Wave rider precursor / three-channel air inlet channel integrated design method based on flow direction double wave rider principle

Abstract

The invention discloses a waverider front body / three-channel air inlet channel integrated design method based on a flow direction double waverider principle, and belongs to the field of hypersonic flight vehicle inner and outer flow integrated design. The method is essentially characterized in that the relation between a waverider precursor external flow field and an inward turning air inlet channel internal flow field is established, an internal and external flow integrated axial symmetry reference flow field model is designed and researched, an osculating flow field is adopted in the reference flow field, and a molded surface is designed through streamline tracking, so that a novel waverider precursor / air inlet channel integrated design theory is developed. The front edge of the waverider front body and the front edges of the three inward turning air inlet lip openings can be attached to a shock wave face, the waverider front body serves as a pre-compression face of the air inlet, pre-compressed airflow can be efficiently captured, and the high lift-drag ratio is achieved. Shock wave sealing can be achieved through the three three-dimensional inward turning air inlet channels, and all flow capturing is achieved. The pneumatic and geometric coupling of the waverider precursor and the three channels can be realized through the'flow direction double waverider 'principle, and the waverider characteristics of the waverider precursor and the three channels cannot be damaged.

Description

Technical Field

[0001] The present invention belongs to the field of integrated design of internal and external flows of hypersonic aircraft, and in particular relates to an integrated design method of a waverider forebody / three-channel air inlet based on the flow direction double waverider principle. Background Art

[0002] In recent years, with people's continuous pursuit of aircraft performance and speed, hypersonic aircraft have become an important research field in aerospace technology. Due to its advantages such as rapid global arrival, high detection difficulty, and strong penetration capability, it will surely occupy a more important strategic position in future military applications and national defense security. Moreover, a large number of studies from the 1960s to the present have fully demonstrated that the integrated design of the propulsion system and the airframe is the key and core to achieve air-breathing hypersonic flight (Ding Feng. Research on the theory and method of aerodynamic design of "full waveriding" for the integration of internal and external flows of air-breathing hypersonic aircraft [D]. National University of Defense Technology, 2019), and the core of it is the integrated design of the aircraft forebody and the air inlet.

[0003] In the development process of integration, the forebody design has gradually transitioned from a two-dimensional wedge to a three-dimensional waverider, and the air inlet has also gradually developed from a two-dimensional compression to a three-dimensional inward contraction. Waveriders are widely used in the forebody design of aircraft. They use the principle of leading edge appendage shock wave compression to achieve the aerodynamic requirements of the waverider configuration with a high lift-to-drag ratio at hypersonic speeds. Moreover, the flow field on its lower surface is relatively uniform, which is conducive to the integrated design of the propulsion system and the airframe. It is considered to be an ideal configuration for hypersonic aircraft. Compared with the two-dimensional flow field waverider configuration, the three-dimensional flow field waverider configuration can make the forebody shock wave outlet profile better match the shape of the air inlet, with flexible design and more suitable for the integrated design of the forebody / air inlet. For the air inlet, two-dimensional compression will have the disadvantages of insufficient compression and a long forebody length, which makes the total pressure recovery coefficient of the air inlet too low. However, the compression of the three-dimensional inward-contracting inlet duct is completely completed inside the channel, which has a higher compression capacity and total pressure recovery coefficient. It can directly compress the incoming flow and meet the conditions of the combustion chamber. In addition, it can be integrated with the waverider precursor through geometric transition and aerodynamic transition to improve the airflow quality in the inlet duct and engine performance.

[0004] In addition to the selection of the aircraft forebody and air inlet configuration, another key technology in the integrated design of the aircraft forebody / air inlet is the matching design of the aircraft forebody and the air inlet. Traditional forebody / air inlet integrated designs mostly adopt the design of the forebody and the air inlet being independent of each other, and use geometric fusion to match the two to obtain an integrated configuration. However, in actual applications, this method will produce complex shock wave trains in the isolation section due to shock wave / boundary layer interference. Therefore, the current integrated design method gradually weakens the boundary between the two, and is more inclined to achieve a smooth transition between the forebody and the air inlet in terms of aerodynamics and geometry, thereby improving the compression efficiency of the air inlet.

[0005] Looking at the research on the integrated design of waverider forebody / inlet at home and abroad, the research is mainly focused on the integrated design of forebody and single / dual channel inlet, among which the research on the integration of waverider forebody / multi-channel inlet is rare. However, in the face of future hypersonic vehicles' round-trip flight between the earth and the sky and near-space cross-domain flight, the existing single / dual scramjet engines cannot meet the thrust requirements of large hypersonic vehicles. Therefore, the use of a power system with multiple inlets in parallel has become an effective technical approach for large-scale and large-scale aircraft to achieve space flight in the future. In the conical hypersonic vehicle project jointly carried out by the United States and Australia in 2010, the integrated design of the conical forebody and three REST inlets was studied, in which the connection between the forebody and the inner transition inlet was achieved by adopting a geometric fusion method (Gollan RJ, Smart MK. Design of modular shape-transition inlets for a conical hypersonic vehicle. Journal of Propulsion and Power. 2013 Jul;29(4):832-8). Subsequently, Zhang Wenhao from China borrowed the design principle of the REST inlet and also used the geometric fusion method to integrate the three-dimensional inward-turning inlets of the minimum resistance rotating body and the rectangular inlet (Zhang Wenhao. Research on the integrated design method of three-dimensional inward-turning inlet and waverider body [D]. National University of Defense Technology, 2019). However, these two types of forebody / multi-channel integrated designs did not consider the combination of geometric fusion and aerodynamic fusion, and could not maximize the advantages of the waverider forebody and the inward-turning inlet. In addition, the inlet layout form in the two integrated configurations is the upright inward-turning inlet, but the overflow window of the upright inward-turning inlet is located on the side away from the body, and the side wall of the inlet will block the forebody from displacing part of the low-energy flow. The overflow window of the inverted inward-turning inlet is located on the forebody, and the side wall of the inlet can provide enough space for the displacing of low-energy flow. Summary of the invention

[0006] The purpose of the present invention is to provide a method for integrating the internal and external flows of a waverider forebody and a three-dimensional inward contraction inlet based on the principle of double waveriders in the flow direction, so as to achieve aerodynamic fusion and geometric fusion of internal and external flows, and improve the aerodynamic performance and flow capture capability of a hypersonic inlet. At the same time, by connecting three inverted three-dimensional inward contraction inlets in parallel in the span direction, the disturbance caused by the lateral flow is solved.

[0007] Based on the perspective of combining aerodynamic fusion and geometric fusion, the present invention innovatively proposes a layout form in which three inverted three-dimensional inward-retracting air inlets are connected in parallel along the span direction and are simultaneously connected in series on the same waverider forebody. At the same time, the method of close flow field is adopted to smoothly integrate the waverider and the inward-turning air inlet along the flow direction, thereby realizing a flow direction double waverider design in which the waverider forebody of the aircraft and the three-dimensional inward-retracting air inlet are integrated with the internal and external flows, in order to introduce new design ideas for the integration of the forebody of the aircraft and the three-dimensional inward-turning air inlet.

[0008] The present invention comprises the following steps:

[0009] 1) Design an axisymmetric reference flow field with integrated internal and external flows;

[0010] The outflow basic flow field is generated by the outflow flow field generator. A quadratic concave curve passing through the origin of the coordinate system is selected as the generator, which is defined by the following expression:

[0011] (1)

[0012] (2)

[0013] (3)

[0014] In the formula, represents the inclination angle at the origin of the coordinate system, represents the inclination angle at point B, and The axial and radial distances at the representative point B; the forebody shock wave can be obtained by moving the generator under the designed working conditions; the flow field between the forebody shock wave and the generator, that is, the external flow basic flow field, is calculated by the characteristic line method; then the starting position of the incident shock wave of the inlet duct is specified on the external flow basic flow field, and the shock wave curve is defined as a quadratic curve by the present invention; the incoming flow condition of the incident shock wave of the inlet duct is determined by interpolation in the external flow basic flow field; at the same time, by giving the pressure distribution of the upper and lower walls of the inlet duct and the position of the inlet duct outlet section, the characteristic line theory is used to solve the internal flow basic flow field;

[0015] 2) Generate the waverider forerunner and the inward-turning air intake;

[0016] Based on the above-mentioned axisymmetric reference flow field of internal and external flow integration, the osculating flow method is used to generate the profiles of the waverider forerunner and the inward-turning air inlet. A part of the waverider forerunner needs to be used as the forerunner of the inward-turning air inlet, so the waverider forerunner is generated in two parts.

[0017] (1) Generate waverider precursors:

[0018] The leading edge profiles of the first and second waverider precursors are designed in the design section respectively, and are discretized by osculating planes; on each osculating plane, the discrete points are projected forward along the direction of the free streamline until they intersect with the forebody shock wave, and the leading edge points of the waverider precursors are determined; the leading edge points of the first part of the forebody are traced by streamlines in the forebody dependent region to generate the wall surface of the first part of the waverider precursors; the leading edge points of the second part of the forebody are traced by streamlines in the isentropic compression region to generate the wall surface of the second part of the waverider precursors;

[0019] (2) Generate an inward-turned inlet: define the trailing edge profile of the second waverider front as the upper capture curve, and define a part of the inlet shock wave profile as the lower capture curve. Design the central angle of the inlet capture shape according to the capture flow rate and other requirements of the inlet to obtain the side capture curves of the three inlets. Discretize these curves using osculating planes, project the discrete points horizontally onto the incident shock wave of the inlet, and obtain the leading edge points of the inlet. Streamline trace these leading edge points in the incident shock wave dependent region of the inlet lip and the stable region of the internal flow field until the exit section of the inlet throat, and generate the profiles of the three inlets.

[0020] 3) Generate the upper surface of the fuselage and the air inlet cover;

[0021] In the present invention, the upper wall surface of the body adopts a free flow surface, and the shape of the outer cover wall surface of the air inlet is generated in a geometric transition manner.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] The present invention designs an integrated axisymmetric reference flow field of internal and external flows based on the principle of double waveriding in the flow direction. The leading edge of the waverider forebody and the leading edge of the three-channel inlet lip can be attached to the shock wave curved surface, maintaining good waveriding characteristics, and realizing independent waveriding of the waverider forebody and the inlet. The waverider forebody itself has a high lift-to-drag ratio. As the pre-compression surface of the inlet, it can efficiently capture the pre-compressed airflow. The inlet lip is attached to the shock wave surface to ensure the shock wave sealing characteristics of the inlet, and realize the efficient capture of the flow by the inlet. At the same time, because it directly captures the hypersonic airflow, it reduces the flow of the airflow on the surface of the fuselage, reduces the capture of the low-speed airflow by the inlet, and improves the overall performance of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is an axisymmetric reference flow field integrating internal and external flows.

[0025] Figure 2 It is a schematic diagram of the main characteristic geometric lines of the streamwise double-rider wave configuration.

[0026] Figure 3 This is a schematic diagram of a half-model of the waverider forebody / three-channel air inlet integrated configuration.

[0027] Figure 4 It is a positive triaxial projection of the integrated configuration of the waverider forebody / three-channel air inlet.

[0028] Figure 5 This is a front view of the integrated waverider precursor / three-channel air inlet configuration.

[0029] Figure 6 Left view of the integrated waverider forebody / three-channel air inlet configuration.

[0030] The meanings of the marks in the figure are as follows: 1 represents the forebody shock wave, 2 represents the secondary concave curve (forebody wall curve), 3 represents the upper and lower walls of the inlet, 4 represents the design section, 5 represents the position of the inlet throat outlet section, 6 represents the incident shock wave of the inlet, 7 represents the upper wall, 8 represents the inlet one, 9 represents the inlet two, 10 represents the inlet three, 11 represents the inlet cover, 12 represents the first part of the waverider forebody, 13 represents the second part of the waverider forebody, and point and Point and Point Indicates the leading edge point of the waverider front, point and Point and Point and Point and Point and Point and Point and Point represents the leading edge of the inlet, OAC represents the forebody shock wave dependent region, ABC represents the isentropic compression region, BCD represents the incident shock wave dependent region of the inlet lip, BDEF represents the internal flow field stable region, and the curve - The leading edge lines and curves representing the first half of the waverider front - - - - The leading edge profile of the second half of the waverider front body (the trailing edge profile of the first half of the waverider front body), the curve - and - Represents the trailing edge of the waverider front body - and - Indicates the inlet shock wave profile curve, curve - The side capture curve and curve representing the inlet 1 - and - Indicates the side capture curve of the second inlet, O- - - -O represents the first part of the waverider front wall, - - - - - - - represents the second part of the waverider precursor wall, - - - - Represents the throat outlet cross section of the second half of the inlet duct, - - - - represents the throat outlet cross section of the inlet 1, and The osculating plane representing the internal compression reference flow field, Represents the osculating plane of the external compression reference flow field. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the following embodiments will further illustrate the present invention in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] The integrated design method of waverider precursor / three-channel inlet based on the double waverider flow is essentially to establish the connection between the external flow field of the waverider precursor and the internal flow field of the inward-turning inlet, design and study the axisymmetric reference flow field model of the internal and external flow integration, adopt the osculating flow field in the reference flow field, and design the profile by streamline tracing, so as to develop a new integrated design theory of waverider precursor / inlet. The leading edge of the waverider precursor and the leading edges of the lips of the three inward-turning inlets can be attached to the shock wave surface. As the pre-compression surface of the inlet, the waverider precursor can not only efficiently capture the pre-compressed airflow, but also has a high lift-to-drag ratio. The three three-dimensional inward-turning inlets can all achieve shock wave sealing and obtain full flow capture. The aerodynamic and geometric coupling of the waverider precursor and the three-channel can be achieved through the principle of "double waverider flow" without destroying the waveriding characteristics of the two.

[0033] like Figures 1 to 3As shown, the specific design method of the embodiment of the present invention includes the following steps:

[0034] 1) Design of axisymmetric reference flow field with integrated internal and external flow

[0035] Design as Figure 1 The internal and external flow integrated axisymmetric reference flow field shown in the figure, the external flow basic flow field is generated by the external flow field generator, and the present invention selects a quadratic concave curve 2 passing through the coordinate origin as the generator, which is defined by the following expression:

[0036] (1)

[0037] (2)

[0038] (3)

[0039] In the above expression represents the inclination angle at the origin of the coordinate system, represents the inclination angle at point B, and The axial and radial distances at the representative point B. The forerunner shock wave 1 can be obtained by moving the generating body under the designed working conditions. The characteristic line method is used to calculate the flow field between the forerunner shock wave and the generating body, that is, the basic external flow field. Then, the starting positions B and C of the incident shock wave of the inlet are specified on the basic external flow field, and the shock wave curve 6 is defined as a quadratic curve in the present invention. By interpolating in the basic external flow field, the incoming flow condition of the incident shock wave 6 of the inlet is determined. At the same time, by giving the pressure distribution of the upper and lower walls 3 of the inlet and the position 5 of the inlet outlet section, the characteristic line theory is applied to solve the basic internal flow field.

[0040] 2) Generate waverider forerunner and inward-turning inlet

[0041] Based on the above-mentioned axisymmetric reference flow field of the integrated internal and external flow, the closed flow method is used to generate the profiles of the waverider forerunner and the inward-turning air inlet. A part of the waverider forerunner needs to be used as the forerunner of the inward-turning air inlet, so the waverider forerunner is generated in two parts. In addition, the integrated configuration is highly symmetrical, so only half of the mold is used for explanation. The design section here is Figure 1 Mark 4 in.

[0042] (1) Generate waverider precursors:

[0043] Design the leading edge profiles of the first and second waverider front bodies in design section 4 respectively - and - - - - . Then use the osculating plane, such as , discretize the leading edge profile, and then on each osculating plane, project the discrete points backward along the direction of the free streamline until they intersect with the forebody shock wave 1 to determine the leading edge point of the waverider forebody, for example , , The leading edge point of the first part of the precursor is traced by streamlines in the precursor dependent area OAC to generate half of the first part of the waverider precursor 12, that is, the surface O- - - -O; the leading edge point of the second part of the precursor is traced in the isentropic compression zone ABC to generate half of the second part of the waverider precursor 13, that is, the surface - - - - - - - Based on this, the waverider precursor can be obtained.

[0044] (2) Generate an inward-turned inlet: The trailing edge profile of the second waverider front - , - Defined as the upper capture curve, part of the inlet shock profile - , - Defined as the lower capture curve, the center angle of the inlet capture shape is designed according to the capture flow of the inlet, so as to obtain the side capture curves of the inlet 1 8 and the inlet 2 9 - , - , - . Use the osculating planes of these curves, such as , , make it discretized, and project the discrete points horizontally onto the incident shock wave 6 of the inlet to obtain the leading edge point of the inlet, for example , , , , , , and . These leading edge points are traced in the incident shock wave dependent region BCD of the inlet lip and the internal flow field stable region BDEF until the exit section of the inlet throat. - - - - , - - - - , generating the profile of the air inlet 1 8 and the half of the air inlet 2 9. The air inlet 3 10 is symmetrical with the air inlet 1 8 about the symmetry plane.

[0045] 3) Generate the upper surface of the fuselage and the air intake cover

[0046] In the present invention, the upper wall surface 7 of the body is a free flow surface, and the shape of the outer cover wall surface 11 of the air inlet is generated in a geometric transition manner.

[0047] Finally, the waverider forebody / three-channel air inlet integrated configuration based on the double waverider principle of flow direction is obtained. The positive tri-axonometric drawing, front view and left view of the waverider forebody / three-channel air inlet integrated configuration are shown in the figure. Figures 4 to 6 Through the above steps, the internal and external flow integrated design of the waverider forebody and the inner turning air inlet is realized.

[0048] The present invention is an internal and external flow integrated configuration of a waverider forebody based on the principle of double waverider flow and three three-dimensional inward contraction air inlets connected in parallel along the span direction, so as to realize the aerodynamic and geometric coupling between the waverider forebody and the air inlet. The "double waverider flow" principle can realize the integrated design of the waverider forebody and the three-channel air inlet without damaging the waveriding characteristics of the two. The waverider forebody and the air inlet are waveriding independently, maintaining good waveriding characteristics. The waverider forebody itself has a high lift-to-drag ratio, and as the pre-compression surface of the air inlet, it can efficiently capture the pre-compressed airflow. The air inlet lip is attached to the shock wave surface to ensure the shock wave sealing characteristics of the air inlet, realize the efficient capture of the air flow by the air inlet, and at the same time, because it directly captures the hypersonic airflow, reduces the flow of the airflow on the surface of the fuselage, reduces the capture of the low-speed airflow by the air inlet, and improves the overall performance of the aircraft. The method of the present invention can introduce new design ideas for the integration of the forebody and the three-dimensional inward turning air inlet of the aircraft.

[0049] The above embodiments are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. The integrated design method of waverider forebody / three-channel air intake based on the double waverider principle of flow direction has the following characteristics: It includes the following steps: 1) Design an axisymmetric reference flow field with integrated internal and external flows: the external flow basic flow field is generated by the external flow field generator, and a quadratic concave curve passing through the coordinate origin is selected as the external flow field generator; The forebody shock wave is obtained by moving the external flow field generating body under the designed working conditions; The characteristic line method is used to calculate the flow field between the forebody shock wave and the generated body, that is, the basic flow field of the external flow; The starting position of the incident shock wave of the inlet is specified on the external flow basic flow field, and the shock wave curve is defined as a quadratic curve. The incoming flow condition of the incident shock wave of the inlet is determined by interpolation in the external flow basic flow field; the pressure distribution on the upper and lower walls of the inlet and the position of the inlet outlet section are given, and the characteristic line theory is used to solve the internal flow basic flow field; 2) Generate the waverider precursor and the inward-turning air inlet: Based on the axisymmetric reference flow field of the internal and external flow integration in step 1), the surface of the waverider precursor and the inward-turning air inlet is generated by adopting the osculating flow field method; a part of the waverider precursor is used as the precursor of the inward-turning air inlet; 3) Generate the upper surface of the fuselage and the air inlet cover.

2. The integrated design method of waverider precursor / three-channel air intake duct based on the double waverider principle of flow direction as claimed in claim 1, characterized in that In step 1), a quadratic concave curve passing through the coordinate origin is selected as the external flow field generator, which is defined by the following expression: （1） （2） （3） In the formula, represents the inclination angle at the origin of the coordinate system, represents the inclination angle at point B, and Represents the axial and radial distances at point B.

3. The integrated design method of waverider precursor / three-channel air intake duct based on the double waverider principle of flow direction as claimed in claim 1, characterized in that In step 2), the waverider precursor and the inward-turning air inlet are generated, wherein a part of the waverider precursor needs to be used as a precursor of the inward-turning air inlet, so the waverider precursor is generated in two parts; the specific method is: (1) Generate waverider precursors: The leading edge profiles of the first and second waverider precursors are designed in the design section respectively, and are discretized by osculating planes; On each osculating plane, the discrete point is projected forward along the direction of the free streamline until it intersects with the forebody shock wave, thereby determining the leading edge point of the waverider forebody; the leading edge point of the first part of the forebody is traced by streamlines in the forebody dependent region to generate the first part of the waverider forebody wall surface; the leading edge point of the second part of the forebody is traced by streamlines in the isentropic compression region to generate the second part of the waverider forebody wall surface; (2) Generate an inward-turned inlet: define the trailing edge profile of the second waverider front as the upper capture curve, and define a part of the inlet shock wave profile as the lower capture curve. Design the central angle of the inlet capture shape according to the capture flow rate and other requirements of the inlet to obtain the side capture curves of the three inlets. Discretize these curves using osculating planes, project the discrete points horizontally onto the incident shock wave of the inlet, and obtain the leading edge points of the inlet. Streamline trace these leading edge points in the incident shock wave dependent region of the inlet lip and the stable region of the internal flow field until the exit section of the inlet throat, and generate the profiles of the three inlets.

4. The integrated design method of waverider precursor / three-channel air intake duct based on the double waverider principle of flow direction as claimed in claim 1, characterized in that In step 3), the specific method of generating the upper surface of the body and the outer cover of the air inlet is: the upper wall of the body adopts the free flow surface, and the shape of the outer cover wall of the air inlet is generated by a geometric transition method.

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