Subsonic diffuser design method based on nonlinear weighted section change rule

Abstract

The invention discloses a method for designing a subsonic diffuser based on a nonlinear weighted section shape change rule, and the method comprises the steps: carrying out the nonlinear control of the shape change rule of the diffuser through a segmented spline, and achieving the local adjustment of the section shape change rule of the diffuser through the local shape change characteristic of the segmented spline. And the flexibility is improved on the basis of being compatible with a conventional section change rule.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft air inlets, and in particular relates to a novel design method for a subsonic diffuser. Background Art

[0002] In the field of aircraft engines, the air intake is responsible for capturing the compressed airflow, slowing down the airflow, increasing its pressure, and finally flowing to the aircraft engine at a suitable speed. A subsonic diffuser is a pipe with a gradually increasing cross-sectional area, and its cross-sectional shape is generally constantly changing, which can slow down the subsonic airflow and increase its pressure. Therefore, the subsonic diffuser is an important component of the aircraft air intake.

[0003] The diffuser design method proposed by CCLee in 1985 is a relatively classic method. He expressed the change law of the center line of the isolation section and the change law of the cross-sectional area of ​​the pipe with a 4th-order polynomial. By taking different polynomial coefficients, three change laws are formed: slow and fast, slow first and fast later, and fast first and slow later. However, the method proposed by CCLee can only determine the center line shape and cross-sectional area change law of the diffuser, but cannot determine the shape of each cross section of the diffuser. Even if the inlet shape and outlet shape are specified, the cross-sectional shape between the inlet and outlet cannot be uniquely determined.

[0004] The general subsonic diffuser design method proposed in patent No. CN201410187196.X inversely calculates the curvature distribution of the inlet and outlet shape lines through given inlet and outlet shape lines, and creates each intermediate cross-sectional shape line through the transition of the curvature distribution of the inlet and outlet shape lines. The improved general subsonic diffuser design method proposed in patent No. CN202110392258.0 obtains a more accurate diffuser structure by dividing the inlet and outlet shape lines into multiple parts and one-to-one correspondence.

[0005] When generating the intermediate cross-sectional shape line, the technical solutions of the above two patents need to first calculate the curvature of the intermediate cross-sectional shape line using the linear transition law, and then inversely calculate the geometric shape of the shape line based on the curvature. This lacks geometric intuitiveness, and the shape design of the intermediate cross-section is not flexible enough.

[0006] Therefore, it is necessary to propose a new diffuser design method with more flexible cross-sectional shape changes. Summary of the invention

[0007] In view of the above problems, the present invention provides a subsonic diffuser design method based on nonlinear weighted cross-section variation law. The main principle of the design method is to regard the discrete coordinates of any intermediate cross-section shape line as a weighted combination of the coordinates of the discrete points of the inlet and outlet cross-section shape lines. The discrete coordinates of the intermediate cross-section shape lines at different positions along the diffuser have different weights, and the weights are controlled by a nonlinear function, specifically a cubic piecewise spline, so as to realize the parametric design of the diffuser.

[0008] In order to achieve the above object, the technical solutions that can be adopted in the present invention are as follows:

[0009] A subsonic diffuser design method based on nonlinear weighted cross-section variation law comprises the following steps:

[0010] (1) Discrete the inlet cross-sectional shape line and the outlet cross-sectional shape line of the diffuser into a plurality of point coordinates;

[0011] (2) calculating the inlet and outlet cross-sectional areas of the diffuser through the coordinates of a number of points, and then dividing the point coordinates of the inlet and outlet cross-sectional lines by the inlet and outlet cross-sectional areas, respectively, so as to scale the discretized inlet and outlet cross-sectional areas to unit area;

[0012] (3) Calculate the centroids of the inlet and outlet cross sections after scaling, and subtract the centroid coordinates from the point coordinates of the inlet and outlet cross section lines, thereby translating the inlet and outlet cross section lines to the origin;

[0013] (4) The coordinates of the points on the translated inlet and outlet cross-sectional shapes are weighted by weights, and the variation of the weights is controlled by piecewise splines, thereby controlling the variation of the cross-sectional shape and obtaining the coordinates of the discrete points on the intermediate cross-sectional shape;

[0014] (5) Determine the law of cross-sectional area change, and scale the coordinates of the inlet and outlet cross-sectional areas and the intermediate cross-sectional areas according to the law;

[0015] (6) Determine the shape of the centerline, translate the centroids of the inlet and outlet sections and the middle section to the same x position on the centerline, and rotate each section so that its surface is perpendicular to the centerline;

[0016] (7) Smoothly connect the discrete points of each cross section to form the final inner surface of the diffuser.

[0017] Furthermore, in step (1), the inlet cross-sectional shape line and the outlet cross-sectional shape line are uniformly discretized. If the inlet cross-sectional shape line has a sharp corner, the sharp corner is taken as an additional point, while keeping the number of discrete points of the outlet cross-sectional shape line and the inlet cross-sectional shape line equal.

[0018] Furthermore, in step (2), the inlet cross-sectional area and the outlet cross-sectional area are calculated by the following formula:

[0019]

[0020] Where S is the inlet cross-sectional area or the outlet cross-sectional area,

[0021] When S is the inlet cross-sectional area, it is denoted as S in , z1, y1 are the z and y coordinates of the first point of the inlet cross-section line in the xyz three-dimensional rectangular coordinate system, z n ,y n is the z and y coordinates of the last point of the inlet cross-section line in the xyz three-dimensional rectangular coordinate system. i ,y i are the z and y coordinates of the i-th point of the inlet cross-section line in the xyz three-dimensional rectangular coordinate system;

[0022] When S is the outlet cross-sectional area, it is denoted as S out , z1, y1 are the z and y coordinates of the first point of the outlet cross-section line in the xyz three-dimensional rectangular coordinate system, z n ,y n is the z and y coordinates of the last point of the outlet cross-section line in the xyz three-dimensional rectangular coordinate system. i ,y i It is the z and y coordinates of the i-th point of the outlet cross-section line in the xyz three-dimensional rectangular coordinate system.

[0023] Furthermore, in step (2), the formula for scaling the inlet and outlet cross sections after being discretized into a number of points to unit area is:

[0024]

[0025] Among them, Z i , Y i They are the coordinates of the point on the z and y axes of the unit area inlet or outlet section, respectively.

[0026] Furthermore, in step (3), the calculation formulas for the centroid coordinates of the inlet section and the centroid coordinates of the outlet section are:

[0027]

[0028] (z c ,y c ) are the centroid coordinates of the inlet section or the centroid coordinates of the outlet section.

[0029] Furthermore, in step (4), the change rule of the control weight is controlled to obtain the coordinates of the discrete points of the middle section using the following formula:

[0030]

[0031] w irepresents the weight of the i-th section coordinate along the way between the inlet and outlet sections; z i,j and i,j They represent the coordinates of the jth point along the i-th cross-sectional line; z in,j and yin ,j They represent the coordinates of the jth point on the inlet cross-sectional line, zout ,j and yout ,j They respectively represent the coordinates of the jth point on the outlet cross-sectional line.

[0032] Furthermore, in step (4), the weight w i The acquisition method is:

[0033] First provide the piecewise cubic spline expression of weight w:

[0034]

[0035] The piecewise cubic spline represented by the above formula consists of three first-connected and smoothly transitioned cubic curves A, B, and C. The expression of the piecewise cubic spline is determined as follows:

[0036] The expression for the piecewise cubic spline is is the independent variable, i.e. the dimensionless x-coordinate of the diffuser length L, with a value range of [0,1]; the x-coordinate of the centroid of the diffuser inlet section x c,in is 0, the corresponding dimensionless coordinate Specify the coordinate weight w of the point on the diffuser inlet cross-section line c,in 1, which is the starting point of the spline That is, P1(0,1); the x coordinate of the centroid of the diffuser outlet section is x c,out is L, the corresponding dimensionless coordinate Specify the weight w of the coordinates of the points on the diffuser outlet cross-section line c,out 0, which is the end point of the spline That is, P1(1,0); In addition, to determine the expression of the piecewise cubic spline, two spline control points are required, namely, the connection points between the cubic curves A and B. and the connection point between the cubic curves B and C The spline starting point P1, the spline ending point P2 and the two spline control points CP1 and CP2 divide the piecewise cubic spline into three segments, namely cubic curves A, B and C;

[0037] a1, b1, c1, d1, a2, b2, c2, d2, a3, b3, c3, d3 are unknown coefficients; is the coordinate of the spline starting point P1 in the x-axis direction, is the coordinate of the spline control point CP1 in the x direction, is the coordinate of the spline control point CP2 in the x direction; is the coordinate of the spline end point in the x direction,

[0038] The dimensionless x-coordinate of the centroid of the ith section along the path is Will Substitute the expression of piecewise cubic spline into it, that is Get the weight w of the coordinates of the point on the cross-sectional line i ,

[0039] Furthermore, the weight w of the coordinates of the points on the cross-sectional line is obtained. i After that, bring in The point coordinates of the middle section shape line are obtained, which means the shapes of all the middle sections are determined.

[0040] Beneficial effects: Compared with the prior art, the beneficial effects of the present invention are:

[0041] The segmented spline is used to control the shape change law of the diffuser. The segmented spline can locally change its shape through the control points, so as to locally adjust the area change law of the diffuser, which increases its flexibility while being compatible with the conventional cross-section change law.

[0042] The design method provided by the present invention can be stored on a storage medium as a computer program, and includes the following technical solutions: an electronic device, including: one or more processors; and a storage device for storing one or more programs, when the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned improved diffuser design method based on matrix transformation.

[0043] as well as:

[0044] A computer readable medium stores a computer program, which, when executed by a processor, implements the above-mentioned improved diffuser design method based on matrix transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a weight regular distribution diagram of different forms in the present invention.

[0046] Figure 2 This is the cross-sectional area variation diagram used in Case 1 and Case 2.

[0047] Figure 3 This is the center line variation pattern diagram used in Case 1 and Case 2.

[0048] Figure 4 It is a comparison diagram of the cross-sectional shapes along the process under different weighting methods.

[0049] Figure 5 It is the inner surface of the diffuser in a linear weighted manner.

[0050] Figure 6 It is the inner surface of the diffuser obtained in Case 1.

[0051] Figure 7 It is the inner surface of the diffuser obtained in Case 2. DETAILED DESCRIPTION

[0052] In order to make the purpose, design process, technical method and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0053] A subsonic diffuser design method based on a nonlinear weighted cross-section variation law comprises the following steps:

[0054] (1) Establish a rectangular coordinate system with the flow direction as the x-axis, the diffuser height direction as the y-axis, and the span direction as the z-axis. The diffuser inlet and outlet cross-sectional lines are evenly discretized into n ordered points, whose coordinates are marked as z i ,y i , i∈1,2,3,...,n. If there are cusps on the shape line, each cusp is regarded as a point, and the total number of points at the inlet and outlet must be equal during the discretization process.

[0055] (2) For the ordered discrete point coordinates obtained in the previous step, the inlet and outlet cross-sectional areas are calculated by the polygon area calculation method shown in formula (1.1), which are denoted as S in , S out , where z and y represent the z and y coordinates of the discrete points on the corresponding cross-sectional shape line, and the subscripts indicate the order of the points. Then, the coordinates of the points on the inlet and outlet cross-sectional shape lines are divided by the inlet and outlet areas respectively according to formula (1.2), thereby scaling the inlet and outlet cross-sectional areas to unit area.

[0056]

[0057] (3) The centroid coordinates z of the inlet and outlet sections after scaling can be calculated by formula (1.3): c ,y c , and then according to formula (1.4), subtract the centroid coordinates from the point coordinates of the inlet and outlet cross-sectional shape lines, so as to translate the inlet and outlet cross-sectional shape lines to the coordinate origin.

[0058]

[0059] (4) Determine the variation law of the cross-sectional shape. Weight the coordinates of the points on the translated inlet and outlet lines to obtain the coordinates of the discrete points of the middle cross section. Use piecewise cubic splines to control the variation law of the weights. By changing the relative coordinates of the spline control points, the weights can be changed within a small range, thereby locally changing the variation law of the cross-sectional shape and making the cross-sectional shape change more flexible.

[0060] In formula (1.5), w i represents the weight of the coordinates of the i-th cross-sectional shape line along the path starting from the inlet; z i,j and i,j They represent the coordinates of the jth point along the i-th cross-sectional line; z in,j and in,j represent the coordinates of the jth point on the inlet cross-sectional line, z out,j and out,j They respectively represent the coordinates of the jth point on the outlet cross-sectional line.

[0061] z i,j =(1-w i ) in,j +w i z out,j

[0062] y i,j =(1-w i )y in,j +w i y out,j (1.5)

[0063] The weighted piecewise cubic spline expression is determined as follows:

[0064] The expression for the piecewise cubic spline is is the independent variable, i.e. the dimensionless x-coordinate of the diffuser length L, with a value range of [0,1], as shown in equation (1.6). The x-coordinate x of the centroid of the diffuser inlet section is c,in is 0, the corresponding dimensionless coordinate Specify the coordinate weight w of the point on the cross-section line c,in 1, which is the starting point of the spline That is, P1(0,1). The x coordinate of the centroid of the diffuser outlet cross section is x c,out is L, the corresponding dimensionless coordinate Specify the coordinate weight w of the point on the cross-section line c,out 0, which is the end point of the spline That is, P1(1,0). In addition, the expression for determining the piecewise cubic spline requires two spline control points, namely the connection points between the cubic curves A and B. and the connection point between the cubic curves B and C The spline starting point P1, the spline ending point P2 and the two spline control points CP1 and CP2 divide the piecewise cubic spline into three segments, namely cubic curves A, B, and C. The cubic curve expression is in the form of Among them, a, b, c, and d are unknown coefficients. The set of equations representing the three curves is shown in formula (1.7), among which a1, b1, c1, d1, a2, b2, c2, d2, a3, b3, c3, and d3 are unknown coefficients.

[0065]

[0066] The equation group (1.7) has 12 unknown coefficients and requires 12 constraints. According to the C0 continuity condition of the spline curve, spline A should pass through the starting point P1 and the control point CP1, spline B should pass through the control points CP1 and CP2, and spline C should pass through the control point CP2 and the end point P2. Substituting the coordinates of each point into the corresponding equation, we can get the following 6 equations.

[0067]

[0068] is the coordinate of the spline starting point P1 in the x-axis direction, is the coordinate of the spline control point CP1 in the x direction, is the coordinate of the spline control point CP2 in the x direction; is the coordinate of the spline end point in the x direction,

[0069] According to the C1 continuity condition of the spline curve, the slopes of the adjacent curve segments that make up the spline curve should be equal at their intersection points. By taking the derivative, we can get equation (1.8). At the control point CP1, the slopes of the cubic curves A and B should be equal. At the control point CP2, the slopes of the cubic curves B and C should be equal, that is, equation (1.10). Combining equation (1.9) and substituting the coordinates of points CP1 and CP2 into equation (1.10) and sorting them out, we can get the two equations shown in equation (1.11).

[0070]

[0071] According to the C2 continuity condition of the spline curve, the curvature of each segment of the spline curve should be equal at the intersection, that is, the second-order derivative should be equal. The cubic curve equation system (1.7) has the following relationship for the independent variable: The second-order derivative can be obtained by equation (1.12). At the control point CP1, the second-order derivatives of the cubic curves A and B should be equal. At the control point CP2, the second-order derivatives of the cubic curves A and B should be equal, that is, equation (1.13). Combining equation (1.12) and substituting the coordinates of points CP1 and CP2 into equation (1.13) and sorting them out, we can get the two equations shown in equation (1.14).

[0072]

[0073]

[0074] Finally, we need to consider the constraints of the endpoints. Given that the slope of spline A at the starting point P1 is s1, and the slope of spline C at the ending point P2 is s2, that is, equation (1.15), substituting the coordinates of points P1 and P2 into equation (1.15) yields the two equations shown in equation (1.16).

[0075] s1=A′(P1)

[0076] s2=C′(P2)(1.15)

[0077] s1=b1

[0078] s2=b3+2c3+3d4(1.16)

[0079] There are 12 simultaneous equations (1.8), (1.11), (1.14), and (1.16), which can be written in matrix form, namely the system of equations shown in (1.17). Solving this system of equations can give the expression (1.18) of the spline curve, which is a piecewise function consisting of three first-connected cubic curves A, B, and C.

[0080]

[0081] The dimensionless x-coordinate of the centroid of the ith section along the path is Substituting it into equation (1.18) we get The weight w of the coordinates of the points on the cross-sectional line can be obtained i ,

[0082] Then, according to formula (1.5), the point coordinates of the middle section shape line are obtained, which means the shapes of all the middle sections are determined.

[0083] (5) Determine the law of cross-sectional area change and scale the coordinates of the inlet and outlet cross-sectional points and the intermediate cross-sectional points according to the law.

[0084] (6) Determine the shape of the center line, translate the centroids of the inlet and outlet sections and the middle section to the same x position on the center line, and rotate each section so that its surface is perpendicular to the center line.

[0085] (7) Smoothly connect the discrete points of each cross section to form the final inner surface of the diffuser.

[0086] The design method uses a piecewise cubic spline with control points to represent the cross-sectional shape variation weight w. i , the cross-section variation law can be arbitrarily controlled by changing the relative coordinates of the control points, which can be used for parametric research on diffusers and local surface optimization.

[0087] The specific implementation of the method will be given below in conjunction with the accompanying drawings:

[0088] Case 1:

[0089] (1) Assume that the inlet is a rectangle with a length of 1m and a width of 3m, and the outlet is a standard circle with a radius of 1.5m. Uniformly discretize the inlet and outlet lines to obtain the coordinates of the ordered points on the zy plane (x i ,y i ), a total of 48 points.

[0090] (2) Calculate the discretized inlet and outlet areas S according to formula (1.1) in , S out , divide the coordinates of the entry and exit points by S in , S out , and obtain the discrete coordinates of the inlet and outlet shape lines per unit area.

[0091] (3) Given the control point coordinates CP1 (0.4, 0.75), CP2 (0.7, 0.43), the starting point slope s1 = 0, the ending point slope s2 = -1.428, the distribution of the weight w along the dimensionless x coordinate can be calculated by solving the linear equation system (1.17). The specific expression is given by equation (1.19), Figure 1 The dotted line in the figure is the curve corresponding to the nonlinear expression. It can be seen from the figure that compared with the linear weighting in the prior art, the nonlinear weighted distribution in this example has the characteristics of slow at the beginning and fast at the end, so that the cross-sectional shape of the front half of the diffuser slowly transitions to the outlet shape, while the second half transitions quickly. Any form of change rule can also be specified as needed.

[0092]

[0093] (4) Given a length of L = 10 m, 34 sections are evenly distributed in the x direction, and the dimensionless x coordinate of the section shown in equation (1.6) is substituted into equation (1.18) to obtain the weight w of the i-th section: i According to formula (1.5), the coordinates of the shape line points of the middle section can be calculated, which determines the changing law of the shape of the middle section.

[0094] (5) Select Figure 2 The cross-sectional area variation law shown in the figure is expressed as (1.20), where x c is the centroid coordinate of any intermediate section (including the inlet and outlet sections), S is the area of ​​the section, S in , S out are the areas of the inlet and outlet respectively. The point coordinates of the middle cross-section line are scaled by formula (1.20).

[0095] (6) Specify eccentricity H = 10m, select Figure 3 The center line change law shown in the equation is shown in formula (1.21), where y c It is the y coordinate of the centroid of any intermediate section (including the inlet and outlet sections). The discrete points of each section shape line are translated so that the coordinates of the section centroid satisfy equation (1.21). Then the discrete points are rotated so that each section is perpendicular to the center line. The adjacent discrete points on the same section are connected with straight line segments to obtain the cross-sectional shape lines along the diffuser. Figure 4 The green lines and green points in the figure represent the cross-sectional shape lines and discrete points along the process, respectively. For the convenience of comparison, the cross-sectional shape lines and discrete points along the process under linear weighting are given in the figure, represented by red lines and red points.

[0096]

[0097] (7) Connect the cross-sectional lines to form the inner surface of the diffuser. Figure 6 The three-dimensional view of the diffuser inner surface obtained under the nonlinear weighted condition of this case is given. As a comparative example of the prior art, Figure 5 A three-dimensional view of the inner surface of the diffuser obtained under linear weighted conditions in the prior art is given.

[0098] Case 2

[0099] Following the steps of Case 1, keeping other parameters unchanged, adjusting the control point coordinates CP1 (0.4, 0.35), CP2 (0.7, 0.13), the starting point slope s1 = -1.732, the ending point slope s2 = -0.466, the specific expression of the cubic piecewise spline is shown in formula (1.22), Figure 1 The dotted line in is the weight distribution piecewise spline curve corresponding to the nonlinear expression. Compared with the linear weighting, the nonlinear weighted distribution in this example has the characteristics of being sharp at the beginning and slow at the end, so that the cross-sectional shape of the front half of the diffuser quickly transitions to the outlet shape, while the transition in the second half becomes slow. Figure 4 The blue points represent the discrete points of the cross-sectional shape line along the process, and the blue lines show the inlet, outlet and part of the intermediate cross-sectional shape lines along the process obtained in this case. Figure 7 The three-dimensional view of the diffuser inner surface obtained in this case is given.

[0100]

[0101] An embodiment of an electronic device includes:

[0102] One or more processors; and a storage device for storing one or more programs, which, when executed by the one or more processors, enable the one or more processors to implement the above-mentioned subsonic diffuser design method based on the nonlinear weighted cross-section variation law.

[0103] An embodiment of a computer-readable medium stores a computer program, which, when executed by a processor, implements the above-mentioned subsonic diffuser design method based on the nonlinear weighted cross-section variation law.

[0104] In addition, there are many specific implementation methods and approaches of the present invention, and the above is only a preferred implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A subsonic diffuser design method based on nonlinear weighted cross-section variation law, characterized in that: The following steps are included: (1) Discrete the inlet cross-sectional shape line and the outlet cross-sectional shape line of the diffuser into a plurality of point coordinates; (2) calculating the inlet and outlet cross-sectional areas of the diffuser through a number of point coordinates, and then dividing the point coordinates of the inlet and outlet cross-sectional lines by the inlet and outlet cross-sectional areas, respectively, so as to scale the discretized inlet and outlet cross-sectional areas to unit area; (3) Calculate the centroids of the inlet and outlet cross sections after scaling, and subtract the centroid coordinates from the point coordinates of the inlet and outlet cross section lines, thereby translating the inlet and outlet cross section lines to the origin; (4) The coordinates of the points on the translated inlet and outlet cross-sectional shapes are weighted by weights, and the variation of the weights is controlled by piecewise splines, thereby controlling the variation of the cross-sectional shape and obtaining the coordinates of the discrete points on the intermediate cross-sectional shape; (5) Determine the law of cross-sectional area change, and scale the coordinates of the inlet and outlet cross-sectional areas and the intermediate cross-sectional areas according to the law; (6) Determine the shape of the centerline, translate the centroids of the inlet and outlet sections and the middle section to the same x position on the centerline, and rotate each section so that its surface is perpendicular to the centerline; (7) Smoothly connect the discrete points of each cross section to form the final inner surface of the diffuser.

2. The design method according to claim 1, characterized in that: In step (1), the inlet cross-sectional shape line and the outlet cross-sectional shape line are uniformly discretized. If the inlet cross-sectional shape line has a sharp corner, the sharp corner is taken as an additional point, while keeping the number of discrete points of the outlet cross-sectional shape line and the inlet cross-sectional shape line equal.

3. The design method according to claim 1, characterized in that: In step (2), the inlet cross-sectional area and the outlet cross-sectional area are calculated by the following formula: Where S is the inlet cross-sectional area or the outlet cross-sectional area, When S is the inlet cross-sectional area, it is denoted as S in , z1, y1 are the z and y coordinates of the first point of the inlet cross-section line in the xyz three-dimensional rectangular coordinate system, z n ,y n is the z and y coordinates of the last point of the inlet cross-section line in the xyz three-dimensional rectangular coordinate system. i ,y i are the z and y coordinates of the i-th point of the inlet cross-section line in the xyz rectangular three-dimensional coordinate system; When S is the outlet cross-sectional area, it is denoted as S out , z1, y1 are the z and y coordinates of the first point of the outlet cross-section line in the xyz three-dimensional rectangular coordinate system, z n ,y n is the z and y coordinates of the last point of the outlet cross-section line in the xyz three-dimensional rectangular coordinate system. i ,y i It is the z and y coordinates of the i-th point of the outlet cross-section line in the xyz three-dimensional rectangular coordinate system.

4. The design method according to claim 1, characterized in that: In step (2), the formula for scaling the inlet and outlet cross-sections to unit area after being discretized into a number of points is: Among them, Z i , Y i They are the coordinates of the point on the z and y axes of the unit area inlet or outlet section, respectively.

5. The design method according to claim 1, characterized in that: In step (3), the calculation formulas for the centroid coordinates of the inlet section and the centroid coordinates of the outlet section are: (z c ,y c ) are the centroid coordinates of the inlet section or the centroid coordinates of the outlet section.

6. The design method according to claim 1, characterized in that: In step (4), the change rule of the control weight is used to obtain the coordinates of the discrete points in the middle section using the following formula: w i represents the weight of the i-th section coordinate along the way between the inlet and outlet sections; z i,j and i,j They represent the coordinates of the jth point along the i-th cross-sectional line; in,j and in,j They represent the coordinates of the jth point on the inlet cross-sectional line, z out,j and out,j They respectively represent the coordinates of the jth point on the outlet cross-sectional line.

7. The design method according to claim 1, characterized in that: In step (4), the weight w i The acquisition method is: First provide the piecewise cubic spline expression of weight w: The piecewise cubic spline represented by the above formula consists of three first-connected and smoothly transitioned cubic curves A, B, and C; the expression of the piecewise cubic spline is determined as follows: The expression of the piecewise cubic spline takes x as the independent variable, that is, the dimensionless x coordinate of the diffuser length L, with a value range of [0,1]; the x coordinate x of the centroid of the diffuser inlet section is c,in is 0, the corresponding dimensionless coordinate Specify the coordinate weight w of the point on the diffuser inlet cross-section line c,in 1, which is the starting point of the spline That is, P1(0,1); the x coordinate of the centroid of the diffuser outlet section is x c,out is L, the corresponding dimensionless coordinate Specify the weight w of the coordinates of the points on the diffuser outlet cross-section line c,out 0, which is the end point of the spline That is, P1(1,0); In addition, to determine the expression of the piecewise cubic spline, two spline control points are required, namely, the connection points between the cubic curves A and B. and the connection point between the cubic curves B and C The spline starting point P1, the spline ending point P2 and the two spline control points CP1 and CP2 divide the piecewise cubic spline into three segments, namely cubic curves A, B and C; a1, b1, c1, d1, a2, b2, c2, d2, a3, b3, c3, d3 are unknown coefficients; is the coordinate of the spline starting point P1 in the x-axis direction, is the coordinate of the spline control point CP1 in the x direction, is the coordinate of the spline control point CP2 in the x direction; is the coordinate of the spline end point in the x direction, The dimensionless x-coordinate of the centroid of the ith section along the path is Will Substitute the expression of piecewise cubic spline into it, that is Get the weight w of the coordinates of the point on the cross-sectional line i , 8. The design method according to claim 7, characterized in that: Get the weight w of the coordinates of the points on the cross-sectional line i After that, bring in The point coordinates of the middle section shape line are obtained, which means the shapes of all the middle sections are determined.

9. An electronic device, comprising: one or more processors; And the storage device is used to store one or more programs, when the one or more programs are executed by the one or more processors, the one or more processors implement the design method described in any one of claims 1 to 8.

10. A computer readable medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the design method according to any one of claims 1 to 8 is implemented.

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