Centrifugal pump and method for calculating flow-induced noise in pipeline

Abstract

The invention discloses a centrifugal pump and a method for calculating flow-induced noise in a pipeline. The method comprises the following steps: calculating an external characteristic result of a closed loop of the centrifugal pump; establishing a fluid numerical simulation calculation model in a ratio of 1: 1 to a centrifugal pump closed loop, and carrying out centrifugal pump hydrodynamic characteristic numerical simulation calculation to obtain pressure pulsation sound source information files of impeller blades, a volute and inlet and outlet pipelines of the centrifugal pump; calculating the structural modes of the centrifugal pump shell, the water inlet pipeline and the water outlet pipeline, and outputting a mode information file; and establishing an acoustic calculation grid of the closed loop calculation model, interpolating data of the pressure sound source information file and the modal information file into the acoustic calculation grid, and then calculating the flow-induced noise in the centrifugal pump and the inlet and outlet pipelines by adopting a finite element method in combination with a sound-vibration coupling calculation method. According to the method, only the rotating speed of the pump is given during calculation, the calculated pressure sound source is closer to the real condition of the centrifugal pump in the actual operation process, and the calculation result is more accurate.

Description

Technical Field

[0001] The present invention relates to the field of calculation of flow-induced noise in rotating impeller machinery, and in particular to a method for calculating flow-induced noise in a centrifugal pump and a pipeline. Background Art

[0002] Pump systems, as the "heart" of pipeline circulation systems, play a vital role in various sectors of the national economy and in high-tech fields such as submarines, ships, and aerospace. Approximately 70% of these systems utilize centrifugal pumps. However, due to the complex flow characteristics of centrifugal pumps, their operation is often accompanied by significant flow-induced noise. This is particularly true in submarine seawater pumps, where the flow noise generated by these centrifugal pumps can propagate along the pipelines and radiate into the marine environment, posing a serious threat to the submarine's stealth.

[0003] Currently, the calculation methods for centrifugal pump flow-induced noise mainly include experimental measurement, numerical simulation, and theoretical analysis. Although experimental measurement can provide relatively accurate results, it is costly, time-consuming, and subject to significant limitations in experimental conditions. Numerical simulation methods, through the combination of computational fluid dynamics (CFD) and acoustic simulation, can more comprehensively reflect the coupling characteristics of the flow and acoustic fields, but the calculations are large and require high computing resources. Theoretical analysis methods, based on fluid mechanics and acoustic theory, predict noise by establishing mathematical models, but their accuracy is often limited by the model's simplified assumptions.

[0004] With the continuous development of computer technology and numerical algorithms, CFD-based flow-induced noise calculation methods have gradually become a research hotspot. However, existing calculation methods still have certain limitations in terms of accuracy, efficiency, and applicability. In particular, the calculation results of related methods proposed in the literature have large errors compared with experimental test results, and the calculated results show that the inlet flow noise of centrifugal pumps is greater than the outlet flow noise. Therefore, developing an efficient and accurate method for calculating the flow-induced noise of centrifugal pumps is of great significance for improving the design level of centrifugal pumps, reducing operating noise, and improving equipment performance. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention proposes a method for calculating the flow-induced noise in centrifugal pumps and pipelines. The specific technical solution is as follows:

[0006] A method for calculating flow-induced noise in a centrifugal pump and pipeline comprises the following steps:

[0007] Step 1: Calculate the external characteristics of the centrifugal pump closed circuit, including the water tank, water inlet pipe, valve, centrifugal pump impeller, volute, and water outlet pipe;

[0008] Step 2: Establish a fluid numerical simulation calculation model with a 1:1 ratio to the centrifugal pump closed loop, carry out numerical simulation calculation of the hydrodynamic characteristics of the centrifugal pump, and obtain the pressure pulsation sound source information file of the centrifugal pump impeller blades, volute, and inlet and outlet pipes;

[0009] Step 3: Calculate the structural modes of the centrifugal pump casing and the water inlet and outlet pipes, and output the modal information file;

[0010] Step 4: Establish an acoustic calculation grid for the closed-loop calculation model, and interpolate the data of the pressure sound source information file and the modal information file to the acoustic calculation grid. Then, use the finite element method combined with the acoustic-vibration coupling calculation method to calculate the flow-induced noise in the centrifugal pump and the inlet and outlet pipelines.

[0011] Furthermore, the step 2 includes the following sub-steps:

[0012] S2.1: Based on the fluid numerical simulation model, draw grids for each component. Data is transferred between each component through interfaces. During the grid drawing process, the interface grid scales of two adjacent components are ensured to be consistent. After the grid is drawn, a turbulence model and a discrete algorithm are selected.

[0013] S2.2: Given a centrifugal pump speed, adjust the valve opening, and perform a constant numerical simulation to calculate the pipeline flow rates corresponding to multiple different valve openings. Based on the pipeline flow rates corresponding to the multiple different valve openings, determine the calculated valve opening value under the rated flow rate or the flow condition where flow noise calculation is required by interpolation. Then, perform a constant numerical simulation again at the calculated valve opening value corresponding to the interpolated flow rate to obtain the actual flow rate under this valve opening. By fine-tuning the valve opening, the actual flow rate matches the interpolated flow rate, and the accurate valve opening value corresponding to the rated flow rate or the flow condition where flow noise calculation is required is obtained.

[0014] S2.3: Perform unsteady numerical simulation calculations of the centrifugal pump closed loop at the accurate value of the valve opening corresponding to the rated flow or the flow at which the flow noise needs to be calculated, and compare the external characteristic results obtained by the simulation calculation with the external characteristic results under the actual test conditions of step one. If the error between the calculation result and the test result is greater than the set threshold, go to step S2.1 and modify the parameters of the numerical simulation calculation; otherwise, output the pressure sound source information file of the centrifugal pump impeller blades, volute, and inlet and outlet pipelines.

[0015] Furthermore, the set threshold is 5%.

[0016] Furthermore, when calculating the pressure sound source information, the flow changes in the pipeline under at least three different valve openings are first calculated, and the relationship curve between the valve opening and the pipeline flow is obtained by fitting. Then, the valve opening under the rated flow or the flow at which the flow noise needs to be calculated is interpolated and calculated, and then the pressure sound source of the centrifugal pump under the rated flow or the flow at which the flow noise needs to be calculated is calculated in detail.

[0017] Furthermore, modifying the parameters of the numerical simulation calculation specifically involves modifying the grid size and the calculation time step.

[0018] Furthermore, the turbulence model uses large eddy simulation or detached eddy simulation.

[0019] Furthermore, the external characteristic results of the closed circuit of the centrifugal pump include the flow rate, head and efficiency of the centrifugal pump.

[0020] The beneficial effects of the present invention are as follows:

[0021] Traditional calculations of the flow field of a centrifugal pump are based on a given pump inlet flow rate or velocity and a given outlet pressure. In the method for calculating flow-induced noise in a centrifugal pump of the present invention, the flow rate and pressure in the pipeline are completely caused by the rotation of the pump. Only the pump speed is given. The calculated pressure sound source is closer to the actual situation of the centrifugal pump during actual operation, so the calculated result is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flowchart of a method for calculating flow-induced noise in a centrifugal pump and pipeline according to an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the computational domain for numerical simulation of a centrifugal pump closed-loop fluid flow. In the figure, 1 is the centrifugal pump, 2 is the water inlet pipe, 3 is the valve, 4 is the water tank, and 5 is the water outlet pipe.

[0024] Figure 3 Schematic diagram of various components of the numerical model of the centrifugal pump according to an embodiment of the present invention. In the figure, 101 is an impeller and 102 is a volute.

[0025] Figure 4 for Figure 2 Schematic diagram of the mesh division of the various parts of the calculation domain for the numerical simulation of the closed-loop fluid flow of a centrifugal pump, where (a) is the impeller, (b) is the water tank, the inlet pipe, and part of the outlet pipe, (c) is the volute and part of the outlet pipe, and (d) is the valve.

[0026] Figure 5 Schematic diagram of pipeline flow corresponding to different valve openings in a closed circuit.

[0027] Figure 6 This is a comparison chart of the numerical simulation and test results of the inlet sound pressure level frequency response curve at rated flow.

[0028] Figure 7 This is a comparison chart of the numerical simulation and test results of the frequency response curve of the outlet sound pressure level at rated flow. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more apparent. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] The pump used in this embodiment is a single-stage centrifugal pump with a design flow rate of 115m 3 / h, the head is 17m, the speed n is 1500rpm, and the main geometric parameters of the pump are shown in Table 1.

[0031] Table 1 Main parameters of the pump

[0032] Geometric parameters value <![CDATA[Rated flow rate Q d , m 3 / h]]> 115 <![CDATA[Rated head H d ,m]]> 17 Rated speed n, r / min 1500 <![CDATA[Impeller inlet diameter D0, mm]]> 136 <![CDATA[Outlet diameter of impeller D2, mm]]> 237.5 <![CDATA[Impeller outlet width b2, mm]]> 25 Number of impeller blades, Z 7+7 <![CDATA[Outlet angle β2, °]]> 25

[0033] like Figure 1 As shown, the method for calculating the flow-induced noise in a centrifugal pump and pipeline of this embodiment includes the following steps:

[0034] Step 1: First, build a test bench. A closed-circuit centrifugal pump circuit, including a water tank, inlet pipe, valve, centrifugal pump impeller, volute, and outlet pipe, is used to conduct external pump characteristic experiments. Flow rate curves of pump head, efficiency, and inlet and outlet noise are obtained. Flow-induced noise is measured using a hydrophone.

[0035] Step 2: Based on the test bench, establish a 1:1 fluid numerical simulation calculation model with a centrifugal pump closed loop, such as Figure 2 and Figure 3 As shown, the grid is drawn by components, and data is transferred between each component through the interface. During the grid drawing process, the interface grid scales of two adjacent components are guaranteed to be consistent. The grid after drawing is as follows Figure 4As shown. Because the outlet pipe is relatively long, a section of the outlet pipe is drawn in Figures (b) and (c) for the convenience of display. After drawing the grid, select the turbulence model and discrete algorithm; given the speed of the centrifugal pump, adjust the valve opening, carry out steady-state numerical simulation calculations, focus only on the flow in the pipeline, and calculate the pipeline flow corresponding to different valve openings. Determine the calculated value of the valve opening under the rated flow or the flow condition where the flow noise needs to be calculated by interpolation; then, carry out steady-state numerical simulation calculations again under the calculated value of the valve opening corresponding to the interpolated flow to obtain the actual flow under the current valve opening; by fine-tuning the valve opening, make the actual flow match the interpolated flow, and obtain the accurate value of the valve opening corresponding to the rated flow or the flow where the flow noise needs to be calculated. An unsteady numerical simulation calculation of the closed loop of a centrifugal pump is performed at the accurate value of the valve opening corresponding to the rated flow or the flow at which the flow noise needs to be calculated. The turbulence model is selected as the detached vortex model or the large eddy simulation model. The time step is the time for the pump impeller to rotate 1°, and the calculation time is the time for the impeller to rotate 10 circles. The results of the last 5 circles are taken for subsequent analysis, and the calculated external characteristic results are compared with the test results. If the error between the calculated results and the test results is greater than 5%, the grid scale and / or calculation step size are modified and the calculation is performed again. If the error between the calculated results and the test results is less than 5%, the pressure pulsation sound source information of the inlet and outlet pipelines, volute and pump blades is output for each time step, and the output file format is CGNS.

[0036] When calculating the pressure pulsation sound source information of a centrifugal pump, the flow rate changes in the pipeline at at least three different valve openings are first calculated. A curve is then fitted to obtain the relationship between valve opening and pipeline flow. The valve opening at the rated flow or the flow at which flow noise needs to be calculated is then interpolated and calculated. Finally, the pressure sound source of the centrifugal pump at the rated flow or the flow at which flow noise needs to be calculated is calculated in detail. In this embodiment, the flow rate changes in the pipeline at a total of 10 different valve openings are calculated, and the curves obtained for the relationship between valve opening and pipeline flow are shown in the figure below. Figure 5 shown.

[0037] Step 3: Calculate the modes of the centrifugal pump housing and the inlet and outlet pipes, and output the structural modal information file. Use ANSYS Workbench for modal calculations, using fixed boundaries consistent with the actual pump. After the calculations are complete, output the modal file with the suffix rst.

[0038] Step 4: Establish an acoustic calculation grid for the closed-loop calculation model. In this embodiment, the acoustic grid size L≤c / (6f max ), where c is the speed of sound propagation, f maxis the maximum calculable frequency. The data from the pressure sound source information file and the modal information file are interpolated into the acoustic calculation grid. Then, the finite element method combined with the acoustic-vibration coupling calculation method is used to calculate the flow-induced noise in the centrifugal pump and the inlet and outlet pipes. This explanatory case uses ANSYS Fluent to calculate the pressure sound source information and LMSVitual.Lab for the acoustic-vibration coupling calculation. When importing the sound source information, check "Create Mesh Part for Centroids" and uncheck "at Elements". Before the acoustic calculation, the pressure sound source data needs to be mapped to the acoustic grid. During the mapping, Fourier transform is used to convert the pressure sound source. The acoustic boundary condition is the converted pressure sound source. The acoustic-vibration coupling surface is the outer wall of the acoustic grid and the inner wall of the modal grid.

[0039] In this embodiment, the sound pressure level frequency response curve at the same measuring point as the experiment is extracted and compared with the experimental results, such as Figure 6 and Figure 7 As shown, it can be seen that the inlet sound pressure and outlet sound pressure obtained by the calculation method of the present invention are relatively close to the experimental results, and the calculated result of the inlet flow noise is smaller than the calculated result of the outlet flow noise, which is relatively close to the actual result.

[0040] Those skilled in the art will understand that the foregoing descriptions are merely preferred embodiments of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art will still be able to modify the technical solutions described in the foregoing examples or substitute equivalents for some of the technical features therein. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the invention shall be included within the scope of protection of the invention.

Claims

1. A method for calculating flow-induced noise in centrifugal pumps and pipelines, characterized in that: The following steps are involved: Step 1: Calculate the external characteristics of the centrifugal pump closed circuit, including the water tank, water inlet pipe, valve, centrifugal pump impeller, volute, and water outlet pipe; Step 2: Establish a fluid numerical simulation calculation model with a 1:1 ratio to the centrifugal pump closed loop, carry out numerical simulation calculation of the hydrodynamic characteristics of the centrifugal pump, and obtain the pressure pulsation sound source information file of the centrifugal pump impeller blades, volute, and inlet and outlet pipes; Step 3: Calculate the structural modes of the centrifugal pump casing and the water inlet and outlet pipes, and output the modal information file; Step 4: Establish an acoustic calculation grid for the closed-loop calculation model, and interpolate the data of the pressure sound source information file and the modal information file to the acoustic calculation grid. Then, use the finite element method combined with the acoustic-vibration coupling calculation method to calculate the flow-induced noise in the centrifugal pump and the inlet and outlet pipelines.

2. The method for calculating flow-induced noise in a centrifugal pump and pipeline according to claim 1, characterized in that: The second step includes the following sub-steps: S2.1: Based on the fluid numerical simulation model, draw grids for each component, and transmit data between each component through the interface. During the grid drawing process, ensure that the interface grid scales of two adjacent components are consistent; After drawing the grid, select the turbulence model and discretization algorithm; S2.2: Given a centrifugal pump speed, adjust the valve opening, and perform a constant numerical simulation to calculate the pipeline flow rate corresponding to multiple different valve openings. Based on the pipeline flow rates corresponding to multiple different valve openings, determine the calculated valve opening value under the rated flow rate or the flow condition where flow noise calculation is required through interpolation. Then, perform a constant numerical simulation again at the calculated valve opening value corresponding to the interpolated flow rate to obtain the actual flow rate at that valve opening. By fine-tuning the valve opening, the actual flow rate is made to match the interpolated flow rate, and the accurate value of the valve opening corresponding to the rated flow rate or the flow rate for which flow noise needs to be calculated is obtained; S2.3: Perform unsteady numerical simulation calculations of the centrifugal pump closed loop at the accurate value of the valve opening corresponding to the rated flow or the flow at which the flow noise needs to be calculated, and compare the external characteristic results obtained by the simulation calculation with the external characteristic results under the actual test conditions of step one. If the error between the calculation result and the test result is greater than the set threshold, go to step S2.1 and modify the parameters of the numerical simulation calculation; otherwise, output the pressure sound source information file of the centrifugal pump impeller blades, volute, and inlet and outlet pipelines.

3. The method for calculating flow-induced noise in a centrifugal pump and pipeline according to claim 2, characterized in that: The set threshold is 5%.

4. The method for calculating flow-induced noise in a centrifugal pump and pipeline according to claim 2, characterized in that: When calculating the pressure sound source information, first calculate the flow changes in the pipeline under at least three different valve openings, obtain the relationship curve between the valve opening and the pipeline flow through fitting, then interpolate and calculate the valve opening at the rated flow or the flow where the flow noise needs to be calculated, and then calculate in detail the pressure sound source of the centrifugal pump at the rated flow or the flow where the flow noise needs to be calculated.

5. The method for calculating flow-induced noise in a centrifugal pump and pipeline according to claim 2, characterized in that: Modifying the parameters of the numerical simulation calculation specifically involves modifying the grid size and the calculation time step.

6. The method for calculating flow-induced noise in a centrifugal pump and pipeline according to claim 2, characterized in that: The turbulence model uses large eddy simulation or detached eddy simulation.

7. The method for calculating flow-induced noise in a centrifugal pump and pipeline according to claim 2, characterized in that: The external characteristic results of the closed circuit of a centrifugal pump include the flow rate, head and efficiency of the centrifugal pump.

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