A design method for a variable geometry asymmetric nozzle coupled with a rocket thrust chamber

Abstract

The present invention discloses a method for designing a variable geometry asymmetric nozzle coupled with a rocket thrust chamber, including a variable geometry three-dimensional asymmetric nozzle designed based on streamline tracing technology; a three-dimensional model of the rocket thrust chamber designed based on the characteristic line method; and a coupling method design for the rocket thrust chamber and the three-dimensional asymmetric nozzle. The present invention installs three rocket thrust chambers on the upper expansion surface of the three-dimensional asymmetric nozzle. The high-energy jet provided by the rocket thrust chambers improves the thrust performance of the three-dimensional asymmetric nozzle at low Mach numbers. The effective combination of the rocket thrust chambers and the asymmetric nozzle ensures high-performance operation of the asymmetric nozzle over a wide speed range, better meeting the use requirements of engines and aircraft.

Description

Technical Field

[0001] The present invention relates to the technical field of aero-engine exhaust systems, and in particular to a design method for a variable-geometry asymmetric nozzle coupled to a rocket thrust chamber. Background Art

[0002] Hypersonic technology is at the forefront of 21st-century aerospace technology, possessing significant military and economic value. The propulsion system is a key technology for achieving hypersonic flight, and the scramjet engine is the optimal propulsion option for achieving this. The asymmetric nozzle is a crucial component of the exhaust system's thrust generation and a crucial factor in determining the overall propulsion system's efficiency.

[0003] Although scramjet engines can meet the power requirements of hypersonic vehicles, they operate only within a specific Mach number range and cannot independently complete the full flight envelope, from takeoff to hypersonic flight. Therefore, hypersonic vehicles require additional propulsion systems to accommodate an extremely wide range of flight Mach numbers. Furthermore, hypersonic propulsion systems have a wide operating range, with an operating pressure drop ratio ranging from 2 to 600. To ensure aerodynamic performance within this envelope, the exhaust system design point is typically set at cruise. However, at low Mach numbers, due to the low operating pressure drop ratio, the exhaust system will overexpand, generating drag on the vehicle's rear body, significantly affecting the vehicle's acceleration. Furthermore, the lower pressure distribution at the rear body generates negative lift and a nose-up moment, which affects the vehicle's stability and balance. Ensuring high-performance asymmetric nozzle operation over this wide range is a pressing issue.

[0004] Regarding the starting problem of scramjet engines and the performance of asymmetric nozzles at low Mach numbers, researchers have mainly conducted relevant research on the combination scheme of rocket engines and scramjet engines, the feasibility of secondary flow injection methods and their impact on the flow field. However, no scholar has directly used the thrust chamber of the rocket engine as the source of secondary flow and used the high-energy jet generated by the thrust chamber of the rocket engine to improve the performance of the asymmetric nozzle at low Mach numbers.

[0005] Therefore, it is necessary to propose a new design method to effectively combine the rocket engine thrust chamber and the asymmetric nozzle, so that the asymmetric nozzle coupled with the thrust chamber is suitable for a wide range of flight Mach numbers and obtains relatively good aerodynamic performance in a wide speed range. Summary of the Invention

[0006] To solve the above problems, the present invention proposes a variable geometry asymmetric nozzle design method coupled with a rocket thrust chamber. The high-energy jet provided by the rocket thrust chamber improves the thrust performance of the three-dimensional asymmetric nozzle at low Mach numbers. Through the effective combination of the rocket thrust chamber and the asymmetric nozzle, the high-performance operation of the asymmetric nozzle in a wide speed range is guaranteed, which better meets the use requirements of the engine and aircraft.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for designing a variable geometry asymmetric nozzle coupled to a rocket thrust chamber. The variable geometry asymmetric nozzle coupled to the rocket thrust chamber comprises a variable geometry three-dimensional asymmetric nozzle and three rocket thrust chambers mounted on the upper expansion surface of the variable geometry three-dimensional asymmetric nozzle. High-energy jets from the three rocket thrust chambers are introduced into the variable geometry three-dimensional asymmetric nozzle to change its internal flow field structure, introduce shock waves, and improve the pressure distribution along its wall surface, thereby increasing the thrust generated and improving thrust performance.

[0009] The design method comprises the following steps:

[0010] Step S1, designing a three-dimensional model of the variable geometry three-dimensional asymmetric nozzle, including: a throat adjustment section, a streamline tracking section, and an outlet adjustment section;

[0011] Step S2, designing three-dimensional models of the rocket thrust chambers;

[0012] Step S3: Design a coupling method for the variable geometry three-dimensional asymmetric nozzle and the three rocket thrust chambers. The coupling method includes a coupling mode between each rocket thrust chamber and the variable geometry three-dimensional asymmetric nozzle and a layout plan for the three rocket thrust chambers.

[0013] Preferably, the step S1 specifically includes:

[0014] Step S101: Design a throat adjustment section: The inlet shape of the throat adjustment section is a rectangle in the upper half and a superellipse in the lower half. The throat height of the throat adjustment section is determined according to the flow rate of the variable geometry three-dimensional asymmetric nozzle. An adjustment plate is installed on the upper wall of the throat adjustment section, and the throat area of ​​the throat adjustment section is adjusted by rotating the adjustment plate. The side wall of the throat adjustment section is directly stretched by its inlet profile without lateral expansion.

[0015] Step S102: Designing a streamline tracking section: Based on the axisymmetric maximum thrust reference flow field, a bidirectional streamline tracking technique is used to obtain the upper expansion surface and sidewall surface of the streamline tracking section. The inlet shape of the streamline tracking section is determined based on the throat adjustment section, and its outlet shape is rectangular. Streamlines are then tracked along the flow direction using the inlet shape and against the flow direction using the outlet shape to obtain multiple streamlines. The two streamlines obtained on the same path, one obtained by tracing the streamlines along the flow direction and the other obtained by tracing the streamlines against the flow direction, are weighted averaged to ensure a smooth transition of the generated three-dimensional nozzle profile.

[0016] Step S103, designing the outlet adjustment section: determining the inlet shape of the outlet adjustment section based on the outlet shape of the streamline tracing section, wherein the upper wall and side wall of the outlet adjustment section are obtained by directly stretching the inlet shape, and the lower wall is a movable adjustment plate, and the outlet area of ​​the variable geometry three-dimensional asymmetric nozzle can be adjusted by rotating the movable adjustment plate.

[0017] Preferably, the step S2 specifically includes:

[0018] Step S201: Obtain the two-dimensional profile of each rocket thrust chamber based on the characteristic line method;

[0019] Step S202: Rotate the two-dimensional profile of each rocket thrust chamber around its central axis to obtain a three-dimensional axisymmetric profile of each rocket thrust chamber.

[0020] Preferably, the step S3 specifically includes:

[0021] Step S301: Design a coupling method for each rocket thrust chamber and the variable geometry three-dimensional asymmetric nozzle: the rocket thrust chamber is installed on the upper expansion surface of the variable geometry three-dimensional asymmetric nozzle. When coupling each rocket thrust chamber, its outlet is placed on the upper expansion surface of the variable geometry three-dimensional asymmetric nozzle. Then, the wall of the rocket thrust chamber is stretched parallel to the outlet direction of the rocket thrust chamber so that it intersects with the upper expansion surface of the variable geometry three-dimensional asymmetric nozzle. Then, the wall of the rocket thrust chamber is beveled, and the beveled cross section serves as a new outlet cross section for the rocket thrust chamber jet to enter the variable geometry three-dimensional asymmetric nozzle, thereby completing the coupling of each rocket thrust chamber and the variable geometry three-dimensional asymmetric nozzle.

[0022] Step S302: design three layout schemes of the rocket thrust chambers: an I-type layout scheme, a V-type layout scheme, and an A-type layout scheme.

[0023] Type I layout scheme, the three rocket thrust chambers are installed at equal intervals in the middle of the upper expansion surface of the streamline tracking section, and the spacing is the maximum spacing that can be achieved under the premise of ensuring that the outer wall surfaces of the three rocket thrust chambers do not interfere with the profile of the variable geometry three-dimensional asymmetric nozzle;

[0024] In a V-shaped layout, one of the rocket thrust chambers is installed at the center of the upper expansion surface of the streamline tracking section, one-quarter of the distance from the streamline tracking section inlet; the other two rocket thrust chambers are installed on both sides of the upper expansion surface of the streamline tracking section, three-quarters of the distance from the streamline tracking section inlet, and are symmetrical to the center;

[0025] In the type A layout scheme, two of the rocket thrust chambers are installed on both sides of the upper expansion surface of the streamline tracking section at a position one-quarter of the distance from the inlet of the streamline tracking section, and are centrally symmetrical; the other two rocket thrust chambers are installed at the center of the upper expansion surface of the streamline tracking section at a position one-quarter of the distance from the inlet of the streamline tracking section.

[0026] Preferably, the throat of the variable geometry three-dimensional asymmetric nozzle is located in the throat adjustment section, and the calculation formula of the throat area is:

[0027]

[0028] Wherein, T* and p* are the total temperature and total pressure of the gas at the inlet of the variable geometry three-dimensional asymmetric nozzle, γ is the specific heat ratio of the gas, R is the gas constant, q(Ma) is the flow function, and the value of q(Ma) at the throat section is taken. A is the throat area of ​​the variable geometry three-dimensional asymmetric nozzle to be obtained. represents the flow rate of the gas flowing into the variable geometry three-dimensional asymmetric nozzle.

[0029] Compared with the prior art, the present invention has the following technical effects:

[0030] (1) The present invention couples the thrust chamber of a rocket engine with an asymmetric nozzle, thereby effectively reducing the overexpansion of the asymmetric nozzle at low Mach numbers, increasing the thrust generated by the asymmetric nozzle, and improving the thrust performance of the asymmetric nozzle;

[0031] (2) The thrust generated by the asymmetric nozzle coupled with the rocket thrust chamber designed in the present invention under the same working conditions is greater than the sum of the thrusts generated by the nozzle working alone and the rocket thrust chamber working alone, resulting in a "1+1>2" effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic structural diagram of a variable geometry asymmetric nozzle model coupled to a rocket thrust chamber according to the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of the variable geometry asymmetric nozzle model used in the present invention;

[0034] Figure 3 This is a schematic diagram of the structure of the rocket thrust chamber model used in the present invention, wherein: Figure 3 a is a two-dimensional profile diagram of the rocket thrust chamber. Figure 3 b is a schematic diagram of the three-dimensional model of the rocket thrust chamber;

[0035] Figure 4 Schematic diagram of the coupling mode of the rocket thrust chamber and the asymmetric nozzle at the center symmetry plane of the variable geometry asymmetric nozzle coupled to the rocket thrust chamber of the present invention;

[0036] Figure 5 Schematic diagrams of three layout schemes of variable geometry asymmetric nozzles coupled to rocket thrust chambers according to the present invention, including, from left to right, an I-type layout scheme, a V-type layout scheme, and an A-type layout scheme;

[0037] Figure 6 This is the flow field Mach number cloud diagram under the Ma6.0 working condition of the variable geometry asymmetric nozzle coupled with the rocket thrust chamber of the present invention, where: Figure 6 a is the Mach number cloud diagram of the flow field under Ma6.0 working condition when the rocket thrust chamber is not coupled. Figure 6 b is the Mach number cloud diagram of the flow field under Ma6.0 condition for the I-type layout scheme. Figure 6 c is the Mach number cloud diagram of the flow field under Ma6.0 working condition for the V-type layout scheme, Figure 6 d is the Mach number cloud diagram of the flow field under Ma6.0 condition for the A-type layout scheme;

[0038] Figure 7 This is the thrust gain diagram after the asymmetric nozzle is coupled to the rocket thrust chamber of the present invention. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0040] The present invention provides a design method for a variable geometry asymmetric nozzle coupled to a rocket thrust chamber, such as Figure 1 As shown, it mainly includes the variable geometry three-dimensional asymmetric nozzle 1 and three rocket thrust chambers 2 installed on the expansion surface of the variable geometry three-dimensional asymmetric nozzle 1. By introducing high-energy jets of the three rocket thrust chambers 2 into the variable geometry three-dimensional asymmetric nozzle 1, its internal flow field structure is changed, shock waves are introduced, and the pressure distribution along its wall is improved, thereby increasing the thrust generated and improving the thrust performance;

[0041] The design method comprises the following steps:

[0042] Step S1, designing a three-dimensional model of the variable geometry three-dimensional asymmetric nozzle 1, including: a throat adjustment section 3, a streamline tracking section 4 and an outlet adjustment section 5;

[0043] Step S2, designing three-dimensional models of the rocket thrust chambers 2;

[0044] Step S3, designing a coupling method for the variable geometry three-dimensional asymmetric nozzle 1 and the three rocket thrust chambers 2, the coupling method including the coupling mode between each rocket thrust chamber 2 and the variable geometry three-dimensional asymmetric nozzle 1 and the layout scheme of the three rocket thrust chambers 2.

[0045] Further, such as Figure 2 Said step S1 specifically includes:

[0046] Step S101, designing the throat adjustment section 3: The inlet shape of the throat adjustment section 3 is a rectangle in the upper half and a superellipse in the lower half. The throat height of the throat adjustment section 3 is determined according to the flow rate of the variable geometry three-dimensional asymmetric nozzle 1. A regulating plate is installed on the upper wall of the throat adjustment section 3, and the throat area of ​​the throat adjustment section 3 is adjusted by rotating the regulating plate. The dotted line in the figure is the geometric throat formed when the regulating plate rotates downward under low Mach number conditions; the side wall surface of the throat adjustment section 3 is obtained by directly stretching its inlet profile without lateral expansion;

[0047] Step S102, designing the streamline tracking section 4: Based on the axisymmetric maximum thrust reference flow field, the upper expansion surface and sidewall surface of the streamline tracking section 4 are obtained using the bidirectional streamline tracking technology; the inlet shape of the streamline tracking section 4 is determined according to the throat adjustment section 3, and its outlet shape is rectangular. Then, streamlines are tracked along the flow direction based on the inlet shape and against the flow direction based on the outlet shape to obtain multiple streamlines. The two streamlines obtained on the same path, one obtained by tracing the streamlines along the flow direction and the other obtained by tracing the streamlines against the flow direction, are weighted averaged to ensure a smooth transition of the generated three-dimensional nozzle profile;

[0048] Step S103, designing the outlet adjustment section 5: Determine the inlet shape of the outlet adjustment section 5 based on the outlet shape of the streamline tracking section 4. The upper wall and side wall surfaces of the outlet adjustment section 5 are obtained by directly stretching its inlet shape. The lower wall surface is a movable adjustment plate. The outlet area of ​​the variable geometry three-dimensional asymmetric nozzle 1 is adjusted by rotating the movable adjustment plate. The dotted line in the figure shows the case where the movable adjustment plate is rotated to the horizontal position under low Mach number conditions.

[0049] Further, such as Figure 3 As shown, the step S2 specifically includes:

[0050] Step S201: Obtain the two-dimensional profile of each rocket thrust chamber 2 based on the characteristic line method;

[0051] Step S202: Rotate the two-dimensional profile of each rocket thrust chamber 2 around its central axis to obtain a three-dimensional axisymmetric profile of each rocket thrust chamber 2.

[0052] Furthermore, the step S3 specifically includes:

[0053] Step S301: Design the coupling mode between each rocket thrust chamber 2 and the variable geometry three-dimensional asymmetric nozzle 1, such as Figure 4 As shown: the rocket thrust chamber 2 is installed on the upper expansion surface of the variable geometry three-dimensional asymmetric nozzle 1. When coupling each rocket thrust chamber 2, its outlet is placed on the upper expansion surface of the variable geometry three-dimensional asymmetric nozzle 1, and then the wall of the rocket thrust chamber 2 is stretched parallel to the outlet direction of the rocket thrust chamber 2 so that it intersects with the upper expansion surface of the variable geometry three-dimensional asymmetric nozzle 1, and then the wall of the rocket thrust chamber 2 is beveled. The dotted line in the figure is the wall of the rocket thrust chamber 2 discarded after beveling, and the beveled section serves as the new outlet section of the rocket thrust chamber 2 jet entering the variable geometry three-dimensional asymmetric nozzle 1, thereby completing the coupling of each rocket thrust chamber 2 and the variable geometry three-dimensional asymmetric nozzle 1;

[0054] Step S302: Design three layout schemes of the rocket thrust chamber 2: I-type layout scheme, V-type layout scheme and A-type layout scheme, such as Figure 5 shown.

[0055] Type I layout scheme, the three rocket thrust chambers 2 are installed at equal intervals in the middle of the upper expansion surface of the streamline tracking section 4, and the spacing is the maximum spacing that can be achieved under the premise of ensuring that the outer wall surfaces of the three rocket thrust chambers 2 do not interfere with the profile of the variable geometry three-dimensional asymmetric nozzle 1;

[0056] In a V-shaped layout, one of the rocket thrust chambers 2 is installed at the center of the upper expansion surface of the streamline tracking section 4, one-quarter of the distance from the inlet of the streamline tracking section 4; the other two rocket thrust chambers 2 are installed on both sides of the upper expansion surface of the streamline tracking section 4, three-quarters of the distance from the inlet of the streamline tracking section 4, and are symmetrical to the center.

[0057] In the type A layout scheme, two of the rocket thrust chambers 2 are installed on both sides of the upper expansion surface of the streamline tracking section 4 at a position one-quarter of the distance from the inlet of the streamline tracking section 4, and are centrally symmetrical; the other two rocket thrust chambers 2 are installed at the center of the upper expansion surface of the streamline tracking section 4 at a position one-quarter of the distance from the inlet of the streamline tracking section 4.

[0058] Furthermore, the throat of the variable geometry three-dimensional asymmetric nozzle 1 is located in the throat adjustment section 3, and the calculation formula of the throat area is:

[0059]

[0060] Wherein, T* and p* are the total temperature and total pressure of the inlet gas of the variable geometry three-dimensional asymmetric nozzle 1, γ is the specific heat ratio of the gas, R is the gas constant, q(Ma) is the flow function, the value of q(Ma) is 1 at the throat section, and A is the throat area of ​​the variable geometry three-dimensional asymmetric nozzle 1. It represents the flow rate of the gas flowing into the variable geometry three-dimensional asymmetric nozzle 1.

[0061] Example

[0062] Based on the overall requirements, the variable geometry asymmetric nozzle design method for coupled rocket thrust chambers described in this invention was applied to perform three-dimensional numerical simulations at typical operating points within the full flight envelope, and the relevant performance parameters were summarized.

[0063] The total length of the asymmetric nozzle is 2.0m, the inlet shape is a rectangle in the upper half, a superellipse in the lower half, and the outlet is a rectangle. According to the calculation conditions, under the Ma2.0 working condition, the nozzle flow requirements are met and the geometric throat is set by rotating the regulating plate; under other working conditions, the incoming flow is supersonic, and the regulating plate is adjusted to the horizontal and remains unchanged. The lower regulating plate is adjusted to the horizontal under the Ma2.0 working condition to approach the ideal expansion ratio of one-dimensional isentropic flow, and the inlet and outlet areas are adjusted to 3.0 under other working conditions and remain unchanged. The inlet and outlet of the rocket thrust chamber are both circular, with the rocket thrust chamber throat as the inlet, the inlet Mach number is 1.0, the inlet total temperature is 1829K, the inlet total pressure is the chamber pressure (2MPa), the outlet Mach number is 2.0, and the flow rate is 10% of the mainstream flow rate of the nozzle at the design point. The rocket thrust chamber is horizontally installed on the upper expansion surface of the asymmetric nozzle, and the coupling method and layout scheme described in the present invention are applied.

[0064] Figure 6Shown are Mach number cloud plots of the flow field near the central symmetry plane under Mach 6.0 conditions for three coupled thrust chamber layouts. After coupling the thrust chamber, the thrust chamber jet enters the nozzle main flow at supersonic speed, continues to expand and accelerate within the nozzle main flow, and forms a barrel-shaped shock wave at the leading edge of the thrust chamber exit. This annular barrel shock wave deflects upward to balance the pressure of the thrust chamber jet and the nozzle main flow. Due to the mutual interference between the thrust chamber jet and the nozzle main flow, a gradually developing bow shock wave forms upstream of the thrust chamber. This bow shock wave is also annular in shape. The nozzle main flow passing through the bow shock wave is decelerated and pressurized, forming an annular low-speed mainstream region between the barrel shock and the bow shock. This low-speed mainstream region gradually develops along the normal direction of the bow shock surface, increasing in area along the flow direction. Within this region, the nozzle main flow expands and accelerates along the flow direction. After entering the main nozzle stream, the rocket thrust chamber jet accelerates along the streamline while continuing to expand in the normal direction, generating normal velocity. After reaching a certain penetration depth, it decelerates and increases in pressure under the influence of the barrel shock wave. Then, under the influence of the main nozzle stream, it changes direction, forming a high-speed jet region that originates and gradually develops at the leading edge of the rocket thrust chamber exit. Shear layers form between the nozzle main stream, which is influenced by the bow shock wave, and the rocket thrust chamber jet, which is influenced by the barrel shock wave. At the trailing edge of the rocket thrust chamber, the jet flows into the main nozzle at a certain angle, forming a localized low-pressure area downstream. Subsequently, the nearby main nozzle stream is injected, forming a shear layer between the jet and the jet, and the jet continues to expand and accelerate along the main nozzle's upper expansion surface. At the inlet section of the outlet regulating section, the rotation of the lower regulating plate generates an expansion wave, which intersects the bow shock wave near the main nozzle exit section. After the layout scheme was changed, the main flow field structure formed by the interaction between the rocket thrust chamber jet and the nozzle mainstream is relatively similar. The barrel-shaped shock wave surface, bow-shaped shock wave surface, low-speed mainstream area and other phenomena can still be clearly captured in the flow field Mach number cloud map, but the influence area of ​​the rocket thrust chamber jet on the nozzle mainstream and the development of the corresponding shock wave surface have changed.

[0065] Figure 7 The thrust gain of an asymmetric nozzle coupled to a rocket thrust chamber under typical operating conditions is demonstrated. The results show that all three layouts can increase the asymmetric nozzle's thrust to varying degrees. Under the same operating conditions, the thrust generated by the asymmetric nozzle coupled to the rocket thrust chamber is greater than the sum of the thrust generated by the nozzle and the rocket thrust chamber operating alone, achieving a "1+1>2" effect. This demonstrates that the design method described in this invention can effectively improve the thrust performance of an asymmetric nozzle at low Mach numbers and increase the thrust generated by the asymmetric nozzle across the entire envelope.

[0066] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A design method for a variable geometry asymmetric nozzle coupled to a rocket thrust chamber, characterized in that: The variable geometry asymmetric nozzle coupled with the rocket thrust chamber comprises a variable geometry three-dimensional asymmetric nozzle (1) and three rocket thrust chambers (2) mounted on the expansion surface of the variable geometry three-dimensional asymmetric nozzle (1). By introducing high-energy jets of the three rocket thrust chambers (2) into the variable geometry three-dimensional asymmetric nozzle (1), the internal flow field structure thereof is changed, shock waves are introduced, and the pressure distribution along the wall surface thereof is improved, thereby increasing the thrust generated and improving the thrust performance. The design method comprises the following steps: Step S1, designing a three-dimensional model of the variable geometry three-dimensional asymmetric nozzle (1), including: a throat adjustment section (3), a streamline tracking section (4) and an outlet adjustment section (5); Step S2, designing three-dimensional models of the rocket thrust chambers (2); Step S3, designing a coupling method between the variable geometry three-dimensional asymmetric nozzle (1) and the three rocket thrust chambers (2), wherein the coupling method includes a coupling mode between each rocket thrust chamber (2) and the variable geometry three-dimensional asymmetric nozzle (1) and a layout scheme of the three rocket thrust chambers (2); Step S3 specifically includes: Step S301, designing a coupling method for each of the rocket thrust chambers (2) and the variable geometry three-dimensional asymmetric nozzle (1): the rocket thrust chamber (2) is installed on the upper expansion surface of the variable geometry three-dimensional asymmetric nozzle (1); when coupling each of the rocket thrust chambers (2), its outlet is placed on the upper expansion surface of the variable geometry three-dimensional asymmetric nozzle (1); then, the wall of the rocket thrust chamber (2) is stretched parallel to the outlet direction of the rocket thrust chamber (2) so that it intersects with the upper expansion surface of the variable geometry three-dimensional asymmetric nozzle (1); then, the wall of the rocket thrust chamber (2) is beveled, and the beveled section is used as a new outlet section for the jet of the rocket thrust chamber (2) to enter the variable geometry three-dimensional asymmetric nozzle (1), thereby completing the coupling of each of the rocket thrust chambers (2) and the variable geometry three-dimensional asymmetric nozzle (1); Step S302, designing three layout schemes of the rocket thrust chambers (2): an I-type layout scheme, a V-type layout scheme, and an A-type layout scheme; Type I layout scheme, the three rocket thrust chambers (2) are installed at equal intervals in the middle of the upper expansion surface of the streamline tracking section (4), and the spacing is the maximum spacing that can be achieved under the premise of ensuring that the outer wall surfaces of the three rocket thrust chambers (2) do not interfere with the profile of the variable geometry three-dimensional asymmetric nozzle (1); In a V-shaped layout scheme, one rocket thrust chamber (2) is installed at the center of a position where the upper expansion surface of the streamline tracking section (4) is one-quarter of the distance from the inlet of the streamline tracking section (4); the other two rocket thrust chambers (2) are installed on both sides of a position where the upper expansion surface of the streamline tracking section (4) is three-quarters of the distance from the inlet of the streamline tracking section (4), and are symmetrical to the center; In the type A layout scheme, two of the rocket thrust chambers (2) are installed on both sides of the upper expansion surface of the streamline tracking section (4) at a distance of one quarter from the inlet of the streamline tracking section (4), and are centrally symmetrical; the other two rocket thrust chambers (2) are installed at the center of the upper expansion surface of the streamline tracking section (4) at a distance of one quarter from the inlet of the streamline tracking section (4).

2. The method for designing a variable geometry asymmetric nozzle coupled to a rocket thrust chamber according to claim 1, characterized in that: The step S1 specifically includes: Step S101, designing a throat regulating section (3): the inlet shape of the throat regulating section (3) is a rectangle in the upper half and a superellipse in the lower half; the throat height of the throat regulating section (3) is determined according to the flow rate of the variable geometry three-dimensional asymmetric nozzle (1); an adjusting plate is installed on the upper wall surface of the throat regulating section (3); and the throat area of ​​the throat regulating section (3) is adjusted by rotating the adjusting plate; the side wall surface of the throat regulating section (3) is obtained by directly stretching its inlet profile without lateral expansion; Step S102, designing the streamline tracing section (4): based on the axisymmetric maximum thrust reference flow field, using the bidirectional streamline tracing technology to obtain the upper expansion surface and the side wall surface of the streamline tracing section (4); determining the inlet shape of the streamline tracing section (4) according to the throat adjustment section (3), and its outlet shape is rectangular, and then tracing the streamlines along the flow direction through the inlet shape and tracing the streamlines against the flow direction through the outlet shape, respectively, to obtain multiple streamlines, and performing weighted averaging on the two streamlines obtained by tracing the streamlines along the flow direction and tracing the streamlines against the flow direction on the same path, so that the generated three-dimensional nozzle profile has a smooth transition; Step S103, designing the outlet adjustment section (5): determining the inlet shape of the outlet adjustment section (5) according to the outlet shape of the streamline tracing section (4), wherein the upper wall surface and the side wall surface of the outlet adjustment section (5) are directly obtained by stretching the inlet shape thereof, and the lower wall surface thereof is a movable adjustment plate, and the outlet area of ​​the variable geometry three-dimensional asymmetric nozzle (1) can be adjusted by rotating the movable adjustment plate.

3. The method for designing a variable geometry asymmetric nozzle coupled to a rocket thrust chamber according to claim 2, characterized in that: The step S2 specifically includes: Step S201, obtaining the two-dimensional profile of each rocket thrust chamber (2) based on the characteristic line method; Step S202: rotate the two-dimensional profile of each rocket thrust chamber (2) around its central axis to obtain a three-dimensional axisymmetric profile of each rocket thrust chamber (2).

4. The method for designing a variable geometry asymmetric nozzle coupled to a rocket thrust chamber according to claim 3, characterized in that: The throat of the variable geometry three-dimensional asymmetric nozzle (1) is located in the throat adjustment section (3), and the calculation formula of the throat area is: Wherein, T* and p* are respectively the total temperature and total pressure of the inlet gas of the variable geometry three-dimensional asymmetric nozzle (1), γ is the specific heat ratio of the gas, R is the gas constant, q(Ma) is the flow function, the value of q(Ma) is 1 at the throat section, and A is the throat area of ​​the variable geometry three-dimensional asymmetric nozzle (1). It represents the flow rate of the gas flowing into the variable geometry three-dimensional asymmetric nozzle (1).

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