Centrifugal compressor impeller and vaned diffuser combined design optimization method

Abstract

The invention belongs to the technical field of aircraft environment control, and discloses a high-pressure-ratio and high-rotating-speed centrifugal compressor impeller and vaned diffuser joint optimization design method, which comprises the following steps of: calculating by using a one-dimensional theory according to a compressor design index to obtain basic geometric parameters of a compressor impeller and a vaned diffuser; the method comprises the following steps: respectively selecting an initial blade root molded line, a blade middle molded line and a blade tip molded line as design optimization objects, and connecting from a blade root to a blade tip by using a smooth curve; according to the scheme, the initial blade molded line and the diffuser guide blade molded line are optimized, complete impeller and vaned diffuser models are obtained, performance calculation is conducted on the obtained N compressor models, and a combination with the optimal efficiency and the optimal pressure ratio is selected as the final scheme of the impeller and the diffuser of the compressor. By means of the design method, the designed impeller can adapt to the flow change of the gas compressor in a large range, so that the operation stability of the gas compressor is improved, and the surge margin of the gas compressor is widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft environmental control, and relates to a design method for the pneumatic structure of a high-compression ratio electric compressor used in an aircraft environmental control system, and specifically to a design method for a centrifugal compressor impeller and a vaned diffuser. Background Art

[0002] Aircraft environmental control systems are used to protect the lives of people on board and protect the aircraft from icing or foggy conditions. The success of its design is directly related to the safety of the passengers and the aircraft. In order to reduce engine thrust loss, reduce product quantity and weight, and reduce pollutant emissions, the electric environmental control system cancels the engine bleed air system, reduces the energy consumption of the engine, and becomes an important development direction of future aircraft environmental control systems. The high-compression ratio electric compressor is the core component and important part of the electric environmental control system. It has the characteristics of high pressure ratio, high temperature resistance, large flow, and small size. The performance of the electric compressor directly determines the quality of the electric environmental control system.

[0003] In order to provide the air source system with stable and appropriate temperature and pressure when the aircraft is cruising, the impeller of the electric compressor needs to be reasonably matched and designed in shape and blade shape to meet the requirements of pressure ratio, flow range and efficiency under different working conditions. In addition, the designed compressor impeller needs to be calculated for the internal three-dimensional flow field and the impeller needs to be optimized to finally obtain a reasonable distribution of aerodynamic loads on the blade surface, maximize the efficiency of the electric compressor, meet the pressure ratio requirements under various working conditions, and reduce the risk of surge.

[0004] There are many types of design methods currently, which are based on indicator requirements to carry out design, including simulation optimization, etc. Generally, the compressor impeller and bladed diffuser are designed separately, and then combined with simulation fine-tuning. The efficiency is low, and the overall performance of the designed aerodynamic structure is average, and stall in the diffuser may occur. Summary of the invention

[0005] The purpose of the present invention is to provide a combined optimization design method for a centrifugal compressor impeller and a vaned diffuser with a high pressure ratio and a high speed, by which the flow separation on the suction surface of the centrifugal impeller can be reduced, thereby improving the aerodynamic efficiency of the impeller. The optimization method can also improve the blade profile of the vaned diffuser according to the design index, thereby reducing the occurrence of stall in the diffuser, improving the overall performance of the compressor, and widening its efficient operation range.

[0006] The technical solution of the present invention is as follows:

[0007] A combined optimization design method for a centrifugal compressor impeller and a vaned diffuser with high pressure ratio and high speed comprises the following steps:

[0008] S1: According to the compressor design index, the basic geometric parameters of the compressor impeller and the vaned diffuser are calculated using one-dimensional theory;

[0009] S2: Select the initial blade root profile, blade middle profile, and blade tip profile as the design optimization objects respectively, and use a smooth curve to connect from the blade root to the blade tip; select the initial guide vane profile in the same way;

[0010] S3: Optimize the initial blade profile and diffuser guide vane profile obtained in S2. The optimization method is a numerical simulation method based on fitting. Different profiles are calculated and N groups of profiles with the highest compressor efficiency are selected.

[0011] S4: thicken the blades and diffuser guide vanes corresponding to the N groups of profiles to obtain a complete impeller and vaned diffuser model;

[0012] S5: Use numerical simulation methods to calculate the performance of the N compressor models obtained, and select the best combination of efficiency and pressure ratio as the final compressor impeller and diffuser solution.

[0013] Furthermore, the basic geometric parameters include: impeller inlet diameter d1, impeller outlet diameter d2, blade inlet height b1, blade outlet height b2, blade inlet tip angle β1t, blade inlet root angle β1h, blade outlet angle β2, diffuser inlet diameter d3, diffuser outlet diameter d4, diffuser blade inlet angle β3 and diffuser blade outlet angle β4.

[0014] Further, in S2, the blade root profile s1, the blade middle profile s2 and the blade tip profile s3 are selected respectively, and the three profiles are expanded along the corresponding impeller height direction to obtain the change curve of the impeller profile on the meridian plane, that is, the initial impeller profile; the change curve of the guide vane profile s4 on the meridian plane is obtained by the same method, that is, the initial guide vane profile;

[0015] Furthermore, the specific process of S3 is:

[0016] S31: Use Bezier curves to fit the impeller profile and the guide vane profile respectively; each profile uses one control point;

[0017] S32: select the coordinates of the control points of the four profiles, the impeller blade inlet tip angle β1t, the blade inlet root angle β1h, the blade outlet angle β2, the diffuser blade inlet angle β3 and the diffuser blade outlet angle β4, a total of 9 variables for optimization, and use a random sampling method to obtain a total of M impeller and diffuser blade models, that is, compressor models;

[0018] S33: Using a numerical simulation method, the obtained M compressor models are calculated at the compressor design point respectively; and finally the optimal N compressor models are selected.

[0019] Furthermore, in S31 and S32, the coordinate positions of the control points are s1-type line a (x1, y1), s2-type line b (x2, y2), s3-type line c (x3, y3), and s4-type line d (x4, y4), respectively. The x range of the control points is 0 to 1, the y range is 0 to 1, and the angle range is -5° to +5°.

[0020] Furthermore, in S33, the numerical simulation method is: the inlet pressure of the design point is P1, the inlet temperature is T1, the speed is n, and the flow rate is m; the calculated compressor efficiency is the x-axis, the pressure ratio is the y-axis, and the compressor pressure ratio and efficiency obtained from different compressor models are made into a point set; the points in the point set and whose pressure ratio meets the requirements are selected, and the formula c=compression ratio+efficiency is defined, and the N compressor models with the largest c value are selected.

[0021] Furthermore, the specific process of S4 is as follows:

[0022] Along the blade profile, the thickness increases in the circumferential direction on both sides:

[0023] Define the profile inlet as 0% and profile outlet as 100%.

[0024] Starting from the 0% position, the blade thickness gradually increases until it reaches a maximum at about 60%, and then the blade thickness gradually decreases to reach the blade outlet thickness at the 100% position; from the 0% position to the 100% position, the blade thickness transitions in a smooth arc.

[0025] Furthermore, S5 is specifically:

[0026] The obtained N compressor models are assembled into the volute, and the performance of the compressor is calculated at the design point using the numerical simulation method to obtain the pressure ratio and efficiency of the N compressor models at the design flow rate; when the design pressure ratio is met, the compressor model with the highest efficiency is selected as the final compressor design scheme.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. The present invention provides a design method for a centrifugal compressor impeller and a vaned diffuser. The method combines the advantages of theoretical empirical design with computer numerical simulation and optimization methods. On the basis of the one-dimensional design of the compressor, the impeller blades and diffuser blades of the compressor are designed in three dimensions. Through this design method, the efficiency of the compressor can be effectively improved, and the designed impeller can adapt to a wide range of compressor flow changes, thereby improving the operating stability of the compressor and widening the surge margin of the compressor.

[0029] 2. The blade profile designed in the present invention is based on the original blade form. By selecting multiple design variables, a large number of impeller and diffuser blade form combinations are made within a reasonable range to find the optimal model, thereby ensuring the optimal design result. The improvement in the efficiency of the optimized impeller and diffuser indicates that the flow separation on the suction surface of the blade flow field is suppressed, which significantly improves the internal flow field of the compressor impeller and diffuser, and improves the performance of the compressor. The compressor designed by this method has high efficiency, effectively reduces the power consumption of the aircraft environmental control system, and is beneficial to the optimization and distribution of the aircraft's power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0031] Figure 1 Schematic diagram of the initial model of the compressor in an embodiment of the present invention.

[0032] Figure 2 This is a cross-sectional view of the initial model of the centrifugal compressor.

[0033] Figure 3 Schematic diagram of the isosurface of the centrifugal compressor impeller.

[0034] Figure 4 It is the curve distribution diagram of the blade after the stream surface diagram is unfolded.

[0035] Figure 5 is the variation curve of blade thickness distribution coefficient. DETAILED DESCRIPTION

[0036] This section is an embodiment of the present invention, which is used to explain and illustrate the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships based on the orientations or positional relationships in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or case referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0038] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be interpreted in a broad sense, for example, it can be a fixed connection, a detachable connection or an integrated connection; it can be a mechanical connection or a point connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0039] Embodiment 1:

[0040] A combined optimization design method for a centrifugal compressor impeller and a vaned diffuser with high pressure ratio and high speed comprises the following steps:

[0041] S1: According to the compressor design index, the basic geometric parameters of the compressor impeller and the vaned diffuser are calculated using one-dimensional theory;

[0042] S2: Select the initial blade root profile, blade middle profile, and blade tip profile as the design optimization objects respectively, and use a smooth curve to connect from the blade root to the blade tip; select the initial guide vane profile in the same way;

[0043] S3: Optimize the initial blade profile and diffuser guide vane profile obtained in S2. The optimization method is a numerical simulation method based on fitting. Different profiles are calculated and N groups of profiles with the highest compressor efficiency are selected.

[0044] S4: thicken the blades and diffuser guide vanes corresponding to the N groups of profiles to obtain a complete impeller and vaned diffuser model;

[0045] S5: Use numerical simulation methods to calculate the performance of the N compressor models obtained, and select the best combination of efficiency and pressure ratio as the final compressor impeller and diffuser solution.

[0046] The basic geometric parameters include: impeller inlet diameter d1, impeller outlet diameter d2, blade inlet height b1, blade outlet height b2, blade inlet tip angle β1t, blade inlet root angle β1h, blade outlet angle β2, diffuser inlet diameter d3, diffuser outlet diameter d4, diffuser blade inlet angle β3 and diffuser blade outlet angle β4.

[0047] In S2, the blade root profile s1, the blade middle profile s2 and the blade tip profile s3 are selected respectively, and the three profiles are expanded along the corresponding impeller height direction to obtain the change curve of the impeller profile on the meridian plane, that is, the initial impeller profile; the change curve of the guide vane profile s4 on the meridian plane is obtained by the same method, that is, the initial guide vane profile;

[0048] The specific process of S3 is:

[0049] S31: Use Bezier curves to fit the impeller profile and the guide vane profile respectively; each profile uses one control point;

[0050] S32: select the coordinates of the control points of the four profiles, the impeller blade inlet tip angle β1t, the blade inlet root angle β1h, the blade outlet angle β2, the diffuser blade inlet angle β3 and the diffuser blade outlet angle β4, a total of 9 variables for optimization, and use a random sampling method to obtain a total of M impeller and diffuser blade models, that is, compressor models;

[0051] S33: Using a numerical simulation method, the obtained M compressor models are calculated at the compressor design point respectively; and finally the optimal N compressor models are selected.

[0052] In S31 and S32, the coordinate positions of the control points are s1-type line a (x1, y1), s2-type line b (x2, y2), s3-type line c (x3, y3), and s4-type line d (x4, y4), respectively. The x range of the control points is 0 to 1, the y range is 0 to 1, and the angle range is -5° to +5°.

[0053] In S33, the numerical simulation method is: the inlet pressure of the design point is P1, the inlet temperature is T1, the speed is n, and the flow rate is m; the calculated compressor efficiency is the x-axis, the pressure ratio is the y-axis, and the compressor pressure ratio and efficiency obtained from different compressor models are made into a point set; select the points in the point set and whose pressure ratio meets the requirements, define the formula c=compression ratio+efficiency, and take the N compressor models with the largest c value.

[0054] The specific process of S4 is as follows:

[0055] Along the blade profile, the thickness increases in the circumferential direction on both sides:

[0056] Define the profile inlet as 0% and profile outlet as 100%.

[0057] Starting from the 0% position, the blade thickness gradually increases until it reaches a maximum at about 60%, and then the blade thickness gradually decreases to reach the blade outlet thickness at the 100% position; from the 0% position to the 100% position, the blade thickness transitions in a smooth arc.

[0058] S5 is as follows:

[0059] The obtained N compressor models are assembled into the volute, and the performance of the compressor is calculated at the design point using the numerical simulation method to obtain the pressure ratio and efficiency of the N compressor models at the design flow rate; when the design pressure ratio is met, the compressor model with the highest efficiency is selected as the final compressor design scheme.

[0060] Embodiment 2:

[0061] In step 1, the impeller geometric parameters obtained are respectively the impeller inlet diameter d1, outlet diameter d2, blade inlet height b1, blade outlet height b2, blade inlet tip angle β1t, blade inlet root angle β1h, blade outlet angle β2, diffuser inlet diameter d3, diffuser outlet diameter d4, diffuser blade inlet angle β3 and diffuser blade outlet angle β4. The basic geometric model of the impeller and diffuser can be obtained through the above design parameters.

[0062] In step 2, select the blade root profile s1, blade middle profile s2 and blade tip profile s3 respectively, expand the three profiles along the corresponding impeller height, and obtain the change curve of the impeller profile on the meridian plane. The change of the guide vane profile s4 on the meridian plane can be obtained by the same method.

[0063] The specific process of step 3 is:

[0064] Step 3-1, use Bezier curves to fit the impeller profile and the guide vane profile respectively. Each profile uses a control point. The coordinate positions of the control points are s1 profile a (x1, y1), s2 profile b (x2, y2), s3 profile c (x3, y3), s4 profile d (x4, y4). The x range of the control point is 0 to 1, and the y range is 0 to 1.

[0065] Step 3-2, select 8 variables for optimization, including the control point coordinates, the impeller blade inlet tip angle β1t, the blade inlet root angle β1h, the blade outlet angle β2, the diffuser blade inlet angle β3 and the diffuser blade outlet angle β4. The x range of the control point is 0 to 1, and the y range is 0 to 1. The angle range is -5° to +5°. Using the random sampling method, a total of 100 impeller and diffuser blade models were obtained.

[0066] Step 3-3, using the numerical simulation method, calculate the 100 models obtained at the compressor design point. The inlet pressure of the design point is P1, the inlet temperature is T1, the speed is n, and the flow rate is m. With the calculated compressor efficiency as the x-axis and the pressure ratio as the y-axis, the compressor pressure ratio and efficiency obtained by different models are made into a point set. Select the point in the point set where the pressure ratio meets the requirements, define the formula c = pressure ratio + efficiency, and take the 10 models with the largest c value.

[0067] The specific process of step 4 is:

[0068] Along the blade profile, the thickness increases in the circumferential direction on both sides. Figure 5 The fitted curve is set, where the profile inlet is defined as 0% and the profile outlet is defined as 100%.

[0069] The specific process of step 5 is:

[0070] The 10 complete impeller and diffuser models were assembled into the volute, and the performance of the compressor was calculated at the design point using the numerical simulation method. The pressure ratio and efficiency of the 10 compressor models at the design flow rate were obtained.

[0071] Under the condition of meeting the design pressure ratio, the model with the highest efficiency is selected as the final compressor design.

[0072] Embodiment 3:

[0073] The present invention provides a combined design optimization method for a high pressure ratio high speed compressor impeller and a vaned diffuser. Figure 1 and Figure 2 As shown, the initial model of the compressor is obtained by theoretical method according to the compressor design index. The compressor model includes an impeller 1, a vaned diffuser 2 and a volute 3. The profile and inlet and outlet angles of the impeller blades 1-1 and the diffuser blades 2-1 play an important role in improving the efficiency and operation stability of the compressor and enhancing the anti-surge performance of the compressor. Therefore, the present invention optimizes the compressor based on the design index by calculating a large number of combinations of the profile and inlet and outlet angles of the impeller and diffuser blades while keeping the basic size of the compressor obtained by theoretical calculation unchanged.

[0074] The specific steps are as follows:

[0075] Step 1, such as Figure 2 As shown in the figure, according to the design indicators, the basic parameters of the compressor are obtained by theoretical calculation method, which are the impeller inlet diameter d1, outlet diameter d2, blade inlet height b1, blade outlet height b2, diffuser inlet diameter d3, and diffuser outlet diameter d4.

[0076] Step 2, such as Figure 2As shown in the figure, select the compressor impeller and make an isosurface a1 with equal distances to the hub and the blade tip along the blade height direction. By intersecting this isosurface with the impeller blade, the blade profile y1 on the isosurface in the middle of the blade can be obtained. Repeat the above steps to obtain the blade profile y0 and blade profile y2 corresponding to the blade root isosurface a0 and the blade tip isosurface a2.

[0077] like Figure 4 As shown, the blade profile y1 is converted to the blade flow surface, and the middle line of the blade contour is taken as the blade profile s1. The angle between the profile s1 at the blade inlet and the circumferential direction is the blade inlet angle β1-1, and the angle between the blade tail and the circumferential direction is the blade outlet angle β1-2.

[0078] By repeating step 2, the profiles of the blade root, blade top and diffuser guide vane and their blade inlet and outlet angles can be obtained.

[0079] Step 3-1, use Bezier curve to fit each type line. The coefficients of Bezier curve are named s1 type line a(x1,y1), s2 type line b(x2,y2), s3 type line c(x3,y3), s4 type line d(x4,y4). The x range of the control point is 0 to 1, and the y range is 0 to 1.

[0080] Step 3-2, select the control point coefficient, impeller blade inlet tip angle β1t, blade inlet root angle β1h, blade outlet angle β2, diffuser blade inlet angle β3 and diffuser blade outlet angle β4, a total of 8 variables for optimization. The x range of the control point is 0 to 1, and the y range is 0 to 1. The angle range is -5° to +5°. Using the random sampling method, a total of 100 impeller and diffuser blade models were obtained.

[0081] Step 3-3, using the numerical simulation method, calculate the 100 models obtained at the compressor design point. The inlet pressure of the design point is P1, the inlet temperature is T1, the speed is n, and the flow rate is m. After each calculation is completed, the optimization combination with divergent or unstable calculation results should be deleted, and only the combination data with results should be selected.

[0082] When all calculation results are completed, select the effective calculation results, take the compressor efficiency as the x-axis and the pressure ratio as the y-axis, and make the compressor pressure ratio pi and efficiency n obtained by different models into a point set. Select the point in the point set where the pressure ratio meets the requirements, define the formula c=pi+n, and select the 10 models with the largest c value.

[0083] In step 4, the blade profile of each model is thickened using the blade thickness distribution in Table 1.

[0084] The specific method of thickening is that the inlet of the profile is defined as 0% and the outlet is defined as 100%. Along the normal direction of each blade, increase the corresponding distance according to the corresponding data in Table 1. After the thickening is completed, the head of the blade should be rounded.

[0085] The method of step 5 is to assemble the optimized candidate models into the compressor volute respectively, and 10 compressor models can be obtained. The numerical simulation method is used again to calculate the pressure ratio and efficiency of the compressor at the design point.

[0086] According to the numerical simulation method, the model with the highest efficiency is selected as the final compressor design scheme while meeting the design pressure ratio.

[0087] The present invention obtains a compressor blade model that meets the design requirements by jointly optimizing the compressor impeller blades and the vaned diffuser blades. The optimization variables for the blades include not only the blade profiles of different blade heights, but also the inlet and outlet angles of the blades. The optimal blade model is obtained through a large number of sampling calculations. The three-dimensional blades obtained by this method can adapt to the flow field distribution of the design point to the greatest extent, reduce the turbulent dissipation and airflow separation inside the impeller, thereby improving the impeller efficiency of the initial design, expanding the stable operation range of the compressor, and achieving the purpose of anti-surge.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A combined optimization design method for a centrifugal compressor impeller and a vaned diffuser with high pressure ratio and high speed, characterized in that: The following steps are involved: S1: According to the compressor design index, the basic geometric parameters of the compressor impeller and the vaned diffuser are calculated using one-dimensional theory; S2: Select the initial blade root profile, blade middle profile, and blade tip profile as the design optimization objects respectively, and use a smooth curve to connect from the blade root to the blade tip; select the initial guide vane profile in the same way; S3: Optimize the initial blade profile and diffuser guide vane profile obtained in S2. The optimization method is a numerical simulation method based on fitting. Different profiles are calculated and N groups of profiles with the highest compressor efficiency are selected. S4: thicken the blades and diffuser guide vanes corresponding to the N groups of profiles to obtain a complete impeller and vaned diffuser model; S5: Use numerical simulation methods to calculate the performance of the N compressor models obtained, and select the best combination of efficiency and pressure ratio as the final compressor impeller and diffuser solution.

2. The combined optimization design method of a centrifugal compressor impeller and a vaned diffuser with high pressure ratio and high speed according to claim 1 is characterized in that: The basic geometric parameters include: impeller inlet diameter d1, impeller outlet diameter d2, blade inlet height b1, blade outlet height b2, blade inlet tip angle β1t, blade inlet root angle β1h, blade outlet angle β2, diffuser inlet diameter d3, diffuser outlet diameter d4, diffuser blade inlet angle β3 and diffuser blade outlet angle β4.

3. The combined optimization design method of a centrifugal compressor impeller and a vaned diffuser with high pressure ratio and high speed according to claim 2 is characterized in that: In S2, the blade root profile s1, the blade middle profile s2 and the blade tip profile s3 are selected respectively, and the three profiles are expanded along the corresponding impeller height direction to obtain the change curve of the impeller profile on the meridian plane, that is, the initial impeller profile; the change curve of the guide vane profile s4 on the meridian plane is obtained by the same method, that is, the initial guide vane profile.

4. The combined optimization design method of a centrifugal compressor impeller and a vaned diffuser with high pressure ratio and high speed according to claim 3 is characterized in that: The specific process of S3 is: S31: Use Bezier curves to fit the impeller profile and the guide vane profile respectively; each profile uses one control point; S32: select the coordinates of the control points of the four profiles, the impeller blade inlet tip angle β1t, the blade inlet root angle β1h, the blade outlet angle β2, the diffuser blade inlet angle β3 and the diffuser blade outlet angle β4, a total of 9 variables for optimization, and use a random sampling method to obtain a total of M impeller and diffuser blade models, that is, compressor models; S33: Using a numerical simulation method, the obtained M compressor models are calculated at the compressor design point respectively; and finally the optimal N compressor models are selected.

5. The combined optimization design method of a centrifugal compressor impeller and a vaned diffuser with high pressure ratio and high speed according to claim 4 is characterized in that: In S31 and S32, the coordinate positions of the control points are s1-type line a (x1, y1), s2-type line b (x2, y2), s3-type line c (x3, y3), and s4-type line d (x4, y4), respectively. The x range of the control points is 0 to 1, the y range is 0 to 1, and the angle range is -5° to +5°.

6. The combined optimization design method of a centrifugal compressor impeller and a vaned diffuser with high pressure ratio and high speed according to claim 4 is characterized in that: In S33, the numerical simulation method is: the inlet pressure of the design point is P1, the inlet temperature is T1, the speed is n, and the flow rate is m; the calculated compressor efficiency is the x-axis and the pressure ratio is the y-axis, and the compressor pressure ratio and efficiency obtained from different compressor models are made into a point set; Select points where the points are concentrated and the pressure ratio meets the requirements, define the formula c = pressure ratio + efficiency, and select the N compressor models with the largest c value.

7. The combined optimization design method of a centrifugal compressor impeller and a vaned diffuser with high pressure ratio and high speed according to claim 1 is characterized in that: The specific process of S4 is as follows: Along the blade profile, the thickness increases in the circumferential direction on both sides: Define the profile inlet as 0% and profile outlet as 100%. Starting from the 0% position, the blade thickness gradually increases until it reaches a maximum at about 60%, and then the blade thickness gradually decreases to reach the blade outlet thickness at the 100% position; from the 0% position to the 100% position, the blade thickness transitions in a smooth arc.

8. The combined optimization design method of a centrifugal compressor impeller and a vaned diffuser with high pressure ratio and high speed according to claim 4 is characterized in that: S5 is as follows: The obtained N compressor models are assembled into the volute, and the performance of the compressor is calculated at the design point using the numerical simulation method to obtain the pressure ratio and efficiency of the N compressor models at the design flow rate; when the design pressure ratio is met, the compressor model with the highest efficiency is selected as the final compressor design scheme.

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