A method for predicting the residual cavitation erosion life of an inducer for a pump based on ultrasonic testing

Abstract

This invention discloses a method for predicting the remaining cavitation erosion life (RCW) of pump induced draft wheels based on ultrasonic testing. It relates to the field of RAW prediction for pump induced draft wheels and includes: analyzing the material properties of the induced draft wheel to determine the weight loss curve per unit cavitation intensity; analyzing the cavitation intensity of the induced draft wheel to obtain the cavitation risk area and its cavitation intensity distribution characteristics; establishing the correspondence between the cavitation loss weight and the average cavitation depth based on the results of the material property analysis and cavitation intensity analysis; and predicting the remaining RAW of the induced draft wheel based on the failure cavitation depth threshold. This invention enables quantitative simulation prediction of the RAW's RAW life and has good engineering applicability.

Description

Technical Field

[0001] This invention relates to the field of predicting the remaining cavitation life of pump induced impellers, and more specifically to a method for predicting the remaining cavitation life of pump induced impellers based on ultrasonic testing. Background Technology

[0002] Cavitation erosion is a common and difficult-to-avoid flow phase change phenomenon in pumps operating under low inlet pressure conditions. As a key component for improving pump inlet flow and enhancing cavitation resistance, the inducer undergoes periodic cavitation generation, growth, and collapse processes on its surface. Local areas are subjected to high-frequency impact loads and microjets. Long-term operation can easily lead to fatigue damage and cavitation erosion on the material surface, resulting in hydraulic performance degradation or even structural failure.

[0003] However, current engineering practice for assessing cavitation damage in inducer impellers primarily relies on operational experience, periodic maintenance, or monitoring of overall pump performance degradation, lacking quantitative analysis methods for the cavitation evolution process of the inducer impeller itself. Existing cavitation research mainly focuses on the initial characteristics of cavitation, cavitation morphology identification, and transient flow structure analysis, with relatively insufficient research on the long-term cumulative effects of cavitation damage and the prediction of the remaining service life of the inducer impeller. With the development of numerical simulation technology, cavitation flow simulation based on computational fluid dynamics (CFD) can capture the cavitation structure and pressure pulsation characteristics within the inducer impeller to some extent. However, most existing studies remain at the flow field level and have not yet established an effective correlation model between cavitation flow characteristics and material damage evolution, making it difficult to quantitatively predict the cavitation damage rate and remaining cavitation life of the inducer impeller. Furthermore, existing simulation methods generally lack correction mechanisms for the actual operating conditions and materials of the inducer impeller, resulting in a significant gap between their prediction results and the needs of engineering applications.

[0004] Therefore, how to provide a simulation and prediction method for the residual cavitation life of pump induced impellers is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for predicting the remaining cavitation life of pump induced impellers based on ultrasonic testing. This method combines the cavitation flow characteristics of the induced impeller with the material erosion damage evolution process. Through numerical simulation of multiple operating conditions and time scales, it achieves a quantitative description of the cavitation damage accumulation process of the induced impeller and predicts its remaining life, providing a predictive means for the optimized design of the induced impeller structure, operation status assessment and life management.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention discloses a method for predicting the residual cavitation life of pump induced impellers based on ultrasonic testing, comprising: Perform material property analysis on the inducer to determine the weight loss curve per unit cavitation intensity; Induced cavitation intensity analysis was conducted to obtain the cavitation risk area and its cavitation intensity distribution characteristics. Based on the analysis of the material properties of the inducer wheel and the analysis of the cavitation intensity of the inducer wheel, a correspondence between the cavitation loss weight of the inducer wheel and the average cavitation depth is established, and the remaining cavitation life of the inducer wheel is estimated according to the failure cavitation depth threshold.

[0007] Furthermore, the material property analysis of the inducer wheel specifically includes: Fabricate cavitation test specimens made of the same material as the inducer wheel; An ultrasonic cavitation test device was used to conduct ultrasonic cavitation tests on the cavitation specimen, and the curve of the material's cavitation weight loss as a function of time was obtained by fitting. The ultrasonic cavitation test conditions were numerically simulated using a cavitation simulation method. The cavitation risk area was extracted, and the average cavitation intensity of the cavitation risk area was calculated. The cavitation weight loss curve over time was divided by the average cavitation intensity to obtain the material weight loss curve per unit cavitation intensity.

[0008] Furthermore, the diameter of the cavitation specimen is not less than 1.5 times the diameter of the ultrasonic cavitation amplitude transformer, the thickness is not less than 2 mm, and the surface roughness is not higher than 0.8 μm.

[0009] Furthermore, throughout the entire ultrasonic cavitation test, the vibration frequency and amplitude of the amplitude transformer are kept consistent, while ensuring that the relative position of the specimen and the amplitude transformer remains unchanged. Throughout the experiment, the cavitation specimens were taken out at preset time intervals, cleaned, dried and weighed, and images of the cavitation surface were recorded. Based on the obtained weight change data, the cavitation weight loss curve of the material over time was obtained by fitting.

[0010] Furthermore, cavitation simulation methods were used to conduct numerical simulations of cavitation on the inducer under different operating conditions to verify the simulation accuracy of the inducer head, critical cavitation specific speed, and cavitation morphology. After meeting the accuracy requirements, cavitation prediction calculations were performed on the inducer to obtain the cavitation risk area and its cavitation intensity distribution characteristics.

[0011] Furthermore, the cavitation simulation method includes: Numerical simulations of hydrofoil test conditions were performed using turbulence and cavitation models to calculate the hydrofoil's lift characteristics, cavitation morphology, and cavitation shedding frequency parameters. The simulation results were compared with experimental data. When the relative error was greater than 10%, the coefficients of the evaporation and condensation terms in the cavitation model were adjusted, or the applicability of the turbulence and cavitation models was corrected, until the relative error between the simulation results and the experimental results was less than 10%, thus obtaining a feasible cavitation simulation method. Based on the feasible cavitation simulation method, unsteady cavitation numerical simulation is carried out on the hydrofoil, and the cavitation risk area of ​​the hydrofoil is predicted by the intensity function method, gray scale method or power erosion method. The prediction results are compared with the experimental cavitation distribution. When the prediction error is less than 10%, the cavitation simulation method is obtained.

[0012] Furthermore, establishing the correspondence between the induced wheel cavitation loss weight and the average cavitation depth specifically includes: Based on simplification and assumptions, and according to the cavitation intensity analysis results of the inducer, the cavitation hazard area of ​​the inducer under the set working conditions is extracted, and the average cavitation intensity of the cavitation hazard area is calculated. Multiply the average cavitation intensity by the weight loss curve per unit cavitation intensity to obtain the weight loss curve of the cavitation region of the inducer wheel as a function of time. Based on the material density formula, establish the corresponding relationship between the cavitation loss weight of the induced wheel and the average cavitation depth: ; in, To lose weight, For material density, Volume of the cavitation hazard zone This represents the area of ​​the cavitation hazard zone. The average cavitation depth is given.

[0013] Furthermore, the step of estimating the remaining cavitation life of the induced wheel based on the failure cavitation depth threshold specifically involves: The failure cavitation depth threshold is set according to the actual structural dimensions of the inducer, the corresponding failure weight is calculated according to the corresponding formula, and the remaining cavitation life of the inducer is finally obtained by combining the weight loss of the inducer with the time curve.

[0014] As can be seen from the above technical solution, compared with the prior art, the present invention provides a method for predicting the residual cavitation life of pump induced impellers based on ultrasonic testing, which has the following beneficial effects: This invention combines the cavitation damage characteristics of materials with the cavitation intensity distribution of the induced wheel, thereby achieving quantitative simulation prediction of the remaining cavitation life of the induced wheel. It solves the problem that existing methods are difficult to accurately assess the cavitation life of the induced wheel, and has strong engineering applicability and promotion value. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the overall process of the present invention.

[0017] Figure 2 This is a schematic diagram of the weight loss variation curve of stainless steel material under unit cavitation intensity, provided for an embodiment of the present invention.

[0018] Figure 3 This is a schematic diagram of the induced wheel cavitation intensity distribution provided in an embodiment of the present invention.

[0019] Figure 4 The curve showing the change in weight of induced wheel cavitation loss provided in an embodiment of the present invention. Detailed Implementation

[0020] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention discloses a method for predicting the residual cavitation life of pump induced draft wheels based on ultrasonic testing, such as... Figure 1 As shown, it includes: Perform material property analysis on the inducer to determine the weight loss curve per unit cavitation intensity; Induced cavitation intensity analysis was conducted to obtain the cavitation risk area and its cavitation intensity distribution characteristics. Based on the analysis of the material properties and cavitation intensity of the inducer wheel, a correlation was established between the weight loss due to cavitation and the average cavitation depth of the inducer wheel, and the remaining cavitation life of the inducer wheel was estimated based on the failure cavitation depth threshold.

[0022] In a specific embodiment, the material property analysis of the inducer wheel includes: Fabricate cavitation test specimens made of the same material as the inducer wheel; Long-cycle ultrasonic cavitation tests were conducted on cavitation specimens using an ultrasonic cavitation testing device, and the curve of cavitation weight loss of the material over time was obtained by fitting. The ultrasonic cavitation test was numerically simulated using the cavitation simulation method. The cavitation intensity index exceeding a threshold (e.g., 1×10⁻⁶) was extracted. 6 The area is designated as the cavitation risk zone, and the average cavitation intensity (2.18 × 10⁻⁶) of the cavitation risk zone is calculated. 6 Dividing the cavitation erosion weight loss curve over time by the average cavitation erosion intensity yields the material's weight loss curve per unit cavitation erosion intensity, as shown below. Figure 2 As shown.

[0023] In one specific embodiment, the diameter of the cavitation specimen is not less than 1.5 times the diameter of the ultrasonic cavitation amplitude transformer, the thickness is not less than 2 mm, and the surface roughness is not higher than 0.8 μm.

[0024] In one specific embodiment, throughout the ultrasonic cavitation test, the vibration frequency and amplitude of the amplitude transformer are kept consistent (e.g., the vibration frequency is 25 kHz and the amplitude is 20 μm), while ensuring that the relative position of the specimen and the amplitude transformer remains unchanged (e.g., concentricity and spacing, for example, the distance between the amplitude transformer and the specimen is kept at 2 mm) to ensure the consistency and repeatability of the test conditions. Throughout the experiment, cavitation specimens were taken out at preset time intervals, cleaned, dried and weighed, and images of the cavitation surface were recorded. Based on the obtained weight change data, the curve of material cavitation weight loss over time was obtained by fitting.

[0025] In one specific embodiment, cavitation simulation is used to conduct numerical simulations of cavitation on the inducer under different operating conditions, verifying the simulation accuracy of the inducer head, critical cavitation specific speed, and cavitation morphology. After meeting the accuracy requirements, cavitation prediction calculations are performed on the inducer to obtain the cavitation risk area and its cavitation intensity distribution characteristics, such as... Figure 3 As shown.

[0026] In one specific embodiment, the cavitation erosion simulation method includes: Numerical simulations of hydrofoil test conditions were conducted using the SST turbulence model and the ZGB cavitation model. The lift characteristics, cavitation morphology, and cavitation shedding frequency parameters of the hydrofoil were calculated. The simulation results were compared with publicly available test data. When the relative error was greater than 10%, the coefficients of the evaporation and condensation terms in the cavitation model were adjusted, or the applicability of the turbulence model and the cavitation model was corrected, until the relative error between the simulation results and the test results was less than 10%, thus obtaining a feasible cavitation simulation method. Based on the established feasible cavitation simulation methods, unsteady cavitation numerical simulations were conducted on hydrofoils. Cavitation prediction algorithms such as intensity function method, grayscale method, or power erosion method were used to predict the cavitation risk areas of the hydrofoils. The prediction results were compared with the experimental cavitation distribution. When the prediction error was less than 10%, the cavitation prediction method was considered effective, thus forming a cavitation-cavitation joint simulation method that can be used for engineering applications, and obtaining the cavitation simulation method.

[0027] In a specific embodiment, the relationship between the induced wheel cavitation loss weight and the average cavitation depth is established, specifically including: Based on simplification and assumptions, and according to the cavitation intensity analysis results of the inducer, the main cavitation hazard areas of the inducer under the set working conditions are extracted, and the average cavitation intensity of the cavitation hazard areas is calculated.

[0028] To combine the cavitation erosion intensity with the change in cavitation erosion loss weight, the following simplifications and assumptions are appropriately proposed: a. Ignore the influence of changes in material surface morphology on cavitation intensity during cavitation erosion; b. Use the average cavitation intensity of the cavitation hazard zone as a representative value; c. Assume that there is a linear correlation between the change in cavitation intensity and the change in cavitation loss weight.

[0029] Multiplying the average cavitation intensity by the weight loss curve per unit cavitation intensity yields the weight loss curve of the cavitation region of the inducer wheel as a function of time, as shown below. Figure 4 As shown.

[0030] Based on the material density formula, establish the corresponding relationship between the cavitation loss weight of the induced wheel and the average cavitation depth: ; in, To lose weight, For material density, Volume of the cavitation hazard zone This represents the area of ​​the cavitation hazard zone. The average cavitation depth is given.

[0031] In one specific embodiment, the remaining cavitation life of the induced wheel is estimated based on the failure cavitation depth threshold, specifically as follows: The failure cavitation depth threshold (e.g., 1 mm) is set according to the actual structural dimensions of the inducer, the corresponding failure weight is calculated according to the corresponding formula, and the remaining cavitation life of the inducer is finally obtained by combining the weight loss curve of the inducer with time.

[0032] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0033] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting the residual cavitation life of a pump induced impeller based on ultrasonic testing, characterized in that, include: Perform material property analysis on the inducer to determine the weight loss curve per unit cavitation intensity; Induced cavitation intensity analysis was conducted to obtain the cavitation risk area and its cavitation intensity distribution characteristics. Based on the analysis of the material properties of the inducer wheel and the analysis of the cavitation intensity of the inducer wheel, a correspondence between the cavitation loss weight of the inducer wheel and the average cavitation depth is established, and the remaining cavitation life of the inducer wheel is estimated according to the failure cavitation depth threshold.

2. The method for predicting the residual cavitation life of a pump induced impeller based on ultrasonic testing according to claim 1, characterized in that, The analysis of the material properties of the inducer wheel specifically includes: Fabricate cavitation test specimens made of the same material as the inducer wheel; An ultrasonic cavitation test device was used to conduct ultrasonic cavitation tests on the cavitation specimen, and the curve of the material's cavitation weight loss as a function of time was obtained by fitting. The ultrasonic cavitation test conditions were numerically simulated using a cavitation simulation method. The cavitation risk area was extracted, and the average cavitation intensity of the cavitation risk area was calculated. The cavitation weight loss curve over time was divided by the average cavitation intensity to obtain the material weight loss curve per unit cavitation intensity.

3. The method for predicting the residual cavitation life of a pump induced impeller based on ultrasonic testing according to claim 2, characterized in that, The diameter of the cavitation specimen is not less than 1.5 times the diameter of the ultrasonic cavitation amplitude transformer, the thickness is not less than 2 mm, and the surface roughness is not higher than 0.8 μm.

4. The method for predicting the residual cavitation life of a pump induced impeller based on ultrasonic testing according to claim 2, characterized in that, Throughout the entire ultrasonic cavitation test, the vibration frequency and amplitude of the amplitude transformer are kept consistent, while ensuring that the relative position of the specimen and the amplitude transformer remains unchanged. Throughout the experiment, the cavitation specimens were taken out at preset time intervals, cleaned, dried and weighed, and images of the cavitation surface were recorded. Based on the obtained weight change data, the cavitation weight loss curve of the material over time was obtained by fitting.

5. The method for predicting the residual cavitation life of a pump induced impeller based on ultrasonic testing according to claim 1, characterized in that, Using cavitation simulation methods, numerical simulations of cavitation were conducted on the inducer under different operating conditions to verify the simulation accuracy of the inducer head, critical cavitation specific speed, and cavitation morphology. After meeting the accuracy requirements, cavitation prediction calculations were performed on the inducer to obtain the cavitation risk area and its cavitation intensity distribution characteristics.

6. A method for predicting the residual cavitation life of a pump induced impeller based on ultrasonic testing, as described in claims 2 and 5, is characterized in that... The cavitation simulation method includes: Numerical simulations of hydrofoil test conditions were performed using turbulence and cavitation models to calculate the hydrofoil's lift characteristics, cavitation morphology, and cavitation shedding frequency parameters. The simulation results were compared with experimental data. When the relative error was greater than 10%, the coefficients of the evaporation and condensation terms in the cavitation model were adjusted, or the applicability of the turbulence and cavitation models was corrected, until the relative error between the simulation results and the experimental results was less than 10%, thus obtaining a feasible cavitation simulation method. Based on the feasible cavitation simulation method, unsteady cavitation numerical simulation is carried out on the hydrofoil, and the cavitation risk area of ​​the hydrofoil is predicted by the intensity function method, gray scale method or power erosion method. The prediction results are compared with the experimental cavitation distribution. When the prediction error is less than 10%, the cavitation simulation method is obtained.

7. The method for predicting the residual cavitation life of a pump induced impeller based on ultrasonic testing according to claim 1, characterized in that, The establishment of the correspondence between the cavitation loss weight of the induced wheel and the average cavitation depth specifically includes: Based on simplification and assumptions, and according to the cavitation intensity analysis results of the inducer, the cavitation hazard area of ​​the inducer under the set working conditions is extracted, and the average cavitation intensity of the cavitation hazard area is calculated. Multiply the average cavitation intensity by the weight loss curve per unit cavitation intensity to obtain the weight loss curve of the cavitation region of the inducer wheel as a function of time. Based on the material density formula, establish the corresponding relationship between the cavitation loss weight of the induced wheel and the average cavitation depth: ； in, To lose weight, For material density, Volume of the cavitation hazard zone This represents the area of ​​the cavitation hazard zone. The average cavitation depth is given.

8. The method for predicting the residual cavitation life of a pump induced impeller based on ultrasonic testing according to claim 7, characterized in that, The method of estimating the remaining cavitation life of the inducer based on the failure cavitation depth threshold is as follows: The failure cavitation depth threshold is set according to the actual structural dimensions of the inducer, the corresponding failure weight is calculated according to the corresponding formula, and the remaining cavitation life of the inducer is finally obtained by combining the weight loss of the inducer with the time curve.

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