General evaluation method for additional resistance of air inlet channel based on reconstruction of capture flow pipe
By reconstructing the intake trap in 3D modeling software and using Poisson or spherical surface of revolution algorithms for pressure integration, the difficulty of evaluating additional drag in complex 3D intakes under complex operating conditions is solved, achieving high-precision evaluation results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-10
- Publication Date
- 2026-04-10
AI Technical Summary
Existing technologies struggle to accurately assess the additional drag of inlet ducts with strong three-dimensional characteristics under complex operating conditions, and the momentum integral method presents difficulties in defining aerodynamic contact surfaces in highly integrated aircraft design.
By extracting the lip edge of the intake model in 3D modeling software, performing CFD simulation calculations, reverse tracing of streamlines, reconstructing the capture tube, forming a surface using Poisson reconstruction or spherical surface of revolution algorithm, performing pressure integration, and directly evaluating the additional drag of the intake.
This paper presents a general and accurate method that solves the difficulty in evaluating the additional drag of the intake under complex operating conditions in the prior art, improves the evaluation accuracy, and is applicable to different types of intakes.
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Figure CN121835472A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of aircraft inlet, in particular to an evaluation method of additional resistance of an aircraft inlet. BACKGROUND
[0002] As the main air flow capturing (compressing) and flow regulating device of air-breathing engines, the inlet connects the upstream aircraft with the downstream engine / combustor and is a key component of the propulsion system. The inlet resistance is an important part of the propulsion system resistance, mainly including additional resistance, cowl resistance and internal resistance. For a fixed-geometry supersonic inlet, the additional resistance accounts for a high proportion of the total aircraft resistance under high subsonic flight conditions. Therefore, the rapid and accurate evaluation of additional resistance is crucial for determining the engine installation thrust.
[0003] The typical working state of a supersonic inlet includes the design state, subcritical state at sub-rating, supercritical state at sub-rating and subcritical state at sub-rating. Different lip cowl leading edge upstream wave systems and flow field structures produce supersonic spillage, subsonic spillage, induce different additional resistance, and result in large changes in additional resistance. Therefore, the inlet spillage resistance is greatly affected by the working state, and it is difficult to accurately evaluate. At present, the inlet and aircraft are highly integrated, which has deviated from the early two-dimensional, axisymmetric and side pressure typical configurations. The inlet and its captured flow tube have strong three-dimensional characteristics, which brings new challenges to the evaluation of additional resistance.
[0004] Based on the shock wave theory and geometric relationship, the additional resistance of a typical simple wave two-dimensional inlet can be theoretically calculated, but it is difficult to use this method to evaluate the spillage resistance of a strong three-dimensional complex wave inlet. The momentum integral method relies on the wall force data in contact with the captured flow tube. At present, the inlet design and aircraft are highly integrated, and it is difficult to define the complex captured flow tube and aerodynamic contact surface.
[0005] Therefore, a new technical solution is needed to solve the above problems. SUMMARY
[0006] To solve the above problems, the present application proposes a general evaluation method of additional resistance of an inlet based on reconstruction of a captured flow tube, which aims to solve the problems of strong three-dimensional characteristics of the inlet for the current highly integrated aircraft design and poor applicability of the theoretical method under complex working conditions, and difficulty in defining the aerodynamic contact surface of the momentum integral method. From the mechanism of additional resistance generation, the captured flow tube of the inlet is restored, interpolated and integrated to directly obtain the additional resistance of the inlet.
[0007] Technical scheme: A general evaluation method of additional resistance of an inlet based on reconstruction of a captured flow tube, comprising the following steps:
[0008] (1) extracting a lip edge of an air intake model in a three-dimensional modeling software, and obtaining a plurality of first discrete point coordinates on the lip edge;
[0009] (2) obtaining data of an entire flow field including pressure data by CFD simulation calculation of the air intake model by using a fluid simulation software, and obtaining a lip capturing streamline in a post-processing software according to the coordinates of the plurality of first discrete points;
[0010] (3) obtaining a plurality of second discrete points on the capturing streamline, and obtaining three-dimensional coordinate data and pressure data of the second discrete points by using data of corresponding positions of the second discrete points in the flow field, the pressure data being static pressure;
[0011] (4) performing surface reconstruction on a point cloud formed by the plurality of second discrete points by using a Poisson reconstruction method or a spherical rotation surface reconstruction algorithm, the reconstructed surface including a plurality of facets, and each facet being composed of a plurality of meshes;
[0012] (5) obtaining a capturing flow tube with static pressure by interpolation on the surface according to the three-dimensional coordinate data and the static pressure of the known second discrete points;
[0013] (6) obtaining a resultant force and projections of the resultant force in various directions on a recovered surface by pressure integration on the capturing flow tube with static pressure, and obtaining an additional resistance of the air intake by projection superposition according to a model coordinate system and a simulation calculation working condition.
[0014] Further, in step (2), when an error occurs in the streamline tracking, the error is eliminated by adjusting the point taking on the lip edge of the air intake model in the software to complete the streamline tracking.
[0015] Further, in step (4), the Poisson reconstruction method includes the following steps:
[0016] (4.1.1) converting point samples into a continuous vector field;
[0017] (4.1.2) solving a Poisson system containing a three-dimensional Laplace equation to find a function whose gradient best describes the point cloud;
[0018] (4.1.3) reconstructing a surface from the function equation.
[0019] Further, in step (4), the spherical rotation surface reconstruction algorithm includes the following steps:
[0020] (4.2.1) setting a plurality of sampling points, contacting a sphere with three sampling points, and forming a plurality of seed triangles from the three sampling points;
[0021] (4.2.2) keep the ball in contact with one side of a seed triangle, and rotate the ball until the ball contacts another sample point as a new sample point, the side and the new sample point define a new triangle;
[0022] (4.2.3) rotate the ball using the new triangle side, repeat the process of rotating and defining a new triangle with a contact point using one side of the new triangle, the triangles formed constitute an interpolated triangular mesh, until all reachable sides are covered;
[0023] (4.2.4) repeat steps (4.2.2) and (4.2.3) from another seed triangle until all seed triangles complete steps (4.2.2) and (4.2.3);
[0024] (4.2.5) repeat steps (4.2.1) to (4.2.4) with a larger radius ball to reconstruct uneven surfaces.
[0025] Further, in step (6), the pressure integration of the trapped flow tube based on the flow direction component of the local pressure of the trapped flow tube is obtained.
[0026] Further, in step (6), the additional resistance of the inlet duct is obtained by integrating the local pressure of the trapped flow tube in the flow direction.
[0027] Further, the pressure integration includes: the area of each face sheet constituting the trapped flow tube, the normal vector of the face sheet, and the static pressure on the face sheet; the pressure on each face sheet can be calculated by the area of the face sheet and the static pressure on the face sheet, i.e. the pressure on the face sheet = face sheet area * static pressure; the pressure vectors on each face sheet are superimposed to obtain the size and direction of the pressure resultant force on the trapped flow tube, i.e. the pressure integration.
[0028] Further, according to the model coordinate system and the simulation calculation condition, the flow direction of the inlet duct is obtained, and the pressure resultant force on the trapped flow tube is projected and superimposed in the direction to obtain the additional resistance of the inlet duct.
[0029] Beneficial effects: compared with the prior art, the present application directly obtains the additional resistance of the inlet duct by restoring, interpolating and integrating the trapped flow tube of the inlet duct from the additional resistance generation mechanism. The problems of poor applicability of shock wave theory and geometric relationship calculation method and difficult aerodynamic contact surface definition of the momentum integration method in the prior art are solved. A general and accurate method is provided for the current strong three-dimensional feature inlet duct and the additional resistance evaluation of the inlet duct under complex working conditions.
[0030] The present application also provides a computer system comprising a memory, a processor and a computer program stored on the memory, wherein the processor executes the computer program to implement the steps of any of the above methods.
[0031] The application also provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of any of the above methods. BRIEF DESCRIPTION OF DRAWINGS
[0032] Figure 1 is a schematic diagram of a model cross-section in a verification example in the application.
[0033] Figure 2 is a schematic diagram of a captured streamline obtained in post-processing software in the application.
[0034] Figure 3 is a schematic diagram of a discrete point data file derived by program reading in the application.
[0035] Figure 4 is a schematic diagram of surface reconstruction of a discrete point cloud by a ball rotation surface reconstruction algorithm or a Poisson reconstruction algorithm in the application.
[0036] Figure 5 is a schematic diagram of a captured flow tube with a flow field pressure parameter obtained by interpolating pressure data on a reconstructed surface in the application.
[0037] Figure 6 is a schematic diagram of calculation of additional drag of a three-dimensional axisymmetric inlet in the application; Figure 6(a) is a schematic diagram of a three-dimensional axisymmetric inlet model and a captured streamline, Figure 6(b) is a schematic diagram of a discrete point cloud on the captured streamline of the three-dimensional axisymmetric inlet, Figure 6(c) is a schematic diagram of a comparison between a reconstructed surface and the discrete point cloud, and Figure 6(d) is a schematic diagram of a captured flow tube with a flow field pressure parameter obtained by interpolating pressure on the reconstructed surface.
[0038] Figure 7 is a schematic diagram of calculation of additional drag of a three-dimensional internal turning inlet in the application; Figure 7(a) is a schematic diagram of a three-dimensional internal turning inlet model and a captured streamline, Figure 7(b) is a schematic diagram of a discrete point cloud on the captured streamline of the three-dimensional internal turning inlet, Figure 7(c) is a schematic diagram of a comparison between a reconstructed surface and the discrete point cloud, and Figure 7(d) is a schematic diagram of a captured flow tube with a flow field pressure parameter obtained by interpolating pressure on the reconstructed surface.
[0039] Figure 8 is a schematic diagram of calculation of additional drag of a two-dimensional adjustable inlet in the application; Figure 8(a) is a schematic diagram of a three-dimensional two-dimensional inlet model, Figure 8(b) is a schematic diagram of a discrete point cloud on the captured streamline of the three-dimensional two-dimensional inlet, Figure 8(c) is a schematic diagram of a comparison between a reconstructed surface and the discrete point cloud, and Figure 8(d) is a schematic diagram of a captured flow tube with a flow field pressure parameter obtained by interpolating pressure on the reconstructed surface. DETAILED DESCRIPTION
[0040] The application provides a general evaluation method for additional drag of an inlet based on captured flow tube reconstruction, comprising the following steps:
[0041] 1. Obtain the lip ridge line of the intake port model in the three-dimensional modeling software, and obtain a plurality of first discrete point coordinates on the lip ridge line.
[0042] 2. Perform CFD simulation calculation on the intake port model using fluid simulation software to obtain data of the entire flow field including pressure data, and perform streamline tracing in the post-processing software according to the coordinates of the plurality of first discrete points to obtain the lip capture streamline. When there is an error in the streamline tracing, the points can also be adjusted at the model lip in the software for streamline tracing, and finally a relatively uniform capture streamline is obtained.
[0043] 3. Obtain a plurality of second discrete points on the capture streamline, and obtain three-dimensional coordinate data and pressure data (static pressure) of the second discrete points through the data of the corresponding positions of the second discrete points in the flow field in the capture streamline. Since the capture streamline is obtained in the CFD simulation flow field, the three-dimensional coordinate data and the pressure data (static pressure) of the second discrete points can be obtained, and these data can be exported as.txt or.dat files.
[0044] 4. Reconstruct the surface of the point cloud formed by the plurality of second discrete points by Poisson reconstruction algorithm or spherical rotation surface reconstruction algorithm through the three-dimensional coordinate data of the second discrete points in the exported data file, and the reconstructed surface includes a plurality of facets, and each facet is composed of a plurality of meshes. The two algorithms are introduced as follows:
[0045] (a) Poisson surface reconstruction algorithm
[0046] The Poisson reconstruction method includes the following steps:
[0047] (1) Convert the point sample to a continuous vector field.
[0048] (2) Solve the Poisson system containing the three-dimensional Laplace equation to find a function whose gradient best describes the point cloud.
[0049] (3) Reconstruct the surface from the function equation.
[0050] This algorithm is suitable for closed surfaces, but requires higher uniformity of the point cloud. If the capture streamline is relatively sparse and the distance between the streamlines is relatively large, the surface reconstruction may be easily broken. Therefore, it is an optional reconstruction algorithm.
[0051] (b) Spherical rotation surface reconstruction algorithm
[0052] The spherical rotation method triangulates a set of points by rolling a sphere with a radius r over the point cloud. Then, based on the triangular surface, the entire surface is continuously extended, and the algorithm consists of the following steps:
[0053] (1) Contact the ball with three sample points. These points form a seed triangle.
[0054] (2) Keep the ball in contact with two of these initial points (one side of the seed triangle) and rotate the ball until it touches another point. This side and the new point define a new triangle.
[0055] (3) Rotate the sphere using the new triangle edge. Using one edge of the new triangle, repeat the process of rotating and defining a new triangle with a contact point. The triangles formed through this process constitute the interpolated triangular mesh.
[0056] (4) Continue this process until all reachable edges are covered, then start from another seed triangle.
[0057] (5) Repeat the entire process with a larger radius to reconstruct the uneven surface.
[0058] This algorithm is suitable for open surfaces and is insensitive to point cloud uniformity. It is well-suited for point cloud data used to capture streamlines, and therefore is the primary algorithm used for reconstruction. However, the radius of the sphere used during reconstruction needs to be adjusted according to the specific point cloud conditions.
[0059] 5. Then, linear interpolation is performed on the surface using the known three-dimensional coordinate data of the second discrete point and the pressure data (static pressure) to obtain the capture flow tube with flow field pressure parameters.
[0060] 6. Therefore, we currently know the area of each surface panel that makes up the flow trap, the normal vector of the surface panel, and the pressure data (static pressure) on the surface panel. We can calculate the pressure on each surface panel using the area of the surface panel and the pressure data (static pressure). That is: Pressure on surface panel = Surface panel area * Static pressure.
[0061] The direction of the pressure is the same as the normal vector of the surface. The pressure vectors on each surface are superimposed to obtain the magnitude and direction of the resultant pressure force on the capture flow tube (i.e., the pressure integral). Then, the direction of the inlet flow is obtained according to the model coordinate system and the simulation calculation conditions. The resultant pressure force on the capture flow tube is projected and superimposed in this direction to obtain the additional drag of the inlet.
[0062] The following application example verifies the evaluation method of the present invention:
[0063] The verification example was designed with a Mach number of 3, a flight altitude of 10 km, a first-stage compression angle δ1 = 10°, a second-stage compression angle δ2 = 10°, an inlet width of 200 mm, and no side plates. The cross-section is as follows: Figure 1 .
[0064] First, a CFD simulation is performed on the intake duct model. Then, the intake duct lip edge is obtained from the intake duct model, and the coordinates of several discrete points are obtained on the edge. The first key aspect of this invention is to use post-processing software to perform streamline tracing based on these point coordinates to obtain the lip capture streamline. Figure 2 Then, discrete points are obtained on the streamline, and the three-dimensional coordinate data of the discrete points and the pressure data are exported. The program reads the exported data file, such as... Figure 3 The second key aspect of this invention is the reconstruction of discrete point clouds onto surfaces using either a spherical surface of revolution reconstruction algorithm or a Poisson reconstruction algorithm. Figure 4 The pressure data (static pressure) is then interpolated onto the curved surface to obtain a capture flow tube with flow field pressure parameters, such as... Figure 5 .
[0065] By directly integrating the pressure of the trapping flow tube with flow field pressure parameters, we can obtain the resultant pressure force on the trapping flow tube and the projection of the resultant force in each direction:
[0066] In this application example, the effective number of facets calculated is 3046;
[0067] The magnitude of the resultant pressure is 2032.8829 N;
[0068] Direction of the resultant pressure force (vector direction):
[0069] X: -0.1213
[0070] Y: 0.0000
[0071] Z: 0.9926.
[0072] The projected magnitudes of the resultant pressure force on the X, Y, and Z axes are: [-246.5140, 0.0104, 2017.8810] N;
[0073] Then, based on the model coordinate system and the simulated operating conditions, the resultant pressure is projected and superimposed in the direction of the incoming flow to obtain the additional drag of the intake duct. In the example above, the incoming flow direction is the X-axis direction; therefore, the magnitude of the additional drag is the projection of the resultant pressure in the capture flow tube onto the X-axis, which is 246.514 N.
[0074] Table 1 shows a comparison of the calculation results of this invention with those calculated by theoretical methods and momentum integration methods. As can be seen from the table, the error of the momentum integration method is -11.02%, while the error of this invention is +3.81%, indicating that the calculation accuracy is better than that of the control volume momentum method.
[0075] Table 1 Comparison of Calculation Results of Additional Resistance of Verification Model by Various Methods
[0076] Computational method Additional resistance Error Theoretical method 238.703N / Momentum integral method 212.447N -0.1102 Trapped stream tube reconstruction 247.8N +0.0381
[0077] The universality of this general evaluation method is reflected in its applicability to the evaluation of additional drag of different types of air intakes, such as the three-dimensional axisymmetric air intake in Figure 6, the three-dimensional inward rotating air intake in Figure 7, and the three-dimensional two-dimensional air intake in Figure 8.
[0078] Figure 6(a) shows the three-dimensional axisymmetric inlet model and the capture streamline; Figure 6(b) shows the discrete point cloud on the capture streamline of the three-dimensional axisymmetric inlet; Figure 6(c) shows the comparison between the restored surface and the discrete point cloud; and Figure 6(d) shows the capture stream with flow field pressure parameters obtained by pressure interpolation on the restored surface.
[0079] Figure 7(a) shows the three-dimensional internal intake duct model and the capture streamline; Figure 7(b) shows the discrete point cloud on the capture streamline of the three-dimensional internal intake duct; Figure 7(c) shows the comparison between the restored surface and the discrete point cloud; and Figure 7(d) shows the capture flow tube with flow field pressure parameters obtained by pressure interpolation on the restored surface.
[0080] Figure 8(a) shows a three-dimensional binary air intake model, Figure 8(b) shows a discrete point cloud on the capture streamline of the three-dimensional binary air intake, Figure 8(c) shows a comparison between the restored surface and the discrete point cloud, and Figure 8(d) shows the capture stream with flow field pressure parameters obtained by pressure interpolation on the restored surface.
[0081] There are many methods and approaches to implement this technical solution, and the above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. All components not explicitly stated in this embodiment can be implemented using existing technology.
Claims
1. A general evaluation method for additional inlet drag based on capture flow tube reconfiguration, characterized in that, Includes the following steps: (1) Extract the lip edge of the intake model in the 3D modeling software, and obtain the coordinates of several first discrete points on the lip edge; (2) The inlet model is simulated by CFD using fluid simulation software to obtain the data of the entire flow field including pressure data. Based on the coordinates of several first discrete points, reverse streamline tracing is performed in post-processing software to obtain the lip capture streamline. (3) Obtain several second discrete points on the capture streamline, and obtain the three-dimensional coordinate data and pressure data of the second discrete points by using the data of the corresponding positions of the second discrete points in the flow field. The pressure data is static pressure. (4) The point cloud formed by several second discrete points is reconstructed by the Poisson reconstruction method or the sphere revolution surface reconstruction algorithm. The reconstructed surface includes several patches, and each patch is composed of several grids. (5) By interpolating the known three-dimensional coordinate data of the second discrete point with the static pressure on the curved surface, a capture flow tube with static pressure is obtained; (6) Perform pressure integration on the capture flow tube with static pressure to obtain the resultant pressure force on the restored surface and the projection of the resultant force in each direction. Then, perform projection superposition based on the model coordinate system and the simulation calculation conditions to obtain the additional resistance of the intake.
2. The general evaluation method for additional inlet drag based on capture flow tube reconstruction as described in claim 1, characterized in that, In step (2), when an error occurs in streamline tracing, the error is eliminated by adjusting the sampling point of the intake duct model lip edge in the software to complete the streamline tracing.
3. The general evaluation method for additional inlet drag based on capture flow tube reconstruction as described in claim 1, characterized in that, In step (4), the Poisson reconstruction method includes the following steps: (4.1.1) Convert the point samples into a continuous vector field; (4.1.2) Solve the Poisson system containing the three-dimensional Laplace equation to find the function whose gradient best describes the point cloud; (4.1.3) Reconstruct the surface from the functional equation.
4. The general evaluation method for additional inlet drag based on capture flow tube reconstruction as described in claim 1, characterized in that, In step (4), the sphere-of-revolution surface reconstruction algorithm includes the following steps: (4.2.1) Set up several sampling points, and make contact between the ball and three of the sampling points. These sampling points form several seed triangles; (4.2.2) Keep the ball in contact with one side of a seed triangle and rotate the ball until it touches another sampling point as a new sampling point. The side and the new sampling point define a new triangle. (4.2.3) Rotate the sphere using the edge of the new triangle, and repeat the process of rotating and defining a new triangle with a contact point using one edge of the new triangle. The resulting triangles form the interpolated triangular mesh until all reachable edges are covered. (4.2.4) Starting from another seed triangle, repeat steps (4.2.2) and (4.2.3) until all seed triangles have completed steps (4.2.2) and (4.2.3). (4.2.5) Repeat steps (4.2.1) through (4.2.4) with a sphere of a larger radius to reconstruct the uneven surface.
5. The general evaluation method for additional inlet drag based on capture flow tube reconfiguration as described in claim 1, characterized in that, In step (6), the pressure integral of the capture tube with static pressure is obtained based on the pressure distribution and area vector integral of the tube.
6. The general evaluation method for additional inlet drag based on capture flow tube reconfiguration as described in claim 5, characterized in that, In step (6), the additional resistance of the intake duct is obtained based on the integral of the local pressure of the capture flow tube in the direction of the incoming flow.
7. The general evaluation method for additional inlet drag based on capture flow tube reconfiguration as described in claim 6, characterized in that, The pressure integral includes: the area of each surface of the capture flow tube, the normal vector of the surface, and the static pressure on the surface; the pressure on each surface can be calculated from the area and the static pressure on the surface, that is: pressure on the surface = surface area * static pressure; the pressure vectors on each surface are superimposed to obtain the magnitude and direction of the resultant pressure force on the capture flow tube, that is, the pressure integral.
8. The general evaluation method for additional inlet drag based on capture flow tube reconfiguration as described in claim 7, characterized in that, The direction of the airflow in the intake is obtained based on the model coordinate system and the simulation calculation conditions. The additional drag of the intake is obtained by projecting and superimposing the resultant pressure on the capture flow tube in this direction.
9. A computer system comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of any of the methods of claims 1 to 8.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of any of the methods described in claims 1 to 8.