Calculation method for cavitation erosion area shape and material loss amount of water pump blade under sand carrying condition

Abstract

The invention relates to the technical field of water pump engineering, and provides a water pump blade cavitation erosion area shape and material loss amount calculation method under a sand carrying condition, and the method comprises the following specific steps: determining characteristic parameters, carrying out transient numerical simulation on a research object to determine a cavitation area, and obtaining related flow field parameters; introducing a flow velocity correction factor and a sediment carrying correction factor to respectively reflect the influence of the water flow velocity and sediment particles on the loss amount of the cavitation erosion material; the cavitation erosion offset distance is calculated, and the shape of the cavitation erosion area is determined according to the cavitation erosion offset distance and the geometric contour of the cavitation area; and calculating the material loss amount of the cavitation erosion area by using the flow velocity correction factor and the sand carrying correction factor. Aiming at a given water pump, the cavitation erosion area shape and the material loss amount of the blade of the water pump under different sand carrying working conditions can be quickly and accurately predicted, the problem that the cavitation erosion area shape and the material loss amount of the blade of the water pump under the sand carrying condition are difficult to accurately predict by an existing method is solved, and effective guarantee is provided for cavitation erosion protection of the water pump under the sand carrying condition.

Description

Technical Field

[0001] The invention relates to the technical field of water pump engineering, and in particular to a method for calculating the shape of cavitation zone and material loss amount of water pump blades under sand-carrying conditions. Background Art

[0002] The prediction of existing pump blade cavitation phenomenon often relies on cavitation calculations, and the cavitation zone is often regarded as equivalent to the cavitation zone in engineering. However, existing studies have shown that the actual cavitation zone is offset in the flow direction relative to the cavitation zone, and is particularly affected by water flow velocity and sediment particles. Existing cavitation assessment methods fail to quantitatively consider these influencing factors, and generally can only achieve cavitation risk assessment, and it is difficult to accurately calculate the amount of material loss caused by cavitation. Summary of the invention

[0003] The present invention provides a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions, so as to solve the problem that the cavitation assessment method in the related art fails to quantitatively consider these influencing factors and generally can only achieve the assessment of the cavitation risk, but is difficult to accurately calculate the amount of material loss caused by cavitation.

[0004] The present invention provides a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions, comprising: Determine the relevant characteristic parameters of the shape of the cavitation zone of the water pump blade and the amount of material loss under the condition of sand entrainment, wherein the relevant characteristic parameters at least include the cavitation time t , Sediment Concentration α , sand particle size d , Material density ρ ; In the process of spatial discretization of the object for which the cavitation zone shape and material loss calculation are to be carried out, transient numerical simulation is carried out, the cavitation zone is determined by the results of the numerical simulation, and relevant flow field parameters are obtained, the relevant flow field parameters at least include the flow velocity V , cavitation zone area A c , the maximum flow length of the cavitation zone l max ; Introducing flow rate correction factor C V and sediment correction factor C P , where the velocity correction factor C V and sediment correction factor C P Respectively reflect the effects of water flow velocity and sediment particles on the amount of cavitation material loss; Calculate the cavitation offset distance Δ l, and determine the shape of the cavitation area, wherein the cavitation offset distance Δ l It is used to reflect the displacement of the cavitation zone position relative to the cavitation zone position in the flow direction; Based on the flow rate correction factor C V and the sediment correction factor C P , calculate the material loss in the cavitation zone E , wherein the material loss in the cavitation zone is E To reflect the cumulative material loss of the pump blades due to continuous cavitation.

[0005] According to a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions provided by the present invention, in the process of spatially discretizing the object to be used for calculating the shape of the cavitation zone and the amount of material loss, a transient numerical simulation is performed, the cavitation zone is determined by the result of the numerical simulation, and relevant flow field parameters are obtained, including: The finite volume method is used to spatially discretize the object for calculating the shape of the cavitation zone and the amount of material loss.

[0006] According to a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions provided by the present invention, in the process of spatially discretizing the object for which the shape of the cavitation zone and the amount of material loss are to be calculated, the cavitation zone is determined and relevant flow field parameters are obtained, which also includes: Select a computational model to carry out transient numerical simulation and obtain numerical simulation results; Based on the numerical simulation results, the cavitation region is determined, and the relevant flow field parameters are obtained therefrom.

[0007] According to a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions provided by the present invention, the selected calculation models include a ZGB cavitation model and an SSTk-ω turbulence model.

[0008] According to a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions provided by the present invention, in the process of spatially discretizing the object to be used for calculating the shape of the cavitation zone and the amount of material loss, the cavitation zone is determined and the relevant flow field parameters are obtained. The relevant flow field parameters include at least the flow velocity V , cavitation zone area A c , the maximum flow length of the cavitation zone l max Also included: The flow velocity V The magnitude is equal to the average axial velocity of the blade inlet edge, and its direction is perpendicular to the axial surface of the blade inlet edge.

[0009] According to a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions provided by the present invention, the velocity correction factor is determined by expression 1: C V , which is calculated as: Expression 1: ; Among them, the expression in V is the streamwise velocity, 1 is the velocity increment base, 1.78×10 -4 , 2.2 is the flow rate increment coefficient.

[0010] According to a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand entrainment conditions provided by the present invention, the sand entrainment correction factor is determined by expression 2: C P , which is calculated as: Expression 2: ; Among them, the expression in α is the sediment concentration, d is the sand-carrying particle size, 1 is the sediment-affected base, -0.005, 0.52, -4.2×10 -5 , -1.62, and 0.044 are all sediment influence coefficients.

[0011] According to a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions provided by the present invention, the cavitation offset distance Δ l , and determining the shape of the cavitation zone, including: According to the cavitation offset distance Δ l and the geometric contours of the cavitation zone to determine the shape of the cavitation zone.

[0012] According to a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions provided by the present invention, the cavitation offset distance Δ is determined by expression 3: l , which is calculated as: Expression three: ; Among them, in expression 3 V is the flow velocity, l max is the maximum flow length of the cavitation zone, and 0.022, 1, and 2 are cavitation offset coefficients.

[0013] According to a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions provided by the present invention, through expression 4, the amount of material loss in the cavitation zone is E, the calculation method is: Expression 4: ; Among them, in expression 4 is the average cavitation material loss rate, ρ is the material density, A e is the area of ​​cavitation zone, and is the area of ​​cavitation zone A c equal, t 1 is the start time of the stage, t 2 is the end time of the stage, t is the cavitation time, 1.454×10 -6 , 0.34, 150, 8.8 are the material loss influence coefficients in the cavitation acceleration stage, 7.74×10 -7 , -1110, 231 is the material loss influence coefficient in the cavitation weakening stage, 3.47×10 -7 is the average material loss rate in the stable stage of cavitation.

[0014] The present invention provides a method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-entrained conditions, which comprehensively considers the influence of water flow velocity and sediment particles on cavitation. For a given water pump, the shape of the cavitation zone and the amount of material loss of its blades under different water flow velocities, sediment concentrations, and sediment particle sizes can be quickly and accurately predicted; the problem that the existing methods are difficult to accurately predict the shape of the cavitation zone and the amount of material loss of water pump blades under sand-entrained conditions is solved, and effective protection is provided for cavitation protection and safe and stable operation of water pumps under sand-entrained conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a flow chart for realizing the method for calculating the shape of the cavitation zone of a water pump blade and the amount of material loss under the condition of sand entrainment provided by the present invention.

[0017] Figure 2 It is a calculated distribution diagram of the cavitation area and cavitation area of ​​the water pump blade provided by the present invention.

[0018] Figure 3 This is an experimental distribution diagram of the cavitation zone of the water pump blade provided by the present invention.

[0019] Figure 4It is a graph showing the relationship between the amount of material loss in the cavitation zone of a water pump blade and time provided by the present invention.

[0020] Figure 5 It is a schematic diagram of Expression 1 provided by the present invention.

[0021] Figure 6 It is a schematic diagram of Expression 2 provided by the present invention.

[0022] Figure 7 It is a schematic diagram of Expression 3 provided by the present invention.

[0023] Figure 8 It is a schematic diagram of Expression 4 provided by the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Combine the following Figure 1-Figure 8 The present invention describes a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions.

[0026] like Figure 1 As shown in FIG. 1 , it is a flow chart of the calculation method of the cavitation zone shape and material loss of water pump blades under sand-carrying conditions provided by the present invention. A centrifugal pump model case is used as an embodiment of this patent. The impeller diameter of the centrifugal pump is 0.427m and the number of blades is 6. In terms of operating conditions, the flow rate is 800m 3 / h, the speed is 1480rpm, and the effective cavitation margin is 8.8m.

[0027] The embodiment of the present invention provides a method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions, comprising: Step 1: Determine the relevant characteristic parameters of the shape of the cavitation zone of the pump blade and the amount of material loss under the condition of sand entrainment. The relevant characteristic parameters include at least the cavitation time t , Sediment Concentration α , sand particle size d , Material density ρ ; Specifically, in the embodiment of the present invention, the relevant characteristic parameters of the shape of the cavitation zone of the water pump blade and the amount of material loss under the condition of sand entrainment are clearly calculated. The relevant characteristic parameters can be obtained by sampling and measuring the specific engineering environment, among which the cavitation time t=0~2500min, sand concentration α =10kg / m 3 , sand particle size d =2.5×10 -5 m, material density ρ =7930kg / m 3 ; Step 2: During the spatial discretization of the object for which the cavitation zone shape and material loss calculation is to be carried out, a transient numerical simulation is carried out to determine the cavitation zone through the results of the numerical simulation and obtain the relevant flow field parameters, which at least include the flow velocity V , cavitation zone area A c , the maximum flow length of the cavitation zone l max ; Step 3: Introducing flow rate correction factor C V and sediment correction factor C P , where the velocity correction factor is C V and sediment correction factor C P Respectively reflect the effects of water flow velocity and sediment particles on the amount of cavitation material loss; Step 4: Calculate the cavitation offset distance Δ l , and determine the shape of the cavitation area, where the cavitation offset distance Δ l It is used to reflect the displacement of the cavitation zone position relative to the cavitation zone position in the flow direction; Step 5: Flow rate correction factor C V and sediment correction factor C P , calculate the material loss in the cavitation zone E , where the material loss in the cavitation zone is E To reflect the cumulative material loss of the pump blades due to continuous cavitation.

[0028] The present invention provides a method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-entrained conditions, which comprehensively considers the influence of water flow velocity and sediment particles on cavitation. For a given water pump, the shape of the cavitation zone and the amount of material loss of its blades under different water flow velocities, sediment concentrations, and sediment particle sizes can be quickly and accurately predicted; the problem that the existing methods are difficult to accurately predict the shape of the cavitation zone and the amount of material loss of water pump blades under sand-entrained conditions is solved, and effective protection is provided for cavitation protection and safe and stable operation of water pumps under sand-entrained conditions.

[0029] In this embodiment, the cavitation time is calculated explicitly by measuring t, Sediment Concentration α , sand particle size d and material density ρ And other data, and further determine the velocity correction factor C V and sediment correction factor C P , and based on the velocity correction factor C V and sediment correction factor C P , further calculations are performed to obtain the material loss E in the cavitation zone; based on the flow velocity V and the maximum flow length of the cavitation zone l max , calculate the cavitation offset distance Δ l , further calculations determine the shape of the cavitation zone.

[0030] In an embodiment of the present invention, in step two, in the process of spatially discretizing the object for which the cavitation zone shape and material loss amount are to be calculated, the cavitation zone is determined and relevant flow field parameters are obtained, including: using the finite volume method to spatially discretize the object for which the cavitation zone shape and material loss amount are to be calculated.

[0031] It can be understood that the finite volume method recognized in the field of water pumps can be used to spatially discretize the object to be used for the calculation of the cavitation zone shape and material loss, and then directly used for the numerical calculation of the cavitation zone shape and material loss to obtain the flow velocity. V , cavitation zone area A c It should be noted that in the actual calculation process, the order of each step can be adjusted according to actual needs, and is not limited here.

[0032] In this embodiment, in step 2, in the process of spatial discretization of the object for which the cavitation zone shape and material loss calculation is to be carried out, the cavitation zone is determined and the relevant flow field parameters are obtained, which also includes: selecting a calculation model to carry out transient numerical simulation and obtain numerical simulation results; based on the numerical simulation results, the cavitation zone is determined and the relevant flow field parameters are obtained therefrom. Specifically, the selected calculation models include the ZGB cavitation model and the SSTk-ω turbulence model. Furthermore, by making the numerical simulation results closer to the experimental values, the flow information in turbulence can be obtained more accurately, which is more suitable for flow calculations in hydraulic machinery.

[0033] In the embodiment of the present invention, further, in step 2, in the process of spatially discretizing the object for calculating the cavitation zone shape and material loss, the cavitation zone is determined, and the relevant flow field parameters are obtained, and the relevant flow field parameters at least include the flow velocity V , cavitation zone area Ac , the maximum flow length of the cavitation zone l max Also included: Flow velocity V The magnitude is equal to the average axial velocity of the blade inlet edge, and its direction is perpendicular to the axial surface of the blade inlet edge.

[0034] In the embodiment of the present invention, further, in step three, Figure 5 As shown, the velocity correction factor is determined by expression 1. C V , which is calculated as: Expression 1: ; Among them, the expression in V is the streamwise velocity, 1 is the velocity increment base, 1.78×10 -4 , 2.2 is the velocity increment coefficient. It can be understood that the derivation steps of Expression 1 are as follows: (1) Based on the study of the influence of velocity on cavitation damage in classic experiments, the relationship between the degree of cavitation damage and the velocity is obtained through fitting analysis; (2) Based on this relationship, it is deduced that the cavitation damage increment ratio caused by a unit velocity change is 1.78×10 -4 · V 2.2 , and the velocity correction factor is obtained based on the increment ratio C V .

[0035] In the embodiment of the present invention, further, in step three, Figure 6 As shown in the figure, the sand correction factor is determined by expression 2: C P , which is calculated as: Expression 2: ; Among them, the expression in α is the sediment concentration, d is the sand-carrying particle size, 1 is the sediment-affected base, -0.005, 0.52, -4.2×10 -5 , -1.62, and 0.044 are all sediment influence coefficients. It can be understood that the derivation steps of Expression 2 are as follows: (1) According to the classic cavitation erosion test results of sand-carrying water, the relationship between the cavitation material loss and the sand concentration and particle size is fitted; (2) The cavitation material loss under sand-carrying water conditions is calculated by ratio to the cavitation material loss under sand-free conditions to obtain the sand correction factor C P .

[0036] Based on flow velocity V and the maximum flow length of the cavitation zonel max , calculate the cavitation offset distance Δ l , and determine the shape of the cavitation area, including: In the embodiment of the present invention, further, the cavitation offset distance Δ is calculated l , and determine the shape of the cavitation area, including: according to the cavitation offset distance Δ l and the geometric contours of the cavitation zone to determine the shape of the cavitation zone.

[0037] In an embodiment of the present invention, further, Figure 7 As shown in the figure, the cavitation offset distance Δ is determined by expression 3. l , which is calculated as: Expression three: ; Among them, in expression 3 V is the flow velocity, l max is the maximum flow length of the cavitation zone, and 0.022, 1, and 2 are all cavitation offset coefficients. It can be understood that the derivation steps of Expression 3 are as follows: (1) Based on the study of the influence of flow velocity on the position of the cavitation zone in classical experiments, the relationship between the ratio of the cavitation offset distance and the maximum flow length of the cavitation zone and the flow velocity is obtained through fitting analysis; (2) Based on the assumption that different cavitation phenomena all conform to this generalized ratio relationship, the cavitation offset distance Δ can be determined by multiplying this ratio by the maximum flow length of the cavitation zone. l .

[0038] In an embodiment of the present invention, further, Figure 8 As shown, using the velocity correction factor C V and sediment correction factor C P , the material loss in the cavitation zone is calculated by expression 4 E , to reflect the cumulative material loss of the pump blades due to continuous cavitation, the material loss in the cavitation area E , the calculation method is: Expression 4: ; Specifically, expression 4 can also be understood as follows: ; Among them, in expression 4 is the average cavitation material loss rate, ρ is the material density, A e is the area of ​​cavitation zone, and is the area of ​​cavitation zone A c equal,t 1 is the start time of the stage, t 2 is the end time of the stage, t is the cavitation time, 1.454×10 -6 , 0.34, 150, 8.8 are the material loss influence coefficients in the cavitation acceleration stage, 7.74×10 -7 , -1110, 231 is the material loss influence coefficient in the cavitation weakening stage, 3.47×10 -7 is the average material loss rate in the stable stage of cavitation. It can be understood that the derivation steps of expression 4 are as follows: (1) According to the results of the standard vibration cavitation test, the expression of cavitation material loss under the condition of static water flow and no sediment is obtained by segment fitting; (2) the velocity correction factor is C V , sand entrainment correction factor C P Introduced into the expression in the form of a correction coefficient, the material loss in the cavitation zone under sand-carrying conditions is obtained E .

[0039] In order to better demonstrate the advantages of the method of the present invention, the calculated cavitation zone distribution characteristics are compared with the experimental cavitation zone distribution characteristics, as shown in FIG. Figure 2 As shown in FIG. 1 , it is a calculated distribution diagram of the cavitation area and cavitation erosion area of ​​the water pump blade provided by the present invention, such as Figure 3 As shown in the figure, it is the experimental distribution diagram of the cavitation area of ​​the water pump blade provided by the present invention. It can be seen from the analysis that the shape of the cavitation area calculated by the method of the present invention is basically consistent with the experimental results and can meet the accuracy requirements of engineering calculations. Figure 4 As shown in FIG. 1 , it is a graph showing the relationship between the amount of cavitation material loss of the water pump blade provided by the present invention and time. It can be seen from the analysis that the change of the amount of cavitation material loss over time has gone through four stages: latent, accelerated, weakened, and stable. t =2500min, cavitation material loss E It is about 1.02 g, which is consistent with engineering experience, indicating that the present invention can efficiently and accurately predict the amount of cavitation material loss at different cavitation development stages.

[0040] In summary, the present invention comprehensively considers the influence of water flow velocity and sediment particles on cavitation. For a given water pump, it can quickly and accurately predict the shape of the cavitation zone and the amount of material loss of its blades under different water flow velocities, sediment concentrations, and sediment particle sizes. This solves the problem that existing methods are difficult to accurately predict the shape of the cavitation zone and the amount of material loss of water pump blades under sediment conditions, and provides effective protection for cavitation protection and safe and stable operation of water pumps under sediment conditions.

[0041] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, i.e., they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Those of ordinary skill in the art may understand and implement it without creative effort.

[0042] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the relevant technology can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods of each embodiment or some parts of the embodiment.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the shape of the cavitation zone and the amount of material loss of a water pump blade under sand-carrying conditions, characterized in that: include: Determine the relevant characteristic parameters of the shape of the cavitation zone of the water pump blade and the amount of material loss under the condition of sand entrainment, wherein the relevant characteristic parameters at least include the cavitation time t , Sediment Concentration α , sand particle size d , Material density ρ ; In the process of spatial discretization of the object to be used for calculating the shape of the cavitation zone and the amount of material loss, a transient numerical simulation is performed, the cavitation zone is determined by the results of the numerical simulation, and relevant flow field parameters are obtained, wherein the relevant flow field parameters include at least the flow velocity V , cavitation zone area A c , the maximum flow length of the cavitation zone l max ; Introducing flow rate correction factor C V and sediment correction factor C P , where the velocity correction factor C V and sediment correction factor C P Respectively reflect the effects of water flow velocity and sediment particles on the amount of cavitation material loss; Calculate the cavitation offset distance Δ l , and determine the shape of the cavitation area, wherein the cavitation offset distance Δ l It is used to reflect the displacement of the cavitation zone position relative to the cavitation zone position in the flow direction; Based on the flow rate correction factor C V and the sediment correction factor C P , calculate the material loss in the cavitation zone E , wherein the material loss in the cavitation zone is E To reflect the cumulative material loss of the pump blades due to continuous cavitation.

2. The method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-carrying conditions according to claim 1 is characterized in that: In the process of spatially discretizing the object for which the cavitation zone shape and material loss amount are to be calculated, the cavitation zone is determined and relevant flow field parameters are obtained, including: using the finite volume method to spatially discretize the object for which the cavitation zone shape and material loss amount are to be calculated.

3. The method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-carrying conditions according to claim 2 is characterized in that: In the process of spatial discretization of the object for which the cavitation zone shape and material loss calculation are to be carried out, transient numerical simulation is carried out, the cavitation zone is determined through the results of the numerical simulation, and relevant flow field parameters are obtained, which also includes: Select a computational model to carry out transient numerical simulation and obtain numerical simulation results; Based on the numerical simulation results, the cavitation region is determined, and the relevant flow field parameters are obtained therefrom.

4. The method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-carrying conditions according to claim 3 is characterized in that: The selected calculation models include the ZGB cavitation model and the SSTk-ω turbulence model.

5. The method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-carrying conditions according to claim 1 is characterized in that: In the process of spatially discretizing the object for calculating the shape of the cavitation zone and the amount of material loss, the cavitation zone is determined and the relevant flow field parameters are obtained. The relevant flow field parameters include at least the flow velocity. V , cavitation zone area A c , the maximum flow length of the cavitation zone l max Also included: The flow velocity V The magnitude is equal to the average axial velocity of the blade inlet edge, and its direction is perpendicular to the axial surface of the blade inlet edge.

6. The method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-carrying conditions according to claim 1 is characterized in that: The velocity correction factor is determined by expression 1: C V , which is calculated as: Expression 1: ； Among them, the expression in V is the streamwise velocity, 1 is the velocity increment base, 1.78×10 -4 , 2.2 is the flow rate increment coefficient.

7. The method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-carrying conditions according to claim 1 is characterized in that: The sand entrainment correction factor is determined by expression 2: C P , which is calculated as: Expression 2: ； Among them, the expression in α is the sediment concentration, d is the sand-carrying particle size, 1 is the sediment impact base, -0.005, 0.52, -4.2×10-5, -1.62, and 0.044 are all sediment impact coefficients.

8. The method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-carrying conditions according to claim 1 is characterized in that: The calculated cavitation offset distance Δ l , and determining the shape of the cavitation zone, including: According to the cavitation offset distance Δ l and the geometric contours of the cavitation zone to determine the shape of the cavitation zone.

9. The method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-carrying conditions according to claim 8 is characterized in that: The cavitation offset distance Δ is determined by expression 3: l , which is calculated as: Expression three: ； Among them, in expression 3 V is the flow velocity, l max is the maximum flow length of the cavitation zone, and 0.022, 1, and 2 are cavitation offset coefficients.

10. The method for calculating the shape of the cavitation zone and the amount of material loss of water pump blades under sand-carrying conditions according to claim 1 is characterized in that: Through expression 4, the material loss E in the cavitation zone is calculated as follows: Expression 4: ； Among them, in expression 4 is the average cavitation material loss rate, ρ is the material density, A e is the area of ​​cavitation zone, and is the area of ​​cavitation zone A c equal, t 1 is the start time of the stage, t 2 is the end time of the stage, t is the cavitation time, 1.454×10 -6 , 0.34, 150, 8.8 are the material loss influence coefficients in the cavitation acceleration stage, 7.74×10 -7 , -1110, 231 is the material loss influence coefficient in the cavitation weakening stage, 3.47×10 -7 is the average material loss rate in the stable stage of cavitation.

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