Method and system for predicting service life of seawater centrifugal pump based on performance degradation

Abstract

The invention provides a seawater centrifugal pump service life prediction method and system based on performance degradation, and relates to the field of reliability service life prediction methods.The seawater centrifugal pump service life prediction method comprises the following steps that S1, a cavitation erosion rate model is constructed; s2, constructing a cavitation erosion depth model; s3, calculating a cavitation rate model parameter A; s4, the value of A obtained in the step S3 and other actual parameter values are substituted into a cavitation model, and the cavitation depth is solved; and S5, the wear-ring gap calculated based on the step S4 is compared with a wear-ring gap threshold value, and when the wear-ring gap is larger than the wear-ring gap threshold value, it is judged that the centrifugal pump fails. According to the method, the building process of the centrifugal pump cavitation model is given, the cavitation depths corresponding to different working times are calculated according to the relation between the centrifugal pump flow and the wear-ring gap, the values of cavitation depth parameters are obtained through experimental data, the cavitation depths and the wear-ring gap are calculated through the parameter values in the actual prediction process, and the service life is predicted based on the wear-ring gap. The life prediction process is simple, rapid and accurate.

Description

Technical Field

[0001] The 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 the impeller to force the liquid in the center of the impeller to be thrown away at a very high speed, thereby forming a low pressure in the center of the impeller, and the liquid in the low-level tank is continuously sucked up. It converts the mechanical energy of the prime mover into fluid kinetic energy and potential energy, thereby achieving fluid transportation, pressurization or providing propulsion power. The water flow impacts different areas of the outlet surface of the pump body. The uneven pressure of the various parts of the water body in contact with the impeller causes bubbles to form and collapse rapidly, continuously generating different impact energy, and synergizing with the corrosive components of seawater (Cl and S), so that local areas of the impeller and the shell surface form severe cavitation pits, which quickly peel off under the action of cavitation, gradually become larger and deeper, and then severely rupture, resulting in the enlargement of the annular gap between the impeller and the pump casing in the centrifugal pump, that is, the centrifugal pump mouth ring gap enlargement. The function of the mouth ring gap is to prevent the high-pressure liquid at the impeller outlet from flowing back to the inlet end to improve the efficiency of the pump. The size of the mouth ring gap has a direct impact on the efficiency of the pump. Too large a gap will lead to a reduced efficiency centrifugal pump, which is reflected in the performance degradation of pressure and flow, and ultimately affects the product life.

[0003] The location and depth of cavitation are greatly affected by the flow state of the medium in the centrifugal pump. Although it is the main reason for the reduction of the life of the centrifugal pump, it is difficult to quantify the amount of cavitation and use it to predict the product life in engineering practice. The reason is that the formation mechanism of cavitation is complex and difficult to detect. First, in engineering practice, to quantitatively detect the degree of cavitation, the centrifugal pump needs to be completely disassembled, and the preparation time before detection is long. Disassembly and reassembly will affect the assembly state of the product, affecting the stable use of the product; second, the location and time of cavitation are somewhat random, and it is difficult to determine a good time for detection; third, cavitation may cause patches of pits or peeling points on the impeller surface, and the shape and depth are irregular. Whether it is detected from the perspective of the number or depth of cavitation points, the detection is difficult. The current method of using cavitation to predict product life in engineering applications has considerable limitations. Therefore, it is urgent to propose a method for predicting the life of a centrifugal pump that can be applied in engineering and ensure 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 a centrifugal pump based on the cavitation depth, and 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 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, 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 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. The prediction method has high feasibility and high accuracy.

[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, in Pa; n is the test-related constant, dimensionless;

[0009] S2. Constructing a cavitation depth model, which specifically includes 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 the cavitation depth model as follows:

[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 clearance between the centrifugal pump rings at each radial position is as follows:

[0020]

[0021] Where, Δd is the mouth ring gap, unit is 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 a linear relationship, the relationship between the two is expressed as follows:

[0023] L=b-kΔd

[0024] In the formula, L is the performance parameter; b, k are function parameters fitted according to the test data;

[0025] S33, constructing a calculation formula for parameter A in the cavitation model and calculating 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, solving the cavitation depth, and further solving 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 numerical 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 value in step S4 is the real-time operation data of the seawater centrifugal pump collected by sensors 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 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 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, 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, and provides 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 a relative error evaluation method. It is found that the average relative error between the model calculation results and the test values ​​at each moment is 19.5%, which is less than 20%. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0044] Figure 3 It 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 drawings.

[0046] The overall method of the present invention predicts the life of a centrifugal pump based on the cavitation depth, and 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, in Pa; n is a test-related constant, dimensionless.

[0051] There are multi-angle evaluation models for quantitative damage of cavitation, and there is a set of evaluation methods for weight loss, damage area, number of pits or cavitation depth. The present invention considers analyzing the change of mouth ring gap caused by cavitation, thereby affecting the flow rate of the centrifugal pump. Therefore, the cavitation depth is selected 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, which specifically includes 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] Among them, ΔT is the operating time of the centrifugal pump in working condition, 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] Wherein, r is the radius of the impeller mouth ring, in mm; N is the impeller speed, in r / min.

[0059] S23, construct the cavitation depth model as follows:

[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 clearance between the centrifugal pump rings at each radial position is as follows:

[0063]

[0064] Where Δd is the mouth ring gap, in mm.

[0065] When the centrifugal pump structural characteristics r, working characteristics N and WSS, and running 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 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 mouth 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 a linear relationship, 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] According to the mechanism analysis, it can be known that the mouth ring gap affects the working performance of the centrifugal pump. The centrifugal pump performance parameters corresponding to each mouth ring gap can be obtained by designing and conducting centrifugal pump performance tests under different mouth ring gaps. By analyzing the change law of centrifugal pump flow with the mouth ring gap, the least squares method is used for fitting regression analysis to obtain a mathematical function that expresses the relationship between the centrifugal pump flow and the mouth ring gap, that is, the centrifugal pump flow characteristic model under the influence of the mouth ring gap.

[0070] In a specific embodiment, the performance parameter in the present application is the flow rate of the centrifugal pump, and the values ​​of b and k can be fitted by the known average flow rate and the mouth ring gap under different mouth ring gaps. In a 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, constructing a calculation formula for parameter A in the cavitation model and calculating the value of parameter A. The calculation formula for parameter A is as follows:

[0072]

[0073] S34. Build a simulated experimental environment that is the same as the actual working condition to simulate the actual working condition of the seawater pump, conduct a life experiment 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 carried out on the seawater pump by building a simulation model based on actual working conditions, a set of simulation performance parameters can be obtained through the simulation experiment, and 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, bring the value of A obtained in step S3 and the actual parameter value into the cavitation model, 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 the operation of the seawater centrifugal pump. The real-time operation data of the seawater centrifugal pump includes water flow velocity, wall shear force, impeller mouth ring position radius, impeller speed and test-related constant n. In the specific collection, the water flow velocity, wall shear force and impeller speed can be collected using sensors, and the test-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, comparing the mouth ring gap calculated based on step S4 with the actual mouth ring gap threshold, and when the actual mouth ring gap is greater than the mouth ring gap threshold, the centrifugal pump is judged to be failed. The mouth ring gap threshold is generally set according to the required scenario, and the data is generally the design factory data.

[0079] In this embodiment, the accuracy of the model is also verified. The mouth ring gap and cavitation depth corresponding to each flow value are calculated by obtaining actual data, and the accuracy of the cavitation depth model is judged by comparing with the cavitation depth calculated based on step S4 at the corresponding moment. Through model verification, it can be concluded that the accuracy of this method is high 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 building unit 1, a cavitation depth model building 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, and when the mouth ring gap is greater than the mouth ring gap threshold, it is judged that the centrifugal pump has failed. Specific embodiments

[0083] The content of the present invention is described in detail through examples below. This example relies on the life test data of a certain type of seawater centrifugal pump to implement a seawater centrifugal pump life prediction method based on performance degradation. Specifically, during the operation of the centrifugal pump, the cavitation phenomenon on the impeller surface is related to the rotation state. During the speed increase during startup or shutdown, the bubble generation and fragmentation state on the impeller surface is unstable, and the damage caused is different from that under constant working conditions. However, due to the short startup or shutdown time history, the performance degradation data under constant working conditions is mainly used to evaluate the cavitation caused by cavitation.

[0084] In order to obtain the relationship between the mouth ring clearance and performance parameters and flow rate of a 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 clearance of the test pump is 0.35mm. The minimum thickness of the gasket used to increase the mouth ring clearance in the test is 0.3mm. During the experiment, 5 kinds of mouth ring clearance values ​​were designed, and centrifugal pump performance tests were carried out under 5 kinds of mouth ring clearances to obtain the corresponding centrifugal pump flow values ​​under different mouth ring clearances 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, and the initial inlet pressure is 78MPa. The final test data is as follows Figure 1 shown.

[0085] According to the test results, it can be seen that the mouth ring gap of the centrifugal pump and the corresponding flow rate are approximately linearly related. In this embodiment, the relationship function between the mouth ring gap and the corresponding flow rate of the known centrifugal pump is obtained by fitting the least square method as follows:

[0086] L=79.9591-7.8616Δd

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

[0088] Referring to Knapp's parameter values, n=6 is taken, and combined with the specific values ​​of other parameters, the A value is calculated 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 also degenerates at the same speed, the relationship between the cavitation depth and the mouth ring clearance at each radial position of the centrifugal pump and the flow rate of the centrifugal pump can be obtained as follows:

[0092]

[0093] 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 is calculated based on the test speed: v = 2πr × N. In this embodiment, r is the radius of the impeller outlet ring position, which is 120 mm; N is 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 through 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 as needed, 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 centrifugal pump result record

[0100]

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

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

[0103] After that, 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 was 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 life of the centrifugal pump used for the test is limited by two aspects. First, when the performance values ​​such as flow and pressure are lower than the design threshold, the product is considered to have reached the end of its life. Second, when the physical quantities such as the mouth ring clearance or the geometric characteristics of the impeller and other components change irreversibly below the design threshold, the product is considered to have reached the end of its life. Due to the high safety design margin of the product, it takes too long and the test cost is too high to operate the centrifugal pump under harsh test conditions until the product life. Here, the prediction of the product life is explained through the mouth ring clearance.

[0109] The total duration of this verification life test was 14700 minutes. After the experiment, the flow detection value was 70.98mm3, and the size of the mouth ring gap was 1.03857mm. 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 predicted value of the mouth ring gap is calculated to be 1.29 mm. Through the calculation of relative error, the error of the predicted value is 19.5%, which is less than 20%, and the current prediction result is considered reliable.

[0112] In summary, the present invention provides a feasible engineering prediction method for the life prediction of centrifugal pumps. The method provides the process of establishing the cavitation model of centrifugal pumps, and uses the relationship between the flow rate of centrifugal pumps and the mouth ring gap to infer the cavitation depth 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, which are further used for life prediction. And 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, which can be applied in a variety of occasions to quickly and accurately predict the life of seawater centrifugal pumps.

[0113] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design 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 all fall within the protection scope 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 in that: It includes the following steps: S1. Construct a cavitation rate model. The cavitation rate model is specifically as follows: ER=A×WSS×v n 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, in Pa; n is the test-related constant, dimensionless; S2. Constructing a cavitation depth model, which specifically includes 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: H=ΔT×ER Among them, ΔT is 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: v=2πr×N Where r is the radius of the impeller ring, in mm; N is the impeller speed, in r / min; S23, construct the cavitation depth model as follows: H=ΔT×ER=A×ΔT×WSS×(2πr×N) n ; S3, calculating the cavitation rate model parameter A, specifically comprising the following steps: S31. The relationship between the cavitation depth and the clearance between the centrifugal pump rings at each radial position is as follows: Where, Δd is the mouth ring gap, unit is 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 a linear relationship, the relationship between the two is expressed as follows: L=b-kΔd In the formula, L is the performance parameter; b, k are function parameters fitted according to the test data; S33, constructing a calculation formula for parameter A in the cavitation model and calculating 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, solving the cavitation depth, and further solving 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 is characterized in that: In step S34, a simulation experiment is performed to calculate the value of parameter A through a set of simulation numerical values.

3. The method for predicting the life of a seawater centrifugal pump based on performance degradation according to claim 1 is characterized in that: In step S32, the values ​​of b and k are 79.9591 and 7.8616 respectively obtained by fitting using the least square method based on the known mouth ring gap and the corresponding performance parameters.

4. The method for predicting the life of a seawater centrifugal pump based on performance degradation according to claim 1 is characterized in that: In step S32, the performance parameter L is flow rate.

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

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

7. The method for predicting the life of a seawater centrifugal pump based on performance degradation according to claim 1 is 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.

8. A centrifugal pump life prediction system for the seawater centrifugal pump life prediction method based on performance degradation as claimed in claim 1, characterized in that: It includes a cavitation rate model building unit, a cavitation depth model building 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 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.

Images