A low-resistance design method for a large electric pump impeller flow passage component

Abstract

The application discloses a low-resistance design method for a large electric pump impeller flow passage component, and steps include: determining design parameters; adopting two-section quadratic functions to respectively define the cross-section equivalent radius variation law of front and rear flow channels, and guaranteeing smooth and continuous profile lines; setting front and rear linear segments tangent to corresponding flow channel profile lines on the hub side; defining two independent dimensionless axial length coefficients and constructing multiple groups of design parameter combinations; fixing flow channel profile line parameters to carry out simulation tests, and selecting an optimal scheme based on performance results. Through the two independent dimensionless design variables, the independent parameterization regulation and control of the blade axial form are realized, the blindness of experience design is got rid of, and the different flow characteristics of the hub and the rim can be adapted. The dimensionless system has cross-size universality, is convenient for forming a standardized design process, and at the same time, provides sufficient adjustment space for multi-target optimization, can consider multiple performance indexes such as head, efficiency, shaft power and the like, and realizes low-resistance optimization of the flow passage.

Description

Technical Field

[0001] This invention relates to the field of water pump design technology, and in particular to a low-resistance design method for the flow-through components of a large electric pump impeller. Background Technology

[0002] Large-scale water pumps are widely used in inter-basin water transfer, urban drainage, and nuclear power plant circulating water systems. Their flow channels consist of a front flow channel (inlet channel), an impeller flow channel (including blades), and a rear flow channel (outlet channel). In existing designs, the axial lengths of the blades on the hub and rim sides are often based on empirical values ​​or linear correlations, lacking independent dimensionless design parameters. Furthermore, the profiles of the front and rear flow channels are often simple straight lines or single curves, making it difficult to adapt to the complex flow conditions at the inlet and outlet, resulting in significant hydraulic losses. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of the prior art by providing a low-resistance design method for the flow-through components of a large electric pump impeller.

[0004] The objective of this invention is achieved through the following technical solution: a low-resistance design method for the flow-through components of a large electric pump impeller, comprising the following specific steps:

[0005] S1: Determine the design parameters; S2: The front flow channel extends from the inlet to the impeller inlet along the flow direction. The front flow channel piecewise function, composed of two quadratic functions, describes the variation of the equivalent radius of the front flow channel cross section with the axial coordinate x of the flow channel, so that the front flow channel profile remains smooth and continuous. S3: The rear flow channel extends from the guide vane outlet to the pump outlet along the flow direction. The equivalent radius of the rear flow channel cross section is described by a piecewise function composed of two quadratic functions, and the profile of the rear flow channel remains smooth and continuous. S4: On the axis of the impeller hub side, a front straight segment is set between the end of the front flow channel profile and the intersection of the blade leading edge hub, and a rear straight segment is set between the intersection of the blade trailing edge hub and the beginning of the rear flow channel profile; the front straight segment is tangent to the front flow channel profile at the connection point, and the rear straight segment is tangent to the rear flow channel profile at the connection point. S5: Define the impeller hub-side axial length as the projected length of the line of intersection between the blade root and the hub in the pump shaft direction, and the impeller rim-side axial length as the projected length of the line of intersection between the blade tip and the rim in the pump shaft direction; take the ratio of the impeller hub-side axial length to the rim radius as the impeller hub-side axial length coefficient, and take the ratio of the impeller rim-side axial length to the impeller hub radius as the impeller rim-side axial length coefficient. Select different impeller hub-side axial length coefficients and impeller rim-side axial length coefficients and combine them to obtain multiple design parameter combinations; S6: Keep the profile parameters of the front and rear flow channels fixed, conduct simulation experiments on different combinations of design variables, and obtain theoretical performance results; select design parameter combinations based on theoretical performance results.

[0006] Preferably, in step S1, the design parameters include design flow rate, design head, rated speed, impeller outer diameter, and hub diameter.

[0007] As a preferred option, the front flow channel piecewise function is: ; in, The equivalent radius of the front flow channel cross section; This is the first segmentation point. a represents the axial coordinate position corresponding to the impeller inlet. 1、 b1, a2, b2, and c1 are all control coefficients for the front flow channel profile.

[0008] As a preferred option, the piecewise function for the rear flow channel is: ; in, The equivalent radius of the rear flow channel cross-section; This is the second segmentation point. This represents the axial coordinate position corresponding to the guide vane outlet. Let a be the axial coordinate position corresponding to the pump outlet. 3、 b3, a4, b4, c2, and c3 are all control coefficients for the rear flow channel profile.

[0009] Preferably, in step S6, a simulation experiment is conducted using a three-dimensional CFD numerical simulation method.

[0010] As a preferred option, the specific method for conducting simulation experiments on different combinations of design variables in step S6 is as follows: N1: A three-dimensional geometric model of the flow channel of the water pump is established based on the piecewise function of the front flow channel, the piecewise function of the rear flow channel, the parameters of the front straight segment, the parameters of the rear straight segment, the axial length coefficient of the impeller hub side, and the axial length coefficient of the impeller rim side; N2: Mesh the 3D geometric model and refine the local mesh in complex flow areas such as the wall, leading edge of the blade, and trailing edge of the blade. N3: Import the meshed file into the CFX solver, set the inlet and outlet boundary conditions, select the turbulence model, and perform numerical calculations using the CFX solver; N4: After solving the convergence condition, extract the theoretical head, theoretical efficiency, and theoretical shaft power as theoretical performance results.

[0011] Preferably, in step S6, after obtaining the theoretical performance results, the curves of theoretical efficiency, theoretical shaft power, and theoretical head as a function of the axial length coefficient of the impeller hub side, and the curves of theoretical efficiency, theoretical shaft power, and theoretical head H as a function of the axial length coefficient of the impeller rim side are plotted respectively. Based on the above curves, the design parameter combination that meets the design head requirement is selected as the pre-selected parameter combination. From the pre-selected parameter combination, the parameter combination with theoretical efficiency greater than the preset efficiency threshold and theoretical shaft power lower than the preset shaft power threshold is selected as the optimal design parameter combination.

[0012] Preferably, in step N3, the turbulence model is selected as k. ω model.

[0013] Preferably, the inlet boundary condition is set as a pressure inlet, with a total pressure of 1 standard atmosphere; the outlet boundary condition is set as a mass flow outlet, with the mass flow rate at the outlet being the design flow rate.

[0014] Preferably, in step S5, the axial length coefficient on the impeller hub side ranges from 0.31 to 0.65, and the axial length coefficient on the impeller rim side ranges from 0.68 to 0.97.

[0015] The beneficial effects of this invention are: 1. To address the shortcomings of existing front and rear flow channels, which use simple straight lines or single curves and are difficult to adapt to complex flows, this invention employs a piecewise function composed of two quadratic functions to accurately describe the axial variation of the equivalent radius of the front and rear flow channels. On one hand, the piecewise structure can separately match the flow diffusion / contraction characteristics of different flow sections from the inlet to the impeller inlet and from the guide vane outlet to the pump outlet, adapting to the differentiated flow requirements of inlet flow homogenization and outlet kinetic energy recovery. On the other hand, the quadratic function profile ensures a continuous and smooth rate of change of the flow channel cross-section, avoiding abrupt changes in cross-section, flow separation, and vortex zones that are prone to occur in straight / single-curve flow channels, effectively reducing hydraulic losses along the flow path and local impact losses, and significantly improving the flow channel efficiency.

[0016] 2. In this invention, at the junction of the front and rear flow channels and the impeller flow channel on the hub side, straight sections tangent to the corresponding flow channel profiles are respectively set. This ensures the continuity of the first derivative of the inner wall surface of the flow channel at the junction, completely eliminates geometric inflection points, dead flow angles, and flow separation vortices at the junction of the profiles, and reduces local impact losses at the impeller inlet and outlet. At the same time, the regular straight transition section can provide uniform inflow / outflow conditions for the leading and trailing edges of the blades, improve the blade inlet angle of attack distribution and outlet flow uniformity, and further reduce hydraulic losses in the impeller flow channel.

[0017] 3. To address the shortcomings of existing designs where the axial lengths of the impeller hub and rim sides rely on experience and cannot be independently adjusted, this invention defines two independent dimensionless design variables: the impeller hub axial length coefficient and the impeller rim axial length coefficient. On one hand, this achieves fully parameterized and independent control of the blade's axial spatial morphology, eliminating the blindness of experience-based design. It allows for matching the optimal blade axial length to different flow characteristics on the hub and rim sides, significantly increasing design freedom. On the other hand, the dimensionless parameter system makes the design method universal across dimensions, adaptable to large-scale water pumps of different specifications, and facilitating standardized design processes. Thirdly, the two independent variables provide ample adjustment space for multi-objective performance optimization, accurately considering multiple performance indicators such as head, efficiency, and shaft power. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the electric pump impeller flow passage component of the present invention.

[0019] Figure 2 This is a graph showing the variation of theoretical efficiency, theoretical shaft power, and theoretical head H with the axial length coefficient of the impeller hub side.

[0020] Figure 3 This is a graph showing the variation of theoretical efficiency, theoretical shaft power, and theoretical head with the axial length coefficient of the impeller rim side. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0022] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0023] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0024] like Figures 1 to 3 As shown, a low-resistance design method for the flow-through components of a large electric pump impeller includes the following specific steps: S1: Determine the design parameters.

[0025] The design parameters include design flow rate Q (m³ / s), design head H (m), rated speed n (r / min), impeller outer diameter D (mm), and hub diameter d. h (mm).

[0026] S2: The front flow channel extends from the inlet to the impeller inlet along the flow direction. The front flow channel piecewise function, composed of two quadratic functions, describes the variation of the equivalent radius of the front flow channel cross section with the axial coordinate x of the flow channel, so that the front flow channel profile remains smooth and continuous.

[0027] Specifically, the front flow channel piecewise function is: ; in, The equivalent radius of the front flow channel cross section; This is the first segmentation point. a represents the axial coordinate position corresponding to the impeller inlet. 1、 b1, a2, b2, and c1 are all control coefficients for the front flow channel profile.

[0028] In this application, =115. x=0 indicates the water inlet.

[0029] a 1、 The range of values ​​for b1, a2, b2, and c1 is as follows: a1∈[0.019,0.021];b1∈[0.28,0.3];a2∈[-0.0093,-0.0091];b2∈[2.23,2.25],c1∈[-27,-29].

[0030] First segment point The range of values ​​for is: ∈[49,51].

[0031] The front flow channel profile is constrained by the two quadratic functions mentioned above to ensure a smooth and continuous profile and reduce drag.

[0032] S3: The rear flow channel extends from the guide vane outlet to the pump outlet along the flow direction. The equivalent radius of the rear flow channel cross section is described by a piecewise function composed of two quadratic functions, which keeps the profile of the rear flow channel smooth and continuous.

[0033] The piecewise function for the back channel is: ; in, The equivalent radius of the rear flow channel cross-section; This is the second segmentation point. This represents the axial coordinate position corresponding to the guide vane outlet. Let a be the axial coordinate position corresponding to the pump outlet. 3、 b3, a4, b4, c2, and c3 are all control coefficients for the rear flow channel profile.

[0034] In this application, =380, =480, the range of values ​​for the rear flow channel profile control coefficient is: a3∈[-0.0093,-0.0091], b3∈[7.13,7.15], c2∈[-1280,-1278]; a4∈[0.0081,0.0083], b4∈[-7.8,-7.78], c3∈[1911,1913]; Second segment point The range of values ​​for is: ∈[429,431].

[0035] S4: On the axis of the impeller hub side, a front straight segment is set between the end of the front flow channel profile and the intersection of the blade leading edge hub, and a rear straight segment is set between the intersection of the blade trailing edge hub and the beginning of the rear flow channel profile; the front straight segment is tangent to the front flow channel profile at the connection point, and the rear straight segment is tangent to the rear flow channel profile at the connection point.

[0036] The axial length of the preceding straight segment is denoted as Ls. This straight segment is continuous with the first derivative of the preceding flow channel profile at the connection point, thus ensuring a smooth transition of the inner wall at the flow channel connection position. Similarly, the axial length of the following straight segment is denoted as Lr. This straight segment is continuous with the first derivative of the following flow channel profile at the connection point, thus ensuring a smooth transition of the inner wall at the flow channel connection position.

[0037] S5: Define the impeller hub-side axial length as the projected length of the line of intersection between the blade root and the hub in the pump shaft direction, and the impeller rim-side axial length as the projected length of the line of intersection between the blade tip and the rim in the pump shaft direction; take the ratio of the impeller hub-side axial length to the rim radius as the impeller hub-side axial length coefficient, and take the ratio of the impeller rim-side axial length to the impeller hub radius as the impeller rim-side axial length coefficient. Select different impeller hub-side axial length coefficients and impeller rim-side axial length coefficients and combine them to obtain multiple design parameter combinations.

[0038] like Figure 1 As shown, the axial length on the impeller hub side is the projected length of the connection point (root) between the blade and the hub in the direction of the pump shaft, and its length is denoted as L. h。

[0039] The axial length of the impeller rim side is the projected length of the connection point between the blade and the rim (top) along the pump shaft direction, and its length is denoted as L. t。

[0040] Impeller hub side axial length coefficient .

[0041] Impeller rim side axial length coefficient .

[0042] Among them, R t R is the rim radius. t =d t / 2. d t The diameter is the rim diameter.

[0043] In this application, λ h and λ t As an independent design variable, it can take values ​​independently.

[0044] Impeller hub side axial length coefficient λ h The value range is 0.31-0.65, and the axial length coefficient λ on the impeller rim side is... t The value range is 0.68-0.97.

[0045] S6: Keep the profile parameters of the front and rear flow channels fixed, conduct simulation experiments on different combinations of design variables, and obtain theoretical performance results; select design parameter combinations based on theoretical performance results.

[0046] In this step, to obtain the hydraulic performance under different design parameters while keeping the front and rear flow channel profile parameters constant, a series of different values ​​(such as λ) defined in step S5 are used. h =0.31, 0.42, 0.54, 0.65 and Different combinations of λ = 0.68, 0.8, 0.91, 0.97 yield the design parameter combinations (λ). h， λ t Each of these steps will be calculated and analyzed one by one.

[0047] In this application, simulation experiments are conducted using a three-dimensional CFD numerical simulation method. The three-dimensional CFD numerical simulation can completely reproduce the three-dimensional turbulent flow within the flow channel of a large water pump, accurately capturing complex local flow phenomena and hydraulic loss distributions such as blade leading-edge impact, secondary flow in the impeller passage, hub / rim boundary layer, and flow separation in the diffuser section of the flow channel. Compared to traditional one-dimensional and two-dimensional empirical design methods, its prediction accuracy for core performance indicators such as head, efficiency, and shaft power is significantly improved. The blade axial length parameter combinations selected based on high-precision simulation results can realistically match actual flow patterns, ensuring that the low-resistance design scheme achieves the expected drag reduction and efficiency improvement effects in engineering applications, avoiding performance deviations and repeated modifications caused by empirical design. For multiple combinations of axial length coefficients on the impeller hub and rim sides, the three-dimensional CFD numerical simulation can quickly complete batch virtual tests without the need to fabricate multiple physical prototypes or build large test benches. Especially for large water pumps, prototype manufacturing and full-scale testing are costly and time-consuming. Virtual simulation can complete full parameter traversal and performance verification during the design phase, significantly shortening the design iteration cycle and reducing prototype manufacturing and testing costs. Simultaneously, it can cover a wider range of parameter values, expanding the search space for optimal design solutions. By keeping the front and rear flow channel profile parameters fixed, CFD simulations are conducted by adjusting only two independent axial length coefficients. This allows for rigorous control variable analysis, accurately separating the independent influence of blade axial length parameters on the hydraulic losses of the flow channel and the overall pump performance, and quantifying the trends of efficiency, shaft power, and head with respect to two dimensionless coefficients. This quantified mapping relationship provides objective data support for optimal parameter selection, replacing the subjective judgment of traditional experience-based selection, and ensuring that the final solution minimizes hydraulic losses and maximizes efficiency while meeting head design constraints.

[0048] The specific methods for conducting simulation experiments on different combinations of design variables are as follows: N1: A three-dimensional geometric model of the flow channel of the water pump is established based on the front flow channel piecewise function, the rear flow channel piecewise function, the front straight segment parameters, the rear straight segment parameters, the impeller hub side axial length coefficient, and the impeller rim side axial length coefficient.

[0049] This step achieves a precise mapping between design parameters and simulation geometry: using the front flow channel segmentation function, the rear flow channel segmentation function, the front and rear straight segments, and the biaxial length coefficient as inputs, a three-dimensional model is directly constructed. This can completely reproduce the core geometric features such as the segmented transition of the flow channel profile and the tangential connection between straight and curved segments, avoiding the contour deviation of manual modeling, ensuring the consistency between simulation geometry and design scheme, and eliminating the interference of geometric errors on hydraulic loss calculation from the source.

[0050] Through parametric modeling logic, geometric models of different schemes can be quickly generated by modifying two axial length coefficients, adapting to the batch simulation requirements of multiple sets of design variable combinations, providing an efficient geometric basis for traversing the parameter space and selecting the optimal low-resistance scheme, and shortening the design iteration cycle.

[0051] N2: Mesh the 3D geometric model and refine the mesh locally in complex flow regions such as the wall, leading edge of the blade, and trailing edge of the blade.

[0052] This step involves covering the mainstream area with a basic grid and then locally refining the grid in complex areas with large flow gradients and concentrated hydraulic losses, such as the wall boundary layer, blade leading edge, and blade trailing edge. Under the premise of controlling the overall grid size and computation time, this step focuses on improving the flow field discretization accuracy in high-loss areas.

[0053] Since the leading edge impact loss, trailing edge wake loss, and wall friction loss are the core sources of hydraulic losses in the flow channel, local densification can accurately analyze the velocity gradient, pressure gradient, and turbulence structure in the above regions, truly restore the generation mechanism and magnitude of the losses, avoid the distortion of loss prediction caused by insufficient grid resolution, and ensure that the performance comparison of different parameter combinations has a reliable numerical basis.

[0054] N3: Import the meshed file into the CFX solver, set the inlet and outlet boundary conditions, select the turbulence model, and perform numerical calculations using the CFX solver; the inlet boundary condition is set to a pressure inlet with a total pressure of 1 standard atmosphere; the outlet boundary condition is set to a mass flow outlet with the design mass flow rate.

[0055] In this step, the boundary conditions are set based on engineering considerations, ensuring that the simulation results have engineering guidance value. Specifically, the inlet uses a pressure inlet with a given standard atmospheric total pressure, matching the actual atmospheric inlet operating conditions of a large water pump; the outlet uses a mass flow rate corresponding to the design flow rate, accurately corresponding to the design operating point. The simulation boundaries are consistent with the engineering operating conditions, allowing the calculated performance indicators such as head and efficiency to be directly used for engineering scheme verification, avoiding the disconnect between simulation results and reality caused by distorted boundary conditions.

[0056] CFX is a professional computational fluid dynamics solver for turbomachinery and internal flow field simulation. The CFX solver is adapted to the flow field solution characteristics of rotating turbomachinery. Combined with the adapted turbulence model, it can accurately simulate the dynamic and static interference effects of turbomachinery and stationary flow channels, reliably reproduce complex flows such as secondary flow and flow separation in the turbomachinery flow channel, and accurately quantify the influence of different blade axial lengths on hydraulic losses.

[0057] N4: After the solution meets the convergence condition, the theoretical head, theoretical efficiency, and theoretical shaft power are extracted as theoretical performance results. The convergence criterion is that the residuals of each item are less than 1×10⁻⁶. 5 Furthermore, the monitored volumes of import and export flow and pressure remain stable.

[0058] In step N3, the turbulence model selected is k ω-model. Where, k The full name of the ω model is ShearStressTransport(SST)k. ω model. k The ω model can directly solve near-wall viscous sublayer flow without relying on wall functions, accurately capturing the shear stress distribution and boundary layer development process of the flow channel wall. Corresponding to the smooth flow channel structure with piecewise quadratic curves and tangential straight transition sections in this invention, the model can accurately calculate the magnitude of wall friction loss under different curve curvatures and transition methods, truly reflecting the drag reduction benefits of smooth curve design. Simultaneously, it can finely distinguish the boundary layer differences between the hub wall and the rim wall, providing reliable friction loss data support for independent optimization of the axial length of the blades on the hub and rim sides, avoiding the loss prediction distortion caused by near-wall estimation bias in traditional models. Furthermore, significant adverse pressure gradients exist on the front flow channel contraction section, rear flow channel diffusion section, and blade surface of large water pumps, easily triggering flow separation and vortices, which are the core sources of local hydraulic losses. The ω model exhibits excellent predictive capabilities for adverse pressure gradient flows, accurately determining whether changes in flow channel profiles or adjustments to blade axial length induce flow separation, and precisely quantifying the extent, intensity, and corresponding loss magnitude of the separation zone. Based on these simulation results, parameter combinations that are prone to causing large-scale flow separation can be proactively avoided during the parameter selection stage, ensuring smooth flow within the flow channel and controllable local losses in the final design, effectively achieving the low-resistance design goal.

[0059] In step S6, after obtaining the theoretical performance results, the curves of theoretical efficiency, theoretical shaft power, and theoretical head H as a function of the axial length coefficient of the impeller hub side, and the curves of theoretical efficiency, theoretical shaft power, and theoretical head as a function of the axial length coefficient of the impeller rim side are plotted respectively. Based on the above curves, the design parameter combination that meets the design head requirement is selected as the pre-selected parameter combination. From the pre-selected parameter combination, the parameter combination with theoretical efficiency greater than the preset efficiency threshold and theoretical shaft power lower than the preset shaft power threshold is selected as the optimal design parameter combination.

[0060] The curves showing the variation of theoretical efficiency, theoretical shaft power, and theoretical head H with the axial length coefficient on the impeller hub side, and the curves showing the variation of theoretical efficiency, theoretical shaft power, and theoretical head with the axial length coefficient on the impeller rim side, are shown in the appendix. Figure 2-3 .

[0061] This invention, by plotting curves showing the variation of efficiency, shaft power, and head with the axial length coefficients of the impeller hub and rim sides respectively, can intuitively and continuously demonstrate the influence trend and sensitivity of two independent design variables on three core performance parameters. When determining the optimal design parameters, "meeting the design head requirement" is used as the first screening threshold. Pre-selected combinations that meet the head index are first selected from all parameter combinations to satisfy the core functional constraints of large-scale water pumps. The primary design goal of large-scale water pumps is to achieve the rated head to meet the engineering needs of water conveyance, flood drainage, etc. This screening logic avoids the problem of simply pursuing drag reduction and efficiency gains, resulting in insufficient head and solutions lacking engineering application value. It ensures that all subsequently selected solutions have the basic feasibility for engineering implementation, avoiding ineffective design investment.

[0062] Secondly, among the pre-selected combinations that meet the head requirements, the optimal solution is selected based on the criterion of "efficiency higher than the preset threshold and shaft power lower than the preset threshold". Since the improvement of pump efficiency and the reduction of shaft power are direct macroscopic manifestations of the reduction of hydraulic losses in the flow channel, the joint selection of efficiency and shaft power can simultaneously take into account energy utilization efficiency and operating energy consumption: improving efficiency directly reduces friction loss, impact loss and separation loss in the flow channel, achieving low resistance design; while reducing shaft power reduces the long-term energy consumption cost of pump operation, achieving synergistic benefits of resistance reduction and energy saving, so that the selected design parameters can meet the design requirements of low resistance and energy saving.

[0063] Compared with the prior art, the present invention has the following advantages: 1. To address the shortcomings of existing front and rear flow channels, which use simple straight lines or single curves and are difficult to adapt to complex flows, this invention employs a piecewise function composed of two quadratic functions to accurately describe the axial variation of the equivalent radius of the front and rear flow channels. On one hand, the piecewise structure can separately match the flow diffusion / contraction characteristics of different flow sections from the inlet to the impeller inlet and from the guide vane outlet to the pump outlet, adapting to the differentiated flow requirements of inlet flow homogenization and outlet kinetic energy recovery. On the other hand, the quadratic function profile ensures a continuous and smooth rate of change of the flow channel cross-section, avoiding abrupt changes in cross-section, flow separation, and vortex zones that are prone to occur in straight / single-curve flow channels, effectively reducing hydraulic losses along the flow path and local impact losses, and significantly improving the flow channel efficiency.

[0064] 2. In this invention, at the junction of the front and rear flow channels and the impeller flow channel on the hub side, straight sections tangent to the corresponding flow channel profiles are respectively set. This ensures the continuity of the first derivative of the inner wall surface of the flow channel at the junction, completely eliminates geometric inflection points, dead flow angles, and flow separation vortices at the junction of the profiles, and reduces local impact losses at the impeller inlet and outlet. At the same time, the regular straight transition section can provide uniform inflow / outflow conditions for the leading and trailing edges of the blades, improve the blade inlet angle of attack distribution and outlet flow uniformity, and further reduce hydraulic losses in the impeller flow channel.

[0065] 3. To address the shortcomings of existing designs where the axial lengths of the impeller hub and rim sides rely on experience and cannot be independently adjusted, this invention defines two independent dimensionless design variables: the impeller hub axial length coefficient and the impeller rim axial length coefficient. On one hand, this achieves fully parameterized and independent control of the blade's axial spatial morphology, eliminating the blindness of experience-based design. It allows for matching the optimal blade axial length to different flow characteristics on the hub and rim sides, significantly increasing design freedom. On the other hand, the dimensionless parameter system makes the design method universal across dimensions, adaptable to large-scale water pumps of different specifications, and facilitating standardized design processes. Thirdly, the two independent variables provide ample adjustment space for multi-objective performance optimization, accurately considering multiple performance indicators such as head, efficiency, and shaft power.

[0066] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A low-resistance design method for the flow-through components of a large electric pump impeller, characterized in that, The specific steps include the following: S1: Determine the design parameters; S2: The front flow channel extends from the inlet to the impeller inlet along the flow direction. The front flow channel piecewise function, composed of two quadratic functions, describes the variation of the equivalent radius of the front flow channel cross section with the axial coordinate x of the flow channel, so that the front flow channel profile remains smooth and continuous. S3: The rear flow channel extends from the guide vane outlet to the pump outlet along the flow direction. The equivalent radius of the rear flow channel cross section is described by a piecewise function composed of two quadratic functions, and the profile of the rear flow channel remains smooth and continuous. S4: On the axis of the impeller hub side, a front straight segment is set between the end of the front flow channel profile and the intersection of the blade leading edge hub, and a rear straight segment is set between the intersection of the blade trailing edge hub and the beginning of the rear flow channel profile; the front straight segment is tangent to the front flow channel profile at the connection point, and the rear straight segment is tangent to the rear flow channel profile at the connection point. S5: Define the impeller hub-side axial length as the projected length of the line of intersection between the blade root and the hub in the pump shaft direction, and the impeller rim-side axial length as the projected length of the line of intersection between the blade tip and the rim in the pump shaft direction; take the ratio of the impeller hub-side axial length to the rim radius as the impeller hub-side axial length coefficient, and take the ratio of the impeller rim-side axial length to the impeller rim radius as the impeller rim-side axial length coefficient. Select different impeller hub-side axial length coefficients and impeller rim-side axial length coefficients and combine them to obtain multiple design parameter combinations; S6: Keep the profile parameters of the front and rear flow channels fixed, conduct simulation experiments on different combinations of design variables, and obtain theoretical performance results; The design parameter combination is selected based on theoretical performance results.

2. The low-resistance design method for the impeller flow passage component of a large electric pump according to claim 1, characterized in that, In step S1, the design parameters include design flow rate, design head, rated speed, impeller outer diameter, and hub diameter.

3. The low-resistance design method for the impeller flow passage component of a large electric pump according to claim 1, characterized in that, The front flow channel piecewise function is: ； in, The equivalent radius of the front flow channel cross section; This is the first segmentation point. a represents the axial coordinate position corresponding to the impeller inlet. 1、 b1, a2, b2, and c1 are all control coefficients for the front flow channel profile.

4. The low-resistance design method for the impeller flow passage component of a large electric pump according to claim 1, characterized in that, The piecewise function of the backflow channel is: ； in, The equivalent radius of the rear flow channel section; This is the second segmentation point. This represents the axial coordinate position corresponding to the guide vane outlet. Let a be the axial coordinate position corresponding to the pump outlet. 3、 b3, a4, b4, c2, and c3 are all control coefficients for the rear flow channel profile.

5. The low-resistance design method for the impeller flow passage component of a large electric pump according to claim 1, characterized in that, In step S6, a simulation experiment is conducted using a three-dimensional CFD numerical simulation method.

6. The low-resistance design method for the flow-through components of a large electric pump impeller according to claim 1, characterized in that, In step S6, the specific method for conducting simulation experiments on different combinations of design variables is as follows: N1: A three-dimensional geometric model of the flow channel of the water pump is established based on the piecewise function of the front flow channel, the piecewise function of the rear flow channel, the parameters of the front straight segment, the parameters of the rear straight segment, the axial length coefficient of the impeller hub side, and the axial length coefficient of the impeller rim side; N2: Mesh the 3D geometric model and refine the local mesh in complex flow areas such as the wall, leading edge of the blade, and trailing edge of the blade; N3: Import the meshed file into the CFX solver, set the inlet and outlet boundary conditions, select the turbulence model, and perform numerical calculations using the CFX solver; N4: After solving the convergence condition, extract the theoretical head, theoretical efficiency, and theoretical shaft power as theoretical performance results.

7. The low-resistance design method for the impeller flow passage component of a large electric pump according to claim 1, characterized in that, In step S6, after obtaining the theoretical performance results, the curves of theoretical efficiency, theoretical shaft power, and theoretical head as a function of the axial length coefficient of the impeller hub side, and the curves of theoretical efficiency, theoretical shaft power, and theoretical head as a function of the axial length coefficient of the impeller rim side are plotted respectively. Based on the above curves, the design parameter combination that meets the design head requirement is selected as the pre-selected parameter combination. From the pre-selected parameter combination, the parameter combination with theoretical efficiency greater than the preset efficiency threshold and theoretical shaft power lower than the preset shaft power threshold is selected as the optimal design parameter combination.

8. The low-resistance design method for the impeller flow passage component of a large electric pump according to claim 6, characterized in that, In step N3, the turbulence model selected is k ω model.

9. The low-resistance design method for the impeller flow passage component of a large electric pump according to claim 6, characterized in that, The inlet boundary condition is set as a pressure inlet, with a total pressure of 1 standard atmosphere; the outlet boundary condition is set as a mass flow outlet, with the mass flow rate at the outlet being the design flow rate.

10. The low-resistance design method for the impeller flow passage component of a large electric pump according to claim 1, characterized in that, In step S5, the value range of the axial length coefficient on the impeller hub side is 0.31-0.65, and the value range of the axial length coefficient on the impeller rim side is 0.68-0.97.

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