Method for designing end wall of inlet section of cascade test piece

Abstract

The invention discloses a cascade test piece inlet section end wall design method, which comprises the steps of dividing an inlet section end wall into a first section and a second section, performing angle adjustment on airflow by using the first section so as to convert an inlet airflow angle into an outlet airflow angle required by a test, and rectifying the angle-adjusted airflow by using the second section so as to convert the angle-adjusted airflow into an outlet airflow angle required by the test. The configuration mode of the first section curve and the second section curve is selected according to the design requirement, stable turning of the airflow from the angle of the outlet of the test vehicle platform to the angle required by the inlet of the cascade test piece is realized, smooth connection of the end wall of the cascade test piece is ensured, the risk of airflow separation is avoided, and the stability and the uniformity of the flow field in the inlet section are ensured; the inlet section structure obtained based on the configuration is determined, parameterization design and analysis can be rapidly carried out, and it is convenient for iterative optimization to ensure that the outlet airflow angle meets the cascade test requirement; parameterization design and analysis work can be conveniently completed, the stability and uniformity of an inlet section flow field are high, and the reliability of a cascade test result can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aero-engine cascade testing, and in particular to a method for designing an end wall of an inlet section of a cascade test piece. Background Art

[0002] In the cascade tests of compressors and turbines of aircraft engines, the control of the angle of attack during the cascade test is a direct means of revealing the evolution of the blade's aerodynamic performance. By analyzing the flow field structure and performance parameters at different angles of attack, it is possible to guide the optimization of blade design, improve the efficiency of turbine machinery, and provide key data support for the stable operation of aircraft engines. Therefore, when conducting characteristic tests at different inlet airflow angles of attack, it is necessary to adjust the angle of the inlet airflow of the cascade test piece to meet the different angle of attack characteristic tests in the cascade test. In specific aircraft engine cascade tests, it is necessary to design a corresponding inlet structure to adjust the angle deflection characteristics of the airflow to achieve the desired effect of the test.

[0003] In existing aircraft engine compressor and turbine cascade tests, the inlet section often uses guide vanes to straighten the inlet airflow to meet the requirements of different inlet airflow angles. The inlet section is designed with guide vanes, and the end wall of the inlet section is designed based on the form of the guide vanes. However, the presence of the guide vanes creates wakes at the blade exit, affecting the stability and uniformity of the inlet flow field of the cascade test piece, increasing inlet airflow losses, and affecting the measurement results. This influences the inlet guide vanes, reducing the reliability of the test results. Furthermore, the need for additional processing of the guide vanes leads to high processing costs for the inlet section of the test piece.

[0004] For example, Chinese invention patent application CN111075513A discloses a fan-shaped blade tester and a method for changing the inlet angle of the fan-shaped blade, which are mainly used in the field of turbine aerodynamic test technology. The tester includes at least one fan-shaped blade and a test section, wherein the fan-shaped blade includes a fan-shaped disk and blades mounted on the fan-shaped disk; the test section is a flow channel with a continuous, smooth and wrinkle-free inner surface. At least the upper curved plate or the lower curved plate of the test section includes building block units, and the building block units are spliced ​​together. This method can conveniently change the airflow inlet angle of the fan-shaped blade while ensuring the airflow quality. The flow channel spliced ​​by the building block units of the present invention can provide different inlet angles for the downstream fan-shaped blade. It can also be flexibly adjusted with a very small index angle, which reduces the material and process costs of manufacturing multiple transition sections, shortens the experimental preparation time, and will expand the use of the fan-shaped blade. That is, the inlet end realizes the connection of the inlet section at different attack angles through oblique building blocks and flexible connecting plates. However, this method completes the connection of the inlet section through passive deformation. The specific structure of the inlet section is unknown, and its corresponding parametric design and analysis work cannot be completed. At the same time, there is the possibility of discontinuous change in the curvature of the inlet section, which makes there is a risk of airflow separation in the inlet section, and the stability and uniformity of the flow field in the inlet section cannot be guaranteed. Summary of the Invention

[0005] The present invention provides a method for designing the end wall of the inlet section of a cascade test piece, so as to solve the technical problems that the existing cascade test is difficult to complete the corresponding parameterized design and analysis work, and the stability and uniformity of the inlet section flow field are low.

[0006] According to one aspect of the present invention, a method for designing an end wall of an inlet section of a cascade test piece is provided. The cascade test piece includes a transition section, an inlet section, and a test section. The design method comprises the following steps: S1: determining an inlet airflow angle of the inlet section based on the structure of a test bench, wherein the end wall of the inlet section is axially divided into a first section for adjusting the airflow angle and a second section for stabilizing the inlet airflow; S2: determining an outlet airflow angle of the inlet section based on test requirements; S3: determining an inlet position point and an outlet position point of the inlet section based on the structural design of the cascade test piece;

[0007] S4: Select the configuration mode of the first section curve according to the design requirements, and select the configuration mode of the second section curve according to the design requirements and the type of test blade; S5: Select the composition ratio of the first section curve and the second section curve; S6: Configure the second section curve based on the outlet position point and the outlet airflow angle; S7: Determine the end point position point of the first section curve according to the configuration of the second section curve; S8: Configure the first section curve based on the inlet position point, the inlet airflow angle, the end point position point and the outlet airflow angle; S9: Combine the first section curve and the second section curve based on the composition ratio to obtain the inlet section combined curve, and continuously obtain the inlet section end wall surface along the radial position of the inlet section combined curve; S10: Analyze the inlet section end wall surface, and judge whether it meets the test requirements based on the analysis results. If it meets the requirements, the design is terminated. If it does not meet the requirements, repeat steps S5-S10.

[0008] As a further improvement of this solution:

[0009] Furthermore, in step S4, the first segment of the curve is configured using a Hermite curve, and its configuration equation is as follows:

[0010]

[0011] Where y i is the coordinate of the location point, m i is the curvature value of the position point, α i (x) is the first basis function of the Hermite curve, β i (x) is the second basis function of the Hermite curve.

[0012] Furthermore, the curvature of the inlet position point of the Hermite curve is equal to the curvature of the outlet connection point of the transition section.

[0013] Furthermore, the curvature of the exit point of the Hermite curve is equal to the curvature of the second segment of the curve.

[0014] Furthermore, in step S4, the first segment of the curve is configured using a Bezier curve. The Bezier curve includes four control points, two of which are respectively identical to the inlet position point and the end position point, and the other two control points are respectively close to the inlet position point and the end position point. The configuration equation is as follows:

[0015]

[0016] Where Pi is the coordinate value of the control point, and t is the control variable value of the Bezier curve.

[0017] Furthermore, the curvature of the inlet position point of the Bezier curve is equal to the curvature of the outlet connection point of the transition section.

[0018] Furthermore, the curvature of the exit point of the Bezier curve is equal to the curvature of the second segment of the curve.

[0019] Furthermore, in step S4, when the type of the test blade cascade is a fan-shaped blade cascade, the configuration of the second curve segment adopts a cylindrical spiral line, and its configuration equation is as follows:

[0020]

[0021] Where R is the radius height of the cylindrical helix, θ is the angle value of the position point, and F(z) is the one-dimensional variation function of θ.

[0022] Furthermore, F(z)=β1×Z, where z is the axial coordinate of the position point and β1 is the outlet airflow angle.

[0023] Furthermore, in step S4, when the type of the test cascade is a plane cascade, the second segment of the curve is configured as a straight line, and its configuration equation is as follows:

[0024] y = β1 × x;

[0025] Where β1 is the outlet airflow angle.

[0026] The present invention has the following beneficial effects:

[0027] The method for designing the end wall of the inlet section of the cascade test piece of the present invention determines the inlet airflow angle, the outlet airflow angle of the inlet section, and the inlet position point and the outlet position point of the inlet section in sequence according to the existing test bench structure, test requirements and the structural design of the cascade test piece, and then selects the configuration mode of the first section curve according to the design requirements, and selects the configuration mode of the second section curve according to the design requirements and the type of the test cascade, so as to configure the second section curve based on the outlet position point and the outlet airflow angle after selecting the composition ratio of the first section curve and the second section curve; then determines the end point of the first section curve according to the configuration of the second section curve, so as to configure the first section curve based on the inlet position point, the inlet airflow angle, the end point point and the outlet airflow angle; then combines the first section curve and the second section curve based on the composition ratio to obtain the inlet section combined curve, and continuously obtains the inlet section end wall surface along the radial position of the inlet section combined curve; finally analyzes the inlet section end wall surface, and judges whether to reselect the composition ratio for iterative optimization based on the analysis result; this scheme is adopted By dividing the end wall of the inlet section into a first section and a second section, the first section is used to adjust the angle of the airflow to convert the inlet airflow angle into the outlet airflow angle required by the test, and the second section is used to rectify the airflow after the adjusted angle to ensure the stability and uniformity of the flow field in the inlet section: then, according to design requirements, the configuration method of the first section curve and the second section curve are selected, and the configuration of the first section curve and the second section curve is completed in sequence so that the curvature of the outlet curve of the test bench, the first section curve and the second section curve are equal, thereby achieving a smooth transition of the airflow from the outlet angle of the test bench to the required angle of the inlet of the cascade test piece, ensuring a smooth connection of the end wall of the cascade test piece without the risk of airflow separation, and the inlet section structure determined based on the configuration can be quickly parametrically designed and analyzed, facilitating iterative optimization to ensure that the outlet airflow angle meets the cascade test requirements; compared with the existing technology, it is easy to complete parametric design and analysis work, the inlet section flow field has high stability and uniformity, which is conducive to improving the reliability of the cascade test results, has strong practicality, and is suitable for wide promotion and application.

[0028] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 This is a flowchart of the steps of the method for designing the inlet end wall of a cascade test piece according to a preferred embodiment of the present invention;

[0031] Figure 21. It is a schematic structural diagram of the inlet section end wall of a cascade test piece adopting the inlet section end wall design method of the cascade test piece according to the preferred embodiment of the present invention;

[0032] Figure 3 1. It is a structural schematic diagram of the inlet section of a sector-shaped cascade test piece adopting the inlet section end wall design method of the cascade test piece according to the preferred embodiment of the present invention;

[0033] Figure 4 1. It is a schematic structural diagram of the inlet section of a plane cascade test piece adopting the inlet section end wall design method of the cascade test piece according to the preferred embodiment of the present invention;

[0034] Figure 5 It is a structural schematic diagram of a fan-shaped cascade test piece adopting the cascade test piece inlet section end wall design method according to the preferred embodiment of the present invention. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0036] The terms "first" and "second" and the like in the specification, claims and drawings of this application are used to distinguish different objects rather than to describe a specific order.

[0037] like Figure 1-5 As shown in the figure, the creep life prediction method for nickel-based single crystal high-temperature alloy blades of this embodiment includes a cascade test piece comprising a transition section, an inlet section, and a test section. The design method includes the following steps: S1: determining the inlet airflow angle of the inlet section based on the structure of the test rig, wherein the end wall of the inlet section is axially divided into a first section for adjusting the airflow angle and a second section for stabilizing the inlet airflow; S2: determining the outlet airflow angle of the inlet section based on test requirements; S3: determining the inlet and outlet points of the inlet section based on the structural design of the cascade test piece;

[0038] S4: Select the configuration mode of the first section curve according to the design requirements, and select the configuration mode of the second section curve according to the design requirements and the type of test blade; S5: Select the composition ratio of the first section curve and the second section curve; S6: Configure the second section curve based on the outlet position point and the outlet airflow angle; S7: Determine the end point position point of the first section curve according to the configuration of the second section curve; S8: Configure the first section curve based on the inlet position point, the inlet airflow angle, the end point position point and the outlet airflow angle; S9: Combine the first section curve and the second section curve based on the composition ratio to obtain the inlet section combined curve, and continuously obtain the inlet section end wall surface along the radial position of the inlet section combined curve; S10: Analyze the inlet section end wall surface, and judge whether it meets the test requirements based on the analysis results. If it meets the requirements, the design is terminated. If it does not meet the requirements, repeat steps S5-S10.

[0039] Specifically, the inlet section end wall design method of the blade test piece of the present invention determines the inlet airflow angle of the inlet section, the outlet airflow angle of the inlet section, and the inlet position point and outlet position point of the inlet section in sequence according to the existing test vehicle platform structure, test requirements and the structural design of the blade test piece, and then selects the configuration mode of the first section curve according to the design requirements, and selects the configuration mode of the second section curve according to the design requirements and the type of the test blade, so as to configure the second section curve based on the outlet position point and the outlet airflow angle after selecting the composition ratio of the first section curve and the second section curve; then, the end point of the first section curve is determined according to the configuration of the second section curve, so as to configure the first section curve based on the inlet position point, the inlet airflow angle, the end point and the outlet airflow angle; then, the first section curve and the second section curve are combined based on the composition ratio to obtain the inlet section combined curve, and the inlet section end wall surface is continuously obtained along the radial position of the inlet section combined curve; finally, the inlet section end wall surface is analyzed, and based on the analysis results, it is determined whether the composition ratio needs to be reselected for iterative optimization; this solution By dividing the end wall of the inlet section into a first section and a second section, the first section is used to adjust the angle of the airflow to convert the inlet airflow angle into the outlet airflow angle required by the test, and the second section is used to rectify the airflow after the adjusted angle to ensure the stability and uniformity of the flow field in the inlet section: then, according to design requirements, the configuration mode of the first section curve and the second section curve are selected, and the configuration of the first section curve and the second section curve is completed in sequence so that the curvature of the outlet curve of the test bench, the first section curve and the second section curve are equal, thereby achieving a smooth transition of the airflow from the outlet angle of the test bench to the required angle of the inlet of the blade test piece, ensuring a smooth connection of the end wall of the blade test piece without the risk of airflow separation, and based on the inlet section structure determined by the configuration, rapid parametric design and analysis can be carried out, facilitating iterative optimization, and achieving the airflow inlet angle of attack characteristics that meet the test requirements; compared with the existing technology, it is easy to complete parametric design and analysis work, the inlet section flow field has high stability and uniformity, which is conducive to improving the reliability of the blade test results, has strong practicality, and is suitable for wide promotion and application.

[0040] It should be understood that the outlet airflow angle of the inlet section determined according to the test requirements refers to the outlet airflow angle required during the cascade test.

[0041] It should be understood that the inlet section end wall designed in this embodiment can be applied to plane blade cascade test pieces and sector blade cascade test pieces of a compressor or turbine.

[0042] It should be understood that the purpose of this embodiment is: when the airflow angle at the wind tunnel outlet of the test vehicle is constant, by adding the end wall of the inlet section of the blade test piece designed in this embodiment, the airflow angle can be adjusted to the required design angle to meet the requirements of different inlet attack angles for different test requirements.

[0043] like Figure 3 As shown, in this embodiment, in step S4, the configuration of the first segment of the curve adopts the Hermite curve, and its configuration equation is as follows:

[0044]

[0045] Where y i is the coordinate of the location point, m i is the curvature value of the position point, α i (x) is the first basis function of the Hermite curve, β i (x) is the second basis function of the Hermite curve.

[0046] Specifically, the first segment of the curve is configured by using the Hermite curve so that the first segment of the curve satisfies the above configuration equation. In the configuration process of the first segment of the curve, the m in the configuration equation is used. i The curvature value of the inlet position point of the inlet section and the curvature value of the end point of the first section of the curve can be directly determined, so that the curvature from the outlet of the test bench to any point in the inlet section is continuous, ensuring smooth connection of the wall surface, smooth turning of the airflow, and no separation risk, effectively improving the stability and uniformity of the flow field in the inlet section.

[0047] It should be understood that the Hermite curve includes two control points, which are respectively equivalent to the entry position point and the end position point.

[0048] like Figure 3 As shown, in this embodiment, the curvature of the Hermite curve at the inlet location is equal to the curvature at the transition section's outlet connection point. Specifically, by using the Hermite curve to construct the first segment, the curvature of the transition section and the inlet section is continuous, and the transition section wall surface and the inlet section wall surface are smoothly connected, eliminating the risk of airflow separation. This effectively improves the stability and uniformity of the flow field, thereby enhancing the reliability of the cascade test results.

[0049] like Figure 3 As shown, in this embodiment, the curvature of the Hermite curve at the exit point is equal to the curvature of the second segment. Specifically, by using the Hermite curve to construct the first segment, the curvature is continuous at any point within the inlet section, and the end wall surface of the inlet section is smoothly connected, eliminating the risk of airflow separation. This effectively improves the stability and uniformity of the flow field, thereby enhancing the reliability of the cascade test results.

[0050] In this embodiment, in step S4, the first segment of the curve is configured using a Bezier curve. The Bezier curve includes four control points, two of which are respectively identical to the inlet position point and the end position point, and the other two control points are respectively close to the inlet position point and the end position point. The configuration equation is as follows:

[0051]

[0052] Where Pi is the coordinate value of the control point, and t is the control variable value of the Bezier curve.

[0053] Specifically, the first section of the curve is configured by using a Bezier curve so that the first section of the curve satisfies the above-mentioned configuration equation. During the configuration process of the first section of the curve, the airflow angle at the inlet of the first section of the curve is determined by controlling two control points adjacent to the inlet of the first section of the curve, and the airflow angle at the inlet of the first section of the curve is determined by controlling two control points adjacent to the outlet of the first section of the curve, thereby determining the curvature value of the inlet position point of the fixed inlet section and the curvature value of the end point of the first section of the curve, so that the curvature from the outlet of the test bench to any point in the inlet section is continuous, ensuring smooth connection of the wall surface, smooth turning of the airflow, and no separation risk, thereby effectively improving the stability and uniformity of the flow field of the inlet section.

[0054] In this embodiment, the curvature of the Bezier curve's inlet point is equal to the curvature of the transition section's outlet connection point. Specifically, by using the Bezier curve to construct the first segment, the curvature is continuous at any point within the inlet section, resulting in a smooth connection between the inlet end walls and eliminating the risk of airflow separation. This effectively improves the stability and uniformity of the flow field, thereby enhancing the reliability of the cascade test results.

[0055] In this embodiment, the curvature of the Bezier curve at the exit point is equal to the curvature of the second segment. Specifically, by using the Bezier curve to construct the first segment, the curvature is continuous at any point within the inlet section, and the end wall surface of the inlet section is smoothly connected, eliminating the risk of airflow separation. This effectively improves the stability and uniformity of the flow field, thereby enhancing the reliability of the cascade test results.

[0056] It should be understood that the configuration of the first segment of the curve using the Hermite curve and the Bezier curve is only different in the implementation method, and the modeling results are the same, that is, the same modeling result can be achieved through different modeling methods.

[0057] It should be understood that the design requirements mentioned in step S4 mean that the walls of the transition section, the inlet section and the test section are smoothly connected, the airflow turns smoothly, and the outlet airflow angle meets the test requirements.

[0058] In this embodiment, in step S4, when the type of the test blade cascade is a fan-shaped blade cascade, the configuration of the second curve segment adopts a cylindrical spiral line, and its configuration equation is as follows:

[0059]

[0060] Where R is the radius height of the cylindrical helix, θ is the angle value of the position point, and F(z) is the one-dimensional variation function of θ.

[0061] Specifically, when the test blade is a fan-shaped blade, a cylindrical spiral is used to configure the second curve segment so that the second curve segment satisfies the above configuration equation. That is, during the configuration process, the curvature of the inlet section and the test section is continuous, the wall surface of the inlet section and the wall surface of the test section are smoothly connected, and there is no risk of airflow separation, which effectively improves the stability and uniformity of the flow field, thereby improving the reliability of the blade test results.

[0062] It should be understood that

[0063] In this embodiment, F(z) = β1 × Z, where z is the axial coordinate of the location point and β1 is the outlet airflow angle. Specifically, by associating the one-dimensional variation function of θ with the outlet airflow angle, and making the derivative of the one-dimensional variation function equal to the outlet airflow angle, the curvature continuity of the inlet section and the test section can be achieved, and the inlet section wall surface and the test section wall surface can be smoothly connected.

[0064] In this embodiment, in step S4, when the type of the test cascade is a plane cascade, the second segment of the curve is configured as a straight line, and its configuration equation is as follows:

[0065] y = β1 × x;

[0066] Where β1 is the outlet airflow angle.

[0067] Specifically, when the test blade cascade is a plane blade cascade, a straight line is used to configure the second curve segment so that the second curve segment satisfies the above configuration equation. That is, during the configuration process, the curvature of the inlet section and the test section is made continuous, and the wall surface of the inlet section and the wall surface of the test section are smoothly connected without the risk of airflow separation, which effectively improves the stability and uniformity of the flow field, thereby improving the reliability of the blade cascade test results.

[0068] like Figure 3 As shown, in one embodiment, the Hermite curve is used to configure the first section of the curve, and the cylindrical spiral is used to configure the second section of the curve. The inlet section includes two side end walls designed using the Hermite curve and the cylindrical spiral, an upper end face in the form of an arc, and a lower end face in the form of an arc, wherein the upper end face in the form of the arc is aligned with the upper end face of the sector blade test piece, and the lower end face in the form of the arc is aligned with the lower end face of the sector blade test piece, and the two side end walls designed using the Hermite curve and the cylindrical spiral are aligned with the side end walls of the transition section and the side end walls of the test section, respectively.

[0069] It should be understood that for aircraft engine compressor and turbine cascade test specimens, when testing different inlet airflow angles, the best straightening effect is achieved when the inlet section is a cylindrical helix. This can achieve a turning effect at different airflow angles within the channel and achieve straightening of the airflow direction. However, since the airflow directions at the transition section outlet and the test specimen inlet differ, an Hermite curve-designed inlet section is required to first adjust the airflow angle. This adjusted airflow is then straightened using the cylindrical helix design to ensure stability and uniformity.

[0070] In one embodiment, a Bessel curve is used to configure the first section of the curve, and a cylindrical spiral is used to configure the second section of the curve. The inlet section includes two side end walls designed using the Bessel curve and the cylindrical spiral, an upper end face in the form of an arc, and a lower end face in the form of an arc, wherein the upper end face in the form of the arc is aligned with the upper end face of the sector blade test piece, and the lower end face in the form of the arc is aligned with the lower end face of the sector blade test piece, and the two side end walls designed using the Bessel curve and the cylindrical spiral are aligned with the side end walls of the transition section and the side end walls of the test section, respectively.

[0071] like Figure 4 As shown, in one embodiment, the first segment of the curve is configured using a Hermite curve, and the second segment of the curve is configured using a straight line.

[0072] like Figure 4 As shown, in one embodiment, a Bessel curve is used to configure the first segment of the curve, and a straight line is used to configure the second segment of the curve.

[0073] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

[0074] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0075] This article uses specific examples to illustrate the principles and implementation methods of this application. The above examples are only used to help understand the method and core ideas of this application. The above is only the preferred implementation method of this application. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of this application, they can make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as protected by this application.

Claims

1. A method for designing the end wall of the inlet section of a cascade test piece, wherein the cascade test piece includes a transition section, an inlet section, and a test section, characterized in that: The design methodology includes the following steps: S1: Determine the inlet airflow angle of the inlet section according to the structure of the test bench, wherein the end wall of the inlet section is axially divided into a first section for adjusting the airflow angle and a second section for stabilizing the inlet airflow; S2: Determine the outlet airflow angle of the inlet section according to the test requirements; S3: Determine the inlet and outlet points of the inlet section according to the structural design of the cascade test piece; S4: Select the configuration of the first curve segment according to design requirements, and select the configuration of the second curve segment according to design requirements and the type of test cascade; S5: Select the composition ratio of the first curve segment and the second curve segment; S6: configure the second curve based on the outlet position point and outlet airflow angle; S7: determining the end point of the first curve segment according to the configuration of the second curve segment; S8: Configure the first curve segment based on the inlet position point, inlet airflow angle, end point and outlet airflow angle: S9: combining the first curve and the second curve based on the composition ratio to obtain an inlet section combined curve, and continuously obtaining an inlet section end wall curved surface by continuously moving the inlet section combined curve along a radial position; S10: Analyze the curved surface of the end wall of the inlet section and determine whether it meets the test requirements based on the analysis results. If it meets the requirements, the design is terminated. If it does not meet the requirements, repeat steps S5-S10.

2. The method for designing the inlet end wall of a cascade test piece according to claim 1, characterized in that: In step S4, the first segment of the curve is configured using the Hermite curve, and its configuration equation is as follows: Where y i is the coordinate of the location point, m i is the curvature value of the position point, α i (x) is the first basis function of the Hermite curve, β i (x) is the second basis function of the Hermite curve.

3. The method for designing the inlet end wall of a cascade test piece according to claim 2, characterized in that: The curvature of the Hermite curve at the inlet position is equal to the curvature of the outlet connection point of the transition section.

4. The method for designing the inlet end wall of a cascade test piece according to claim 2, characterized in that: The curvature of the exit point of the Hermite curve is equal to the curvature of the second segment of the curve.

5. The method for designing the inlet end wall of a cascade test piece according to claim 1, characterized in that: In step S4, the first segment of the curve is configured using a Bezier curve. The Bezier curve includes four control points, two of which are respectively identical to the inlet position point and the end position point, and the other two control points are respectively close to the inlet position point and the end position point. The configuration equation is as follows: Where Pi is the coordinate value of the control point, and t is the control variable value of the Bezier curve.

6. The method for designing the inlet end wall of a cascade test piece according to claim 5, characterized in that: The curvature of the Bezier curve at the inlet position point is equal to the curvature of the outlet connection point of the transition segment.

7. The method for designing the inlet end wall of a cascade test piece according to claim 5, characterized in that: The curvature of the exit point of the Bezier curve is equal to the curvature of the second segment of the curve.

8. The method for designing the inlet end wall of a cascade test piece according to any one of claims 1 to 7, characterized in that: In step S4, when the type of the test blade cascade is a fan-shaped blade cascade, the configuration of the second curve segment adopts a cylindrical spiral line, and its configuration equation is as follows: Where R is the radius height of the cylindrical helix, θ is the angle value of the position point, and F(z) is the one-dimensional variation function of θ.

9. The method for designing the inlet end wall of a cascade test piece according to claim 8, characterized in that: F(z)=β1×Z, where z is the axial coordinate of the position point and β1 is the outlet airflow angle.

10. The method for designing the inlet end wall of a cascade test piece according to any one of claims 1 to 7, characterized in that: In step S4, when the type of the test cascade is a plane cascade, the second segment of the curve is configured as a straight line, and its configuration equation is as follows: y = β1 × x; Where β1 is the outlet airflow angle.

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