Design method for inlet section of fan-shaped cascade test piece

Abstract

The invention discloses a fan-shaped blade grid test piece inlet section design method, which is used for designing an inlet section for connecting a transition section and a test section, and the inlet section comprises an upper curved surface, a lower curved surface and two side end surfaces. The method comprises the following steps: determining an airflow angle beta 1; selecting one curve of the side end face, and converting point coordinates on the curve between a Cartesian coordinate system and a cylindrical coordinate system; selecting a curve configuration style by combining the rotation angle beta 2; repeatedly designing curves with different radial heights on the side end surface; a side end surface is formed through curved surface stacking; rotating the curve of the maximum radial height and the curve of the minimum radial height to form an upper curved surface and a lower curved surface; and the array side end surface completes the integral design of the inlet section. According to the invention, a cylindrical coordinate system and Cartesian coordinate system conversion and curved surface stacking technology is adopted, high-precision curved surface configuration can be carried out on the inlet section of the fan-shaped blade grid test piece, accurate control of an airflow angle is realized, and the stability of a flow field of the inlet section of the fan-shaped blade grid test piece is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of turbine aerodynamic tests, and in particular, to a design method for the inlet section of a sector cascade test piece. Background Art

[0002] A sector cascade test piece of an aeroengine generally has structures such as a transition section, an inlet section, and a test section. The purpose of the transition section is to smoothly transition the outlet shape of the test typhoon wind tunnel to the inlet shape of the required sector section for the test. The purpose of the inlet section is to rectify the air flow at the inlet of the test section to ensure the uniformity and stability of the inlet flow field of the cascade test section. In the sector cascade tests of aeroengine compressors and turbines, it is often necessary to conduct cascade tests with different inlet air flow attack angle characteristics. Therefore, it is necessary to adjust the outlet air flow angle of the inlet section of the sector cascade test piece to meet the different attack angle characteristic tests of the sector cascade test piece. Therefore, in specific aeroengine sector cascade tests, it is necessary to design a corresponding inlet structure to adjust the angle deflection characteristics of the air flow to achieve the required test effect.

[0003] Currently, the inlet section of the sector cascade test piece is mainly a straight section, and only sector cascade tests with a fixed inlet attack angle can be carried out. When conducting tests with different inlet attack angles, less research has been done on the inlet section. In the prior art, when conducting tests with different inlet attack angles, the shape of the inlet section basically remains unchanged, and usually, the air flow angle is adjusted by adding guide vanes. However, this method has a high cost, and there is an influence of the blade wake. Moreover, when the form of the end wall of the inlet section remains unchanged, the outflow end wall flow field is uneven and has poor stability, affecting the test effect.

[0004] Chinese Patent with Publication No. CN111075513B discloses a sector cascade tester and a method for changing the inlet air angle of a sector cascade. The tester at least includes a sector cascade and a test section. The sector cascade includes a sector disk and blades installed on the sector disk. The test section is a flow channel with a continuous, smooth, and non-creased inner surface. At least the upper curved plate or the lower curved plate of the test section includes building blocks that are spliced with each other. This method generates the inlet section of the sector cascade through a curved surface composed of inclined building blocks, and can provide different inlet air angles for the downstream sector cascade. However, this method can only achieve physical continuity by using a flexible structure or a variable structure, and does not form an actual design method and theoretical analysis. It can only forcibly change the inlet section after determining the inlet and outlet of the test piece, and cannot accurately model and analyze the shape of the inlet section of the test piece. Moreover, the upper end wall of the test piece designed by this method also has to be a flexible structure or an adjustable structure, which cannot ensure the stability of the air flow in the inlet section of the test piece, and there is a great risk of air flow separation, affecting the inlet flow field effect of the cascade test. Summary of the Invention

[0005] The present invention provides a design method for the inlet section of a sector cascade test piece to solve the technical problem of poor inlet flow field effect in the inlet section of the existing sector cascade test piece.

[0006] According to one aspect of the present invention, there is provided a design method for the inlet section of a sector cascade test piece, which is used to design the inlet section of the sector cascade test piece. The inlet section is used to connect the transition section and the test section and transmit the air flow to the inlet end of the test section at a set air flow angle for testing. The inlet section includes an upper curved surface, a lower curved surface, and two side end faces. The design method for the inlet section of the sector cascade test piece is characterized by the following steps: S1: According to the test requirements of the sector cascade, determine the air flow angle β1 of the inlet section; S2: Select one of the curves on the side end face for design, determine the point coordinates (X, Y, Z) of each point on this curve in the Cartesian coordinate system, and convert them one by one into the point coordinates (R, θ, z) in the cylindrical coordinate system. Among them, R is the radial height of this point on this curve from the axis of the inlet section; S3: Determine the rotation angle β2 of the sector cascade test piece rotating around the engine axis, select the configuration style of the first curve according to the air flow angle β1 and the rotation angle β2, and design and form the first curve with a radial height of R; S4: Repeat steps S2 and S3 to design the curves with different radial heights on the side end face to design and form all the curves on the side end face; S5: Convert the cylindrical coordinate system into the Cartesian coordinate system, and perform curvilinear surface stacking of all the curves designed in step S4 in the radial direction to form one side end face of the inlet section; S6: Rotate the curves with the maximum radial height and the minimum radial height on the side end face to design and form the upper curved surface and the lower curved surface. Furthermore, by arraying the designed one side end face, form the other side end face, thereby completing the design of the entire inlet section.

[0007] Further, in step S2, the origin of the Cartesian coordinate system is set at the geometric center point of the inlet end of the inlet section, and the air flow direction is set as the X-axis.

[0008] Further, in step S2, the conversion between the point coordinates (X, Y, Z) in the Cartesian coordinate system and the point coordinates (R, θ, z) in the cylindrical coordinate system is obtained through the calculation formula X = R sinθ or Y = R cosθ and Z = z; Among them, θ is the angle value of the position point, and z is the axial coordinate of the position point.

[0009] Further, in step S3, the configuration style of the first curve on the side end face can be selected from a cylindrical helix, a B-spline curve, or a Bezier curve according to the values of the airflow angle β1 and the rotation angle β2, so that the angle formed after the selected curve configuration style rotates around the X-axis by the same angle as the rotation angle β2 is consistent with the airflow angle β1.

[0010] Further, the curvature of the curve on the side end face at the inlet position point is equal to the curvature of the outlet connection point of the transition section.

[0011] Further, the curvature of the curve on the side end face at the outlet position point is equal to the curvature of the inlet connection point of the test section.

[0012] Further, in step S4, the intervals between the curves at different radial heights are equally spaced or variably spaced.

[0013] Further, in step S5, the method of surface stacking includes one of linear interpolation or NURBS surface fitting.

[0014] Further, in step S6, the rotation angles of the curves with the maximum radial height and the minimum radial height on the side end face are adjusted according to the airflow angle β1 and the rotation angle β2 of the inlet section.

[0015] Further, the design method of the inlet section of the sector cascade test piece further includes step S7: analyzing the designed inlet section to determine whether the analysis results meet the test requirements. If the requirements are met, the design is completed; if the requirements are not met, steps S2 to S6 are repeated. In step S7, the analysis of the designed inlet section specifically includes: Analyzing whether the total pressure data of the inlet section is within the range required by the test; Analyzing whether the outlet airflow angle of the inlet section meets the deflection requirements; Analyzing whether the airflow in the inlet section is separated.

[0016] The present invention has the following beneficial effects: The design method of the inlet section of the sector cascade test piece of the present invention can ensure that the air flow at the inlet section is stably introduced into the test section at a set angle, reduce flow distortion, and improve the air flow conduction accuracy by accurately calculating the air flow angle β1 and the rotation angle β2 at the inlet section and combining multi-curve design; by using the conversion between the cylindrical coordinate system and the Cartesian coordinate system and the surface stacking technology, the high-precision surface configuration of the side end face, the upper surface and the lower surface of the inlet section can be realized, ensuring that there is no separation risk in the inlet flow field of the sector cascade test piece and effectively improving the stability of the inlet flow field; by selecting a curve configuration style adapted to the rotation angle β2 to configure the curves at different radial heights of the side end face, the air flow angle can be accurately controlled, adapting to various test requirements and enhancing the flexibility of the design; by performing iterative analysis and verification on the designed inlet section, it can be ensured that the designed inlet section meets the test requirements and reduces the cost of repeated debugging; the present invention provides direct data input for numerical control machining through clear coordinate conversion and surface generation steps, realizes the parametric modeling of the inlet section, and the designed inlet section is integrally formed. Compared with the prior art, it can achieve a smooth turning of the air flow without adding guide vanes, reduce the processing cost and manufacturing difficulty of the test, has high test efficiency, can meet the test requirements of the inlet air flow angle of the sector cascade test piece, and will not generate the wake effect of the air flow due to the guide vanes, improving the accuracy of air flow conduction and the reliability of test data.

[0017] In addition to the purposes, features and advantages described above, the present invention has other purposes, features and advantages. The present invention will be further described in detail below with reference to the drawings. Brief Description of the Drawings

[0018] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is the design flow chart of the design method of the inlet section of the sector cascade test piece of the preferred embodiment of the present invention; Figure 2 is the structural schematic diagram of the sector cascade test piece of the design method of the inlet section of the sector cascade test piece of the preferred embodiment of the present invention; Figure 3 is the spatial surface structure schematic diagram of the side end face of the inlet section of the design method of the inlet section of the sector cascade test piece of the preferred embodiment of the present invention; Figure 4 is the structural schematic diagram of the designed inlet section of the design method of the inlet section of the sector cascade test piece of the preferred embodiment of the present invention.

[0019] Legend Explanation: 100. Transition section; 200. Inlet section; 201. Upper surface; 202. Lower surface; 203. Side end face; 300. Test section. Detailed implementation manners

[0020] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways defined and covered by the following.

[0021] As Figures 1 to 4 shown, in the sector cascade test of an aero-engine compressor and turbine, it is often necessary to conduct cascade tests with different inlet air flow attack angles. Therefore, it is necessary to adjust the outlet air flow angle of the inlet section 200 of the sector cascade test piece to meet the different attack angle characteristic tests of the sector cascade test piece. The design method of the inlet section of the sector cascade test piece in this embodiment is used to design the inlet section 200 of the sector cascade test piece to ensure that the outlet air flow of the inlet section 200 deflects stably at a set angle and meets the test requirements of different inlet air flow attack angles of the sector cascade test piece. The sector cascade test piece includes a transition section 100, an inlet section 200, and a test section 300. The transition section 100 is used to smoothly transition the outlet shape of the test typhoon tunnel to the sector inlet shape required by the time. The inlet section 200 is used to connect the transition section 100 and the test section 300, and rectify the air flow at the inlet of the test section 300 to transmit the air flow to the inlet end of the test section 300 at a set air flow angle for testing. The inlet section 200 includes an upper curved surface 201, a lower curved surface 202, and two side end faces 203. Since the inlet section 200 is an annular structure, the inlet air flow angle of the sector cascade is the calculation result in the cylindrical coordinate system. When conducting tests with different air flow attack angles, the test section 300 of the sector cascade cannot be simply translated and rotated, but needs to be rotated around the rotation axis of the aero-engine, and then the inlet section 200 is refined according to the rotated structure to make its inlet air flow angle meet the angle in the cylindrical coordinate system and meet the test requirements. Specifically, the design method of the inlet section of the sector cascade test piece includes the following steps: S1: Determine the air flow angle β1 of the inlet section 200 according to the test requirements of the sector cascade. Specifically, first determine the design range of the inlet section 200 according to the test vehicle platform and the test requirements, that is: since the height of the test section 300 is determined by the test requirements during the design process, the height of the inlet section 200 can be determined according to the height of the test section 300. Then, according to the test requirements for the inlet air flow angle of the test section 300, the outlet air flow angle β1 of the inlet section 200 can be determined.

[0022] S2: Select one of the curves on the side end face 203 for design, determine the point coordinates (X, Y, Z) of each point on this curve in the Cartesian coordinate system, and convert them one by one into the point coordinates (R, θ, z) in the cylindrical coordinate system, where R is the radial height of this point on this curve from the axis of the inlet section 200, θ is the angle of this point in the cylindrical coordinate system, z is the axial coordinate of this point, and Z = z. Preferably, in the Cartesian coordinate system, select the point coordinates of three characteristic points of this curve on the side end face 203 for coordinate system conversion. The three characteristic points of this curve are respectively the inlet point of this curve at the inlet section 200, the midpoint of this curve, and the outlet point of this curve at the inlet section 200.

[0023] S3: Determine the rotation angle β2 of the sector cascade test piece rotating around the engine axis. Select the configuration style of the curve in step S2 according to the flow angle β1 and the rotation angle β2 to design and form the first curve. Specifically, select different curve configuration styles according to different rotation angles β2 to adapt to the required flow angle β1 of the test, which can ensure that the airflow uniformly changes the turning angle and guarantee the uniformity and stability of the flow field of the designed inlet section 200.

[0024] S4: Repeat steps S2 and S3 to design the curves at different radial heights on the side end face 203 to design and form all the curves on the side end face 203. The side end face 203 is divided into curves with different radial heights. By sequentially selecting and designing the curves at different radial heights on the side end face 203 respectively, the design configuration of each curve on the side end face 203 can be completed.

[0025] S5: Convert the cylindrical coordinate system to the Cartesian coordinate system. In the radial direction, perform surface area stacking on all the curves designed in step S4 to form a side end face 203 of the inlet section 200. Specifically, perform equal-parameter discretization processing on each designed curve to generate a dense cloud of profile points, and then convert the point coordinates on all the designed curves from the cylindrical coordinate system to the Cartesian coordinate system to convert the discrete points on all the designed curves to the unified global coordinates. Preferably, adopt the B-spline surface fitting method to fit all the curves in step S4 into a continuous surface in the radial direction and make the curvature change satisfy the second-order derivative continuity, thereby completing the modeling of the side end face 203.

[0026] S6: Rotate the curves of the maximum radial height and the minimum radial height on the opposite end face 203 to design and form the upper surface 201 and the lower surface 202. Then, by arraying one designed end face 203, form the other end face 203, thus completing the design of the entire inlet section 200. Specifically, in the cylindrical coordinate system, rotate the curves of the maximum radial height and the minimum radial height on the end face 203 around the X-axis by an angle β1 respectively to generate the upper surface 201 and the lower surface 202, so as to form the flow channels of the upper and lower walls of the inlet section 200. And copy the designed end face 203 to the other side through mirror array to complete the three-dimensional parametric model of the inlet section 200.

[0027] S7: Analyze the designed inlet section 200 and determine whether the analysis results meet the test requirements. If they meet the requirements, end the design; if not, repeat steps S2 to S6.

[0028] The design method of the inlet section of the sector cascade test piece of the present invention can ensure that the air flow of the inlet section 200 is stably introduced into the test section 300 at a set angle, reduce flow distortion, and improve the air flow conduction accuracy by accurately calculating the air flow angle β1 and the rotation angle β2 of the inlet section 200 and combining multi-curve design; by using the conversion between the cylindrical coordinate system and the Cartesian coordinate system and the surface stacking technology, the high-precision surface configuration of the end face 203, the upper surface 201 and the lower surface 202 of the inlet section 200 can be realized, ensuring that there is no separation risk in the inlet flow field of the sector cascade test piece and effectively improving the stability of the flow field of the inlet section 200; by selecting a curve configuration style adapted to the rotation angle β2 to configure the curves of different radial heights of the end face 203, the air flow angle can be accurately controlled, adapting to various test requirements and enhancing the flexibility of the design; by performing iterative analysis and verification on the designed inlet section 200, it can be ensured that the designed inlet section 200 meets the test requirements and reduce the cost of repeated debugging; the present invention provides direct data input for numerical control machining through clear coordinate conversion and surface generation steps, realizes the parametric modeling of the inlet section 200, and the designed inlet section 200 is integrally formed. Compared with the prior art, it can achieve the turning effect of the air flow without adding guide vanes, reduce the processing cost and manufacturing difficulty of the test, has high test efficiency, will not produce the wake effect of the air flow due to the guide vanes, and improves the accuracy of air flow conduction and the reliability of test data.

[0029] In this embodiment, in step S2, the origin of the Cartesian coordinate system is set at the geometric center point of the inlet end of the inlet section 200. The air flow direction is set as the X-axis. Thus, the coordinates of the points on each curve on the side end face 203 can be located, which is also convenient for describing the positions of the points in the inlet flow field and is beneficial for flow field analysis and calculation. The origin of the Cartesian coordinate system is set according to the design and test requirements of the sector cascade test piece. Optionally, the origin of the Cartesian coordinate system can also be set at any point on the central axis of the inlet section 200; optionally, the origin of the Cartesian coordinate system can also be set at a specific point on the inlet edge of the inlet section 200 to match specific test conditions or measuring equipment.

[0030] In step S2, the conversion between the point coordinates (X, Y, Z) of the Cartesian coordinate system and the point coordinates (R, θ, z) of the cylindrical coordinate system is obtained through the calculation formulas X = R sinθ or Y = R cosθ and Z = z, where R is the radial height of the point on this curve from the axis of the inlet section 200, θ is the angle of the point in the cylindrical coordinate system, and z is the axial coordinate of the position point. When designing the curve, fixing the R value in the cylindrical coordinate system can ensure that the radial height of this curve remains unchanged, so that the air flow angle of the curve design at this radial height meets the angle requirements in the cylindrical coordinate system.

[0031] Optionally, if the inlet section 200 is a non-axisymmetric structure, correction terms △X and △Y can be introduced in the Cartesian coordinate system to adapt to the non-uniform flow field and optimize the coordinate conversion.

[0032] As Figure 3 shown, in step S3, the configuration style of the first curve of the side end face 203 can select one of a cylindrical helix, a B-spline curve, or a Bezier curve according to the values of the air flow angle β1 and the rotation angle β2, so that the angle formed after the selected curve configuration style rotates around the X-axis by an angle equal to the rotation angle β2 is consistent with the air flow angle β1. Specifically, if the change range of the air flow angle β1 is less than or equal to 10°, the configuration style adopts a cylindrical helix. If the change range of the air flow angle β1 is greater than 10°, the configuration style is designed using a B-spline curve or a Bezier curve to guide the air flow to change the turning angle evenly. Among them, if the rotation angle β2 is less than or equal to 20°, the configuration style selects a B-spline curve, and if the rotation angle β2 is greater than 20°, the configuration style selects a Bezier curve.

[0033] Preferably, in the sector cascade test pieces of the compressors and turbines of aeroengines, for tests with different inlet air flow angles, when the inlet section 200 is a cylindrical helix, the rectification effect is the best, which can achieve the turning effect of different air flow angles in the channel and can also achieve the rectification effect in the air flow direction.

[0034] Optionally, since the air flow directions at the outlet of the transition section 100 and the inlet of the test section 300 are not the same, the same curve on the side end face 203 can be segmented and shaped. Different configuration styles can be adopted for the curves at the air inlet end and the air outlet end of the inlet section 200, so that the designed inlet section 200 adjusts the angle of the air flow first at the air inlet end and then rectifies the air flow with the adjusted angle at the air outlet end of the inlet section 200, ensuring the stability and uniformity of the flow field in the inlet section 200.

[0035] Combined with the content of step S2, when designing the curve of the side end face 203, keeping the radial height R of the curve unchanged, and there are only two variables, θ and z, in the curve design, it can be transformed into a two-dimensional curve design, reducing the curve dimension, controlling variables, and realizing the optimization of the curve design.

[0036] As Figure 3 and Figure 4 shown, when designing the inlet section 200, the curvature value of the curve of the side end face 203 at the inlet position point of the inlet section 200 can be directly determined, so that the curvature of the curve on the side end face 203 at the inlet position point is equal to the curvature of the connection point at the outlet of the transition section 100, and the curvature radius of the inlet end of the inlet section 200 matches the curvature radius of the outlet end of the transition section 100. By configuring the curve of the side end face 203 with the selected configuration style, the curvature continuity at any point in the inlet section 200 and the curvature continuity between the transition section 100 and the inlet section 200 can be realized. The wall surfaces of the transition section 100 and the inlet section 200 are smoothly connected, avoiding flow separation caused by sudden curvature change from the transition section 100 to the inlet section 200 and preventing the formation of local adverse pressure gradients and eddies. Thus, the curvature continuity from the outlet of the test bench to any point in the inlet section 200 is ensured, the wall surfaces are smoothly connected, the air flow turns smoothly without separation risk, effectively improving the stability and uniformity of the flow field in the inlet section 200 and enhancing the reliability of the test results of the fan cascade.

[0037] As Figure 3 and Figure 4As shown, when designing the inlet section 200, the curvature value of the curve of the side end face 203 at the outlet position point of the inlet section 200 can be directly determined, so that the curvature of the curve on the side end face 203 at the outlet position point is equal to the curvature of the inlet connection point of the test section 300, and the curvature radius of the outlet end of the inlet section 200 is matched with the curvature radius of the inlet end of the test section 300. By configuring the curve of the side end face 203 with the selected configuration style, the curvature continuity of any point in the inlet section 200 and the curvature continuity between the inlet section 200 and the test section 300 can be achieved. The inlet section 200 is avoided from being smoothly connected to the wall surface of the test section 300, and the flow separation caused by the sudden change of curvature from the inlet section 200 to the test section 300 is avoided. At the same time, it can ensure that the air flow enters the test section 300 uniformly at the set air flow angle, avoid the deviation of the air flow angle, reduce the total pressure loss, and improve the accuracy and repeatability of the sector cascade test.

[0038] In step S4, the intervals between the curves at different radial heights are equidistant or variable-spacing.

[0039] As Figure 3 shown, in step S5, the method of surface stacking includes one of linear interpolation or NURBS surface fitting. Preferably, in this embodiment, NURBS surface fitting is used for surface stacking, which can accurately convert multiple curves into high-quality surfaces, realize the precise forming of the side end face 203 of the inlet section 200, and make the designed inlet section 200 meet the test requirements.

[0040] As Figure 4 shown, in step S6, the rotation angles of the curve with the maximum radial height and the curve with the minimum radial height on the side end face 203 are adjusted according to the air flow angle β1 and the rotation angle β2 of the inlet section 200. Specifically, the rotation axis is the axis of the aeroengine, that is, the axial reference line of the inlet section 200, and the X-axis of the Cartesian coordinate system. The rotation center is the fixed point of the curve at the inlet end, that is, the origin of the Cartesian coordinate system. The rotation angle β2 and the air flow angle β1 jointly determine the initial configuration of the curve, and the influence of the rotation angle β2 needs to be superimposed during the rotational forming. Thus, by rotating the curve with the maximum radial height on the side end face 203 around the axis of the inlet section 200 to form the upper boundary, a continuous surface is generated through lofting operation to form the upper surface 201 of the inlet section 200. By rotating the curve with the minimum radial height on the side end face 203 around the axis of the inlet section 200 to form the lower boundary, a continuous surface is generated through lofting operation to form the lower surface 202 of the inlet section 200. Through this parametric rotational design, the air flow guidance of the inlet section 200 can be accurately controlled to ensure that the inlet flow field of the test section 300 meets the air flow angle requirements.

[0041] In step S7, the analysis of the designed inlet section 200 includes: Analyze whether the total pressure data of the inlet section 200 is within the range required by the test. Specifically, simulate the total pressure distribution of the inlet section 200 through CFD, and require that the total pressure loss ≤ 2%.

[0042] The flow channel inlet surface of the designed inlet section 200 is connected to the flow channel outlet surface of the transition section 100, and the end of the flow channel of the inlet section 200 can form an angle different from the axis of the test section 300, that is, the fan-shaped cascade air inlet angle. Analyze whether the outlet air flow angle of the inlet section 200 meets the deflection requirement, and require that the deviation of the outlet air flow angle of the inlet section 200 be controlled within ±1°.

[0043] Analyze whether the air flow in the inlet section 200 is separated, and conduct separation detection on the flow field of the inlet section 200. If a recirculation area appears in the streamline diagram, adjust the curve curvature and repeat steps S2 - S6. The analysis of the inlet section 200 also includes the smooth connection of the walls of the transition section 100, the inlet section 200, and the test section 300, and the smooth turning of the air flow.

[0044] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A design method for the inlet section of a sector cascade test piece, which is used to design the inlet section (200) of the sector cascade test piece. The inlet section (200) is used to connect the transition section (100) and the test section (300) and transmit the air flow to the inlet end of the test section (300) at a set air flow angle for testing. The inlet section (200) includes an upper curved surface (201), a lower curved surface (202) and two side end faces (203), and is characterized in that, The design method for the inlet section of the sector cascade test piece includes the following steps: S1: According to the test requirements of the sector cascade, determine the airflow angle β1 of the inlet section (200); S2: Select one of the curves on the side end face (203) for design, determine the point coordinates (X, Y, Z) of each point on this curve in the Cartesian coordinate system, and convert them one by one into the point coordinates (R, θ, z) in the cylindrical coordinate system, where R is the radial height of this point on this curve from the axis of the inlet section (200); S3: Determine the rotation angle β2 of the sector cascade test piece rotating around the engine axis, select the configuration style of the curve in step S2 according to the airflow angle β1 and the rotation angle β2, and design and form the first curve; S4: Repeat steps S2 and S3 to design the curves at different radial heights on the side end face (203) to design and form all the curves on the side end face (203); S5: Convert the cylindrical coordinate system into the Cartesian coordinate system, and perform surface stacking of all the curves designed in step S4 in the radial direction to form one side end face (203) of the inlet section (200); S6: Rotate the curve with the maximum radial height and the curve with the minimum radial height on the side end face (203) to design and form the upper surface (201) and the lower surface (202), and form the other side end face (203) by arraying one designed side end face (203), thereby completing the design of the entire inlet section (200).

2. The design method of the inlet section of the sector cascade test piece according to claim 1, characterized in that, In step S2, the origin of the Cartesian coordinate system is set at the geometric center point of the inlet end of the inlet section (200), and the airflow direction is set as the X-axis.

3. The design method of the inlet section of the sector cascade test piece according to claim 1, characterized in that, In step S2, the conversion between the point coordinates (X, Y, Z) in the Cartesian coordinate system and the point coordinates (R, θ, z) in the cylindrical coordinate system is obtained by calculating the equations X = R sinθ or Y = R cosθ and Z = z; Wherein, θ is the angular value of the position point, and z is the axial coordinate of the position point.

4. The design method of the inlet section of the sector cascade test piece according to claim 1, characterized in that, In step S3, the configuration style of the first curve of the side end face (203) can select one of the cylindrical helix, B-spline curve or Bezier curve according to the values of the airflow angle β1 and the rotation angle β2, so that the angle formed after the selected curve configuration style rotates around the X-axis by the same angle as the rotation angle β2 is consistent with the airflow angle β1.

5. The design method of the inlet section of the sector cascade test piece according to claim 4, characterized in that, The curvature of the curve on the side end face (203) at the inlet position point is equal to the curvature of the outlet connection point of the transition section (100).

6. The design method of the inlet section of the sector cascade test piece according to claim 4, characterized in that, The curvature of the curve on the side end face (203) at the outlet position point is equal to the curvature of the inlet connection point of the test section (300).

7. The design method of the inlet section of the sector cascade test piece according to claim 1, characterized in that, In step S4, the interval between the curves at different radial heights is equally spaced or variably spaced.

8. The design method of the inlet section of the sector cascade test piece according to claim 1, characterized in that, In step S5, the method of surface stacking includes one of linear interpolation or NURBS surface fitting.

9. The design method of the inlet section of the sector cascade test piece according to claim 1, characterized in that In step S6, the rotation angles of the curve with the maximum radial height and the curve with the minimum radial height on the side end face (203) are adjusted according to the airflow angle β1 and the rotation angle β2 of the inlet section (200).

10. The design method of the inlet section of the sector cascade test piece according to claim 1, characterized in that, The design method for the inlet section of the sector cascade test piece further includes step S7: Analyze the designed inlet section (200), judge whether the analysis result meets the test requirements. If it meets the requirements, end the design. If it does not meet the requirements, repeat steps S2 to S6; In step S7, the analysis of the completed inlet section (200) specifically includes: Analyzing whether the total pressure data of the inlet section (200) is within the range required by the test; Analyzing whether the outlet airflow angle of the inlet section (200) meets the deflection requirements; Analyzing whether the airflow in the inlet section (200) is separated.

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