Wide-range intelligent morphing aircraft design method based on curved shock wave theory

Abstract

The wide-range intelligent variable aircraft design method based on the curved shock wave theory comprises the following steps: 1) according to a flight envelope, the aerodynamic design of the wide-range intelligent variable aircraft is divided into a minimum resistance state, an optimal lift-drag ratio state and a maximum lift state, wherein the minimum resistance state corresponds to a boost climb section and a free flight section, the optimal lift-drag ratio state corresponds to a re-entry glide section, and the maximum lift state corresponds to a terminal down pressure section; 2) the aerodynamic design of the minimum resistance state is as follows: the aerodynamic profile of the wide-range intelligent variable aircraft is inversely designed based on a full three-dimensional curved shock wave surface; 3) the aerodynamic design of the optimal lift-drag ratio state is as follows: the aerodynamic profile of the wide-range intelligent variable aircraft is designed based on a full three-dimensional curved shock wave surface and a wall surface pressure distribution simultaneously controllable inverse method; 4) the aerodynamic design of the maximum lift state is as follows: the aerodynamic profile of the wide-range intelligent variable aircraft is inversely designed based on a three-dimensional wall surface pressure distribution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wide-speed-range intelligent variable configuration wave-riding aircraft, in particular to a wide-range intelligent variable configuration aircraft design method based on curved shock wave theory. BACKGROUND

[0002] Hypersonic vehicles have the ability of global real-time reconnaissance, rapid deployment and long-range precision strike, and are the carriers of near-space force deployment, which has an important impact on national strategic security. At the same time, hypersonic vehicles can provide new technical approaches for space transportation, interstellar exploration and space transportation, and have great civil and economic value. Therefore, hypersonic vehicles have very broad application prospects, and the development of related technologies has become the focus of competition among countries.

[0003] However, existing hypersonic vehicles are mostly fixed configuration aircraft with "single point design". The design point is usually selected at the cruise state point or a certain long-time working state point in the flight envelope. Once the flight condition deviates from the design point, the aerodynamic performance of the fixed configuration aircraft will obviously decline, and it is difficult to meet the needs of wide-speed-range and pan-air-domain maneuvering flight. Taking a fixed-geometry air-breathing hypersonic vehicle as an example, when the flight condition changes greatly, the forebody incident shock wave will be swallowed into the inlet, thereby causing serious shock boundary layer interference, significantly reducing the internal and external flow performance, and even causing the inlet to be unstarted, resulting in the failure of the entire flight mission (X-51A, 2011). Therefore, for hypersonic vehicles, it is almost impossible to achieve wide-speed-range and pan-air-domain large maneuvering flight, which is required by major engineering, if the aerodynamic shape remains unchanged.

[0004] By comparison, hypersonic intelligent variable configuration aircraft can change its own configuration autonomously according to task requirements and flight environment, and can achieve optimal aerodynamic performance throughout the envelope. It can be seen that hypersonic vehicles urgently need to revolutionize and leap from "single point optimization, acceptable throughout the envelope" of fixed configuration to "variable configuration, sustained optimization throughout the envelope". The primary technical bottleneck faced by intelligent variable configuration aircraft is the lack of accurate and efficient wide-range continuous variable configuration aerodynamic shape design principles and methods. As the most significant physical feature in hypersonic flow, shock wave is the key to determining the success or failure of aerodynamic shape design. Therefore, it has great application value to carry out research on intelligent variable configuration aircraft aerodynamic design methods based on curved shock wave theory. SUMMARY

[0005] The present application aims to solve the above problems in the prior art, and provides a wide-range intelligent variable configuration aircraft design method based on curved shock wave theory, which can realize rapid inverse design of aerodynamic shape according to changes in flight tasks and working conditions, and then guide the variable configuration operation of the aircraft, thereby ensuring wide-speed-range and pan-air-domain large maneuvering flight required by major engineering.

[0006] To achieve the above object, the present application adopts the following technical scheme:

[0007] The wide-range intelligent variable aircraft design method based on curved shock wave theory comprises the following steps:

[0008] 1) According to the flight envelope, the aerodynamic design of the wide-range intelligent variable aircraft is divided into a minimum drag state, an optimal lift-drag ratio state and a maximum lift state, wherein the minimum drag state corresponds to the boost climb segment and the free flight segment, the optimal lift-drag ratio state corresponds to the re-entry glide segment, and the maximum lift state corresponds to the terminal down pressure segment;

[0009] 2) The aerodynamic design of the minimum drag state is as follows: the aerodynamic profile of the wide-range intelligent variable aircraft is inversely designed based on a full three-dimensional curved shock wave surface;

[0010] 3) The aerodynamic design of the optimal lift-drag ratio state is as follows: the aerodynamic profile of the wide-range intelligent variable aircraft is designed based on a full three-dimensional curved shock wave surface and a wall surface pressure distribution simultaneously controllable inverse method;

[0011] 4) The aerodynamic design of the maximum lift state is as follows: the aerodynamic profile of the wide-range intelligent variable aircraft is inversely designed based on a three-dimensional wall surface pressure distribution.

[0012] The design of step 2) is as follows: firstly, the full three-dimensional shock wave surface is discretized into a series of shock wave curves in the reference plane, according to the shock wave angle, shock wave curvature and flow parameters, the corresponding flow field and aircraft lower wall surface are solved by using the curved shock wave theory.

[0013] In step 2), the full three-dimensional curved shock wave surface is of any non-axisymmetric shape.

[0014] The design of step 3) is as follows: the lower wall surface of the aircraft is divided into a shock wave control area and a pressure control area, the shock wave control area is used to ensure the wave-riding characteristics of the aircraft, and the pressure control area is used to control the change of the pressure center position of the aircraft; the full three-dimensional shock wave surface corresponding to the shock wave control area and the wall surface pressure distribution corresponding to the pressure control area are specified, and are discretized according to the reference plane, and then the corresponding flow field and the lower wall surface of the aircraft are solved by using the curved shock wave theory.

[0015] The design of step 4) is as follows: according to the change of the flight condition, a continuous time-varying three-dimensional wall surface pressure distribution is specified, and is discretized according to the reference plane to obtain the wall surface pressure distribution in each plane, and according to the flow conditions, the corresponding flow field and the lower wall surface of the aircraft are solved by using the curved shock wave theory.

[0016] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0017] The present application can continuously adjust the corresponding three-dimensional shock wave shape and wall surface parameter distribution according to the change of flight task and working condition, design the corresponding aerodynamic profile in real time, ensure the continuous transition of the shape, and avoid the geometric jump. In the free flight stage, the aircraft maintains the minimum drag state to achieve the maximum initial handover speed; in the re-entry glide stage, the aircraft maintains the optimal lift-drag ratio state to achieve the maximum range; in the terminal depression section, the aircraft maintains the maximum lift state to ensure stronger maneuverability. In summary, the intelligent variable aircraft designed by the present application can meet the needs of wide-speed domain and all-airspace maneuvering flight, and maintain the optimal aerodynamic characteristics within the full envelope. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a wide-range intelligent variable aircraft flight envelope schematic diagram;

[0019] Figure 2 is an aerodynamic design schematic diagram of the wide-range intelligent variable aircraft in the minimum drag state;

[0020] Figure 3 is an aerodynamic design schematic diagram of the wide-range intelligent variable aircraft in the optimal lift-drag ratio state;

[0021] Figure 4 is an aerodynamic design schematic diagram of the wide-range intelligent variable aircraft in the maximum lift state.

[0022] Reference signs: aircraft leading edge line 1, aircraft upper wall surface 2, aircraft lower wall surface 3, full three-dimensional shock wave curved surface 4, symmetric reference plane inner shock wave curve 5, symmetric reference plane inner aircraft lower wall surface compression line 6, shock wave control area 7, pressure control area 8, aircraft center of pressure position 9, aircraft lower wall surface three-dimensional pressure distribution 10, ① represents that the aircraft is in the minimum drag state, ② represents that the aircraft is in the optimal lift-drag ratio state, and ③ represents that the aircraft is in the maximum lift state. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects of the present application more clear, specific embodiments will be described in detail below.

[0024] The wide-range intelligent variable aircraft design method based on the curved shock wave theory of the present application comprises the following steps:

[0025] 1. The typical flight envelope of the unpowered hypersonic aircraft can be roughly divided into four stages: boost climb stage, free flight stage, re-entry glide stage, and terminal depression stage, as shown in Figure 1The different stages have different requirements for the aerodynamic performance of the aircraft. The boost climb and free flight stages require less drag, the reentry glide stage requires a larger lift-drag ratio, and the terminal descent stage requires a larger lift. Therefore, the aerodynamic design of the wide-range intelligent variable aircraft can be divided into a minimum drag state ①, an optimal lift-drag ratio state ②, and a maximum lift state ③. The design requirements of different states are different, and the design methods are also different.

[0026] 2. In the minimum drag state ①, the aerodynamic shape of the intelligent variable aircraft is designed reversely based on a full three-dimensional curved shock wave surface, as shown in Figure 2 According to the change of the flight state, a continuous time-varying full three-dimensional shock surface 4 is specified. The shock can be designed in any non-axisymmetric shape. In the present application, the full three-dimensional shock surface 4 is specified as a Bezier surface. The full three-dimensional shock surface 4 is discretized into a series of shock curves in the reference plane, and according to the shock angle, shock curvature and flow parameters, the corresponding flow field and aircraft lower wall surface 3 are solved by using the curved shock theory. The present application only takes the symmetric reference plane as an example to introduce the solving process. According to the shock angle, shock curvature and flow parameters of the discrete points on the shock curve 5 in the symmetric reference plane, the curved shock theory is used to solve the aircraft lower wall surface compression profile 6 in the symmetric reference plane. The complete three-dimensional flow field and aircraft lower wall surface 3 can be obtained by combining the flow field and compression profile in all reference planes, and the aircraft upper wall surface 2 is formed by tracing the aircraft leading edge profile 1 horizontally forward along the flow direction. The control equation of the curved shock theory is as follows, wherein p is the pressure, δ is the flow angle, μ is the Mach angle, ρ is the density, V is the flow velocity, w is the circumferential velocity, γ is the specific heat ratio, j is the judgment factor, s is the streamline, l is the characteristic line, φ is the circumferential angle, P is the derivative of pressure along the streamline, D is the derivative of airflow angle along the streamline, y is the longitudinal coordinate in the Cartesian coordinate system, and a is the local sound speed.

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[0034] 3. In the optimal lift-to-drag ratio state ②, the aerodynamic profile of the wide-range intelligent variator is designed based on a reverse method that simultaneously controls the three-dimensional shock wave shape and wall pressure distribution. In this state, the lower wall 3 of the aircraft is divided into two parts: the shock wave control region 7 and the pressure control region 8, as shown below. Figure 3 As shown. Shock control region 7 is used to ensure the aircraft's wave-riding characteristics, while pressure control region 8 controls the aircraft's pressure center position 9 through wall pressure distribution. This achieves control without control surfaces while maintaining lift-to-drag ratio. The full three-dimensional shock surface 4 corresponding to shock control region 7 and the wall pressure distribution corresponding to pressure control region 8 are discretized according to a reference plane. Based on the shock angle, shock curvature, and incoming flow parameters, the corresponding flow field and the lower wall 3 of the aircraft can be solved using bending shock wave theory. This invention only uses a symmetrical reference plane as an example to introduce the solution process. Based on the shock curve 5 in the symmetrical reference plane, the compression profile ab and the corresponding flow field in the symmetrical reference plane are obtained using bending shock wave theory. Simultaneously, based on the wall pressure distribution, the compression profile bc and the corresponding flow field in the symmetrical reference plane are further obtained using bending shock wave theory. Compression profiles ab and bc together form the lower wall compression profile 6 in the symmetrical reference plane. By combining the flow fields and compression profiles in all reference planes, a complete three-dimensional flow field and the lower wall 3 of the aircraft can be obtained, while the upper wall 2 of the aircraft is formed by the leading edge profile 1 of the aircraft horizontally forward along the flow direction.

[0035] 4. In maximum lift state ③, the aerodynamic profile of the wide-area intelligent variator is designed based on the three-dimensional wall pressure distribution, such as... Figure 4 As shown. Based on the changes in flight conditions, the continuously time-varying three-dimensional pressure distribution 10 of the aircraft's lower wall is specified and discretized according to a reference plane to obtain the wall pressure distribution within each plane. Subsequently, based on the incoming flow conditions, the corresponding flow field and the aircraft's lower wall 3 can be obtained using the bending shock wave theory. Therefore, its essence is to map the three-dimensional pressure distribution 10 of the aircraft's lower wall onto the aircraft's lower wall 3. This invention only uses a symmetrical reference plane as an example to introduce the solution process. The pressure distribution within the symmetrical reference plane is obtained based on the three-dimensional pressure distribution 10 of the aircraft's lower wall. Then, the compression profile 6 of the aircraft's lower wall within the symmetrical reference plane can be obtained by iteratively solving using the bending shock wave theory. Combining the flow fields and compression profiles within all reference planes yields the full three-dimensional flow field and the aircraft's lower wall 3, while the aircraft's upper wall 2 is formed by horizontally tracing the aircraft's leading edge profile 1 forward along the flow direction.

[0036] The present application utilizes curved shock wave theory to carry out the aerodynamic design of wide-range intelligent variable aircraft, and the transition deformation between different aerodynamic profiles can be realized by driving the flexible skin through telescopic rotary lever; the present application can continuously adjust the corresponding three-dimensional shock wave shape and wall surface parameter distribution according to the change of flight tasks and working conditions, and design the corresponding aerodynamic profile in real time, so as to ensure the continuous transition of the shape and avoid the geometric jump. In the free flight stage, the aircraft maintains the minimum resistance state to realize the maximum initial handover speed; in the re-entry sliding stage, the aircraft maintains the optimal lift-drag ratio state to realize the maximum range; in the terminal down-pressing stage, the aircraft maintains the maximum lift state to ensure stronger maneuvering performance. In summary, the intelligent variable aircraft designed by the present application can meet the requirements of wide-speed range and pan-air domain maneuvering flight, and maintain the optimal aerodynamic characteristics within the full envelope.

Claims

1. A design method for a wide-area intelligent variator aircraft based on curved shock wave theory, characterized in that... Includes the following steps: 1) Based on the flight envelope, the aerodynamic design of the wide-range intelligent variant aircraft is divided into the minimum drag state, the optimal lift-to-drag ratio state, and the maximum lift state. The minimum drag state corresponds to the boost climb phase and the free flight phase, the optimal lift-to-drag ratio state corresponds to the reentry glide phase, and the maximum lift state corresponds to the terminal descent phase. 2) The aerodynamic design for the minimum drag state is as follows: The aerodynamic profile of the wide-range intelligent variator aircraft is reverse-engineered based on the full three-dimensional curved shock surface. Specifically, the full three-dimensional shock surface is first discretized into a series of shock curves in a reference plane. Based on the shock angle, shock curvature, and incoming flow parameters, the corresponding flow field and the lower wall of the aircraft are solved using the curved shock theory. The full three-dimensional curved shock surface is an arbitrary non-axisymmetric shape. 3) The aerodynamic design for the optimal lift-to-drag ratio is as follows: The aerodynamic profile of the wide-range intelligent morphing aircraft is designed based on a reverse method that allows for simultaneous control of the full three-dimensional curved shock surface and wall pressure distribution. Specifically, the lower wall of the aircraft is divided into a shock wave control region and a pressure control region. The shock wave control region is used to ensure the aircraft's wave-riding characteristics, while the pressure control region is used to control the change in the aircraft's pressure center position. The full three-dimensional shock wave surface corresponding to the shock wave control region and the wall pressure distribution corresponding to the pressure control region are specified and discretized according to the reference plane. Then, the corresponding flow field and the lower wall of the aircraft can be solved using the curved shock wave theory. 4) The aerodynamic design for maximum lift is as follows: The aerodynamic profile of the wide-range intelligent morphing aircraft is reverse-engineered based on the three-dimensional wall pressure distribution. Specifically, according to the changes in flight conditions, a continuously time-varying three-dimensional wall pressure distribution is specified, and the pressure is discretized according to the reference plane to obtain the wall pressure distribution in each plane. Based on the incoming flow conditions, the corresponding flow field and the lower wall of the aircraft can be obtained using the bending shock wave theory. The governing equations for bending shock waves are shown below: in, p For pressure, δ The flow angle, μ Mach angle, ρ For density, V For flow velocity, w For circumferential velocity, γ For specific heat ratio, j As a judgment factor, s For streamlined, l For characteristic lines, For circumferential angle, P The derivative of the pressure along the streamline. D The derivative of the airflow angle along the streamline. y The ordinate in the Cartesian coordinate system. The speed of sound is the local speed.

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