An axisymmetric rocket-based combined cycle engine with variable geometry throat

Abstract

The application discloses a shaft-symmetrical rocket-based combined engine with a variable geometry throat, which comprises a combustion chamber and a square flow channel section in communication in an axial direction from front to back; the shell of the combustion chamber is surrounded by a bottom support bottom plate and a top plate, the bottom support bottom plate is horizontal, and the top plate is a semicircular arc shape which is arched upward; the square flow channel section is a cuboid cavity, and an upper variable structure geometry throat and a lower variable structure geometry throat which are consistent with the size of corresponding holes are embedded in the holes at the upper part and the lower part; the upper variable structure geometry throat and the lower variable structure geometry throat are both plate bodies in the shape of an inclined wedge, the tip of the inclined wedge faces the rear, and the inclined surface sides of the inclined wedge both face the cavity; the upper variable structure geometry throat and the lower variable structure geometry throat are used for changing the flow channel geometry throat area in the square flow channel section. The engine is matched with the flight state by reducing the throat area with the increase of the flight Mach number, the engine performance is improved, and the engine thrust vector adjustment can be realized.

Description

Technical Field

[0001] This invention belongs to the field of rocket-based combined cycle engine technology, specifically relating to an axisymmetric rocket-based combined cycle engine with a variable geometry throat. Background Technology

[0002] Rocket-Based Combined Cycle (RBCC) engines are combined propulsion systems that organically integrate a high thrust-to-weight ratio, low specific impulse rocket engine with a low thrust-to-weight ratio, high specific impulse ramjet engine. RBCC engines integrate ejection mode, subsonic combustion mode, scramjet mode, and pure rocket mode, enabling them to self-start, possess a wide flight envelope, and exhibit strong mission adaptability, making them one of the most promising new propulsion devices for future development. The combustion chamber / nozzle is a crucial component of the engine. For air-breathing engines, the combustion chamber must enable fuel to complete injection, atomization, evaporation, mixing, and combustion within a limited space and time in a high-speed airflow, maximizing the conversion of chemical energy into thermal energy. This thermal energy is then converted into kinetic energy to the maximum extent possible through the nozzle, thereby generating thrust. In scramjet mode, to meet the requirements of supersonic combustion, the combustion chamber flow channel needs to maintain an expanding structure; while in ejector and subsonic modes, the combustion chamber flow channel can adopt a convergent-expanding structure to meet the requirements of efficient combustion. Simultaneously, as the flight Mach number increases, the heating ratio within the combustion chamber gradually decreases, and the combustion chamber expansion ratio needs to be reduced accordingly to meet high performance at different flight Mach numbers. Given that multiple modes share a single flow channel, variable structure engine technology is one of the effective ways to ensure optimal performance throughout the entire process. Currently, engines employing variable structure combustion chambers include dual-mode ramjet engines, such as the French WRR (wide-range ramjet) engine, which uses a wide-range variable combustion chamber profile to meet high performance across the entire Mach number range (AIAA Paper 2000-3340, 2000); the PIAF engine, on the other hand, uses the horizontal movement of the outer casing to change the geometry of the combustion chamber to achieve wide-range combustion chamber operation (AIAA Paper 2003-7031, 2003). For RBCC engines, the variable structure scheme is only applied to the intake and exhaust components, and there is little research on the variable structure combustion chamber scheme for axisymmetric RBCC engines. Summary of the Invention

[0003] The purpose of this invention is to provide an axisymmetric rocket-based combined engine with variable geometric throats. As the flight Mach number increases, the two geometric throats rotate symmetrically toward the flow channel center, reducing the throat area to match the flight state and improving engine performance; and it can also realize engine thrust vector adjustment.

[0004] The present invention adopts the following technical solution: an axisymmetric rocket-based combined engine with a variable geometry throat, comprising, from front to back, an axially connected combustion chamber and a square flow channel section;

[0005] The combustion chamber is formed by a bottom support plate and a top plate. The bottom support plate is horizontal and the top plate is an upward-arched semi-circular shape.

[0006] The square flow channel section is a cuboid cavity with holes on both the upper and lower shells that are consistent with the width of the flow channel. The upper and lower holes are fitted with upper and lower variable structure geometric throats that are consistent with the size of the corresponding holes.

[0007] Both the upper and lower variable structure geometric throats are wedge-shaped plates, with the tips of the wedges pointing backward and the inclined surfaces of the wedges facing into the cavity.

[0008] Both the upper and lower variable structure geometric throats can move towards or away from the cavity using their rear tip as a support point, thereby changing the flow channel geometric throat area within the square flow channel segment.

[0009] Furthermore, a central support rocket is axially mounted on the bottom plate of the middle section of the combustion chamber for injecting fuel into the combustion chamber.

[0010] Furthermore, a round-to-square device is axially connected between the combustion chamber and the square flow channel section. The round-to-square device is a cavity structure, with its front section being semi-cylindrical and connected to the combustion chamber, and its rear section being cuboid and connected to the shell of the square flow channel section.

[0011] Furthermore, a tail nozzle is axially connected to the rear of the square flow channel section.

[0012] Furthermore, the intake manifold is axially connected to the front end of the combustion chamber. The intake manifold is a cavity structure with open ends. Its shell is formed by a bottom plate and a top plate. The bottom plate is a horizontal plate that is integrally connected with the bottom support plate. The top plate is an upwardly arched semi-circular arc shape, and its front end is an outwardly flared semi-trumpet shape.

[0013] An air passage center body is axially fitted inside the constriction section of the air intake. The air passage center body is a semi-conical shape with a pointed front end and a horizontal bottom. It is integrally connected with the bottom support plate and forms a semi-annular gas flow channel with an inner diameter that decreases from large to small along the axial direction inside the constriction section of the air intake.

[0014] Furthermore, an air intake cover is provided outside the inner contraction section of the air intake and on the arched side. The air intake cover is semi-cylindrical and its bottom is slidably connected to the bottom plate, allowing it to move back and forth along the bottom plate.

[0015] The inner constriction section shell and the outer cover of the air intake move forward or backward simultaneously. Moving forward reduces the area of ​​the throat of the inner constriction section of the air intake; moving backward increases the area of ​​the throat of the inner constriction section of the air intake.

[0016] Furthermore, the upper and lower variable structure geometric throats are connected to the upper and lower geometric throat actuators, respectively. The upper and lower geometric throat actuators are used to drive the upper and lower variable structure geometric throats to rotate in directions away from and towards the chamber, respectively, with the rear tip as support.

[0017] The beneficial effects of this invention are: 1. Both the upper and lower variable-structure geometric throats can move towards or away from the cavity using their rear tip as a support point, thereby changing the flow channel geometric throat area within the square flow channel section to meet the performance requirements of the RBCC engine at different Mach numbers; they also allow for thrust vector adjustment, providing vertical takeoff and landing (VTOL) or short takeoff and landing (STOVL) capabilities, and providing additional maneuverability for the aircraft in air combat. 2. The method of adjusting the geometric throat is simple and easy to implement. The axisymmetric configuration makes the stress distribution on the engine casing structure more uniform and the gas flow effect better, resulting in more complete fuel combustion in the combustion chamber compared to the binary configuration. 3. By adjusting the geometric throat area and the intake duct contraction ratio, different incoming flow and fuel injection states in the combustion chamber can be matched, achieving stable and efficient combustion. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an axisymmetric rocket-based combined engine with a variable geometry throat.

[0019] Figure 2 A schematic diagram of the connection between the square flow channel section and the nozzle;

[0020] Figure 3 This is a schematic diagram of the circular-to-square device;

[0021] Figure 4 The Ma contour plot for the symmetrical oscillation of the upper and lower variable structure geometric throats;

[0022] Figure 5 The pressure contour diagram is shown when the upper and lower variable structure geometric throats oscillate symmetrically.

[0023] Figure 6 The Ma contour plot is shown when the upper variable structure's geometric throat oscillates.

[0024] Figure 7 This is a pressure cloud diagram of the upper variable structure's geometric throat swinging.

[0025] The components are: 1. Inlet center body; 2. Inlet outer cover; 3. Inlet inner constriction section; 4. Central support plate rocket; 5. Circular to cuboid; 6. Upper geometric throat actuator; 7. Upper variable structure geometric throat; 8. Tail nozzle; 9. Lower geometric throat actuator; 10. Lower variable structure geometric throat; 11. Combustion chamber; 12. Bottom support plate; 13. Square flow channel. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] This invention discloses an axisymmetric rocket-based combined engine with a variable geometry throat, such as... Figure 1 and 2 As shown, from front to back, it includes a combustion chamber 11 and a square flow channel section 13 that are connected in the axial direction; the combustion chamber 11 has a shell that is surrounded by a bottom support plate 12 and a top plate. The bottom support plate 12 is horizontal and the top plate is an upwardly arched semi-circular arc shape.

[0028] The square flow channel section 13 is a cuboid cavity with holes 13-1 on both the upper and lower shells that are consistent with the width of the flow channel. The upper and lower holes 13-1 are fitted with upper variable structure geometric throat 7 and lower variable structure geometric throat 10 that are consistent with the size of the corresponding holes.

[0029] Both the upper variable structure geometric throat 7 and the lower variable structure geometric throat 10 are wedge-shaped plates, with the tips of the wedges facing backward and the inclined surfaces of the wedges facing into the cavity.

[0030] Both the upper variable structure geometric throat 7 and the lower variable structure geometric throat 10 can move towards or away from the cavity using their rear tip as a support point, thereby changing the flow channel geometric throat area within the square flow channel section 13.

[0031] A central support rocket 4 is axially mounted on the bottom plate of the middle section of the combustion chamber 11 for injecting fuel into the combustion chamber 11. This significantly improves fuel penetration, achieves stable and efficient combustion, and enhances combustion organization and engine performance in large-scale structures.

[0032] like Figure 3 As shown, a round-to-square device 5 is axially connected between the combustion chamber 11 and the square flow channel section 13. The round-to-square device 5 is a cavity structure, with its front section being semi-cylindrical and connected to the combustion chamber 11, and its rear section being cuboid and connected to the shell of the square flow channel section 13.

[0033] A tail nozzle 8 is axially connected to the rear of the square flow channel section 13.

[0034] The intake manifold 3 is axially connected to the front end of the combustion chamber 11. The intake manifold 3 is a cavity structure with open ends. Its shell is surrounded by a bottom plate and a top plate. Its bottom plate is a horizontal plate and is integrally connected with the bottom support plate 12. Its top plate is an upwardly arched semi-circular arc shape, and its front end is an outwardly flared semi-horn.

[0035] An air duct center body 1 is axially fitted inside the constriction section 3 of the intake duct. The air duct center body 1 is a semi-conical shape with a pointed front end and a semi-cylindrical shape with an upwardly convex rear end. The bottom of the air duct center body 1 is horizontal and is integrally connected to the bottom support plate 12. A semi-annular gas flow channel with an inner diameter that decreases from large to small and then becomes constant is formed along the axial direction inside the constriction section 3 of the intake duct. A flow channel that acts as an isolation section between the semi-cylindrical shape and the outer shell of the combustion chamber 11 is formed to match the incoming flow and the combustion gas. The rear end of the air duct center body 1 is located at approximately one-third of its length inside the combustion chamber 11. A central support rocket 4 is axially arranged inside the combustion chamber 11, located at the rear end of the air duct center body 1. Fuel is injected into the combustion chamber 11 from its rear end and mixed with the incoming flow. The fuel injection by the central support rocket 4 can significantly improve fuel penetration, improve combustion organization, and enhance engine performance.

[0036] Outside the inner contraction section 3 of the air intake duct, and on the arched side, there is an outer cover 2 for the air intake duct. The outer cover 2 is semi-cylindrical, and its bottom is slidably connected to the bottom plate, and can move back and forth along the bottom plate.

[0037] The inner constriction section 3 of the intake duct and the outer casing 2 of the intake duct move forward or backward simultaneously. Moving forward reduces the area of ​​the throat of the inner constriction section 3; moving backward increases the area of ​​the throat. An intake throat adjusting block actuator is located at the rear end of the outer casing 2, used to push the outer casing 2 forward and backward. The front end of each outer casing actuator is connected to the outer casing of the intake duct via an actuator block, and the rear end is connected to the outer casing of the combustion chamber 11, used to push the outer casing of the intake duct 1 to move forward and backward along the base plate. The actuator block 1 is cubic in shape and serves a connecting function.

[0038] The upper variable-structure geometric throat 7 and the lower variable-structure geometric throat 10 are connected to the upper geometric throat actuator 6 and the lower geometric throat actuator 9, respectively. The upper geometric throat actuator 6 and the lower geometric throat actuator 9 are used to drive the upper variable-structure geometric throat 7 and the lower variable-structure geometric throat 10 to rotate in directions away from and towards the chamber, respectively, with their rear end tips as support. Both the upper geometric throat actuator 6 and the lower geometric throat actuator 9 include an outer cylinder, and a piston rod is coaxially arranged inside the outer cylinder. The piston rod is hydraulically controlled to push or pull the upper variable-structure geometric throat 7 and the lower variable-structure geometric throat 10.

[0039] To verify the performance of an axisymmetric rocket-based combined engine with a variable geometry throat according to the present invention, the following simulation was performed:

[0040] Operating Condition 1:

[0041] In ejector mode, the adjustable inlet front body 1 is at its maximum opening, and the upper variable structure geometric throat 7 and the lower variable structure geometric throat 10 at the rear rotate into the flow channel, forming a geometric throat in the combustion chamber, which obstructs the airflow and optimizes the performance of ejector mode. In sub-fuel mode, as the flight speed increases, the inlet throat gradually shrinks, and the upper variable structure geometric throat 7 and the lower variable structure geometric throat 10 gradually rotate symmetrically towards the center of the flow channel to change the geometric throat area, thereby optimizing engine performance.

[0042] Simulation calculations were performed on a high Mach number geometric throat. The 3D model was created using UG, and the mesh was a hexahedral unstructured mesh generated by FluentMeshing. The calculation software was Fluent. The simulated incoming flow had a Mach number of 6 and a height of 24 km. The upper variable-structure geometric throat 7 and the lower variable-structure geometric throat 10 symmetrically oscillated into the cavity, with an oscillation angle of 17.5°. Figure 4 and 5 As shown in the cloud diagram, the upper variable-structure geometric throat 7 and the lower variable-structure geometric throat 10 symmetrically swing into the chamber, forming a geometric throat in the rear section of the combustion chamber 11 and in front of the tail nozzle. The geometric throat becomes smaller. Under the congestion effect of the geometric throat, the airflow undergoes a contraction-expansion surface, completing an acceleration process from subsonic to sonic to supersonic speeds, and then accelerates towards the tail nozzle 8 at the expansion surface of the geometric throat.

[0043] Operating Condition 2:

[0044] Simulations were performed on vector control of high Mach number geometric throats. The mesh was a hexahedral unstructured mesh generated by FluentMeshing, and the calculation software was Fluent. The simulated incoming flow had a Mach number of 6 and a height of 24 km. The upper variable-structure geometric throat 7 oscillated downwards by 17.5°, while the lower variable-structure geometric throat 10 remained stationary with an oscillation angle of 0°. Figure 6 and 7 As shown in the cloud map, only the upper variable geometry throat 7 swings downwards, while the lower variable geometry throat 10 does not swing, resulting in combustion chamber congestion. Compared to the symmetrical swinging case described above, the flow field exhibits weaker uniformity. The Mach number cloud map shows that high Mach number regions are concentrated near the upper variable geometry throat 7, while the Mach number is lower near the lower variable geometry throat 10, indicating successful thrust vector control. Changes in thrust vector not only provide vertical takeoff and landing (VTOL) or short takeoff and landing (STOVL) capabilities but also offer additional maneuverability during air combat.

[0045] Thrust statistics were performed for the two operating conditions calculated above, as shown in Table 1:

[0046] Table 1 Thrust Statistics

[0047]

[0048] As can be seen from the thrust statistics in Table 1, in operating condition 1, with the upper variable structure geometric throat 7 and the lower variable structure geometric throat 10 symmetrically swinging, the thrust is only -1.8N along the engine axis, which is negligible compared to the axial force of 7688N. In operating condition 2, only the upper variable structure geometric throat 7 swings, while the lower variable structure geometric throat 10 swings at 0°. The engine has not only an axial thrust of 2960N but also a vertical thrust of 1528N, resulting in a combined thrust of 3331N and a thrust vector angle of 76°. From the above data, it can be seen that by setting the upper variable structure geometric throat 7 and the lower variable structure geometric throat 10, and adjusting the swing of the variable structure geometric throat 7 and the lower variable structure geometric throat 10 toward the inner chamber, the engine thrust vector can be controlled.

Claims

1. An axisymmetric rocket-based combined engine with a variable geometry throat, characterized in that, From front to back, it includes an axially connected combustion chamber (11) and a square flow channel section (13). The combustion chamber (11) is formed by a bottom support plate (12) and a top plate. The bottom support plate (12) is horizontal and the top plate is an upwardly arched semi-circular arc shape. The square flow channel section (13) is a cuboid cavity with holes (13-1) on both the upper and lower shells that are consistent with the width of the flow channel. The upper and lower holes (13-1) are fitted with upper variable structure geometric throats (7) and lower variable structure geometric throats (10) that are consistent with the size of the corresponding holes. The upper variable structure geometric throat (7) and the lower variable structure geometric throat (10) are both wedge-shaped plates, with the tip of the wedge facing backward and the inclined side of the wedge facing into the cavity. Both the upper variable structure geometric throat (7) and the lower variable structure geometric throat (10) can move towards or away from the cavity with their rear tip as a support point, in order to change the flow channel geometric throat area in the square flow channel section (13). A round-to-square device (5) is axially connected between the combustion chamber (11) and the square flow channel section (13). The round-to-square device (5) is a cavity structure. Its front section is semi-cylindrical and connected to the combustion chamber (11). Its rear section is cuboid and connected to the shell of the square flow channel section (13).

2. The axisymmetric rocket-based combined engine with a variable geometry throat as described in claim 1, characterized in that, A central support plate rocket (4) is provided axially on the bottom plate of the middle section of the combustion chamber (11) for injecting fuel into the combustion chamber (11).

3. An axisymmetric rocket-based combined engine with a variable geometry throat as described in claim 2, characterized in that, A tail nozzle (8) is axially connected to the rear of the square flow channel section (13).

4. An axisymmetric rocket-based combined engine with a variable geometry throat as described in claim 3, characterized in that, The front end of the combustion chamber (11) is axially connected to the inner constriction section (3) of the intake duct. The inner constriction section (3) of the intake duct is a cavity structure with open ends. Its shell is surrounded by a bottom plate and a top plate. Its bottom plate is a horizontal plate and is integrally connected with the bottom support plate (12). Its top plate is an upwardly arched semi-circular arc shape, and its front end is an outwardly flared semi-trumpet shape. An air passage center body (1) is axially fitted inside the constriction section (3) of the air intake passage. The air passage center body (1) is a semi-conical shape with a pointed front end and a horizontal bottom. It is integrally connected with the bottom support plate (12) and forms a semi-circular gas flow channel with an inner diameter that decreases from large to small in the axial direction inside the constriction section (3) of the air intake passage.

5. An axisymmetric rocket-based combined engine with a variable geometry throat as described in claim 4, characterized in that, Outside the inner contraction section (3) of the air intake duct, and on the arched side, an air intake duct cover (2) is provided. The air intake duct cover (2) is semi-cylindrical, and its bottom is slidably connected to the bottom plate, and can move back and forth along the bottom plate. The air intake duct cover (2) moves forward or backward. Moving forward reduces the area of ​​the throat of the constriction section (3) inside the air intake duct; moving backward increases the area of ​​the throat of the constriction section (3) inside the air intake duct.

6. An axisymmetric rocket-based combined engine with a variable geometry throat as described in claim 5, characterized in that, The upper variable structure geometric throat (7) and the lower variable structure geometric throat (10) are connected to the upper geometric throat actuator (6) and the lower geometric throat actuator (9) respectively. The upper geometric throat actuator (6) and the lower geometric throat actuator (9) are used to drive the upper variable structure geometric throat (7) and the lower variable structure geometric throat (10) to rotate in the direction away from the chamber and towards the chamber with the rear tip as support.

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