Life prediction method and system for seawater centrifugal pumps based on performance degradation

Abstract

The present invention provides a method and system for predicting the life of a seawater centrifugal pump based on performance degradation, which relates to the field of reliability life prediction methods. The method includes the following steps: S1, constructing a cavitation rate model; S2, constructing a cavitation depth model; S3, calculating the cavitation rate model parameter A; S4, substituting the value of A obtained in step S3 and the values ​​of other actual parameters into the cavitation model to solve for the cavitation depth; S5, comparing the mouth ring gap calculated based on step S4 with the mouth ring gap threshold. When the mouth ring gap is greater than the mouth ring gap threshold, the centrifugal pump is judged to have failed. The present invention provides a process for establishing a centrifugal pump cavitation model, utilizes the relationship between the centrifugal pump flow rate and the mouth ring gap to infer the cavitation depth corresponding to different operating times, obtains the value of the cavitation depth parameter through experimental data, calculates the cavitation depth and the mouth ring gap using the parameter value during actual prediction, and performs life prediction based on the mouth ring gap. The life prediction process is simple, fast, and accurate.

Description

Technical Field

[0001] The present invention relates to the field of reliability life prediction methods, and in particular to a method and system for predicting the life of a seawater centrifugal pump based on performance degradation. Background Art

[0002] A centrifugal pump is a hydraulic machine that relies on the high-speed rotation of its impeller, forcing the liquid at its center to be ejected at high speed. This creates a low pressure at the center of the impeller, which continuously draws up liquid from the low-level tank. It converts the mechanical energy of the prime mover into kinetic and potential energy, thereby transporting fluids, increasing pressure, or providing propulsion. The uneven pressure of the water impinging on different areas of the pump's outlet surface creates bubbles that rapidly form and collapse. This continuously generates varying impact energy, which, in combination with the corrosive components of seawater (Cl and S), creates severe cavitation pits in localized areas of the impeller and casing surfaces. These pits rapidly erode under cavitation, gradually growing larger and deeper, and eventually collapsing. This increases the annular gap between the impeller and casing, known as the mouth ring gap. The mouth ring gap prevents high-pressure liquid at the impeller outlet from flowing back to the inlet, thereby improving pump efficiency. The size of the mouth ring gap has a direct impact on pump efficiency. Excessive gaps can reduce the efficiency of the centrifugal pump, resulting in degraded pressure and flow performance, and ultimately shortening the product life.

[0003] The location and depth of cavitation are significantly affected by the flow state of the medium within a centrifugal pump. Although cavitation is the primary cause of reduced centrifugal pump life, it is difficult to quantify and assess the amount of cavitation and use it to predict product life in practical engineering applications. This is due to the complex mechanism of cavitation formation and the difficulty of detection. First, quantitatively measuring the extent of cavitation in practical engineering requires complete disassembly of the centrifugal pump, which requires a long preparation time before testing. Disassembly and reassembly also affect the product's assembly state, affecting its stable operation. Second, the location and timing of cavitation are somewhat random, making it difficult to determine the optimal timing for detection. Third, cavitation can cause large areas of pits or spalling points on the impeller surface, with irregular shapes and depths. Detection is difficult regardless of the number or depth of cavitation points. Current methods for predicting product life using cavitation amount in engineering applications have significant limitations. Therefore, there is an urgent need for a method for predicting centrifugal pump life that can be applied in engineering and ensures accuracy. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for predicting the life of a seawater centrifugal pump based on performance degradation. The method can predict the life of the centrifugal pump based on the cavitation depth. It aims to infer the changes in the mouth ring gap at each radial position of the centrifugal pump through the performance degradation law of the centrifugal pump flow, establish a relationship between the mouth ring gap and the cavitation depth at each radial position of the centrifugal pump, construct a cavitation depth model of the centrifugal pump, and solve the parameters of the cavitation depth model of the centrifugal pump under specific working conditions. Finally, the cavitation depth and mouth ring gap are calculated using the cavitation depth model. The life of the centrifugal pump is predicted by comparing the calculated mouth ring gap with the mouth ring gap threshold. The prediction method is highly feasible and accurate.

[0005] Specifically, the present invention provides a method for predicting the life of a seawater centrifugal pump based on performance degradation, which comprises the following steps:

[0006] S1. Construct a cavitation rate model. The cavitation rate model is specifically as follows:

[0007] ER=A×WSS×v n

[0008] Where ER is the cavitation rate, in mm / year; A is the test constant, dimensionless; v is the water velocity, in m·s -1 ;WSS is the wall shear force, unit is Pa;n is the test-related constant, dimensionless;

[0009] S2. Constructing a cavitation depth model, specifically including the following sub-steps:

[0010] S21. Assuming that the centrifugal pump maintains the same damage rate under the same operating conditions, the cavitation depth H is expressed as:

[0011] H=ΔT×ER

[0012] Among them, ΔT is the operating time of the centrifugal pump in working condition, in years;

[0013] S22. Assuming that the water flow velocity on the impeller surface is the same as the impeller rotation linear velocity, the water flow velocity at the outlet ring position can be calculated based on the test speed. The water flow velocity calculation formula is:

[0014] v=2πr×N

[0015] Where r is the radius of the impeller ring, in mm; N is the impeller speed, in r / min;

[0016] S23. Construct a cavitation depth model:

[0017] H=ΔT×ER=A×ΔT×WSS×(2πr×N) n ;

[0018] S3, calculating the cavitation rate model parameter A, specifically comprising the following steps:

[0019] S31. The relationship between the cavitation depth and the ring clearance at each radial position of the centrifugal pump is as follows:

[0020]

[0021] Where, Δd is the gap between the mouth rings, in mm;

[0022] S32. Construct a relationship between the centrifugal pump mouth ring clearance and performance. When the relationship between the centrifugal pump mouth ring clearance and performance is linear, the relationship between the two is expressed as follows:

[0023] L=b-kΔd

[0024] Where L is the performance parameter; b and k are function parameters fitted based on the test data;

[0025] S33. Construct a calculation formula for parameter A in the cavitation erosion model and calculate the value of parameter A. The calculation formula for parameter A is as follows:

[0026]

[0027] S34, performing a life test on the seawater pump to obtain actual performance parameters, and calculating the value of parameter A in the cavitation model based on the calculation formula in step S33;

[0028] S4, bringing the value of A obtained in step S3 and the actual parameter value into the cavitation depth model to solve the cavitation depth, and further solve the actual mouth ring gap;

[0029] S5. Compare the actual mouth ring gap calculated based on step S4 with the mouth ring gap threshold. When the mouth ring gap is greater than the mouth ring gap threshold, it is determined that the centrifugal pump has failed.

[0030] Preferably, a simulation experiment is performed in step S34, and the value of parameter A is calculated through a set of simulation values.

[0031] Preferably, in step S32, the values ​​of b and k obtained by fitting using the least square method based on the known mouth ring gap and the corresponding performance parameters are 79.9591 and 7.8616 respectively.

[0032] Preferably, the performance parameter L in step S32 is flow rate.

[0033] Preferably, the actual parameter values ​​in step S4 are real-time operating data of the seawater centrifugal pump collected by sensors during the operation of the seawater centrifugal pump, and the real-time operating data of the seawater centrifugal pump include water flow velocity, wall shear force, impeller mouth ring position radius, impeller speed and test-related constant n.

[0034] Preferably, the real-time operating data of the seawater centrifugal pump is obtained through simulation or experiment.

[0035] Preferably, the accuracy of the cavitation depth model is determined by calculating the mouth-ring gap and cavitation depth corresponding to each flow value and comparing them with the cavitation depth calculated based on step S4 at the corresponding moment.

[0036] On the other hand, the present invention provides a centrifugal pump life prediction system based on a performance degradation-based seawater centrifugal pump life prediction method, which includes a cavitation rate model construction unit, a cavitation depth model construction unit, a cavitation rate model parameter calculation unit, a cavitation depth calculation unit, and a life prediction unit;

[0037] The cavitation rate model construction unit is used to construct a cavitation rate model; the cavitation depth model construction unit is used to construct a cavitation depth model; the cavitation rate model parameter calculation unit is used to calculate the cavitation rate model parameter A; the cavitation depth calculation unit is used to bring the value of A obtained in step S3 and the remaining actual parameter values ​​into the cavitation model to solve the cavitation depth; the life prediction unit is used to compare the calculated actual mouth ring gap with the mouth ring gap threshold, and when the mouth ring gap is greater than the mouth ring gap threshold, it is determined that the centrifugal pump has failed.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The life prediction method of a seawater centrifugal pump based on performance degradation of the present invention can predict the life of a centrifugal pump based on the cavitation depth. It aims to infer the change of the mouth ring gap at each radial position of the centrifugal pump through the performance degradation law of the centrifugal pump flow, establish the relationship between the mouth ring gap and the cavitation depth at each radial position of the centrifugal pump, construct a cavitation depth model of the centrifugal pump and solve the parameters of the cavitation depth model of the centrifugal pump under specific working conditions, and finally use the cavitation depth model to calculate the cavitation depth and further calculate the mouth ring gap. The life of the centrifugal pump is predicted by comparing the calculated mouth ring gap with the mouth ring gap threshold. The prediction method is simple, fast and accurate and can perform non-destructive prediction of the life of the centrifugal pump.

[0040] (2) The present invention proposes a life prediction method for seawater centrifugal pumps based on performance degradation, providing a feasible engineering method for life prediction of centrifugal pumps. The method gives the process of establishing a cavitation model of a centrifugal pump, and uses the relationship between the flow rate of the centrifugal pump and the mouth ring gap to calculate the cavitation amount corresponding to different working times. The parameters of the cavitation model are determined by calculating the life test data of a certain type of centrifugal pump. Through the practical case of a certain seawater centrifugal pump, the feasibility and effectiveness of the centrifugal pump life prediction method based on this technical method are preliminarily proved, and it can be applied in various occasions.

[0041] (3) The cavitation depth model of the present invention has high model accuracy and can quickly calculate the cavitation depth and the mouth ring gap and perform life prediction. The accuracy of the cavitation model calculation results is evaluated by the relative error evaluation method. It is found that the average relative error between the model calculation results and the experimental values ​​at each moment is 19.5%, which is less than 20%. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the relationship between the mouth ring gap and flow rate of the centrifugal pump of the present invention;

[0043] Figure 2 Schematic diagram of the overall process of the method for predicting the life of a seawater centrifugal pump based on performance degradation according to the present invention;

[0044] Figure 3 This is a structural block diagram of the centrifugal pump life prediction system of the present invention. DETAILED DESCRIPTION

[0045] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0046] The overall method of the present invention predicts the life of a centrifugal pump based on the cavitation depth. It aims to derive the change of the mouth ring gap at each radial position of the centrifugal pump through the performance degradation law of the centrifugal pump flow rate, establish the relationship between the mouth ring gap and the cavitation depth at each radial position of the centrifugal pump, construct a cavitation depth model of the centrifugal pump and solve the parameters of the cavitation depth model of the centrifugal pump under specific working conditions, and finally use the cavitation depth model to calculate the cavitation depth and further calculate the mouth ring gap, and predict the life of the centrifugal pump by comparing the calculated mouth ring gap with the mouth ring gap threshold.

[0047] The present invention provides a method for predicting the life of a seawater centrifugal pump based on performance degradation, such as Figure 1 and Figure 2 As shown, it includes the following steps:

[0048] S1. Construct a cavitation rate model. The cavitation rate model is specifically as follows:

[0049] ER=A×WSS×v n

[0050] Where ER is the cavitation rate, in mm / year; A is the test constant, dimensionless; v is the water velocity, in m·s -1 ; WSS is the wall shear force, unit is Pa; n is the test-related constant, dimensionless.

[0051] There are multiple evaluation models for quantitative cavitation damage, including one based on weight loss, damage area, number of pits, or cavitation depth. The present invention considers analyzing how cavitation causes changes in the mouth-ring gap, which in turn affects the flow rate of a centrifugal pump. Therefore, the cavitation depth is used to further select the mouth-ring gap to evaluate the flow performance, thereby predicting the life of the centrifugal pump.

[0052] S2. Constructing a cavitation depth model, specifically including the following sub-steps:

[0053] S21. Assuming that the centrifugal pump maintains the same damage rate under the same operating conditions, the cavitation depth H is expressed as:

[0054] H=ΔT×ER

[0055] Wherein, ΔT is the operating time of the centrifugal pump in working condition, expressed in years.

[0056] S22. Assuming that the water flow velocity on the impeller surface is the same as the impeller rotation linear velocity, the water flow velocity at the outlet ring position can be calculated based on the test speed. The water flow velocity calculation formula is:

[0057] v=2πr×N

[0058] Where r is the radius of the impeller mouth ring, in mm; N is the impeller speed, in r / min.

[0059] S23. Construct a cavitation depth model:

[0060] H=ΔT×ER=A×ΔT×WSS×(2πr×N) n .

[0061] S3, calculating the cavitation rate model parameter A, specifically comprising the following steps:

[0062] S31. The relationship between the cavitation depth and the ring clearance at each radial position of the centrifugal pump is as follows:

[0063]

[0064] Where Δd is the gap between the mouth ring and the unit is mm.

[0065] When the centrifugal pump's structural characteristics r, operating characteristics N and WSS, and operating time are known, only one set of cavitation depth data is needed to fit the value of parameter A. If it is assumed that cavitation occurs at the same speed at the centrifugal pump impeller diameter, and that the flow velocity on the casing surface is consistent with the flow velocity at the impeller diameter, and cavitation degradation also occurs at the same speed, the relationship between the cavitation depth and the ring clearance at each radial position of the centrifugal pump can be obtained.

[0066] S32. Construct a relationship between the centrifugal pump mouth ring clearance and performance. When the relationship between the centrifugal pump mouth ring clearance and performance is linear, the relationship between the two is expressed as follows:

[0067] L=b-kΔd

[0068] Where L is the performance parameter; b and k are function parameters fitted according to the test data.

[0069] Mechanism analysis shows that the mouth ring gap affects the performance of the centrifugal pump. By designing and conducting centrifugal pump performance tests under different mouth ring gaps, the centrifugal pump performance parameters corresponding to each mouth ring gap can be obtained. By analyzing the variation of centrifugal pump flow rate with the mouth ring gap and using the least squares method for fitting regression analysis, a mathematical function that expresses the relationship between centrifugal pump flow rate and mouth ring gap is obtained, namely, the centrifugal pump flow characteristic model under the influence of mouth ring gap.

[0070] In a specific embodiment, the performance parameter in this application is the flow rate of a centrifugal pump. The values ​​of b and k can be fitted using the known average flow rate and the known ring gap at different ring gaps. In one specific embodiment, this step uses the least squares method for fitting, and the values ​​of b and k obtained after fitting are 79.9591 and 7.8616, respectively.

[0071] S33. Construct a calculation formula for parameter A in the cavitation erosion model and calculate the value of parameter A. The calculation formula for parameter A is as follows:

[0072]

[0073] S34. Build a simulated experimental environment identical to the actual working conditions to simulate the actual working conditions of the seawater pump, conduct a life test on the seawater pump in the simulated experimental environment, and calculate the value of parameter A in the cavitation model based on the calculation formula in step S33 based on the actual performance parameters and other parameter values ​​obtained from the actual experiment.

[0074] In other embodiments, a simulation experiment can also be conducted on the seawater pump by building a simulation model based on actual working conditions, and a set of simulation performance parameters can be obtained through the simulation experiment. The value of parameter A can be obtained by fitting the obtained simulation performance parameters.

[0075] In one embodiment, the value of the cavitation model parameter A is obtained as follows:

[0076] A=4.8605e -44 .

[0077] S4. Substitute the value of A obtained in step S3 and the actual parameter value into the cavitation model to solve the cavitation depth and further solve the actual mouth ring gap. The actual parameter value in step S4 is to collect the real-time operation data of the seawater centrifugal pump during its operation. The real-time operation data of the seawater centrifugal pump includes water flow rate, wall shear force, impeller mouth ring position radius, impeller speed and experimental related constant N. In the specific collection, the water flow rate, wall shear force and impeller speed can be collected using sensors, and the experimental related constant N is taken as 6 according to the experience of Knapp et al. Alternatively, the real-time operation data of the seawater centrifugal pump can be obtained by conducting other experiments or simulations.

[0078] S5. Compare the ring gap calculated in step S4 with the actual ring gap threshold. If the actual ring gap is greater than the ring gap threshold, the centrifugal pump is determined to be faulty. The ring gap threshold is generally set based on the desired scenario and is generally factory-designed data.

[0079] This embodiment also includes verifying the accuracy of the model. Actual data is obtained to calculate the ring clearance and cavitation depth corresponding to each flow rate value. The accuracy of the cavitation depth model is then compared with the cavitation depth calculated in step S4 at the corresponding moment. This model verification demonstrates that this method is highly accurate and can be used for life prediction of seawater centrifugal pumps.

[0080] On the other hand, Figure 3 As shown, the present invention provides a centrifugal pump life prediction system based on performance degradation, which includes a cavitation rate model construction unit 1, a cavitation depth model construction unit 2, a cavitation rate model parameter calculation unit 3, a cavitation depth calculation unit 4 and a life prediction unit 5.

[0081] The cavitation rate model construction unit 1 is used to construct a cavitation rate model; the cavitation depth model construction unit 2 is used to construct a cavitation depth model; the cavitation rate model parameter calculation unit 3 is used to calculate the cavitation rate model parameter A; the cavitation depth calculation unit 4 is used to bring the value of A obtained in step S3 and the remaining actual parameter values ​​into the cavitation model to solve the cavitation depth; the life prediction unit 5 is used to compare the calculated actual mouth ring gap with the mouth ring gap threshold. When the mouth ring gap is greater than the mouth ring gap threshold, it is determined that the centrifugal pump has failed. Specific embodiments

[0083] The following examples illustrate the present invention in detail. This example utilizes life test data from a certain type of seawater centrifugal pump to implement a method for predicting the life of a seawater centrifugal pump based on performance degradation. Specifically, during centrifugal pump operation, cavitation on the impeller surface is associated with the rotational state. During startup or shutdown, the bubble generation and breakup on the impeller surface are unstable during the speed increase process, resulting in damage that differs from that under constant operating conditions. However, due to the relatively short startup and shutdown time history, performance degradation data under constant operating conditions is primarily used as a reference for evaluating cavitation-induced erosion.

[0084] In order to obtain the relationship between the mouth ring gap and the performance parameters and flow rate of the centrifugal pump, this embodiment uses a certain type of seawater centrifugal pump to carry out a life test. The initial measured value of the mouth ring gap of the test pump is 0.35mm. The minimum thickness of the gasket used to increase the mouth ring gap in the test is 0.3mm. During the experiment, 5 kinds of mouth ring gap values ​​were designed, and centrifugal pump performance tests were carried out under 5 kinds of mouth ring gaps to obtain the corresponding centrifugal pump flow values ​​under different mouth ring gaps under the same speed and initial inlet pressure conditions. Referring to the use conditions of the centrifugal pump, the speed value of the designed centrifugal pump is 4000r / min, the initial inlet pressure is 78MPa, and the final test data are as follows. Figure 1 shown.

[0085] According to the test results, the ring clearance of the centrifugal pump and the corresponding flow rate are approximately linearly related. In this embodiment, the relationship function between the ring clearance of the centrifugal pump and the corresponding flow rate is obtained by fitting the least squares method based on the known ring clearance of the centrifugal pump and the corresponding flow rate as follows:

[0086] L=79.9591-7.8616Δd

[0087] Where, L is the performance parameter; Δd is the mouth ring gap.

[0088] Referring to Knapp's parameter values, take n=6, combine the specific values ​​of other parameters, and calculate the A value based on the calculation formula of parameter A through experimental data.

[0089] Finally, the calculated value of the cavitation model parameter A is:

[0090] A=4.8605e -44 .

[0091] If it is assumed that cavitation occurs at the same speed at the impeller diameter of the centrifugal pump, and the flow velocity on the shell surface is consistent with the flow velocity at the impeller diameter, and cavitation degradation also occurs at the same speed, the relationship between the cavitation depth and the ring clearance at each radial position of the centrifugal pump and the centrifugal pump flow rate can be obtained as follows:

[0092]

[0093] Assuming the impeller surface water velocity is the same as the impeller's linear velocity, the water velocity at the outlet ring is calculated based on the test speed as: v = 2πr × N. In this example, r represents the impeller outlet ring radius, which is 120 mm. N represents the impeller speed, which is 4000 r / min based on the test conditions. The wall shear force is 1.6 MPa.

[0094] Then, the cavitation depth model is specifically expressed as:

[0095] H=ΔT×ER=4.8605e -44 ΔT×WSS×(2πr×N) 6 .

[0096] The mouth ring gap is calculated based on the calculated cavitation depth and the relationship between the cavitation depth and the mouth ring gap.

[0097] The calculated mouth ring gap is compared with the actual mouth ring gap threshold at that moment. When the actual mouth ring gap is greater than the mouth ring gap threshold at that moment, the centrifugal pump is judged to have failed. The mouth ring gap threshold is set according to needs, generally the mouth ring gap corresponding to the factory designed life value.

[0098] Finally, the accuracy of the cavitation depth model was verified: a verification life test was carried out using a seawater centrifugal pump of the same model, and the changes in the centrifugal pump outlet flow rate were shown in Table 1.

[0099] Table 1 Verification test results record of centrifugal pump

[0100]

[0101] The design parameters and test conditions of a seawater centrifugal pump are set as follows: speed 4000 r / min, impeller radius 120 mm, wall shear force 1.2 MPa, and the calculated cavitation depth is obtained by substituting the cavitation depth model into the following:

[0102] H=ΔT×ER=4.8605e -44 ΔT×WSS×(2πr×N) 6 .

[0103] Afterwards, an experiment was conducted. The flow characteristics of the centrifugal pump obtained from the experiment were used to calculate the mouth ring gap and cavitation depth corresponding to each flow value. The cavitation depth calculated through the experiment was compared with the cavitation depth calculated by the cavitation model at the corresponding time. The comparison results are shown in Table 2.

[0104] Table 2 Comparison of experimental and simulation strain values ​​after model correction

[0105]

[0106]

[0107] Based on the above comparison results, the accuracy of the cavitation model calculation results was evaluated by the relative error evaluation method. It was found that the average relative error between the model calculation results and the experimental values ​​at each moment was 15.87%, which is less than 20%. It is believed that the current impeller cavitation model parameter acquisition method is feasible, the parameter values ​​are reasonable, and the model accuracy is high.

[0108] The lifespan of centrifugal pumps used in testing is limited by two factors: First, the product is considered to have reached its end of life when performance values ​​such as flow and pressure fall below design thresholds; second, the product is considered to have reached its end of life when physical quantities such as the ring clearance or geometric characteristics of components such as the impeller irreversibly change below their design thresholds. Due to the high safety design margins, operating a centrifugal pump under harsh test conditions to its full lifespan is both time-consuming and costly. Therefore, the prediction of product lifespan is illustrated here using the ring clearance as an example.

[0109] The total duration of this life test was 14,700 minutes. After the test, the flow rate was 70.98 mm³, and the ring gap was 1.03857 mm. Substituting the test conditions and test duration into the impeller cavitation model confirmed above, the cavitation depth was calculated as:

[0110] H=ΔT×ER=4.8605e -44 ×14700×1.2×(2π×120×4000) 6 =0.645mm.

[0111] The calculated predicted value of the mouth ring gap is 1.29mm. Through the calculation of relative error, the error of the predicted value is 19.5%, which is less than 20%. The current prediction result is considered reliable.

[0112] In summary, this invention provides a feasible engineering prediction method for centrifugal pump lifespan. This method describes the process of establishing a centrifugal pump cavitation model, uses the relationship between centrifugal pump flow rate and ring clearance to infer the cavitation depth corresponding to different operating times, and calculates the parameters of the cavitation model using life test data from a certain type of centrifugal pump for further lifespan prediction. The feasibility and effectiveness of this method for centrifugal pump lifespan prediction have been preliminarily demonstrated through practical application on a seawater centrifugal pump. This method can be applied in a variety of situations to quickly and accurately predict the lifespan of seawater centrifugal pumps.

[0113] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for predicting the life of a seawater centrifugal pump based on performance degradation, characterized by: It includes the following steps: S1. Construct a cavitation rate model. The cavitation rate model is specifically as follows: ； Wherein, ER is the cavitation rate, in mm / year; A is the cavitation rate model parameter; is the water flow velocity, in units of ;WSS is the wall shear force, unit is Pa;n is the test-related constant, dimensionless; S2. Constructing a cavitation depth model, specifically including the following sub-steps: S21. Assuming that the centrifugal pump maintains the same damage rate under the same operating conditions, the cavitation depth H is expressed as: ； in, The operating time of the centrifugal pump in working condition, in years; S22. Assuming that the water flow velocity on the impeller surface is the same as the impeller rotation linear velocity, the water flow velocity at the outlet ring position can be calculated based on the test speed. The water flow velocity calculation formula is: ； Where r is the radius of the impeller ring, in mm; N is the impeller speed, in r / min; S23. Construct a cavitation depth model: ； S3. Calculate cavitation rate model parameters , specifically including the following steps: S31. The relationship between the cavitation depth and the ring clearance at each radial position of the centrifugal pump is as follows: ； Where, is the mouth ring gap, in mm; S32. Construct a relationship between the centrifugal pump mouth ring clearance and performance. When the relationship between the centrifugal pump mouth ring clearance and performance is linear, the relationship between the two is expressed as follows: ； Where L is the performance parameter, the performance parameter is the flow rate; b, k are the function parameters fitted according to the test data; S33. Construct a calculation formula for parameter A in the cavitation erosion model and calculate the value of parameter A. The calculation formula for parameter A is as follows: ； S34, performing a life test on the seawater pump to obtain actual performance parameters, and calculating the value of parameter A in the cavitation model based on the calculation formula in step S33; S4, bringing the value of A obtained in step S3 and the actual parameter value into the cavitation depth model to solve the cavitation depth, and further solve the actual mouth ring gap; S5. Compare the actual mouth ring gap calculated based on step S4 with the mouth ring gap threshold. When the mouth ring gap is greater than the mouth ring gap threshold, it is determined that the centrifugal pump has failed.

2. The method for predicting the life of a seawater centrifugal pump based on performance degradation according to claim 1, characterized in that: In step S34, a simulation experiment is performed to calculate the value of parameter A through a set of simulation values.

3. The method for predicting the life of a seawater centrifugal pump based on performance degradation according to claim 1, characterized in that: In step S32, the values ​​of b and k are obtained by fitting the known ring gap and the corresponding performance parameters using the least square method. , .

4. The method for predicting the life of a seawater centrifugal pump based on performance degradation according to claim 1, characterized in that: The actual parameter values ​​in step S4 are collected during the operation of the seawater centrifugal pump, and the real-time operation data of the seawater centrifugal pump includes water flow velocity, wall shear force, impeller ring position radius, impeller speed and test-related constant n.

5. The method for predicting the life of a seawater centrifugal pump based on performance degradation according to claim 4, characterized in that: The real-time operating data of the seawater centrifugal pump is obtained through simulation or experiments.

6. The method for predicting the life of a seawater centrifugal pump based on performance degradation according to claim 1, characterized in that: The accuracy of the cavitation depth model is determined by calculating the mouth ring gap and cavitation depth corresponding to each flow value and comparing them with the cavitation depth calculated based on step S4 at the corresponding moment.

7. A centrifugal pump life prediction system for the seawater centrifugal pump life prediction method based on performance degradation according to claim 1, characterized in that: It includes a cavitation rate model construction unit, a cavitation depth model construction unit, a cavitation rate model parameter calculation unit, a cavitation depth calculation unit and a life prediction unit; The cavitation rate model construction unit is used to construct a cavitation rate model; the cavitation depth model construction unit is used to construct a cavitation depth model; the cavitation rate model parameter calculation unit is used to calculate the cavitation rate model parameters ; The cavitation depth calculation unit is used to bring the value of parameter A obtained in step S3 and the other actual parameter values ​​into the cavitation model to solve the cavitation depth; the life prediction unit is used to compare the calculated actual mouth ring gap with the mouth ring gap threshold. When the mouth ring gap is greater than the mouth ring gap threshold, it is judged that the centrifugal pump has failed.

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