A method for designing an integrated centrifugal impeller

Abstract

The embodiment of the application is a design method of an integrated centrifugal impeller, and belongs to the technical field of centrifugal pump design. The design method comprises the following steps: determining a necessary net positive suction head of an original centrifugal impeller, and determining a design head of a pre-work section based on a target net positive suction head; obtaining a first target parameter of the original centrifugal impeller; determining a second target parameter of the pre-work section according to the design head of the pre-work section; determining a third target parameter of a centrifugal section; establishing an integrated blade angle change equation based on the second target parameter and the third target parameter, and designing an integrated blade; determining the number of the integrated blade and a target centrifugal blade; and arranging the integrated blade and the target centrifugal blade between a front cover plate and a rear cover plate of an integrated centrifugal impeller to obtain the integrated centrifugal impeller. The design method of the integrated centrifugal impeller can make the integrated impeller have high anti-cavitation performance and high efficiency.

Description

Technical Field

[0001] This application relates to the field of centrifugal pump design technology, and more specifically, to an integrated centrifugal impeller design method. Background Technology

[0002] Cavitation is a common and harmful phenomenon during the operation of centrifugal pumps. Cavitation leads to performance degradation, structural vibration and radiated noise, and damage to flow-through components. Improving the cavitation resistance of centrifugal pumps is crucial for ensuring their hydraulic performance and operational stability, and for extending their service life.

[0003] Common methods to improve the cavitation resistance of centrifugal pumps include increasing the impeller inlet diameter during the design process and installing an inducer in front of the impeller. Increasing the impeller inlet diameter can reduce flow losses in front of the impeller inlet by lowering the flow velocity, but it may increase the blade inlet angle of attack, causing flow separation on the blade suction surface and reducing impeller efficiency. The inducer has the ability to pre-do work on the fluid entering the centrifugal impeller, which can increase the pressure of the fluid entering the centrifugal impeller inlet. A well-designed inducer can better improve the cavitation resistance of the centrifugal pump, but installing an inducer will increase the axial dimension of the centrifugal pump, and the axial space between the inducer and the centrifugal impeller will bring new energy losses, reducing the operating efficiency of the centrifugal pump.

[0004] Integrating the inducer and centrifugal impeller can improve the cavitation resistance of centrifugal pumps while avoiding the increase in axial size and efficiency reduction caused by axial space constraints. Currently, in the process of integrating the inducer and centrifugal impellers, the inducer blade outlet and centrifugal blade inlet are usually directly connected to form an integrated impeller, lacking research on integrated impeller design methods. Furthermore, the inducer blade outlet angle and the centrifugal blade inlet angle are often not equal in practice. Directly connecting the inducer blade outlet and the centrifugal blade inlet will cause abrupt changes in the blade angle, leading to flow separation and other phenomena, resulting in energy loss and limiting further efficiency improvements of the integrated impeller. Summary of the Invention

[0005] The present application provides an integrated centrifugal impeller design method, which aims to make the integrated impeller have both high cavitation resistance and high efficiency.

[0006] This application provides an integrated centrifugal impeller design method, wherein the blades of the integrated centrifugal impeller include a pre-work section and a centrifugal section, and the design method includes:

[0007] Determine the required net positive suction head (NPSH) for the original centrifugal impeller, and determine the design head for the pre-work section based on the target NPSH;

[0008] Obtain the first target parameters of the original centrifugal impeller, the first target parameters including the meridional flow surface of the centrifugal blades and the outlet angle of the centrifugal blades;

[0009] The second target parameters of the pre-work section are determined based on the design head of the pre-work section. The second target parameters include the inlet angle, outlet angle, wrap angle, and meridional surface of the pre-work section.

[0010] The third target parameters of the centrifugal section are determined based on the first target parameters, the design head of the pre-work section, and the outlet angle of the pre-work section. The third target parameters include the centrifugal section inlet angle, the centrifugal section wrap angle, the centrifugal section outlet angle, and the centrifugal section meridional flow surface.

[0011] Based on the second and third target parameters, an integrated blade angle variation equation is established, and the integrated blade is designed.

[0012] Design the target centrifugal blade based on the third target parameter;

[0013] Determine the number of the integrated blade and the target centrifugal blade;

[0014] The lengths of the front and rear cover plates of the original centrifugal impeller are extended to obtain the front and rear cover plates of the integrated centrifugal impeller. The integrated blades and the target centrifugal blades are arranged between the front and rear cover plates of the integrated centrifugal impeller to obtain the integrated centrifugal impeller.

[0015] Optionally, in the step of determining the required net positive suction head (NPSH) of the original centrifugal impeller, the design method includes:

[0016] Determine the inlet pressure of the original centrifugal impeller under the target condition, and determine the required net positive suction head (NPSH) based on the inlet pressure.

[0017] Optionally, the design head of the pre-work section is 2-4 times the design net positive suction head (NPSH).

[0018] The value of the design net positive suction head (NPSH) is obtained by subtracting the value of the target NPSH from the value of the required NPSH.

[0019] Optionally, in the step of obtaining the first target parameters of the original centrifugal impeller, the design method includes:

[0020] Multiple target points are determined on the inlet edge, outlet edge, hub profile, and rim line of the blades of the original centrifugal impeller, and the cylindrical coordinates of the multiple target points are obtained.

[0021] Multiple target points are projected onto the target meridional surface, and the target points on the inlet edge, outlet edge, hub profile, and rim line of the target meridional surface are connected by curves to obtain the meridional flow surface of the centrifugal blade.

[0022] Measure the exit angle of the centrifuge blade at the height of each blade on the centrifuge blade.

[0023] Optionally, in the step of determining the second target parameter of the pre-work section based on the design head of the pre-work section, the design method includes:

[0024] The inlet angle and outlet angle of the pre-working section are calculated based on the hub radius, flange radius, and design head of the pre-working section.

[0025] The wrap angle of the pre-working section is calculated based on the inlet angle of the pre-working section, the outlet angle of the pre-working section, the blade chord length and blade pitch of the original centrifugal impeller.

[0026] The axial length of the meridional flow surface of the pre-work section is calculated based on the wrap angle of the pre-work section, and the meridional flow surface of the pre-work section is determined based on the meridional flow surface of the centrifugal blade.

[0027] The hub radius and rim radius of the pre-work section are equal to the inlet hub radius and rim radius of the original centrifugal impeller.

[0028] Optionally, the step of designing the integrated blade by establishing an integrated blade angle variation equation based on the second target parameter and the third target parameter includes:

[0029] The integrated blade meridional flow surface is obtained based on the pre-work section wrap angle, the centrifugal section wrap angle, the pre-work section meridional flow surface, and the centrifugal section meridional flow surface;

[0030] The equation for the change of the blade angle of the integrated blade with the relative position of the meridional flow surface of the integrated blade is obtained based on the inlet angle of the pre-work section, the outlet angle of the pre-work section, and the outlet angle of the centrifugal section.

[0031] The cylindrical coordinates of each point on the blade profile are obtained based on the relative position change equation and the meridional flow surface of the integrated blade, so as to obtain the integrated blade.

[0032] Optionally, in the step of determining the number of the integrated blade and the target centrifugal blade, the design method includes:

[0033] Determine the total number of blades of the integrated impeller;

[0034] The number of target centrifugal blades is determined based on the total number of blades and the number of integrated blades;

[0035] The total number of blades in the integrated impeller is the same as the total number of blades in the original centrifugal impeller, and the number of integrated blades is two or three.

[0036] Optionally, the extension length of the front and rear cover plates of the original centrifugal impeller is 1.0-1.2 times the axial length of the pre-work section.

[0037] Beneficial effects:

[0038] This application provides an integrated offline impeller design method. By designing an integrated impeller based on the key parameters of the centrifugal blades, the design method is simple and efficient. At the same time, a pre-work section is designed based on the target NPSH, so that the fluid entering the centrifugal section has a certain pressure, thereby giving the integrated impeller high cavitation resistance. In addition, the outlet angle of the pre-work section is used as the inlet angle of the centrifugal section to design the centrifugal section, avoiding the energy loss caused by the transition section between the outlet of the pre-work section and the inlet of the centrifugal section. Furthermore, by establishing a blade angle variation equation for the integrated blades, the blade angle is controlled to gradually change, so that the fluid flow direction gradually changes, suppressing the generation of separation, backflow and other phenomena, reducing flow losses, and making the integrated impeller highly efficient. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a flowchart illustrating the steps of a design method for an integrated centrifugal impeller according to an embodiment of this application;

[0041] Figure 2 This is a NPSH curve of a pump with an original centrifugal impeller installed according to an embodiment of this application;

[0042] Figure 3 This is a schematic diagram of a centrifugal blade meridional flow surface according to an embodiment of this application;

[0043] Figure 4 This is a schematic diagram of an inlet velocity triangle for the pre-work section according to an embodiment of this application;

[0044] Figure 5 This is a schematic diagram of the outlet rim velocity triangle of the pre-work section according to an embodiment of this application;

[0045] Figure 6 This is a schematic diagram of a pre-work section meridional flow surface according to an embodiment of this application;

[0046] Figure 7 This is a schematic diagram of an integrated blade meridional flow surface according to an embodiment of this application;

[0047] Figure 8 This is a graph showing the change of the blade angle of an integrated blade as a function of the relative position of the meridional flow surface, according to an embodiment of this application.

[0048] Figure 9 This is a schematic diagram of an integrated blade according to an embodiment of this application;

[0049] Figure 10 This is a schematic diagram of an integrated impeller according to an embodiment of this application;

[0050] Figure 11 This is a schematic diagram of the blade arrangement behind the concealed front cover of an integrated impeller according to an embodiment of this application;

[0051] Figure 12 This is a NPSH curve of a pump with an integrated impeller proposed in one embodiment of this application.

[0052] Explanation of reference numerals in the attached diagram: 1. Centrifugal blade; 2. Centrifugal blade inlet edge; 3. Pre-work section outlet edge; 4. Pre-work section hub; 5. Pre-work section rim; 6. Pre-work section inlet edge; 7. Pre-work section; 8. Centrifugal section; 9. Centrifugal section outlet edge; 10. Integrated blade; 11. Target centrifugal blade; 12. Front cover plate; 13. Rear cover plate. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0054] It should be noted that the embodiments of this application are designed based on a certain centrifugal impeller to create an integrated centrifugal impeller. In the embodiments of this application, the centrifugal impeller is referred to as the original centrifugal impeller. In addition, the blades of the integrated centrifugal impeller proposed in the embodiments of this application include a pre-work section 7 and a centrifugal section 8. The pre-work section 7 can increase the pressure of the fluid at the inlet of the centrifugal impeller by a certain amount, and the centrifugal section 8 is the part of the blade that generates centrifugal force.

[0055] Figure 1 A flowchart illustrating the steps of an integrated centrifugal impeller design method is shown, with reference to... Figure 1As shown in the figure, this application discloses a design method for an integrated centrifugal impeller, the design method comprising:

[0056] Step S01: Determine the required net positive suction head (NPSH) of the original centrifugal impeller and determine the design head of the pre-work section based on the target NPSH.

[0057] Specifically, the required net positive suction head (NPSH) of the original centrifugal impeller can be determined through numerical simulation or experiment. In this embodiment, the method for determining the required NPSH may include: determining the inlet pressure of the original centrifugal impeller under a target condition, and determining the required NPSH based on the inlet pressure. The target condition refers to the state where the original centrifugal impeller is under sufficient pressure and cavitation does not occur, and the target NPSH is the expected NPSH that the integrated centrifugal impeller designed in this embodiment should possess.

[0058] In this process, the designer can first apply sufficient pressure to the inlet of the original centrifugal impeller and record the head of the original centrifugal impeller under this condition (hereinafter referred to as the original head). Then, the inlet pressure of the original centrifugal impeller is gradually reduced, and the change in the head of the original centrifugal impeller with the decrease of the inlet pressure is observed. When the head of the original centrifugal impeller decreases by 3% compared with the original head, the inlet pressure corresponding to the head of the original centrifugal impeller under this state is obtained (hereinafter referred to as the required inlet pressure). Then, the saturated vapor pressure is subtracted from the required inlet pressure, and the final value is the value of the required net positive suction head (NPSH).

[0059] Furthermore, the design head for the pre-work section is 2-4 times the design net positive suction head (NPSH). The design NPSH is the value obtained by subtracting the target NPSH from the required NPSH.

[0060] For example, in this application embodiment, an integrated centrifugal impeller is designed based on an original centrifugal impeller with a design flow rate Qv = 610 m3 / h, a rotation speed of 2900 r / min, and six centrifugal blades. Figure 2 The numerical simulation structure of the NPSH curve of the original centrifugal impeller pump is shown, with reference to... Figure 2 As shown, the required net positive suction head (NPSHr) for this original centrifugal impeller is... c The value is 10.15m. Then, the target net positive suction head (NPSHr) for the integrated centrifugal impeller designed in this embodiment is set. o The value is 6.5m; in order to ensure that the target net positive suction head can be achieved, in this embodiment of the application, a head coefficient K is also required to calculate the design head of the pre-work section.

[0061] The calculation is as follows:

[0062] H po =K(NPSHr i -NPSHr o )

[0063] Among them, H po The head is designed for the pre-work section, where K is the head coefficient, and the value of K is 2-4.

[0064] In this embodiment, K = 3, and the design head H of the pre-work section can be obtained according to the above calculation formula. po =10.95m.

[0065] Step S02: Obtain the first target parameters of the original centrifugal impeller. The first target parameters include the meridional flow surface of the centrifugal blades and the outlet angle of the centrifugal blades.

[0066] Specifically, the first target parameter of the original centrifugal impeller can be obtained through the following steps:

[0067] S021: Determine multiple target points on the inlet edge, outlet edge, hub profile, and rim of the original centrifugal impeller blades, and obtain the cylindrical coordinates of the multiple target points.

[0068] Specifically, designers can establish a cylindrical coordinate system with a base point of the original centrifugal impeller blade (hereinafter referred to as centrifugal blade 1) as the origin. Then, multiple target points are selected on the centrifugal blade inlet side 2 (the side facing the centrifugal pump inlet), outlet side (the side facing the centrifugal pump outlet), hub profile, and rim line. These target points can be randomly selected or selected according to a certain rule. Based on this cylindrical coordinate system, the coordinates (R, Z, θ) of each target point are obtained. For example, the cylindrical coordinates of a target point are (5, 5, 35°).

[0069] S022: Project multiple target points onto the target meridional surface, and connect the target points on the inlet edge, outlet edge, hub profile, and rim line of the target meridional surface with curves to obtain the meridional flow surface of the centrifugal blade.

[0070] Specifically, designers can take any equal value for the θ value of the cylindrical coordinates of each target point, for example, setting the θ value of the cylindrical coordinates of each target point to 35°. In this case, the plane containing the θ value of 35° in the above cylindrical coordinate system is the target meridional plane. This step also realizes the projection of multiple target points onto the target meridional plane. Then, the designers connect the multiple target points projected onto the target meridional plane with a curve, and the final closed figure is the meridional flow surface of the centrifugal blade.

[0071] Meanwhile, after obtaining the meridional flow surface of the centrifugal blades, the inlet hub radius and rim radius of the original centrifugal impeller can be obtained based on the meridional flow surface of the centrifugal blades.

[0072] For example, Figure 3The meridional flow surface of the centrifugal blades of the original centrifugal impeller proposed in this application embodiment is shown. Measurements are taken at different positions of the meridional flow surface of the centrifugal blades from the central axis. Figure 3 The distance from the dashed line (in the middle) can be used to obtain the inlet hub radius r of the original centrifugal impeller. hc and rim radius r sc Among them, the imported wheel hub radius r hc The distance from the blade tip to the central axis in the meridional flow plane of the centrifugal blade is given by the rim radius r. sc This is the distance from the rim to the central axis in the meridional flow surface of the centrifugal blade.

[0073] S023: Measure the centrifugal blade exit angle at the height of each blade on the centrifugal blade.

[0074] Specifically, the centrifugal blade exit angle at each blade height refers to the angle between the profile of each centrifugal blade at each blade height and the tangent at the outlet of the original centrifugal impeller, and the circumferential tangent at the intersection of the profile of each centrifugal blade at each blade height and the outlet of the original impeller (i.e., a straight line perpendicular to the diameter direction of the original centrifugal impeller).

[0075] Step S03: Determine the second target parameters of the pre-work section 7 based on the design head of the pre-work section. The second target parameters include the inlet angle, outlet angle, wrap angle, and meridional surface of the pre-work section.

[0076] Specifically, the second target parameter for the pre-work stage 7 can be obtained through the following steps:

[0077] S031: The inlet angle and outlet angle of the pre-work section are calculated based on the hub radius, flange radius and design head of the pre-work section 7.

[0078] Specifically, the hub radius and rim radius of the pre-working section are equal to the inlet hub radius and rim radius of the original centrifugal impeller. By combining the design head of the pre-working section with velocity trigonometric calculations, the inlet angle and outlet angle of the pre-working section can be calculated.

[0079] Reference Figure 4 As shown, the inlet velocity triangle in the pre-work section includes the axial velocity V. m1 Circular velocity u 1i Flow angle β′1 and inlet angle β of the pre-work section 1i Their respective calculation formulas are as follows:

[0080]

[0081]

[0082]

[0083] β 1i =β′ 1i +Δβ

[0084] Among them, Q v -Volume flow rate, m 3 / h;d h - Hub diameter, mm; D1 - Blade inlet diameter, mm; subscript i - Blade height position; n - Rotational speed, r / min; Δβ - Design angle of attack, range 0°-5°.

[0085] Reference Figure 5 As shown, the velocity triangle at the exit rim of the pre-work section includes the axial velocity V. m2p Circumferential velocity u at the rim 2py Circumferential velocity V at the rim u2y Exit angle β at the rim 2py and the exit angle β of the pre-work section 2pi Their respective calculation formulas are as follows:

[0086]

[0087]

[0088]

[0089]

[0090] R pi tanβ 2pi =R py tanβ 2py

[0091] Wherein, subscript p - pre-work section; subscript y - rim; R - radius at that location; subscript i - blade height position.

[0092] The inlet angle and outlet angle of the pre-working section of the integrated centrifugal impeller blades can be calculated using the above formulas.

[0093] Step S032: Calculate the wrap angle of the pre-work section based on the inlet angle of the pre-work section, the outlet angle of the pre-work section, the blade chord length and blade pitch of the original centrifugal impeller.

[0094] Specifically, the formula for calculating the wrap angle of the pre-work segment is as follows:

[0095]

[0096]

[0097] in, t represents the blade cascade density, which ranges from 1 to 3; l represents the blade pitch and chord length.

[0098] Based on the above calculation formula, the pre-work section wrap angle of the blades of the integrated centrifugal impeller can be obtained.

[0099] Step S033: Calculate the axial length of the meridional flow surface of the pre-work section based on the wrap angle of the pre-work section, and determine the meridional flow surface of the pre-work section based on the meridional flow surface of the centrifugal blade.

[0100] Specifically, the formula for calculating the axial length of the meridional flow surface in the pre-work section is as follows:

[0101]

[0102] S i =D i πtanβ

[0103] Among them, S i This is the lead for the pre-work section.

[0104] Then, on the meridional flow surface of the centrifugal blade, the inlet edge of the centrifugal blade is taken as the outlet edge 3 of the pre-work section, and the radius r of the hub 4 of the pre-work section is taken. hp =r hc The radius r of the pre-work section rim 5 sp =r sc Based on the axial length of each blade, the position of the inlet edge 6 of the pre-work section is determined by the outlet edge 3 on the meridional surface of the centrifugal blade, resulting in the following: Figure 6 The pre-work section of the meridional flow surface is shown.

[0105] Step S04: Determine the third target parameters of centrifugal section 8 based on the first target parameters, the design head of the pre-work section, and the outlet angle of the pre-work section. The third target parameters include the inlet angle, wrap angle, outlet angle, and meridional flow surface of the centrifugal section.

[0106] Specifically, the design method for centrifugal section 8 includes the following steps:

[0107] Step S041: Take the outlet angle of the pre-work section as the inlet angle of the centrifugal section, and take the outlet angle of the centrifugal blade as the outlet angle of the centrifugal section.

[0108] Step S042: Subtract the design head of the pre-work section from the original centrifugal impeller head to obtain the design head of the centrifugal section. Calculate the specific speed of the centrifugal section from the design head of the centrifugal section, and determine the wrap angle of the centrifugal section based on the specific speed of the centrifugal section.

[0109] Specifically, the formula for calculating the design head of the centrifugal section is as follows:

[0110] H co =H c -Hpo

[0111] Among them, H c The original centrifugal impeller head.

[0112] The formula for calculating the specific speed of the centrifugal section is as follows:

[0113]

[0114] The centrifugal segment wrap angle calculated according to the above formula For those with higher specific speeds, take the smaller value; for those with lower specific speeds, take the larger value.

[0115] Step S043: Use the meridional flow surface of the centrifugal blade as the meridional flow surface of the centrifugal segment.

[0116] The third target parameter of centrifugal segment 8 can be obtained through the above steps.

[0117] Step S05: Based on the second and third objective parameters, establish the integrated blade angle variation equation and design the integrated blade.

[0118] Specifically, the design method for integrated blades includes the following steps:

[0119] Step S051: Obtain the integrated blade meridional flow surface based on the pre-work section wrap angle, the centrifugal section wrap angle, the pre-work section meridional flow surface, and the centrifugal section meridional flow surface.

[0120] Specifically, connecting the outlet side of the pre-work section meridional flow surface and the inlet side of the centrifugal section meridional flow surface yields... Figure 7 The integrated blade meridional flow surface shown is used to determine the relative position of the pre-work section exit edge 3 by comparing the streamline length of the pre-work section meridional surface at each blade height with the streamline length of the integrated blade meridional surface.

[0121] Step S052: Based on the blade angles of the inlet side 6 of the pre-work section, the outlet side 3 of the pre-work section, and the outlet side 10 of the centrifugal section, obtain the equation for the change of the blade angle of the integrated blade with the relative position of the meridional flow surface of the integrated blade.

[0122] Specifically, the blade angles at the inlet edge 6 of the pre-work section, the outlet edge 3 of the pre-work section, and the outlet edge 10 of the centrifugal section are fitted with a quadratic polynomial to obtain the following equations for the variation of each blade height and blade angle with the relative position of the meridional streamline:

[0123]

[0124] Where β is the blade angle and M is the relative position of the meridional streamline.

[0125] Do it from the equation as follows Figure 8The curve showing the change of the blade angle of the integrated blade 9 with the relative position of the meridional streamline shows that the blade angle changes gradually.

[0126] The formula for calculating the wrap angle of the integrated blade is as follows:

[0127]

[0128] Step S053: Obtain the cylindrical coordinates of each point on the blade profile based on the relative position change equation and the meridional flow surface of the integrated blade to obtain the integrated blade 9.

[0129] Specifically, by measuring and obtaining the cylindrical coordinates (r, z, θ) of each point on the integrated blade profile along the meridional flow surface, the values ​​of r and z can be calculated based on the equation governing the change of the blade angle with respect to the relative position of the meridional streamline, as follows:

[0130]

[0131] in, -Pre-work section inlet edge sweep angle

[0132] Based on the above calculation formula, the cylindrical coordinates of each point on each blade height profile can be calculated. Then, the points are connected by a curve to obtain the blade profile for each blade height. Using 3D drawing software, the blade profiles are connected to obtain an integrated blade surface. The surface is thickened along the normal direction to obtain the integrated blade 9. Figure 9 As shown.

[0133] Step S06: Design the target centrifugal blade 11 based on centrifugal segment 8.

[0134] Specifically, the various parameters of the target centrifugal blade 11 are equal to the third target parameters of the centrifugal section 8. In other words, in this embodiment, the centrifugal section 8 is directly designed as the target centrifugal blade 11.

[0135] Step S07: Determine the number of integrated blades 9 and target centrifugal blades 11.

[0136] Specifically, the method for determining the number of integrated blades 9 and target centrifugal blades 11 is as follows:

[0137] Step S071: Determine the total number of blades in the integrated impeller.

[0138] Specifically, the total number of blades in the integrated impeller is equal to the total number of blades in the original centrifugal impeller.

[0139] Step S072: Determine the number of target centrifugal blades 11 based on the total number of blades and the number of integrated blades 9.

[0140] Specifically, the number of integrated blades 9 can be two or three, and the number of target centrifugal blades 11 is the total number of blades minus the number of integrated blades.

[0141] In this embodiment, the total number of blades is six, the number of integrated blades 9 is three, and the number of target centrifugal blades 11 is three.

[0142] Step S08: Extend the length of the front cover plate and the rear cover plate of the original centrifugal impeller to obtain the front cover plate 12 and the rear cover plate 13 of the integrated centrifugal impeller. Arrange the integrated blade and the target centrifugal blade between the front cover plate and the rear cover plate of the integrated centrifugal impeller to obtain the integrated centrifugal impeller.

[0143] Specifically, extending the length of the original centrifugal impeller's front and rear cover plates means fabricating a front cover plate 12 and a rear cover plate 13 adapted to the integrated blades, based on the original centrifugal impeller. It's important to understand that this extension does not involve directly continuing the fabrication on the original centrifugal impeller. The extension length of the original centrifugal impeller's front and rear cover plates is 1.0-1.2 times the axial length of the pre-work section.

[0144] Furthermore, the integrated blade 9 and the target centrifugal blade 11 are evenly spaced along the circumferential direction on the rear cover plate 13, as shown in the blade arrangement. Figure 11 As shown.

[0145] Finally, by connecting the integrated blade 9 and the target centrifugal blade 11 to the front cover plate 12 and the rear cover plate 13, the integrated blade can be obtained, as shown below. Figure 10 As shown.

[0146] Figure 12 For the NPSH curve of a centrifugal pump with an integrated impeller model, from Figure 12 As can be seen, the NPSH of the integrated impeller designed using the design method provided in this application embodiment is reduced to 6.7m compared to the original centrifugal impeller, and the simulated centrifugal pump efficiency is 89%. Therefore, the integrated impeller designed using the design method provided in this application embodiment has both high cavitation resistance and high efficiency.

[0147] This application provides an integrated impeller design method. This method designs a pre-work section based on the target cavitation margin, so that the fluid entering the centrifugal section can have a certain pressure, thereby giving the integrated impeller a certain high cavitation resistance. On the other hand, by establishing the blade angle change equation of the integrated blade, the blade angle is controlled to gradually change, so that the fluid flow direction gradually changes, suppressing the generation of separation, backflow and other phenomena, reducing flow loss, and making the integrated impeller highly efficient.

[0148] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0149] It should also be noted that, in this document, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations, nor should they be construed as indicating or implying relative importance. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. In the absence of further restrictions, an element defined by the phrase "includes a..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes the element.

[0150] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand this application, and the content of this specification should not be construed as a limitation of this application. Furthermore, for those skilled in the art, there will be different forms of changes in the specific implementation methods and application scope based on this application. It is neither necessary nor possible to exhaustively list all implementation methods here, and obvious changes or modifications derived therefrom are still within the protection scope of this application.

Claims

1. A method for designing an integrated centrifugal impeller, wherein the blades of the integrated centrifugal impeller include a pre-work section and a centrifugal section, characterized in that, The design method includes: Determine the required net positive suction head (NPSH) for the original centrifugal impeller, and determine the design head for the pre-work section based on the target NPSH; Obtain the first target parameters of the original centrifugal impeller, the first target parameters including the meridional flow surface of the centrifugal blades and the outlet angle of the centrifugal blades; The second target parameters of the pre-work section are determined based on the design head of the pre-work section. The second target parameters include the inlet angle, outlet angle, wrap angle, and meridional surface of the pre-work section. The third target parameters of the centrifugal section are determined based on the first target parameters, the design head of the pre-work section, and the outlet angle of the pre-work section. The third target parameters include the centrifugal section inlet angle, the centrifugal section wrap angle, the centrifugal section outlet angle, and the centrifugal section meridional flow surface. Based on the second and third target parameters, an integrated blade angle variation equation is established, and the integrated blade is designed. Design the target centrifugal blade based on the aforementioned centrifugal section; Determine the number of the integrated blade and the target centrifugal blade; The lengths of the front and rear cover plates of the original centrifugal impeller are extended to obtain the front and rear cover plates of the integrated centrifugal impeller. The integrated blades and the target centrifugal blades are arranged between the front and rear cover plates of the integrated centrifugal impeller to obtain the integrated centrifugal impeller.

2. The centrifugal impeller design method according to claim 1, characterized in that, The design method includes the following steps in determining the required net positive suction head (NPSH) for the original centrifugal impeller: Determine the inlet pressure of the original centrifugal impeller under the target condition, and determine the required net positive suction head (NPSH) based on the inlet pressure.

3. The centrifugal impeller design method according to claim 1, characterized in that: The design head of the pre-work section is 2-4 times the design net positive suction head; The value of the design net positive suction head (NPSH) is obtained by subtracting the value of the target NPSH from the value of the required NPSH.

4. The centrifugal impeller design method according to claim 1, characterized in that, In the step of obtaining the first target parameters of the original centrifugal impeller, the design method includes: Multiple target points are determined on the inlet edge, outlet edge, hub profile, and rim line of the blades of the original centrifugal impeller, and the cylindrical coordinates of the multiple target points are obtained. Multiple target points are projected onto the target meridional surface, and the target points on the inlet edge, outlet edge, hub profile, and rim line of the target meridional surface are connected by curves to obtain the meridional flow surface of the centrifugal blade. Measure the exit angle of the centrifuge blade at the height of each blade on the centrifuge blade.

5. The centrifugal impeller design method according to claim 1, characterized in that, The design method includes the step of determining the second target parameter of the pre-work section based on the design head of the pre-work section: The inlet angle and outlet angle of the pre-working section are calculated based on the hub radius, flange radius, and design head of the pre-working section. The wrap angle of the pre-working section is calculated based on the inlet angle of the pre-working section, the outlet angle of the pre-working section, the blade chord length and blade pitch of the original centrifugal impeller. The axial length of the meridional flow surface of the pre-work section is calculated based on the wrap angle of the pre-work section, and the meridional flow surface of the pre-work section is determined based on the meridional flow surface of the centrifugal blade. The hub radius and rim radius of the pre-work section are equal to the inlet hub radius and rim radius of the original centrifugal impeller.

6. The centrifugal impeller design method according to claim 1, characterized in that, The step of designing the integrated blade by establishing an integrated blade angle variation equation based on the second and third objective parameters includes: The integrated blade meridional flow surface is obtained based on the pre-work section wrap angle, the centrifugal section wrap angle, the pre-work section meridional flow surface, and the centrifugal section meridional flow surface; The equation for the change of the blade angle of the integrated blade with the relative position of the meridional flow surface of the integrated blade is obtained based on the inlet angle of the pre-work section, the outlet angle of the pre-work section, and the outlet angle of the centrifugal section. The cylindrical coordinates of each point on the blade profile are obtained based on the relative position change equation and the meridional flow surface of the integrated blade, so as to obtain the integrated blade.

7. The centrifugal impeller design method according to claim 1, characterized in that, In the step of determining the number of the integrated blades and the target centrifugal blades, the design method includes: Determine the total number of blades of the integrated impeller; The number of target centrifugal blades is determined based on the total number of blades and the number of integrated blades; The total number of blades in the integrated impeller is the same as the total number of blades in the original centrifugal impeller, and the number of integrated blades is two or three.

8. The centrifugal impeller design method according to claim 1, characterized in that: The extension length of the front and rear cover plates of the original centrifugal impeller is 1.0-1.2 times the axial length of the pre-work section.

Images