A method for evaluating vibration fatigue life of a disc pump under internal flow action

Abstract

The application provides a disc pump vibration fatigue life evaluation method under internal flow action and belongs to the technical field of offshore oil engineering. The method comprises the following steps: a disc pump model is established; a transient fluid-structure coupling calculation is performed on the pump body structure to obtain a pump body internal flow pulsating pressure time domain load; the pump body displacement time domain load is calculated by using ANSYS with the internal flow pulsating pressure time domain load as input; the pump body displacement time domain load is processed by using software to obtain a pump body acceleration power spectral density; a harmonic response analysis is performed by using ANSYS to obtain a pump body acceleration load frequency response curve; and pump body fatigue life evaluation is performed based on the pump body acceleration power spectral density and a material SN curve. The application can accurately evaluate the fatigue life of the disc pump by establishing a model of vibration and fatigue caused by internal flow pulsating pressure and by using a finite element software simulation calculation method, thereby improving the design quality of the disc pump, reducing maintenance costs and prolonging the service life of the disc pump.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of offshore oil engineering, and particularly relates to a vibration fatigue life evaluation method of a disc pump under internal flow action. BACKGROUND

[0002] A disc pump is a fluid conveying device widely used in the fields of offshore oil and gas, deep-sea mining, chemical industry, and water treatment. Its working principle is to generate negative pressure through the rotation or oscillation of the disc, thereby sucking and discharging the liquid. The disc pump is favored due to its compact structure, high working efficiency, wear resistance, and ability to transport large particles. During operation, the disc pump often suffers from vibration, which may be caused by factors such as imbalance, mechanical friction, and fluid turbulence. Long-term vibration can lead to material fatigue of the disc pump, affecting the service life of the equipment, and even causing the failure of the equipment. Evaluating the fatigue life of the disc pump is crucial to ensure its reliability and safety. Traditional fatigue life prediction methods often rely on experimental data and empirical formulas, which cannot fully reflect the complex working environment and actual operating conditions. Currently, many fatigue life evaluation methods do not consider the complexity and variability of vibration, resulting in insufficient accuracy and reliability of the evaluation results. At the same time, with the continuous development of new materials and new technologies, existing methods need to be updated and improved. Therefore, it is of great significance to develop a new evaluation method. SUMMARY

[0003] Therefore, the present application aims to provide a vibration fatigue life evaluation method of a disc pump under internal flow action, which can accurately evaluate the fatigue life of the disc pump by establishing a model between the vibration caused by internal flow pulsating pressure and fatigue, and using finite element software simulation calculation method, thereby improving the design quality of the disc pump, reducing maintenance costs, and prolonging the service life of the disc pump.

[0004] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows: a vibration fatigue life evaluation method of a disc pump under internal flow action, comprising the following steps:

[0005] Step 1: establishing a disc pump model;

[0006] Step 2: performing transient fluid-structure coupling calculation on the pump body structure to obtain the internal flow pulsating pressure time domain load of the pump body, and using ANSYS to calculate the pump body displacement time domain load based on the input;

[0007] Step 3: processing the pump body displacement time domain load using Matlab software and origin software to obtain the pump body acceleration power spectral density;

[0008] Step 4: performing harmonic response analysis using ANSYS to obtain the pump body acceleration load frequency response curve;

[0009] Step 5, pump body fatigue life assessment based on pump body acceleration power spectral density and material SN curve.

[0010] Further, step 2 includes:

[0011] Step 21, using computer finite element simulation software ANSYS Fluent module and static structure analysis module to calculate the transient fluid-structure coupling of the pump body structure, and calculate the numerical value of the pressure change with time at different positions in the pump body internal flow area;

[0012] Step 22, export the finite element analysis result file in step 21, import ANSYS CFD-Post module for data processing, set several monitoring points in the rotor area, oil suction area and oil discharge area of the disc pump, and extract the pressure change with time;

[0013] Step 23, compare the pressure change curves of each monitoring point with time, select the area with the largest change for analysis; use the pressure change curve extracted in step 22 as the load input, and use computer finite element simulation software ANSYS to perform static structure analysis to obtain the pump body displacement time domain load.

[0014] Further, step 3 includes:

[0015] Step 31, compare the displacement time domain loads of the several monitoring points set in step 22, select the monitoring point with the largest displacement time domain load change, and extract the pump body displacement time domain load at this point;

[0016] Step 32, use computer origin drawing software to perform second-order differential processing on the pump body displacement change curve in step 31 to obtain the acceleration change curve with time;

[0017] Step 33, use Matlab software to perform fast Fourier transform on the acceleration change curve with time to obtain the acceleration frequency domain load, and further calculate the acceleration power spectral density.

[0018] Further, step 4 includes:

[0019] Step 41, use ANSYS software to perform modal analysis on the pump body structure of the disc pump, and give the disc pump support fixed constraint;

[0020] Step 42, perform harmonic response analysis on the pump body of the disc pump, apply a unit g lateral acceleration load, and use the results of the modal analysis in step 41 as the initial condition for analysis to obtain the disc pump acceleration load frequency response curve.

[0021] Further, step 5 comprises: using the harmonic response analysis result in step 4 as an initial condition, using the ANSYS n-Code module, defining the input pump body acceleration power spectral density, defining the material attribute mapping of the pump body, performing fatigue life calculation, obtaining the pump body loss cloud map and the fatigue life cloud map, and evaluating the vibration fatigue life of the disc pump pump body.

[0022] Compared with the prior art, the disc pump vibration fatigue life evaluation method under the action of internal flow has the following advantages: the model of vibration and fatigue caused by internal flow pulsating pressure is established, the fatigue life of the disc pump is accurately evaluated through the finite element software simulation calculation method, the design quality of the disc pump is improved, the maintenance cost is reduced, and the service life of the disc pump is prolonged.

[0023] (1) For the method of evaluating the fatigue life of the pump body by using the empirical formula in the past, the finite element software is used to establish the fatigue calculation model of the pump body under the action of internal flow, so that the fatigue evaluation has more reference significance;

[0024] (2) The finite element simulation software ANSYS Fluent module and the static structure analysis module are used to perform transient fluid-structure coupling calculation on the pump body structure, so that the extracted pump body displacement time domain load is more accurate, and a foundation is laid for subsequent accurate fatigue life evaluation;

[0025] (3) The ANSYS n-Code module is used to define the input pump body acceleration power spectral density, define the material attribute mapping of the pump body, and perform fatigue life calculation. In this calculation method, the statistical properties of the power spectral density are more suitable for the fatigue life evaluation of the pump body working in the frequency domain in the random vibration environment. DETAILED DESCRIPTION

[0026] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the present application illustrated in the drawings and their descriptions are used to explain the present application and are not intended to limit the present application. In the drawings:

[0027] Figure 1 The technical flow chart of the method of the present application is shown in the figure;

[0028] Figure 2 The finite element model of the disc pump is shown in the figure;

[0029] Figure 3 The material SN curve of the disc pump is shown in the figure;

[0030] Figure 4 The model of the disc pump after fixing the bottom support is shown in the figure;

[0031] Figure 5 The pressure fluctuation curve of the pump body rotor area monitoring point is shown in the figure;

[0032] Figure 6 Load definition for pump body harmonic response analysis;

[0033] Figure 7 This is a graph showing the pump body's frequency response.

[0034] Figure 8 The graph shows the calculation results of the pump body fatigue life.

[0035] Figure 9 The diagram shows the calculation results of pump body fatigue damage. Detailed Implementation

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] like Figures 1-9 As shown, this invention provides a method for assessing the vibration fatigue life of a disc pump under internal flow conditions. The method mainly includes obtaining the power spectral density (PSD) spectrum of the pump body using numerical simulation, deriving the pump body's vibration frequency response curve based on harmonic response analysis, and assessing the pump body's fatigue life based on the PSD spectrum and material SN curves. This method eliminates the need for experiments and allows for direct assessment of the disc pump's vibration fatigue life through numerical simulation. It effectively avoids dangerous frequencies and operating conditions during disc pump use, extending its service life. Specifically, the method includes the following steps:

[0039] Step 1: Establish a disc pump model;

[0040] Step 2 involves performing transient fluid-structure interaction calculations on the pump body structure to obtain the time-domain load of the pulsating pressure within the pump body. Using this as input, ANSYS is used to calculate the time-domain load of the pump body displacement. Specifically, this includes:

[0041] Step 21: Use the ANSYS Fluent module and static structure analysis module of the computer finite element simulation software to perform transient fluid-structure interaction calculations on the pump body structure, and calculate the values ​​of pressure changes over time at different locations in the flow region inside the pump body.

[0042] Step 22: Export the finite element analysis result file from Step 21, import it into the ANSYS CFD-Post module for data processing, set up several monitoring points in the rotor area, suction area, and discharge area of ​​the disc pump, and extract the pressure change over time.

[0043] Step 23: Compare the pressure change curves of each monitoring point over time, and select the area with the largest change for analysis; use the pressure change curve extracted in step 22 as the load input, and use the computer finite element simulation software ANSYS to perform static structural analysis to obtain the pump body displacement cloud map that changes over time, i.e., the pump body displacement time-domain load.

[0044] Step 3: Process the pump body displacement time-domain load using Matlab and Origin software to obtain the pump body acceleration power spectral density (PSD spectrum); specifically, this includes:

[0045] Step 31: Compare the displacement time-domain loads of several monitoring points set in Step 22, select the monitoring point with the largest change in displacement time-domain load, and extract the displacement time-domain load of the pump body at this point.

[0046] Step 32: Use the computer Origin plotting software to perform second-order differential processing on the pump body displacement versus time curve in Step 31 to obtain the acceleration versus time curve.

[0047] Step 33: Use Matlab software to perform a Fast Fourier Transform (FFT) on the acceleration versus time curve to obtain the acceleration frequency domain load, and further calculate the acceleration power spectral density (PSD) spectrum. The basic FFT code is as follows:

[0048] clc;

[0049] Data15 = xlsread('acc.xlsx')

[0050] y=Data15 (:,2)

[0051] Fs=1000

[0052] T=1 / Fs

[0053] N=length(y)

[0054] t=(0:1:N-1)*T

[0055] t=t'

[0056] figure

[0057] plot(t,y)

[0058] xlabel('time')

[0059] ylabel('signal value')

[0060] Y=fft(y)

[0061] Y=Y(1:N / 2+1)

[0062] A = abs(Y)

[0063] f=(0:1:N / 2)*Fs / N

[0064] f=f'

[0065] A_adj=zeros(N / 2+1,1)

[0066] A_adj(1)=A(1) / N

[0067] A_adj(end) = A(end) / N

[0068] A_adj(2:end-1)=2*A(2:end-1) / N

[0069] figure

[0070] plot(f,A_adj)

[0071] xlabel('Frequency (Hz)')

[0072] ylabel('amplitude')

[0073] Step 4: Perform harmonic response analysis using ANSYS to obtain the pump body acceleration load frequency response curve, i.e., the pump body vibration frequency response curve; specifically, this includes:

[0074] Step 41: Use ANSYS software to perform modal analysis on the pump body structure of the disc pump and give fixed constraints on the disc pump support.

[0075] Step 42: Perform harmonic response analysis on the pump body of the disc pump. Apply a lateral acceleration load of unit g and use the results of the modal analysis in step 41 as the initial conditions to perform the analysis and obtain the frequency response curve of the disc pump under acceleration load.

[0076] After verifying from the modal analysis results that no resonance phenomenon will occur, the frequency response curve can be used to determine the frequency range at which the acceleration load frequency has a significant impact on the pump body life.

[0077] Harmonic response analysis is used to determine the steady-state response of a linear structure under sinusoidal loads at different frequencies, yielding the single-degree-of-freedom frequency response function H(ω). In engineering, amplitude and phase can be described separately or in complex form.

[0078]

[0079] The amplitude of the frequency response function is the ratio of the input amplitude to the output amplitude, that is:

[0080]

[0081] The ratio of the imaginary part to the real part of the frequency response function is equal to the tangent of the phase angle, i.e.:

[0082]

[0083] According to the random vibration theory, the response RPSD of the power spectral density is defined by multiplying the input power spectral density by the transfer function, and the formula is as follows:

[0084]

[0085] In the formula, is the spectral density input (from the input PSD curve);

[0086] is the spectral density response;

[0087] is the single degree of freedom input;

[0088] is the single degree of freedom output obtained by analysis;

[0089] is the single degree of freedom frequency response function; is the imaginary unit; and A are the same designator, both of which are the real part of the frequency response function; and B are the same designator, both of which are the imaginary part of the frequency response function; is the phase angle.

[0090] Step 5, fatigue life evaluation of the pump body based on the PSD spectrum and the material SN curve, specifically:

[0091] The harmonic response analysis result in step 4 is used as the initial condition, the ANSYS n-Code module is used, the input acceleration power spectral density PSD spectrum is defined, the material properties of the pump body are assigned, the material SN curve is defined, the fatigue life calculation is performed, and the pump body loss cloud and the fatigue life cloud are obtained, i.e. the vibration fatigue life of the pump body of the disc pump can be evaluated.

[0092] The present application obtains the vibration response of the pump body under the action of internal and external flow through harmonic response analysis, mainly the unstable flow in the centrifugal pump significantly affects the energy conversion and hydraulic performance of the pump, and the pressure pulsation in the fluid is the main excitation source causing vibration; in view of the deep water operation environment, the flow velocity of the bottom sea current is small, and the vibration caused by the external flow is mainly transmitted to the pump body part through the wave-induced vibration of the riser section. In view of the above problems, the vibration fatigue life evaluation method of the disc pump under the action of internal flow of the present application establishes the relationship model between vibration and fatigue by analyzing the vibration of the pump body caused by the change of the internal flow pulsation pressure of the disc pump, and calculates the fatigue life of the disc pump by using the finite element simulation software. The method of the present application can evaluate the vibration fatigue life of the disc pump according to the numerical simulation method, and given the material properties and working conditions of the pump body, the vibration fatigue life of the disc pump under the working condition can be evaluated, which will help to improve the design quality of the equipment, reduce the maintenance cost and prolong the service life.

[0093] Embodiment

[0094] In this example, a certain disc pump prototype is selected as the analysis model, and the pump body part parameters are as follows: design head: 150 m, inlet diameter: 150 mm, outlet diameter: 80 mm, rated speed: 1800 rpm, and the pump body material is selected from a certain stainless steel, and the material parameters are as follows: tensile strength: 880 MPa, yield strength: 410 MPa; the internal fluid is mud, and the specific parameters are as follows: mud specific gravity: 1100-1400 kg / m, mud flow Q: 3270 m3 / h (4500 L / min), drilling fluid funnel viscosity (s): 50-60 s, drilling fluid viscosity (PV): 20-40 mPa.s, and drilling fluid viscosity (YP): 15-30 Pa.

[0095] ANSYS is used for modeling and finite element calculation.

[0096] 1. Component: establish a disc pump model, as shown in Figure 2 .

[0097] 2. Material properties: the values are as above when setting parameters, and the SN curve is as shown in Figure 3 ; it can be seen from Figure 3 that the fatigue life of the pump body material under different stress levels.

[0098] 3. Boundary conditions: fix the bottom support, as shown in Figure 4 .

[0099] 4. Load conditions: the internal flow pulsation pressure curve calculated by fluid-structure interaction is as shown in Figure 5 ; it can be seen from Figure 5 that the change of the internal flow pulsation pressure of the pump body with time; the harmonic response analysis transverse acceleration load g is as shown in Figure 6 .

[0100] 5. Meshing: selecting appropriate mesh number.

[0101] The frequency response curve is calculated by using ANSYS harmonic response analysis, and the result is shown in Figure 7 From Figure 7 it can be seen that the acceleration load frequency has an influence on the service life of the disc pump body at different frequency bands according to the frequency response curve; the PSD load input is defined, the input is set at the corresponding input of the N-CODE module, the simplified acceleration power spectral density is shown in Table 1, the material attribute is given, the material SN curve is defined, the finite element calculation is carried out by using ANSYS n-Code software, and the fatigue life calculation result is shown in Figure 8 、 Figure 9 From Figure 8 it can be seen that the fatigue life calculation result of the pump body is distributed as shown in the figure, the fatigue failure occurs first at the connecting position of the bottom support and the pump shell, and the calculation result at this position is the fatigue life of the pump body; from Figure 9 it can be seen that the maximum fatigue damage of the pump body is located at the connecting position of the bottom support and the pump shell.

[0102] Table 1: Simplified acceleration power spectral density

[0103]

[0104] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for assessing the vibration fatigue life of a disc pump under internal flow conditions, characterized in that, Includes the following steps: Step 1: Establish a disc pump model; Step 2: Perform transient fluid-structure interaction calculations on the pump body structure to obtain the time-domain load of the pulsating pressure in the pump body. Using this as input, calculate the time-domain load of the pump body displacement using ANSYS. Step 3: Use Matlab and Origin software to process the time-domain load of the pump body displacement and obtain the pump body acceleration power spectral density. Step 4: Use ANSYS to perform harmonic response analysis and obtain the pump body acceleration load frequency response curve. Step 5: Evaluate the pump body fatigue life based on the pump body acceleration power spectral density and material SN curve; Step 2 includes: Step 21: Use the ANSYS Fluent module and static structure analysis module of the computer finite element simulation software to perform transient fluid-structure interaction calculations on the pump body structure, and calculate the values ​​of pressure changes over time at different locations in the flow region inside the pump body. Step 22: Export the finite element analysis result file from Step 21, import it into the ANSYS CFD-Post module for data processing, set up several monitoring points in the rotor area, suction area, and discharge area of ​​the disc pump, and extract the pressure change over time. Step 23: Compare the pressure change curves of each monitoring point over time, and select the area with the largest change for analysis; use the pressure change curve extracted in step 22 as the load input, and use the computer finite element simulation software ANSYS to perform static structural analysis to obtain the pump body displacement time-domain load.

2. The method for evaluating the vibration fatigue life of a disc pump under internal flow action according to claim 1, characterized in that, Step 3 includes: Step 31: Compare the displacement time-domain loads of several monitoring points set in Step 22, select the monitoring point with the largest change in displacement time-domain load, and extract the displacement time-domain load of the pump body at this point. Step 32: Use the computer Origin plotting software to perform second-order differential processing on the pump body displacement versus time curve in Step 31 to obtain the acceleration versus time curve. Step 33: Use Matlab software to perform a fast Fourier transform on the acceleration-time curve to obtain the acceleration frequency domain load, and further calculate the acceleration power spectral density.

3. The method for evaluating the vibration fatigue life of a disc pump under internal flow action according to claim 1, characterized in that, Step 4 includes: Step 41: Use ANSYS software to perform modal analysis on the pump body structure of the disc pump and give fixed constraints on the disc pump support. Step 42: Perform harmonic response analysis on the pump body of the disc pump. Apply a lateral acceleration load of unit g and use the results of the modal analysis in step 41 as the initial conditions to perform the analysis and obtain the frequency response curve of the disc pump under acceleration load.

4. The method for evaluating the vibration fatigue life of a disc pump under internal flow action according to claim 1, characterized in that, Step 5 includes: using the harmonic response analysis results in Step 4 as initial conditions, using the ANSYS n-Code module, defining the input pump body acceleration power spectral density, defining the material property mapping of the pump body, performing fatigue life calculation, and obtaining the pump body loss cloud map and fatigue life cloud map, which can then evaluate the vibration fatigue life of the disc pump body.

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