Cartridge receiver stability expansion device design method for improving aerodynamic stability of high-speed centrifugal fan

Abstract

A design method of a casing stability expansion device for improving aerodynamic stability of a high-speed centrifugal fan mainly comprises a design method of an air injection section and a connection bridge section, molded line control parameters of the air injection section comprise an air injection angle, an expansion coefficient, an arc coefficient and a throat height, and a control parameter of the connection bridge section is only a bridge road angle. The air injection section molded line and the connecting bridge section molded line control parameters are combined, the air injection section and the connecting bridge section are molded through a specific molding method to obtain a two-dimensional plane molded line of the cartridge receiver stability extension device, and then the two-dimensional plane molded line is rotated by a certain angle in the circumferential direction to obtain the space structure of the cartridge receiver stability extension device. According to the method, the two-dimensional molded line design of the self-adaptive casing treatment stability extension device is achieved through a small number of parameters, the air injection effect of the air injection section is enhanced and the suction effect under the large-flow working condition is weakened are fully considered in the design process, the pneumatic stability of the centrifugal fan is improved, surge or rotating stall of the centrifugal fan is avoided, and the service life of the centrifugal fan is prolonged. The method has high engineering applicability in the field of enhancing the pneumatic stability of the centrifugal impeller.

Description

Technical Field

[0001] The present invention belongs to the field of application of impeller machinery flow control technology, and specifically relates to a design method for a casing stabilization device for improving the aerodynamic stability of a high-speed centrifugal fan. Background Art

[0002] High-speed centrifugal fans are widely used in numerous areas of national production due to their efficient airflow organization and processing capabilities. In the industrial sector, they are used for ventilation in production workshops, as cooling air delivery equipment for high-tech machinery, and for efficient process gas processing. With the continued advancement of Industry 4.0 and the development of intelligent manufacturing, the demand for high-performance, high-speed centrifugal fans will rapidly increase. High-speed centrifugal fans will play a significant role in industries such as high-end equipment manufacturing, new energy, and environmental protection. However, ensuring the safe and stable operation of high-speed centrifugal fans is particularly important during operation. Therefore, rotational stall or surge must be avoided as much as possible.

[0003] When a high-speed centrifugal fan is working, if rotational stall or surge occurs, the working performance of the high-speed centrifugal fan will drop sharply (the aerodynamic efficiency and total pressure ratio will drop sharply), accompanied by huge aerodynamic noise and mechanical vibration, which may cause irreversible catastrophic consequences for the high-speed centrifugal fan. Therefore, effective measures must be taken to avoid rotational stall or surge when the high-speed centrifugal fan is working.

[0004] In the field of turbomachinery, it is particularly important to adopt flow control methods to improve the aerodynamic stability of turbomachinery components to prevent rotational stall or surge during operation. Compared with active flow control technologies (such as tip jets, boundary layer suction, and plasma excitation), passive flow control technologies (such as casing stabilization devices, tip winglets, and endwall shaping) are widely used due to their simple structure, ease of application, and lack of additional control devices. In passive flow control technologies, casing stabilization devices improve the aerodynamic stability of turbomachinery components by modifying the casing components at the top of the impeller to improve the flow field in the impeller tip area. Therefore, casing stabilization devices are widely used.

[0005] When the casing stability enhancement device is applied, although it significantly improves the aerodynamic stability of the impeller machinery components, it usually causes a decrease in the aerodynamic performance of the impeller machinery components (a decrease in aerodynamic efficiency). Therefore, designing a casing stability enhancement device that can not only significantly improve the aerodynamic stability of the impeller machinery components but also have a relatively small negative impact on the aerodynamic performance of the impeller machinery components has always been the goal pursued by researchers. Adaptive casing treatment belongs to a type of passive flow control technology and has been widely concerned by researchers because it has a relatively small negative impact on the impeller performance when improving the aerodynamic stability of the rotor impeller. Currently, for the structural design of adaptive casing treatment, there are numerous parameters involved in the design method. When optimizing the design of its structure, the curse of dimensionality is often encountered, which brings resistance to engineering applications. Therefore, developing a simple, convenient, and effective design method for adaptive casing treatment has great engineering application value. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a design method for a casing stability enhancement device for improving the aerodynamic stability of a high-speed centrifugal fan. This design method for the casing stability enhancement device for improving the aerodynamic stability of a high-speed centrifugal fan passes through

[0007] The present invention is achieved through the following technical solutions.

[0008] A design method for a casing stability enhancement device for improving the aerodynamic stability of a high-speed centrifugal fan provided by the present invention includes the following steps:

[0009] Step S1, obtain the casing line, jet position, and circumferential coverage ratio of the impeller object, and select the specific numerical values of the control parameters of the jet angle (α), expansion coefficient (γ), circular arc coefficient (λ), throat height (h), and bridge angle (β);

[0010] Step S201, use a semi-circular arc with a radius of λh as the preliminary suction surface profile of the jet section, and use the jet position A as the lower end point of the preliminary suction surface profile of the jet section;

[0011] Step S202, first perform polynomial fitting on the casing of the impeller object to obtain the functional relationship of the casing line, and establish a coordinate system based on the plane where the casing line is located. According to the horizontal coordinate of the jet position A point in the coordinate system, obtain the tangent slope k1 of the jet position A. Assume that the tangent slope of the suction surface profile of the jet section at the jet position A is k2. From the relationship between the slopes of the two straight lines and their included angle (i.e., the jet angle (α)), it can be obtained that:

[0012]

[0013] Accordingly, the tangent slope k2 (k2 is negative) of the suction surface profile at the jet position is obtained, and then the angle between the tangent of the suction surface profile at the jet position A and the longitudinal coordinate axis of the coordinate system is arctan(k2). Rotate the preliminary suction surface profile of the jet section clockwise around the jet position point by (π - arctan(k2)), make a tangent on the rotated profile so that the angle between the tangent and the longitudinal coordinate axis of the coordinate system is β, and set the tangent point as point C. Point C is the end point of the suction surface profile of the jet section. The arc segment between the starting point A and the end point C is the suction surface profile of the jet section with a jet angle of α;

[0014] Step S203: Solve the coordinate values of point C. According to the semi-circular arc function equation, take the derivative of the semi-circular arc function equation to obtain the first derivative function, make the value of the first derivative function be tanβ, obtain the horizontal coordinate value of point C according to the first derivative function, and then substitute the horizontal coordinate value into the semi-circular arc function equation to solve the vertical coordinate value of point C;

[0015] Step S204: Make a tangent at point C so that the tangent intersects the casing line, and take the intersection point as the end point D of the suction surface connecting the bridge path. Connect points C and D to obtain the two-dimensional suction surface profile of the connecting bridge path;

[0016] Step S205: Draw a straight line from the center O of the suction surface profile of the jet section through the suction surface profile of the jet section. The intersection point of the straight line and the suction surface profile of the jet section is P, and the intersection point of the straight line and the casing line is E. Make the length of PE be h, and take point E as the starting point of the pressure surface profile of the jet section;

[0017] Step 206: Find a point B on the suction surface profile of the jet section such that the angle between the tangent at point B and the horizontal axis of the coordinate system is 90°. Then draw a straight line parallel to the Z axis through point B, and take a line segment with a length of γh on the left side of the point. The left end point F of the line segment is the point on the pressure surface profile of the jet section;

[0018] Step 207: Assume that the vertical coordinate values of points B and P are RB and RP respectively. Take n points at equal radial dimensions between points P and B on the suction surface profile of the jet section, and make tangents at these n points respectively; Connect the center O with these n points and extend them respectively. There is a point on the extended line corresponding to each point such that the distance between the two points is [(Ri - RP) / (RB - RP)×(γ - 1)h + h], where Ri is the vertical coordinate value of the point taken between points P and B. The points on the corresponding extended lines are the discrete points on the pressure surface profile of the jet section;

[0019] Step 208: At the endpoint C of the suction profile of the jet section, draw a perpendicular line to the tangent line at point C. Select a point G on the perpendicular line, so that the length of line segment CG is γh. Point G is then the endpoint of the pressure profile of the jet section. Take n points of equal radial dimensions between points B and C, and draw tangent lines to each of these n points. Draw perpendicular lines to the corresponding tangent lines at the corresponding points, and intercept line segments of length γh on these perpendicular lines. The endpoints of the n corresponding line segments are the discrete points on the pressure profile of the jet section.

[0020] Step 209: Starting from point E, sequentially connect the discrete points on the pressure surface profile of the jet section obtained in step 207 to point F. Then, starting from point F, sequentially connect the discrete points on the pressure surface profile of the jet section obtained in step 208 to point G to obtain a two-dimensional profile of the pressure surface of the jet section.

[0021] Step 210: Take point G as the starting point of the pressure surface profile of the connecting bridge, draw a tangent line at point G, and the intersection of the tangent line and the casing line is point H. Point H is then the end point of the pressure surface of the connecting bridge. Connecting points G and H, the two-dimensional pressure surface profile of the connecting bridge is obtained.

[0022] Step 3: With the fan shaft as the rotation axis, according to the value of the circumferential coverage ratio, the two-dimensional profile of the jet section and the two-dimensional profile of the connecting bridge are rotated circumferentially to obtain the three-dimensional spatial structure diagram of the adaptive casing stabilization device to complete the modeling.

[0023] Furthermore, in step 208, the method for intercepting a fixed length line segment on the perpendicular line of the tangent line of any point on the semicircle arc is as follows: since the equation of the semicircle arc is known, it is set as g(Z,R), where Z is the horizontal axis coordinate and R is the vertical axis coordinate. According to its derivative function, the point on the semicircle arc (Z x , R x ) has a slope of k x , then the slope of the perpendicular line to the tangent is -1 / k x , then the equation of the perpendicular line to the tangent is as follows:

[0024] RR x =-1 / k x (ZZ x )

[0025] The slope of the vertical line is -1 / k x The angle between the vertical line and the Z axis can be obtained as arctan(-1 / k x ), the included angle can be further obtained as arctan(-1 / k x ) of the sine value sin(arctan(-1 / k x )) and cosine value cos(arctan(-1 / k x )), when the length of the line segment intercepted on the vertical line is γh (taking γh as an example), the endpoint of the line segment with a length of γh is (Z x, R x ), and (Z y , R y ), Z y and R y The solution formulas for are as follows:

[0026] Z y = Z x - γhcos(arctan(-1 / k x )

[0027] R y = R x ± γhsin(arctan(-1 / k x )

[0028] For the selection of "±" in the formula, when arctan(-1 / k x ) is an acute angle, take "-"; when arctan(-1 / k x ) is an obtuse angle, then take "+".

[0029] Furthermore, the bridge path angle β is the angle between the tangent of the bridge path section line and the Z-axis, and the range of the bridge path angle (β) is between 20° and 45°.

[0030] Furthermore, the casing line equation is obtained by polynomial fitting, and the fitting order ≥ 3 to ensure the smoothness of the curve.

[0031] Furthermore, in step 3, when rotating the two-dimensional profile of the jet section and the two-dimensional profile of the connecting bridge path along the circumferential direction according to the value of the circumferential coverage ratio, the rotation angle is the circumferential coverage ratio × 360°.

[0032] Furthermore, the value range of the circumferential coverage ratio is 20% - 50%.

[0033] Furthermore, the value range of the throat height (h) is 2 times to 10 times the tip clearance size of the fan impeller.

[0034] Furthermore, the range of the jet angle (α) is 5° to 20° to ensure that the high-speed jet ejected from the jet section clings to the casing wall, reducing the mixing loss caused by the jet effect.

[0035] Furthermore, the range of the expansion coefficient (γ) is 1.2 to 1.8 to ensure that the jet section is of a contraction type, thus ensuring that the air flows out of the jet port at high speed.

[0036] Furthermore, the range of the circular arc coefficient (λ) is 1.5 to 2.5.

[0037] The beneficial effects of the present invention are as follows:

[0038] 1. The present invention can quickly realize the two-dimensional structural modeling of the adaptive casing stability augmentation device only through 5 control parameters, reducing the parametric difficulty of the adaptive casing stability augmentation device and providing an engineering application reference for quickly realizing the optimal design of the structure of the adaptive casing stability augmentation device;

[0039] 2. The casing stability augmentation device of the present invention belongs to the category of adaptive casing treatment. The jet effect of the adaptive casing treatment can increase the intensity of the tip inflow to suppress the motion form of the tip leakage flow in the blade passage, delay the breakup of the tip leakage vortex, reduce the deterioration rate of the tip region flow field, broaden the flow range in which the impeller can operate stably, and improve the stall margin of the impeller;

[0040] 3. The design method of the casing stability augmentation device of the present invention not only considers improving the aerodynamic stability of the high-speed centrifugal impeller, but also takes into account reducing the negative impact of the casing stability augmentation device on the centrifugal impeller at large flow operating points. Therefore, the design method of the casing stability augmentation device in the present invention is expected to become an important design guide for improving the aerodynamic stability of high-speed centrifugal impellers, which has important engineering application value for ensuring the safe and stable operation of high-speed centrifugal impeller components and reducing the negative impact of flow control technology.

[0041] 4. Applying the present invention to the impeller of a certain high-speed centrifugal fan, the results show that for the fan impeller applying the design method of this casing stability augmentation device, compared with the fan impeller without using the design method of this casing stability augmentation device, the minimum flow coefficient at which the fan impeller can operate stably changes from 0.56 to 0.41, and the flow margin is broadened by 26.79%, proving that the present invention has excellent stability augmentation effect on this high-speed centrifugal fan. Brief Description of the Drawings

[0042] Figure 1 is the parametric schematic diagram of the present invention;

[0043] Figure 2 is the three-dimensional structure diagram of the adaptive casing stability augmentation device designed by the method of the present invention;

[0044] Figure 3 is the spatial distribution diagram of the adaptive casing stability augmentation device designed by the method of the present invention at the top of the impeller;

[0045] Figure 4 is the performance change comparison of a certain high-speed centrifugal fan after applying the present invention;

[0046] In the figure: 1 - Centrifugal impeller casing line, 2 - Suction surface profile of the jet section, 3 - Pressure surface profile of the jet section, 4 - Suction surface profile of the connecting bridge section, 5 - Pressure surface profile of the connecting bridge section, 6 - Blade, 7 - Adjacent blade, 8 - Leading edge of the blade tip, 9 - Trailing edge of the blade tip, 10 - Adaptive casing stability augmentation device; α - Jet angle, γ - Expansion coefficient, λ - Circular arc coefficient, h - Throat height, β - Bridge section angle, k1 - Tangent slope of the casing line at the jet position, k2 - Tangent slope of the suction surface profile of the jet section at the jet position; A, B, C, D, E, F, G, H, P, O are characteristic points, and R and Z respectively represent the longitudinal and axial directions. Detailed implementation mode

[0047] The technical solution of the present invention will be further described below, but the scope of protection claimed is not limited thereto.

[0048] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "left", "right", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are all based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention patent and should not be construed as a limitation to the present invention.

[0049] Based on the problem that it is difficult to optimize the structure of the adaptive casing stability augmentation device based on the existing technology, the present invention proposes a design method for an adaptive casing stability augmentation device with a low number of parameters. Referring to Figures 1 to 3 , the specific implementation mode of the present invention will be elaborated in detail below. The research object selected in this implementation case is the impeller of a certain high-speed centrifugal fan. The following table gives the main design parameters of the impeller of this centrifugal fan, but the applicable object of the present invention is not limited to this research object only.

[0050] Table 1 Main design parameters of the high-speed centrifugal fan

[0051] parameter numerical value Design rotational speed / rpm 48000 Number of rotor blades 12 Rotor tip clearance / mm 0.5 Design pressure ratio 2.10 Design flow rate / kg 0.13

[0052] Referring to Figure 1 shown below, the application of the method of the present invention will be introduced in detail, mainly divided into the following steps:

[0053] (1) Determine relevant parameters. The jet position is at 25% of the axial chord length downstream of the leading edge of the blade tip, and the circumferential coverage ratio is 25%; the jet angle (α) is 15°, the expansion coefficient (γ) is 1.3, the circular arc coefficient (λ) is 1.5, the throat height (h) is 4 mm, and the bridge section angle (β) is 30°.

[0054] (2) According to the given parameters, perform profiling of the jet section profiles, and respectively profile the suction surface profile and the pressure surface profile of the jet section.

[0055] (3)Model the profile of the connecting bridge section according to the control parameters of the jet section profile and the connecting bridge path.

[0056] (4)Connect the jet section profile and the connecting bridge section profile to obtain the complete two-dimensional profile of the adaptive casing stability augmentation device.

[0057] (5)Taking the rotating shaft as the axis of rotation, rotate the two-dimensional profile of the adaptive casing stability augmentation device circumferentially by 7.5° to obtain the three-dimensional model of the adaptive casing stability augmentation device, completing the modeling.

[0058] Specifically, in the step (2), the initial suction surface profile of the jet section is a semi-circular arc with a radius of 6 mm (radius λh), and one end point of the semi-circular arc is placed at the jet position point A. The tangent slope k1 at the jet position point A on the casing line is obtained as 0.364. Assuming the tangent slope of the suction surface profile of the jet section at the jet position is k2, from the relationship between the slopes of two straight lines and their included angle (jet angle (α)), we can get:

[0059]

[0060] Since α is 15°, the tangent slope k2 of the suction surface profile of the jet section at the jet position is obtained as -0.0873. It can be obtained that the included angle between the tangent at the jet position of the suction surface profile of the jet section and the Z-axis is 175°. Rotate the initial suction surface profile of the jet section clockwise by 5° around the jet position point A. On the rotated profile, find a point (assumed to be point C) where the tangent makes an angle β with the Z-axis. Point C is the end point of the suction surface profile of the jet section. The circular arc segment between the starting point A and the end point C is the suction surface profile of the jet section with a jet angle of α.

[0061] Specifically, point C is the starting point of the suction surface profile of the connecting bridge path. Make a tangent at the end point C of the suction surface profile of the jet section, and the intersection point of the tangent and the casing line is point D. Then point D is the end point of the suction surface of the connecting bridge path. Connect points C and D to obtain the two-dimensional suction surface profile of the connecting bridge path.

[0062] Specifically, in the step (3), draw a straight line from the center O of the suction surface profile of the jet section through the suction surface profile of the jet section. The intersection point of the straight line and the suction surface profile of the jet section is P, and the intersection point of the straight line and the casing line is E. When the length of PE is exactly 4 mm, point E is the starting point of the pressure surface profile of the jet section.

[0063] Specifically: In the step (2), find a point B on the suction surface profile of the jet section where the tangent makes a right angle with the Z-axis. Then draw a straight line parallel to the Z-axis through point B, and take a line segment with a length of 5.2 mm (γh) on the left side of the point. Then the left end point F of the line segment is a local point on the pressure surface profile of the jet section.

[0064] Specifically, in the step (2), assuming that the R coordinates of points B and P are RB and RP respectively, 30 points are evenly taken at equal radial dimensions between points P and B on the suction surface profile of the jet section, and tangents are drawn at these 30 points respectively. Taking the point (point i) with the longitudinal coordinate Ri as an example to illustrate the solution of the point j on the pressure surface profile of the jet section. Connect points O and i and extend the line. There is a point j on the extended line. When the distance between points i and j is [(Ri - RP) / (RB - RP)*(γ - 1)h + h], point j is the point on the pressure surface profile of the jet section. Solve in this way 30 times, and 30 discrete points on the pressure surface profile of the jet section can be obtained.

[0065] Specifically, in the step (2), at the end point C of the suction surface profile of the jet section, draw a perpendicular line to the tangent at point C, and take a point G on the perpendicular line such that the length of CG is 5.2 mm (γh), then point G is the end point of the pressure surface profile of the jet section. 30 points are evenly taken at equal radial dimensions between points B and C, and tangents are drawn at these 30 points respectively. Taking the point (point x) with the longitudinal coordinate Rx as an example to illustrate the solution of the point y on the pressure surface profile of the jet section. Draw a perpendicular line to the tangent at point x, and take a point y on the perpendicular line such that the length of xy is 5.2 mm (γh), then point y is the local point on the pressure surface profile of the jet section. Solve in this way 30 times, and 30 discrete points on the pressure surface profile of the jet section can be obtained.

[0066] Specifically, in the step (3), connect the discrete points in turn between the starting point E and the end point G of the pressure surface profile of the jet section, and the two-dimensional profile of the pressure surface of the jet section can be obtained.

[0067] Specifically, in the step (4), point G is the starting point of the pressure surface profile of the connecting bridge path. Draw a tangent at the end point G of the pressure surface profile of the jet section, and the intersection point of the tangent and the casing line is point H, then point H is the end point of the pressure surface of the connecting bridge path. Connect points G and H, and the two-dimensional profile of the pressure surface of the connecting bridge path can be obtained.

[0068] Specifically, in the step (5), taking the rotating shaft as the rotation axis, according to the circumferential coverage ratio of 25%, rotate the two-dimensional profile of the jet section and the two-dimensional profile of the connecting bridge path circumferentially by 7.5° to obtain the three-dimensional spatial structure diagram of the adaptive casing stability augmentation device, as Figure 2 and Figure 3 , and the modeling is completed.

[0069] Use the commercial computational fluid dynamics software NUMECA 13.2 to conduct numerical calculation research on this high-speed centrifugal fan. The impeller models without the casing stability augmentation device and the impeller model with the casing stability augmentation device of the present invention are calculated respectively. The specific implementation process is as follows:

[0070] (1) The impeller passage grid model adopts an O4H grid topology structure, with an O-type grid on the blade surface and an H-type grid surrounding it; both the impeller inlet section and the outlet section are H-type grids, and the tip clearance grid topology is a butterfly grid structure; the grid of the casing stability enhancement device module is an H-type grid, and the casing stability enhancement device model is connected to the impeller top grid in a completely non-matching manner.

[0071] (2) For numerical calculation, the total temperature and total pressure boundaries are given at the inlet, the mass flow boundary is given at the outlet, the wall surface is an adiabatic no-slip boundary, the difference scheme is a central difference scheme, the turbulence model is SST, and the periodic boundary condition is set between channels.

[0072] (3) The research results are as Figure 4 shown. The results show that for the low-flow unstable condition of a high-speed centrifugal fan, the casing stability enhancement device of the present invention can reduce the minimum flow coefficient for the stable operation of the high-speed centrifugal fan from 0.56 to 0.41. Compared with other casing stability enhancement devices with the same design, the casing stability enhancement device of the present invention has a very significant stability enhancement effect, and the increase in the flow margin is as high as 26.79%. It shows significant advantages in improving the aerodynamic stability of high-speed centrifugal fans.

[0073] The above takes a certain high-speed centrifugal fan as an example to show the effect of the present invention, but it is only exemplary and should not be construed as a limitation of the present invention. Those skilled in the relevant art can make changes, modifications, substitutions, and deformations to the above examples within the scope of the present invention without departing from the basic principles and usage methods of the present invention.

Claims

1. A design method of a casing stability-enhancing device for improving the aerodynamic stability of a high-speed centrifugal fan, characterized in that It includes the following steps: Step S1: Obtain the casing line, jet position, and circumferential coverage ratio of the impeller object, and select the specific numerical values of the control parameters of the jet angle (α), expansion coefficient (γ), circular arc coefficient (λ), throat height (h), and bridge passage angle (β). Step S201: Use a semi-circular arc with a radius of λh as the preliminary suction surface profile of the jet section, and use the jet position A as the lower end point of the preliminary suction surface profile of the jet section. Step S202: First, perform polynomial fitting on the casing of the impeller object to obtain the functional relationship of the casing line, establish a coordinate system based on the plane where the casing line is located, obtain the tangent slope k1 of the jet position A according to the horizontal coordinate of point A of the jet position in the coordinate system, and assume that the tangent slope of the suction surface profile of the jet section at the jet position A is k2. From the relationship between the slopes of the two straight lines and their included angle (jet angle (α)), we can get: Based on this, the tangent slope k2 of the suction surface profile of the jet section at the jet position is obtained (k2 is negative), and the included angle between the tangent of the suction surface profile of the jet section at the jet position A and the longitudinal coordinate axis of the coordinate system can be obtained as arctan(k2). Rotate the preliminary suction surface profile of the jet section clockwise around the jet position point by (π - arctan(k2)), make a tangent on the rotated profile so that the included angle between the tangent and the horizontal coordinate axis of the coordinate system is β, and set the tangent point as point C. Point C is the end point of the suction surface profile of the jet section. The circular arc section between the starting point A and the end point C is the suction surface profile of the jet section with a jet angle of α. Step S203: Solve the coordinate value of point C. According to the semi-circular arc function equation, take the first derivative of the semi-circular arc function equation to obtain the first derivative function, make the value of the first derivative function be tanβ, obtain the horizontal coordinate value of point C according to the first derivative function, and then substitute the horizontal coordinate value into the semi-circular arc function equation to solve the vertical coordinate value of point C. Step S204: Make a tangent at point C so that the tangent intersects with the casing line, and use the intersection point as the end point D of the suction surface connecting the bridge passage. Connect points C and D to obtain the two-dimensional suction surface profile of the connecting bridge passage. Step S205: Draw a straight line from the center O of the suction surface profile of the jet section through the suction surface profile of the jet section. The intersection point of the straight line and the suction surface profile of the jet section is P, and the intersection point of the straight line and the casing line is E. Make the length of PE be h, and use point E as the starting point of the pressure surface profile of the jet section. Step 206: Find a point B on the suction surface profile of the jet section such that the included angle between its tangent and the horizontal axis of the coordinate system is 90°. Then draw a straight line parallel to the Z axis through point B, and take a line segment with a length of γh on the left side of the point. Then the left end point F of the line segment is the point on the pressure surface profile of the jet section. Step 207: Let the longitudinal coordinate values of points B and P be RB and RP respectively. At equal radial dimensions between points P and B on the suction surface profile of the jet section, evenly take n points, and respectively draw the tangents of these n points; respectively connect the center O with these n points and extend the lines. There is a point on each corresponding extended line such that the distance between the two points is [(Ri - RP) / (RB - RP)×(γ - 1)h + h], where Ri is the longitudinal coordinate value of the point taken between points P and B, and the points on the corresponding extended lines are the discrete points on the pressure surface profile of the jet section; Step 208: At the end point C of the suction surface profile of the jet section, draw a perpendicular line to the tangent at point C. Take a point G on this perpendicular line such that the length of line segment CG is γh, then point G is the end point of the pressure surface profile of the jet section. At equal radial dimensions between points B and C, evenly take n points, and respectively draw the tangents of these n points; at the corresponding points, draw perpendicular lines to the corresponding tangents and intercept line segments with a length of γh on these perpendicular lines. The n end points of the corresponding line segments are the discrete points on the pressure surface profile of the jet section; Step 209: Starting from point E, sequentially connect the discrete points on the pressure surface profile of the jet section obtained in Step 207 to point F, and then starting from point F, sequentially connect the discrete points on the pressure surface profile of the jet section obtained in Step 208 to point G to obtain the two-dimensional profile of the pressure surface of the jet section; Step 210: Take point G as the starting point of the pressure surface profile of the connecting bridge path. Draw a tangent at point G, and the intersection point of the tangent and the casing line is point H, then point H is the end point of the pressure surface of the connecting bridge path. Connect points G and H to obtain the two-dimensional profile of the pressure surface of the connecting bridge path; Step 3: Taking the fan rotating shaft as the rotation axis, according to the value of the circumferential coverage ratio, rotate the two-dimensional profile of the jet section and the two-dimensional profile of the connecting bridge path circumferentially to obtain the three-dimensional spatial structure diagram of the adaptive casing stability augmentation device, and complete the modeling.

2. The design method of the casing stability enhancement device for improving the aerodynamic stability of a high-speed centrifugal fan according to claim 1, characterized in that: In step 208, the method of intercepting a line segment of a fixed length on the perpendicular line of the tangent at any point on the semi-circular arc is as follows. From the semi-circular arc equation, let it be g(Z, R), where Z is the abscissa and R is the ordinate. According to its derivative function, the tangent slope at the point (Z x , R x ) on the semi-circular arc is k x , then the slope of the perpendicular line to the tangent is -1 / k x , and the equation of the perpendicular line to the tangent is as follows: R-R x = -1 / k x (Z-Z x ) The slope of the vertical line is -1 / k x The angle between the vertical line and the Z axis can be obtained as arctan(--1 / k x ), the included angle can be further obtained as arctan(--1 / k x )'s sine value sin(arctan(--1 / k x )) and cosine value cos(arctan(--1 / k x )), when the length of the line segment intercepted on the vertical line is γh (taking γh as an example), the endpoint of the line segment with a length of γh is (Z x , R x ) and (Z y , R y ),Z y and R y The solution formula is as follows: Z y = Z x -γhcos(arctan(-1 / k x ) R y = R x ±γhsin(arctan(-1 / k x ) For the selection of "±" in the formula, when arctan(-1 / k x ) is an acute angle, take "-"; when arctan(-1 / k x ) is an obtuse angle, then take "+".

3. The design method of the casing stability-enhancing device for improving the aerodynamic stability of a high-speed centrifugal fan according to claim 1, characterized in that: The bridge path angle β is the angle between the tangent of the connecting bridge path section profile and the Z axis, and the range of the bridge path angle (β) is between 20° and 45°.

4. The design method of the casing stability enhancement device for improving the aerodynamic stability of a high-speed centrifugal fan according to claim 1, characterized in that: The casing line equation is obtained by polynomial fitting, and the fitting order ≥3 to ensure the smoothness of the curve.

5. The design method of the casing stability enhancement device for improving the aerodynamic stability of a high-speed centrifugal fan according to claim 1, characterized in that: In Step 3, when rotating the two-dimensional profile of the jet section and the two-dimensional profile of the connecting bridge path circumferentially according to the value of the circumferential coverage ratio, the rotation angle is the circumferential coverage ratio × 360°.

6. The design method of the casing stability-enhancing device for improving the aerodynamic stability of a high-speed centrifugal fan according to claim 1, characterized in that: The value range of the circumferential coverage ratio is 20% - 50%.

7. The design method of the casing stability enhancement device for improving the aerodynamic stability of a high-speed centrifugal fan according to claim 1, characterized in that: The value range of the throat height (h) is 2 times to 10 times the tip clearance size of the fan impeller.

8. The design method of the casing stability enhancement device for improving the aerodynamic stability of a high-speed centrifugal fan according to claim 1, characterized in that: The range of the jet angle (α) is 5° to 20° to ensure that the high-speed jet ejected from the jet section closely adheres to the casing wall surface and reduces the mixing loss caused by the jet effect.

9. The design method of the casing stability enhancement device for improving the aerodynamic stability of a high-speed centrifugal fan according to claim 1, characterized in that: The range of the expansion coefficient (γ) is 1.2 to 1.8 to ensure that the jet section is in a contraction type, so as to ensure that the air flow is ejected at high speed from the jet orifice.

10. The design method of the casing stability-enhancing device for improving the aerodynamic stability of a high-speed centrifugal fan according to claim 1, characterized in that: The range of the arc coefficient (λ) is 1.5 to 2.5.

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