Plane embedded air intake and optimization method considering comprehensive performance under multiple working conditions

Abstract

The present invention relates to a planar embedded air inlet and an optimization method that considers comprehensive performance under multiple working conditions. The invention belongs to the field of aircraft technology and solves the problem of poor comprehensive performance of the air inlet under cruise state, different engine working conditions and external flow field conditions, and the lack of a better improvement strategy when improving the comprehensive performance of the air inlet under multiple working conditions. The planar embedded air inlet of the present invention includes a lip, an inlet guide section and a diffuser section; the inlet guide section is arranged between the lip and the diffuser section, and the connection between the inlet guide section and the diffuser section is interface 1; an outlet section is arranged where the diffuser section is connected to the aircraft engine inlet; and interface 2 is arranged where the lip is connected to the aircraft fuselage.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft, and in particular relates to a planar embedded air inlet taking into account comprehensive performance under multiple working conditions and an optimization method. Background Art

[0002] Compared to traditional precision strike weapons, such as precision-guided bombs and cruise missiles, loitering missiles offer unique advantages, including the ability to remain in the air for extended periods and flexible target selection. These features make loitering missiles highly effective for precision strikes against key battlefield nodes and high-value targets.

[0003] The performance of the air inlet directly affects the engine's propulsion efficiency and operational stability, and is crucial to the flight performance of a jet-powered loitering missile. The flat, embedded air inlet effectively shields the fan and compressor blades downstream of the inlet, significantly reducing the aircraft's radar scattering area. Compared to conventional S-curved inlets, it offers superior stealth.

[0004] However, because flat embedded inlets lack boundary layer separators and their lip edges entrain the boundary layer in front of the fuselage, they are susceptible to ingesting the low-energy boundary layer from the forward fuselage. Once these low-energy boundary layers enter the inlet, they significantly distort the airflow within the inlet, reducing the total pressure recovery coefficient and hindering engine stability. Therefore, optimizing the design of flat embedded inlets has important practical implications, helping to enhance the stealth performance of aircraft, improve engine propulsion efficiency, and expand the flight envelope of cruise missiles.

[0005] Existing optimization design methods for planar embedded inlets primarily focus on the inlet's performance during the vehicle's cruise state. Considering the mission requirements of jet-powered cruise missiles, it is necessary to ensure stable engine operation during cruise, maneuvering, and exposure to external disturbances. This requires the inlet to exhibit minimal intake distortion and a large total pressure recovery coefficient not only at the design point in cruise state, but also under various engine operating conditions and external flow field conditions (primarily angle of attack and sideslip angle). Therefore, a more comprehensive inlet aerodynamic performance evaluation method is needed to measure the inlet's comprehensive performance under different operating conditions and optimize its design based on its comprehensive performance under multiple operating conditions. Summary of the Invention

[0006] In response to the aforementioned issues, the present invention provides a planar submerged inlet and optimization method that considers comprehensive performance under multiple operating conditions. This method addresses the problem of poor overall inlet performance under cruise conditions, various engine operating conditions, and external flow field conditions (primarily angle of attack and sideslip angle), and the lack of a robust strategy for improving inlet performance under these conditions.

[0007] The present invention provides a planar embedded air inlet that takes into account comprehensive performance under multiple working conditions, comprising a lip, an inlet guide section and a diffuser section; the inlet guide section is arranged between the lip and the diffuser section, and the connection between the inlet guide section and the diffuser section is interface 1; an outlet section is provided at the connection between the diffuser section and the aircraft engine inlet; and interface 2 is provided at the connection between the lip and the aircraft fuselage.

[0008] Optionally, the ratio of the cross-sectional area of ​​the second interface to the cross-sectional area of ​​the outlet cross section is the pressure diffusion ratio.

[0009] Optionally, the angle between the side wall of the inlet guide section and the line parallel to the axis of the inlet guide section is the lip side angle.

[0010] The present invention also provides a method for optimizing a planar embedded air intake duct that considers comprehensive performance under multiple operating conditions. The method optimizes the aforementioned planar embedded air intake duct, and is characterized by the following specific steps:

[0011] S1. Establish a parametric surface model of the planar embedded air inlet;

[0012] S2. Initializing the parameters of the parametric surface model of the planar embedded air inlet;

[0013] The parameterized surface model includes the first-stage model parameters and the second-stage model parameters;

[0014] S3. Let k = 0. When k = 0, it is the initial moment of the first stage;

[0015] S4. Based on the parameters of the parametric surface model of the planar embedded air inlet at the kth moment and the parametric surface model of the planar embedded air inlet in step S1, a first-stage planar embedded air inlet at the kth moment is generated; meshing the plane embedded air inlet surface model at the kth moment to obtain the first-stage mesh at the kth moment;

[0016] S5. Based on the first-stage grid and the first-stage boundary conditions at the k-th moment in step S4, perform aerodynamic numerical simulation on the inlet duct to obtain the flow field data at each point on the outlet cross section of the inlet duct at the k-th moment;

[0017] S6. Input the flow field data obtained in S5 into the simulation data post-processing module to obtain the first stage evaluation index at the kth moment;

[0018] S7. Determine, based on the first-stage evaluation indicators, whether the first-stage planar embedded air intake at time k has achieved the first-stage optimization target. If so, obtain the first-stage optimized air intake and proceed to step S8. If not, obtain the first-stage model parameters at time k+1, set k=k+1, and return to step S4.

[0019] S8. Initializing the second stage model parameters of the intake duct after the first stage optimization;

[0020] S9. Let t = 0. When t = 0, it is the initial time of the second stage;

[0021] S10. Based on the second-stage model parameters of the optimized first-stage intake at time t and the parameterized surface model of the planar embedded intake in step S1, a second-stage planar embedded intake at time t is generated;

[0022] S11. Meshing the second-stage planar embedded air inlet at time t to obtain a second-stage mesh at time t;

[0023] S12. Based on the second-stage grid and the second-stage boundary conditions at time t in step S11, perform batch aerodynamic numerical simulations on the intake duct to obtain the total pressure at each point on the outlet cross section of the intake duct under the corresponding boundary conditions and the second-stage grid at time t;

[0024] S13. Inputting the corresponding boundary conditions and the total pressure at each point on the outlet cross section of the inlet duct under the second-stage grid at time t into the simulation data post-processing module, the post-processing module outputting the evaluation index of the second-stage inlet duct at time t;

[0025] S14. Based on the evaluation indicators of the second-stage intake duct, determine whether the performance of the second-stage intake duct at time t meets the second-stage optimization target. If so, obtain the optimized planar embedded intake duct surface model and proceed to step S15. If not, obtain the second-stage model parameters of the first-stage optimized intake duct at time t+1, set t=t+1, and return to step S10.

[0026] S15. Output the optimized surface model of the embedded plane air inlet.

[0027] Optionally, the first stage model parameters include a diffuser centerline shape control coefficient and a diffuser cross-sectional area distribution law control coefficient;

[0028] The second stage model parameters include the lip side angle and the diffusion ratio.

[0029] Optionally, the first-stage boundary condition in step S5 is the state of the external gas in the air inlet when the aircraft is in a cruising state.

[0030] Optionally, the process data in step S5 are the total pressure and dynamic pressure of the flow field at each point on the outlet cross section of the inlet duct at the kth moment and the far-field free stream total pressure of the flow field outside the inlet duct.

[0031] Optionally, the first stage evaluation index at the kth moment includes the intake duct total pressure distortion index DC60 k and total pressure recovery coefficient PR k .

[0032] Optionally, the parameters of the parameterized surface model of the planar embedded air inlet include coefficients of the first-stage air inlet centerline expression and coefficients of the diffuser section area distribution law expression.

[0033] Optionally, the second-stage evaluation index includes the performance index of the second-stage inlet at the inlet design point at time t, the inlet performance index considering the change of the inlet angle under the outlet flow of the inlet when the aircraft is in the cruising state, and the inlet stability index considering the engine operating conditions and the change of the inlet state.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] 1. The comprehensive performance evaluation method of the air inlet in the optimization method of the present invention comprehensively considers the comprehensive performance of the air inlet in the cruising state, different engine operating conditions and external flow field conditions. It can be used to evaluate the comprehensive performance of the air inlet of an aircraft in the cruising state and when performing maneuvers, and the method is applicable to air inlets of different shapes.

[0036] 2. The present invention divides the optimization process of the planar embedded air inlet into a pre-optimization stage with the performance in the cruise state as the optimization target and a comprehensive optimization stage with the comprehensive performance under various working conditions as the optimization target. This reduces the dimension of the design space, saves the time required for optimization, and improves the optimization efficiency.

[0037] 3. The optimization method of the present invention takes into account the intake principle of the planar embedded air inlet. Aiming at the negative impact of the low total pressure area at the inlet outlet caused by the separation of the low total pressure area at the inlet outlet and the diffuser section caused by the lip suction vortex on the aerodynamic performance of the inlet, the inlet lip parameters are associated with the diffuser section parameters to achieve comprehensive optimization considering the coupling influence of the lip shape and the diffuser section shape on the inlet performance, which can achieve more comprehensive optimization of the inlet performance and improve the optimization effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings are only for purposes of illustrating particular embodiments and are not to be considered limiting of the invention.

[0039] Figure 1 It is a schematic structural diagram of the planar embedded air inlet of the present invention;

[0040] Figure 2 Schematic diagram of the centerline of the diffuser section of the planar embedded air inlet of the present invention;

[0041] Figure 3 Schematic diagram of the lip side angle μ of the planar embedded air inlet of the present invention;

[0042] Figure 4 is a flow chart of the planar embedded air inlet optimization method of the present invention;

[0043] Figure 5 This is a schematic diagram of the solution principle of the total pressure distortion index DC60 in the post-processing module. DETAILED DESCRIPTION

[0044] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0045] A specific embodiment of the present invention, as Figure 1-5 , discloses a planar embedded air inlet that takes into account comprehensive performance under multiple working conditions, including a lip 1, an inlet guide section 2 and a diffuser section 3; the inlet guide section 2 is arranged between the lip 1 and the diffuser section 3, and the connection between the inlet guide section 2 and the diffuser section 3 is an interface 1 5; an outlet section 6 is provided at the connection between the diffuser section 3 and the aircraft engine inlet; an interface 2 4 is provided at the connection between the lip 1 and the aircraft fuselage.

[0046] Furthermore, the ratio of the cross-sectional area of ​​the second interface 4 to the cross-sectional area of ​​the outlet cross section 6 is the pressure diffusion ratio Ad.

[0047] Further, see Figure 3 The angle between the side wall 7 of the inlet guide section 2 and the line 8 parallel to the axis of the inlet guide section 2 is the lip side angle μ.

[0048] Another specific embodiment of the present invention is as follows Figure 4 , discloses an optimization method for a planar embedded air intake that considers comprehensive performance under multiple operating conditions. The specific steps are as follows:

[0049] S1. Establish a parametric surface model of the planar embedded air inlet.

[0050] Furthermore, the parameterized surface model includes first-stage design variables and second-stage design variables.

[0051] Furthermore, the first-stage design variables include a diffuser centerline shape control coefficient and a diffuser cross-sectional area distribution law control coefficient.

[0052] Among them, the control coefficient of the centerline shape of the diffuser section includes the fourth power coefficient n1, the cubic coefficient p1, and the quadratic coefficient q1 of the centerline shape of the diffuser section; the control coefficient of the cross-sectional area distribution law of the diffuser section includes the fourth power coefficient n2, the cubic coefficient p2, and the quadratic coefficient q2 of the cross-sectional area distribution law of the diffuser section.

[0053] The expression of the centerline shape of the diffuser is:

[0054] Y=n1X 4 +p1X 3 +q1X 2

[0055] Where Y represents the y-axis coordinate value of any point on the centerline of the diffuser in the inlet body coordinate system; X represents the x-axis coordinate value of the corresponding point in the inlet body coordinate system.

[0056] Understandably, see Figure 2 The origin O of the coordinate system is located at the geometric center point of the intake duct interface 24, the x-axis is located in the intake duct symmetry plane, and the direction points to the intake duct outlet; the y-axis is located in the intake duct symmetry plane, perpendicular to the x-axis, and points to the top of the intake duct; the z-axis is perpendicular to the intake duct symmetry plane.

[0057] The expression of the cross-sectional area distribution law of the diffuser section is:

[0058] A=n2X 4 +p2X 3 +q2X 2

[0059] Where A represents the cross-sectional area of ​​the diffuser corresponding to a plane passing through any point on the diffuser centerline and perpendicular to the diffuser centerline; X represents the x-axis coordinate value of the corresponding point in the inlet body coordinate system.

[0060] Furthermore, the second-stage design variables include the lip side angle μ and the diffusion ratio Ad.

[0061] S2. Initialize the parameters of the parametric surface model of the planar embedded air inlet.

[0062] Specifically, the initial diffuser centerline shape control coefficient is n 10 、p 10 ,q 10 , the control coefficient of the cross-sectional area distribution law of the diffuser section is n 20 、p 20 ,q 20 .

[0063] Set the target value DC60 of the total pressure distortion index of the inlet duct to be achieved in the first stage 1 and the total pressure recovery coefficient target value PR 1 . Entering the first stage of optimization.

[0064] S3. Let k = 0. When k = 0, it is the initial moment of the first stage.

[0065] S4. Based on the diffuser centerline shape control coefficient at time k and the parameterized surface model of the planar embedded inlet from step S1, generating a first-stage planar embedded inlet at time k; meshing the planar embedded inlet surface model at time k to obtain a first-stage mesh at time k;

[0066] S5. Import the first-stage grid obtained at time k in step S4 into aerodynamic numerical simulation software. Using the state of the gas outside the inlet in the aircraft's cruise state as the first-stage boundary condition, perform an aerodynamic numerical simulation of the inlet to obtain the total pressure and dynamic pressure of the flow field at each point (i.e., each grid point) on the outlet cross-section 6 of the inlet at time k, as well as the far-field free stream total pressure of the flow field outside the inlet.

[0067] S6. Input the flow field data obtained in S5 (i.e., total pressure, dynamic pressure, and far-field free stream total pressure) into the simulation data post-processing module to obtain the inlet total pressure distortion index DC60 at the kth moment k and total pressure recovery coefficient PR k .

[0068] The specific steps are:

[0069] S61. Based on the flow field data obtained in S5, the total pressure and dynamic pressure of each point on the outlet section 6 of the flow field at the kth moment are averaged to obtain the average total pressure p of the outlet section at the kth moment. av，k and the average dynamic pressure q at the outlet section av，k .

[0070] S62. Figure 5 As shown, at the outlet section 6 at the kth moment, with the center of the outlet section 6 at the kth moment as the center of the circle, set the step length to r, and establish A sector area with a central angle of 60°.

[0071] S63. The average total pressure of the flow field in the fan-shaped area is solved, and the average total pressure in each fan-shaped area is compared to obtain the minimum average total pressure (p min，k ) 60° .

[0072] S64. Average total pressure p at the outlet section at time k av，k , average dynamic pressure q at the outlet section av，k and the minimum average total pressure (p min，k ) 60° Get the total pressure distortion index DC60 of the inlet at the kth moment k , the expression is:

[0073]

[0074] S65. Average total pressure p of the outlet section based on the kth moment av，k , obtain the intake duct total pressure recovery coefficient PR at the kth moment k , the expression is:

[0075]

[0076] Among them, p t∞，k represents the far-field free stream total pressure of the inlet external flow field at the kth moment.

[0077] S7. Inlet total pressure distortion index DC60 based on the kth moment k and total pressure recovery coefficient PR k , judge whether the first-stage plane embedded air intake duct reaches the first-stage optimization target at the k-th moment. If it reaches the first-stage optimization target, obtain the first-stage optimized air intake duct and enter step S8. If it does not reach the first-stage optimization target, obtain the first-stage air intake duct centerline expression coefficient n at the k+1-th moment by the optimization algorithm. 1(k+1) 、p 1(k+1) ,q 1(k+1) , the coefficient n of the expression of the distribution law of the diffuser area 2(k+1) 、p 2(k+1) ,q 2(k+1) , let k=k+1, and return to step S4;

[0078] Furthermore, the optimization target of the first stage is DC60 k ≤DC60 1 , PR k ≥PR 1 , DC60 1 Indicates the target value of the total pressure distortion index in the first stage; PR 1 Indicates the target value of the total pressure recovery coefficient in the first stage.

[0079] S8. Initialize the second-stage parameters of the intake duct after the first-stage optimization.

[0080] Specifically, initially, the inlet lip side angle is μ0 and the expansion ratio is Ad0.

[0081] The present invention uses the lip side angle μ, a parameter for controlling the inlet lip shape, and the diffusion ratio Ad, a parameter for coupling controlling the lip shape and the diffusion section shape, as design variables for the second-stage optimization, effectively avoiding the degradation of the aerodynamic performance of the plane embedded inlet caused by the low total pressure area at the inlet outlet caused by the separation of the low total pressure area at the inlet outlet from the diffusion section caused by the lip entrainment vortex of the designed plane embedded inlet.

[0082] Obtain the second-stage optimization target and enter the second-stage optimization.

[0083] Preferably, the optimization objectives of the second stage include the performance index at the inlet design point, the inlet performance index considering the change of the inlet angle under the inlet outlet flow rate when the inlet is in the cruising state of the aircraft, and the inlet stability index considering the engine operating conditions and the change of the inlet flow state.

[0084] It can be understood that the design point refers to the external flow field conditions of the inlet duct in the cruising state and the flow conditions at the outlet of the inlet duct (at the outlet section 6); the performance index at the design point of the inlet duct refers to the performance index of the inlet duct when the inlet duct is working at the design point (cruising state).

[0085] Preferably, the performance index at the design point of the inlet duct includes a total pressure distortion index DP_DC60 at the design point and a total pressure recovery coefficient DP_PR at the design point.

[0086] Furthermore, the design point is (β0, α0), which means that the sideslip angle of the external flow of the inlet is β0 and the angle of attack is α0 under the designed cruise state.

[0087] Preferably, the inlet performance index considering the change of the inlet angle at the inlet outlet flow rate when the aircraft is in the cruising state includes the total pressure distortion index WM_DC60 considering the change of the inlet angle at the design point DPmassflow and total pressure recovery coefficient WM_PR DPmassflow

[0088] Furthermore, within the inlet flow angle range, the total pressure distortion index WM_DC60 considering the change of the inlet flow angle at the design point is DPmassflow and total pressure recovery coefficient WM_PR DPmassflow The expression is:

[0089]

[0090]

[0091] Where W DC60 (β, α) represents the weight of the total pressure distortion index DP_DC60(β, α) at ​​the design point under the working point (β, α) in the total pressure distortion index considering the change of the inflow angle; W PR(β, α) represents the weight of the total pressure recovery coefficient DP_PR(β, α) in the total pressure recovery coefficient at the working point (β, α); β represents the sideslip angle at the working point; α represents the angle of attack at the working point; β min and β max They represent the lower and upper bounds of the sideslip angle of the working point respectively; α min and α max They represent the lower and upper bounds of the angle of attack of the working point respectively.

[0092] It will be appreciated that the operating point is the operating condition of the intake duct.

[0093] Because in the aircraft mission profile, the air inlet works for a longer time at the working point close to the design point, and the working point deviates significantly from the design point only when it is subject to large external disturbances and when climbing or diving at large angles of attack. Therefore, the performance of the air inlet at the working point close to the design point has a greater impact on the flight performance of the aircraft throughout the mission process. The present invention assigns a higher weight to the air inlet performance at the working point near the design point, and a lower weight to the air inlet performance at the working point far from the design point, so that the weight decreases faster as the distance of the working point from the design point increases. This ensures that the optimized air inlet meets the mission requirements of the adapted aircraft.

[0094] Furthermore, using a quadratic function as the weight function, the expression is:

[0095]

[0096]

[0097] Where l(β,α) represents the distance between the working point (β,α) and the design point (β0,α0), l max Indicates the farthest distance between the design point and the working point, b DC60 with b PR They represent the total pressure distortion index DC60 at the farthest working point and the total pressure recovery coefficient PR when considering the change of the incoming flow angle. DPmassflow and total pressure recovery coefficient WM_PR DPmassflow The weight of b DC60 with b PR The value range is (0, 1).

[0098] Further b DC60 with b PR All are taken as 0.5.

[0099] Further, l(β,α)=|(β0,α0)-(β,α)|;

[0100] Total pressure distortion index considering the change of the incoming flow angle at the flow rate at the design point of the present invention

[0101] WM_DC60 DPmassflow The total pressure recovery coefficient WM_PR considering the change of the inflow angle under the flow rate at the design point DPmassflow It measures the global performance of the inlet at the design point flow rate within a specified range of sideslip angles and angles of attack. DPmassflow The smaller the total pressure distortion, the better the inlet performance. DPmassflow The larger the value, the greater the global total pressure recovery coefficient and the better the inlet performance.

[0102] The optimization method of the present invention measures the comprehensive aerodynamic performance of the inlet at different inlet angles (angle of attack and sideslip angle) by taking into account the inlet performance index of the change in inlet angle at the inlet outlet flow rate when the inlet is in the cruising state of the aircraft, thereby ensuring that the optimized inlet can have relatively good performance even when it deviates from the working state within a certain range.

[0103] Furthermore, the intake stability index considering the engine operating conditions and the changes in the incoming flow state includes the total pressure distortion index change rate WM_DC60 Sensitivity and the total pressure recovery coefficient change rate WM_PR Sensitivity .

[0104] The present invention considers the total pressure distortion index of the flow angle change at the design point

[0105] WM_DC60 DPmassflow and total pressure recovery coefficient WM_PR DPmassflow On the basis of the total pressure distortion index change rate WM_DC60 Sensitivity and the total pressure recovery coefficient change rate WM_PR Sensitivity , which is used to measure the stability of the comprehensive aerodynamic performance of the air inlet under different working conditions of the engine and different external flow angles. Taking into account that the cruise missile adapted by the air inlet has not only the design point of the cruise stage, but also the design requirement of full throttle high-speed penetration, when the engine switches from the cruise throttle to the full throttle in the acceleration stage, the air inlet faces the situation of working point switching. At this time, it is necessary to consider the stability of the air inlet operation to avoid excessive changes in performance parameters of the air inlet when the working point is switched, resulting in unstable engine operation or even surge. This ensures that the performance parameters of the selected air inlet change little when the engine working state switches under different flow angles.

[0106] Furthermore, the total pressure distortion index change rate WM_DC60 Sensitivity and the total pressure recovery coefficient change rate WM_PR Sensitivity The expression is:

[0107]

[0108]

[0109] Among them, WM_DC60 DPmassflow with WM_PR DPmassflow They represent the total pressure distortion index and total pressure recovery coefficient of the inlet considering the change of the inlet flow angle at the design point flow rate; WM_DC60 full thr ottle massflow with WM_PR full thr ottle massflow They respectively represent the total pressure distortion index and total pressure recovery coefficient considering the change of the inflow angle at the operating point when the engine is at full throttle.

[0110] S9. Let t = 0. When t = 0, it is the initial moment of the second stage.

[0111] S10. Based on the control coefficient of the diffuser section cross-sectional area distribution law at the tth moment and the parameterized surface model of the planar embedded air inlet in step S1, a second-stage planar embedded air inlet at the tth moment is generated.

[0112] S11. Meshing the second-stage planar embedded air inlet at time t to obtain a second-stage mesh at time t;

[0113] S12. Import the second-stage grid at time t in step S11 into the aerodynamic numerical simulation software; within the preset sideslip angle range, angle of attack range and inlet outlet flow range of the inlet external flow field, take the sideslip angle matrix, angle of attack matrix and outlet flow matrix with equal steps; use the combination of the elements of the sideslip angle matrix, angle of attack matrix and outlet flow matrix as the second-stage boundary conditions, and perform batch aerodynamic numerical simulations on the inlet to obtain the total pressure at each point on the outlet section 6 of the inlet under different boundary conditions and the second-stage grid at time t.

[0114] S13. The total pressure at each point on the outlet section 6 of the inlet duct under different boundary conditions and the second-stage grid at time t is input into the simulation data post-processing module. The post-processing module outputs the performance index of the inlet duct design point of the second-stage inlet duct at time t: the total pressure distortion index DP_DC60 at the design point t and the total pressure recovery coefficient DP_PR at the design point t 2. Inlet performance index considering the change of inlet angle under the outlet flow of the inlet when the aircraft is in the cruising state: inlet global total pressure distortion index WM_DC60 DPmassflow，t , the inlet total pressure recovery coefficient WM_PR DPmassflow，t And the intake stability index considering the engine operating conditions and the changes in the incoming flow state: the total pressure distortion index sensitivity WM_DC60Sensitivity，t and total pressure recovery coefficient sensitivity WM_PR Sensitivity，t .

[0115] S14. Performance index of the intake duct design point of the second stage intake duct at time t: Total pressure distortion index DP_DC60 at the design point t and the total pressure recovery coefficient DP_PR at the design point t 2. Inlet performance index considering the change of inlet angle under the outlet flow of the inlet when the aircraft is in the cruising state: inlet global total pressure distortion index WM_DC60 DPmassflow，t , the inlet total pressure recovery coefficient WM_PR DPmassflow，t And the intake stability index considering the engine operating conditions and the changes in the incoming flow state: the total pressure distortion index sensitivity WM_DC60 Sensitivity，t and total pressure recovery coefficient sensitivity WM_PR Sensitivity，t , determine whether the performance of the second-stage air intake at time t reaches the second-stage optimization target. If it reaches the second-stage optimization target, obtain the optimized plane embedded air intake surface model and enter step S15. If it does not reach the second-stage optimization target, obtain the lip side edge angle μ of the second-stage air intake at time t+1 by the optimization algorithm. (t+1) , expansion ratio Ad (t+1) Let t=t+1, and return to step S10;

[0116] S15. Output the optimized surface model of the embedded plane air inlet.

[0117] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for optimizing a planar embedded air intake considering comprehensive performance under multiple operating conditions, characterized in that: The planar embedded air inlet comprises a lip, an inlet guide section and a diffuser section; the inlet guide section is arranged between the lip and the diffuser section, and the connection between the inlet guide section and the diffuser section is a first interface; the diffuser section is provided at the connection between the diffuser section and the aircraft engine inlet; the lip is provided at the connection between the lip and the aircraft fuselage. The specific steps are as follows: S1. Establish a parametric surface model of the planar embedded air inlet; S2. Initializing the parameters of the parametric surface model of the planar embedded air inlet; The parameterized surface model includes the first-stage model parameters and the second-stage model parameters; S3. Let k = 0. When k = 0, it is the initial moment of the first stage; S4. Based on the parameters of the parametric surface model of the planar embedded air inlet at the kth moment and the parametric surface model of the planar embedded air inlet in step S1, a first-stage planar embedded air inlet at the kth moment is generated; meshing the plane embedded air inlet surface model at the kth moment to obtain the first-stage mesh at the kth moment; S5. Based on the first-stage grid and the first-stage boundary conditions at the k-th moment in step S4, perform aerodynamic numerical simulation on the inlet duct to obtain the flow field data at each point on the outlet cross section of the inlet duct at the k-th moment; S6. Input the flow field data obtained in S5 into the simulation data post-processing module to obtain the first stage evaluation index at the kth moment; S7. Determine, based on the first-stage evaluation indicators, whether the first-stage planar embedded air intake at time k has achieved the first-stage optimization target. If so, obtain the first-stage optimized air intake and proceed to step S8. If not, obtain the first-stage model parameters at time k+1, set k=k+1, and return to step S4. S8. Initializing the second stage model parameters of the intake duct after the first stage optimization; S9. Let t = 0. When t = 0, it is the initial time of the second stage; S10. Based on the second-stage model parameters of the optimized first-stage intake at time t and the parameterized surface model of the planar embedded intake in step S1, a second-stage planar embedded intake at time t is generated; S11. Meshing the second-stage planar embedded air inlet at time t to obtain a second-stage mesh at time t; S12. Based on the second-stage grid and the second-stage boundary conditions at time t in step S11, perform batch aerodynamic numerical simulations on the intake duct to obtain the total pressure at each point on the outlet cross section of the intake duct under the corresponding boundary conditions and the second-stage grid at time t; S13. Inputting the corresponding boundary conditions and the total pressure at each point on the outlet cross section of the inlet duct under the second-stage grid at time t into the simulation data post-processing module, the post-processing module outputting the evaluation index of the second-stage inlet duct at time t; S14. Based on the evaluation indicators of the second-stage intake duct, determine whether the performance of the second-stage intake duct at time t meets the second-stage optimization target. If so, obtain the optimized planar embedded intake duct surface model and proceed to step S15. If not, obtain the second-stage model parameters of the first-stage optimized intake duct at time t+1, set t=t+1, and return to step S10. S15. Outputting the optimized surface model of the embedded inlet; The first-stage model parameters include the diffuser centerline shape control coefficient and the diffuser cross-sectional area distribution law control coefficient; The second-stage model parameters include the lip side angle and the diffusion ratio; The second-stage evaluation indicators include the performance indicators of the second-stage inlet at the inlet design point at time t, the inlet performance indicators considering the change of the inlet angle under the outlet flow of the inlet when the aircraft is in the cruising state, and the inlet stability indicators considering the changes in engine operating conditions and inlet flow conditions.

2. The optimization method of a planar embedded air intake considering comprehensive performance under multiple working conditions according to claim 1, characterized in that: The ratio of the cross-sectional area of ​​the second interface to the cross-sectional area of ​​the outlet cross section is the expansion ratio.

3. The optimization method of a planar embedded air intake considering comprehensive performance under multiple working conditions according to claim 1, characterized in that: The angle between the side wall of the inlet guide section and the line parallel to the axis of the inlet guide section is the lip side angle.

4. The optimization method of a planar embedded air intake considering comprehensive performance under multiple working conditions according to claim 1, characterized in that: The first-stage boundary condition in step S5 is the state of the external gas in the air inlet when the aircraft is in the cruising state.

5. The optimization method of a planar embedded air intake considering comprehensive performance under multiple working conditions according to claim 1, characterized in that: The process data in step S5 are the total pressure and dynamic pressure of the flow field at each point on the outlet cross section of the inlet duct at the kth moment and the far-field free stream total pressure of the flow field outside the inlet duct.

6. The optimization method of a planar embedded air intake considering comprehensive performance under multiple working conditions according to claim 1, characterized in that: The first stage evaluation index at the kth moment includes the inlet total pressure distortion index DC60 k and total pressure recovery coefficient PR k .

7. The optimization method of a planar embedded air intake considering comprehensive performance under multiple working conditions according to claim 1, characterized in that: The parameters of the parametric surface model of the plane embedded inlet include the coefficients of the first stage inlet centerline expression and the coefficients of the diffuser area distribution law expression.

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