6. A scramjet engine employing the composite concave cavity combustion chamber as described in any one of claims 1 to 5, characterized in that, include: The intake duct isolation section and the composite concave cavity combustion chamber are connected sequentially from front to back along the direction of the combustion chamber flow; The intake duct isolation section is connected to and fixed to the main body (1) of the composite cavity combustion chamber.

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