A method for aerodynamic design of a curved-wall large-opening-angle diffusion section with constant pressure gradient and the large-opening-angle diffusion section

Abstract

The application discloses a kind of pressure gradient constant curve wall large opening diffusion section aerodynamic design method and large opening diffusion section, it is related to high-low speed wind tunnel airflow pipeline design field, to the problem that existing linear wall large opening diffusion section is caused by adverse pressure gradient and needs to increase fairing device inside air flow is seriously separated, the application is by determining diffusion section length and import / export size, calculates area ratio and equivalent diffusion angle, according to the corresponding isobaric pressure gradient curve equation of cross-sectional shape selection, calculates wall surface generatrix profile coordinate and constructs aerodynamic profile, so that air flow along the pressure gradient keeps constant.The application eliminates air flow separation from flow mechanism, can obtain uniform outlet flow field without internal fairing device, effectively reduce pressure loss, can be self-adapting different working conditions, reduce design manufacturing cost.

Description

Technical Field

[0001] This invention relates to the field of high and low speed wind tunnel airflow duct design, specifically to an aerodynamic design method for a large-angle diffuser section with a constant pressure gradient on a curved wall, and the large-angle diffuser section itself. Background Technology

[0002] In wind tunnel loop design, the large-angle diffuser section (typically referring to a diffuser section with an equivalent diffusion angle of approximately 20 to 90 degrees) is used to significantly expand the cross-sectional area of ​​the wind tunnel within a short axial distance, facilitating a rapid transition between two different cross-sectional sections. When airflow passes through the large-angle diffuser section, it undergoes a rapid deceleration and pressurization process. The significant static pressure difference leads to a large adverse pressure gradient within the section, triggering strong secondary flows and extensive airflow separation. This results in turbulent flow field and a significant increase in pressure loss within the wind tunnel, failing to meet the wind tunnel flow field quality requirements and adding an extra load to the power system.

[0003] To eliminate airflow separation, conventional design methods involve adding rectifiers (such as honeycomb structures or damping nets) inside the large-angle diffuser section to artificially increase flow resistance and suppress separation vortices. However, adding rectifiers not only increases the difficulty of structural fabrication and installation, but also makes their design parameters highly dependent on the deceleration and pressurization characteristics of the large-angle diffuser section. When wind tunnel operating conditions change, the existing rectifiers often fail to adapt to the new flow patterns. To meet different operating conditions, rectifiers with different parameters must be replaced, leading to a significant increase in manufacturing and operation / maintenance costs.

[0004] Therefore, there is an urgent need in this field to develop a new design method for a large-angle diffuser section that can eliminate the airflow separation phenomenon from the mechanism of flow separation, so that a uniform and stable outlet flow field can be obtained without the need for additional rectification devices inside the diffuser section. Summary of the Invention

[0005] The purpose of this invention is to overcome the severe airflow separation problem in the large-angle diffuser section of wind tunnels in the prior art, and to provide an aerodynamic design method for a large-angle diffuser section with a constant pressure gradient on a curved wall. The large-angle diffuser section designed by this method can eliminate airflow separation without the need for an internal rectifier, thereby reducing pressure loss, improving outlet airflow uniformity, and reducing manufacturing and operation and maintenance costs.

[0006] To achieve the above-mentioned objectives, this invention provides an aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient, the method comprising:

[0007] Step 1: Determine the length of the large-angle diffuser section Calculate the inlet cross-sectional dimensions and outlet cross-sectional dimensions of the large-angle diffuser section, and calculate the inlet area of ​​the large-angle diffuser section. Exit area of ​​the large-angle diffusion section Area ratio and equivalent diffusion angle ;

[0008] Step 2: Satisfying the area ratio And the equivalent diffusion angle Under conditions ranging from 20 degrees to 90 degrees, the corresponding isobaric gradient curve equation is selected based on the cross-sectional shapes of the inlet and outlet of the large-angle diffuser section. Using the selected isobaric gradient curve equation, and based on the inlet cross-sectional dimensions, outlet cross-sectional dimensions, and length of the large-angle diffuser section... Calculate the different axial positions along the airflow direction. radial dimension of the cross section Obtain the coordinates of the wall generatrix surface;

[0009] Step 3: Based on the coordinates of the wall generatrix, construct the aerodynamic profile of the large-angle diffuser section, so that the pressure gradient of the airflow along the large-angle diffuser section is constant.

[0010] Existing technologies for large-angle diffuser design lack a universal profile design method that can eliminate airflow separation at the mechanistic level, necessitating reliance on rectifiers, which increases cost and complexity. This method determines the basic geometric parameters of the diffuser section and calculates the area ratio and equivalent diffusion angle in step 1; step 2 sets the applicable conditions for the area ratio... And the equivalent diffusion angle Located within the 20° to 90° range, ensuring the design object conforms to the large opening angle characteristic, and selecting the corresponding isobaric gradient curve equation based on the cross-sectional shape for coordinate calculation; in step 3, the aerodynamic profile is constructed based on the coordinates to ensure that the airflow exhibits an isobaric gradient distribution. This method provides a general and systematic aerodynamic design process for large opening angle diffusers with constant pressure gradients. The airflow inside the diffuser designed using this method... Since it is a constant, the adverse pressure gradient is eliminated, thereby suppressing airflow separation at the source.

[0011] Preferred area ratio The calculation method is as follows:

[0012] .

[0013] Preferably, the equivalent diffusion angle The calculation method is as follows:

[0014] .

[0015] Preferably, in step 2, when both the inlet cross-section and the outlet cross-section of the large-angle diffuser are circular or square, the equation for the isobaric gradient curve is:

[0016] ;

[0017] in, The radial dimension of the inlet section of the large-angle diffuser is given. This represents the radial dimension of the outlet section of the large-angle diffuser.

[0018] This method provides an accurate surface calculation formula for symmetrical cross-sections, ensuring a constant airflow pressure gradient within the circular-circular or square-square diffuser section, thereby suppressing separation.

[0019] Preferably, in step 2, when at least one of the inlet cross-sectional shape and the outlet cross-sectional shape of the large-angle diffuser section is rectangular, the equation of the isobaric gradient curve is:

[0020] ;

[0021] in, The radial dimension of the inlet section of the large-angle diffuser is given. This represents the radial dimension of the outlet section of the large-angle diffuser.

[0022] This method provides a formula for calculating the diffuser profile with a rectangular cross section, enabling equal pressure gradient flow to be achieved inside a non-completely axisymmetric rectangular diffuser section, thus eliminating airflow separation.

[0023] Preferably, in step 2, when the inlet cross-sectional shape of the large-angle diffuser section and the outlet cross-sectional shape of the large-angle diffuser section are circular and square respectively, and a transition from circular to square is required, the transition arc radius is... The calculation formula is:

[0024] When the cross-sectional shape changes from a square to a circle, the calculation formula is: ;

[0025] When the cross-sectional shape changes from a circle to a square, the calculation formula is: ;

[0026] in, The radius is the radius when the inlet or outlet cross-section of the large-angle diffuser section is circular.

[0027] In wind tunnels, the transition between a circular duct and a square (or rectangular) test section presents unique design challenges at the four corners. Conventional straight-line transitions are prone to flow separation at these corners. The radius of the circular arc is given for each transition direction. Axial position Based on the linear variation law, this method provides an accurate calculation formula for the radius of the transition arc in the corner region of the transition section from circle to square or square to circle, which makes the flow in the corner region smooth, avoids local vortices, and ensures the constantness of the pressure gradient in the entire diffusion section.

[0028] Preferably, this method uses the center of the inlet section of the large-angle diffuser section as the design origin (0,0), with the direction along the flow direction as the positive direction of the x-axis and perpendicular to the flow direction as the positive direction of the y-axis. The generatrix profile of the wall forms an axisymmetric inner wall surface of the diffuser section around the central axis of the large-angle diffuser section. This method clarifies the design origin and coordinate axis directions, and specifies the structural relationship for generating the axisymmetric inner wall surface of the diffuser section by rotating the generatrix around the central axis, providing a geometric basis for the correct generation from two-dimensional generatrix coordinates to three-dimensional profiles.

[0029] Preferably, the method further includes step 4: performing numerical simulation verification on the aerodynamic profile of the large-angle diffuser section constructed based on the coordinates of the wall generatrix to confirm that there are no separation vortices in the internal flow field of the large-angle diffuser section. This method adds a numerical simulation verification step, which can predict and confirm the flow field quality of the design scheme in advance, ensuring that there are no separation vortices inside the final manufactured large-angle diffuser section, and improving the design success rate.

[0030] Preferably, the large-angle diffuser section is applied in a wind tunnel loop and does not have an additional internal rectifier. In the prior art, large-angle diffusers must rely on internal rectifiers to eliminate separation, resulting in complex structures and high costs. The large-angle diffuser section designed in this invention, when applied in a wind tunnel loop, can operate normally without any additional internal rectifier.

[0031] The present invention also provides a curved wall large-angle diffuser section with constant pressure gradient. The wall surface of the curved wall large-angle diffuser section is a curved wall, and its generatrix profile is a constant pressure gradient curve, so that the pressure gradient along the airflow remains constant. The coordinates of the generatrix profile are calculated by the method described above, and the generatrix profile is rotated around the central axis of the diffuser section to form the inner wall surface of the diffuser section.

[0032] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0033] Eliminating airflow separation: By rationally designing the wall busbar form, the airflow separation phenomenon in the large-angle diffuser section is effectively eliminated from the mechanism of flow separation.

[0034] Reduced pressure loss: Since there is no need to add a rectifier to create artificial resistance, the pressure loss of the large-angle diffuser section can be effectively reduced by about 20%.

[0035] Adaptable to different operating conditions: The large-angle diffuser section with constant pressure gradient curve wall can adapt to different incoming flow states, eliminating the need to replace the rectifier for different operating conditions, which significantly reduces operating costs and operational difficulty.

[0036] Uniform outlet airflow: The velocity distribution at the outlet cross section is more uniform, which improves the quality of the wind tunnel flow field.

[0037] Reduced design and manufacturing complexity: No need to process and install complex rectifier devices, simplifying the structure and saving processing and installation costs.

[0038] The design methodology is standardized and universal: This invention provides clear design steps and guidelines, applicable to the design of large-angle diffuser sections of various shapes and sizes, with a high degree of automation and wide applicability. Attached Figure Description

[0039] The accompanying drawings, which are provided to further illustrate embodiments of the invention and constitute a part of this invention, are not intended to limit the scope of the invention.

[0040] Figure 1 A flowchart illustrating an aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient.

[0041] Figure 2 A schematic diagram of the aerodynamic profile of the large-angle diffuser section obtained by the design method of the constant pressure gradient curve generatrix, wherein 1-inlet section of the large-angle diffuser section; 2-wall generatrix of the large-angle diffuser section of the constant pressure gradient curve; 3-outlet section of the large-angle diffuser section.

[0042] Figure 3 This is a schematic diagram of the aerodynamic profile of the large-angle diffuser wall drawn based on the generatrix coordinates. Detailed Implementation

[0043] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments of the present invention and the features thereof can be combined with each other.

[0044] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0045] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0046] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0047] Example 1;

[0048] Please refer to Figure 1 , Figure 1 This invention provides an aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient. The method includes:

[0049] Step 1: Determine basic parameters: Determine the length of the large-angle diffuser section. Calculate the inlet cross-sectional dimensions and outlet cross-sectional dimensions of the large-angle diffuser section, and calculate the inlet area of ​​the large-angle diffuser section. Exit area of ​​the large-angle diffusion section Area ratio and equivalent diffusion angle ;

[0050] Step 2: Calculation of wall generatrix coordinates: Under the condition that the area ratio is satisfied... And the equivalent diffusion angle Under conditions ranging from 20 degrees to 90 degrees, the corresponding isobaric gradient curve equation is selected based on the cross-sectional shapes of the inlet and outlet of the large-angle diffuser section. Using the selected isobaric gradient curve equation, and based on the inlet cross-sectional dimensions, outlet cross-sectional dimensions, and length of the large-angle diffuser section... Calculate the different axial positions along the airflow direction. radial dimension of the cross section Obtain the coordinates of the wall generatrix surface;

[0051] Step 3: Aerodynamic profile construction step: Based on the coordinates of the wall generatrix profile, construct the aerodynamic profile of the large-angle diffuser section, so that the pressure gradient of the airflow along the large-angle diffuser section is constant.

[0052] Among them, the large-angle diffuser section refers to a diffuser section component installed in the wind tunnel airflow channel to connect two sections with large differences in cross-sectional area and to achieve airflow deceleration and pressurization within a short axial distance. It meets the following geometric characteristics: area ratio... And the equivalent diffusion angle It is located in the range of 20 degrees to 90 degrees.

[0053] The principle of this invention is as follows:

[0054] This invention, starting from the principle of airflow separation, provides a design method for large-angle diffusers that uses an equal pressure gradient curve as the generatrix of the large-angle diffuser section through engineering derivation, numerical simulation, and wind tunnel testing. In fluid mechanics, the direct cause of airflow separation is the adverse pressure gradient existing along the flow direction (i.e., the pressure gradient that exists along the flow direction). When pressure increases rapidly along the flow direction, the fluid with lower kinetic energy within the boundary layer cannot overcome the pressure increase and is forced to stagnate or even flow backward, forming separation vortices. This invention, through a specific curved wall design, makes the pressure of the airflow in the large-angle diffuser section change linearly along the flow direction, creating a constant pressure gradient curve within the large-angle diffuser section. The flow is a potential flow with an equal pressure gradient, and this gradient is either zero or compressive, thus theoretically eliminating the adverse pressure gradient that causes separation and completely suppressing airflow separation from the flow mechanism perspective. Using an equal pressure gradient curve instead of the currently used straight-wall design for the large-angle diffuser section prevents pressure recovery along the diffuser's path, eliminating the adverse pressure gradient and thus eliminating airflow separation from the flow mechanism perspective. The equal pressure gradient curve wall for the large-angle diffuser section can replace the current design method of adding a rectifier to the straight-wall large-angle diffuser section, eliminating the need for an additional rectifier to eliminate airflow separation. This design method effectively reduces the manufacturing difficulty, installation, maintenance, and operating costs of the large-angle diffuser section.

[0055] This invention provides a design method for the generatrix profile of the large-angle diffuser section wall panel under constant pressure gradient curves: First, based on the cross-sectional parameters of the sections to be connected by the large-angle diffuser section and the length occupied by the large-angle diffuser section in the wind tunnel loop, the basic dimensions such as the inlet and outlet cross-sectional areas and lengths of the large-angle diffuser section are determined. Then, based on the basic dimensions of the large-angle diffuser section, design parameters such as the area ratio and equivalent diffusion angle are calculated. Finally, based on the design parameters and cross-sectional shape of the large-angle diffuser section, the appropriate equations are selected for calculation to obtain the generatrix coordinates of the wall panel of the large-angle diffuser section, thus completing the design of the large-angle diffuser section under constant pressure gradient curves.

[0056] The design method and steps for the curved generatrix profile of the large-angle diffuser section wall panel with a constant pressure gradient along the friction path, as involved in this invention, are as follows:

[0057] (1) Determine the length of the large-angle diffuser section in the wind tunnel. The inlet and outlet dimensions are used to calculate the inlet area of ​​the large-angle diffuser section. and the exit area of ​​the large-angle diffusion section Calculate the area ratio of the diffusion section. Equivalent diffusion angle ;

[0058] ;

[0059] ;

[0060] (2) Based on the calculation results obtained in the previous step, when the area ratio Equivalent diffusion angle When the diffusion section is determined to be a large-angle diffusion section, it meets the condition of designing the wall generatrix according to the curve with constant pressure gradient.

[0061] (3) For the large-angle diffuser section that meets the conditions of step (2) above, the generatrix parameters of the large-angle diffuser section curve are calculated using the formula based on the inlet and outlet cross-sectional shapes of the large-angle diffuser section:

[0062] a. When the inlet and outlet cross-sectional shapes of the large-angle diffuser section are circular or square, the equation for calculating the curvilinear coordinates is:

[0063] ;

[0064] b. When one of the inlet and outlet sections of the large-angle diffuser is rectangular, and the other is rectangular, circular, or square, the equation for calculating the curve coordinates is:

[0065] ;

[0066] c. When the inlet and outlet cross-sectional shapes of the large-angle diffuser section are circular and square respectively, and a transition from circular to square is required in the four corner areas, the formula for calculating the radius of the transition arc is:

[0067] When the cross-section changes from square to circular, the calculation formula is: ;

[0068] When the cross-section changes from circular to square, the calculation formula is: ;

[0069] in, The dimensions of the inlet cross-section of the large-angle diffuser section are given. For circular cross-sections, the radius is given; for square cross-sections, half the side length is given; for rectangular cross-sections, half the length or width is given. The unit is meters (m). The radius of the outlet section of the large-angle diffuser is the dimension of the cross-section. For a circular cross-section, it is the radius; for a square cross-section, it is half the side length; and for a rectangular cross-section, it is half the length or width of the side. The unit is meters (m). The position of the large-aperture diffuser section along the airflow direction is expressed in meters (m). The position of the large-angle diffuser section in the direction of airflow. The radial dimension of the cross-section is the radius for a circular cross-section, half the side length for a square cross-section, and half the length or width for a rectangular cross-section, in meters (m). The length of the large-angle diffuser section is in meters (m). When the large-angle diffuser section changes from a circle to a square or from a square to a circle, the position along the airflow direction... The radius of the transition arc at the cross-section, in meters; The radius of the circular cross-section when the inlet or outlet cross-section is circular, in meters, is when the large-angle diffuser section changes from a circle to a square or from a square to a circle.

[0070] (4) Based on the above steps, the profile of the large-angle diffuser section with constant pressure gradient is obtained and used for the design and manufacturing of the large-angle diffuser section;

[0071] The calculated large-angle diffuser section is an axisymmetric section. The design origin (0,0) is the center of the inlet section of the large-angle diffuser section. The positive x-axis is along the flow direction, and the positive y-axis is vertically upward perpendicular to the flow direction.

[0072] Given the inlet and outlet parameters and length of the large-angle diffuser section, the profile parameters and coordinates of the generatrix of the isobaric gradient curve can be calculated according to the above design steps, thus obtaining the aerodynamic profile of the large-angle diffuser section. Based on the design results, the profile of the large-angle diffuser section with the isobaric gradient curve can be given, which is used for the design and manufacturing of the large-angle diffuser section, so that the airflow exhibits an isobaric gradient along the diffuser section direction. The distribution pattern of the diffuser section can be analyzed. When computational resources permit, numerical simulations can be performed on the aerodynamic shape of the large-angle diffuser section to verify the effectiveness of the flow field design.

[0073] Please refer to Figure 2 , Figure 2 A schematic diagram of the aerodynamic profile of the large-angle diffuser section obtained by the design method of the equal pressure gradient curve generatrix, where 1 is the inlet section of the large-angle diffuser section; 2 is the generatrix of the wall of the large-angle diffuser section of the equal pressure gradient curve; and 3 is the outlet section of the large-angle diffuser section.

[0074] In this embodiment, a large-angle diffuser section with a curved wall and a constant pressure gradient is also provided. The wall of the diffuser section is a curved wall, and its generatrix profile is a constant pressure gradient curve, so that the pressure gradient along the airflow remains constant. The coordinates of the generatrix profile are calculated by the aforementioned design method, and the generatrix profile is rotated around the central axis of the diffuser section to form the inner wall of the diffuser section.

[0075] Example 2;

[0076] Based on Example 1, this example demonstrates the application of this design method in the design of a large-angle diffuser section of a wind tunnel. The design scheme was verified by scaled-down model tests and achieved the expected design goals. There was no obvious airflow separation within the section, effectively reducing the pressure loss of the large-angle diffuser section by about 20%, and obtaining a uniform outlet airflow velocity distribution.

[0077] Based on the known aerodynamic parameters of the large-angle diffuser section in the wind tunnel, the specific design steps for the aerodynamic profile of the large-angle diffuser section with constant pressure gradient curves are as follows:

[0078] 1. The inlet section of the large-angle diffuser is circular with a radius of 265mm, the outlet section is circular with a radius of 408mm, and the length of the diffuser section is 348mm.

[0079] 2. The calculated inlet cross-sectional area of ​​the large-angle diffuser section is 0.22 m². 2 The outlet cross-sectional area is 0.524m². 2 The area ratio is 2.38, and the equivalent diffusion angle is 44.7°. The area ratio of the diffusion section is greater than 2, and the equivalent diffusion angle is between 20° and 90°. This diffusion section is judged to be a large-angle diffusion section. The generatrix of the wall of the large-angle diffusion section is designed according to the equal pressure gradient curve.

[0080] 3. The inlet and outlet cross-sections are circular. Calculate the profile using the generatrix equation of a curved, gradually expanding pipe:

[0081] The radius of the inlet section of the large-angle diffuser is... mm;

[0082] The radius of the outlet section of the large-angle diffuser is... mm;

[0083] The length of the large-angle diffuser section. mm;

[0084] The axial position of the cross-section along the airflow direction for the large-angle diffuser section is calculated in mm;

[0085] The radius of the cross-section at any position along the airflow direction in the large-angle diffuser section is the radial dimension, in mm.

[0086] Table 1 presents the coordinates of the generatrix profile of the wall surface of the large-angle diffuser section with a circular-to-circular cross-section, based on the constant pressure gradient curve. The aerodynamic profile of the generatrix of the wall surface of the large-angle diffuser section can be derived from these coordinates, as shown below. Figure 3 As shown, the design of the large-angle diffuser section on the wall of the constant pressure gradient curve is completed. Figure 3This is a schematic diagram of the aerodynamic profile of the large-angle diffuser wall generatrix, drawn based on the generatrix coordinates. Figure 3 The horizontal axis represents the axial position. (mm), with the vertical axis representing the radial dimension of the cross-section. (mm).

[0087] Table 1. Coordinates of the generatrix profile of the wall surface of the large-angle diffuser section of the circular-to-circular cross-section.

[0088]

[0089] After the design is completed, numerical simulation (CFD) is used to check whether separation vortices exist in the flow field within the large-angle diffuser section, and whether the design requirements are met under various operating conditions. This embodiment eliminates airflow separation from the flow separation generation mechanism, can adapt to different wind tunnel operating conditions, does not require additional rectification devices, and obtains a large-angle diffuser section that can generate stable attached flow, while achieving a stable and uniform velocity distribution at the outlet section.

[0090] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0091] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient, characterized in that, The method includes: Step 1: Determine the length of the large-angle diffuser section Calculate the inlet cross-sectional dimensions and outlet cross-sectional dimensions of the large-angle diffuser section, and calculate the inlet area of ​​the large-angle diffuser section. Exit area of ​​the large-angle diffusion section Area ratio and equivalent diffusion angle ; Step 2: Satisfying the area ratio And the equivalent diffusion angle Under conditions ranging from 20 degrees to 90 degrees, the corresponding isobaric gradient curve equation is selected based on the cross-sectional shapes of the inlet and outlet of the large-angle diffuser section. Using the selected isobaric gradient curve equation, and based on the inlet cross-sectional dimensions, outlet cross-sectional dimensions, and length of the large-angle diffuser section... Calculate the different axial positions along the airflow direction. radial dimension of the cross section Obtain the coordinates of the wall generatrix surface; Step 3: Based on the coordinates of the wall generatrix, construct the aerodynamic profile of the large-angle diffuser section, so that the pressure gradient of the airflow along the large-angle diffuser section is constant.

2. The aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient according to claim 1, characterized in that, Area ratio The calculation method is as follows: 。 3. The aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient according to claim 1, characterized in that, Equivalent diffusion angle The calculation method is as follows: 。 4. The aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient according to claim 1, characterized in that, In step 2, when both the inlet cross-section and the outlet cross-section of the large-angle diffuser are circular or square, the equation for the isobaric gradient curve is: ； in, The radial dimension of the inlet section of the large-angle diffuser is given. This represents the radial dimension of the outlet section of the large-angle diffuser.

5. The aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient according to claim 1, characterized in that, In step 2, when at least one of the inlet cross-sectional shape and the outlet cross-sectional shape of the large-angle diffuser section is rectangular, the equation for the isobaric gradient curve is: ； in, The radial dimension of the inlet section of the large-angle diffuser is given. This represents the radial dimension of the outlet section of the large-angle diffuser.

6. The aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient according to claim 1, characterized in that, In step 2, when the inlet cross-sectional shape of the large-angle diffuser section and the outlet cross-sectional shape of the large-angle diffuser section are circular and square respectively, and a transition from circular to square is required, the transition arc radius is... The calculation formula is: When the cross-sectional shape changes from a square to a circle, the calculation formula is: ; When the cross-sectional shape changes from a circle to a square, the calculation formula is: ; in, The radius is the radius when the inlet or outlet cross-section of the large-angle diffuser section is circular.

7. An aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient, as described in any one of claims 1-6, characterized in that, With the center of the inlet section of the large-angle diffuser section as the design origin (0,0), the direction along the flow direction is the positive direction of the x-axis, and the direction perpendicular to the flow direction is the positive direction of the y-axis. The generatrix surface of the wall forms an axisymmetric inner wall surface of the diffuser section around the central axis of the large-angle diffuser section.

8. The aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient according to claim 1, characterized in that, The method further includes step 4: numerically simulating and verifying the aerodynamic profile of the large-angle diffuser section constructed based on the coordinates of the wall generatrix to confirm that there are no separation vortices in the internal flow field of the large-angle diffuser section.

9. The aerodynamic design method for a large-angle diffuser section on a curved wall with a constant pressure gradient according to claim 1, characterized in that, The large-angle diffuser section is used in the wind tunnel loop and does not have an additional rectifier inside.

10. A large-angle diffuser section with a constant pressure gradient on a curved wall, characterized in that, The wall surface of the large-angle diffuser section with curved walls is a curved wall, and its generatrix profile is an equal pressure gradient curve, so that the pressure gradient along the airflow remains constant; the coordinates of the generatrix profile are calculated by the method of any one of claims 1 to 9, and the generatrix profile is rotated around the central axis of the diffuser section to form the inner wall surface of the diffuser section.

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