A simulation calculation method for weakening pressure fluctuation at inlet and outlet of a rotor pump

Abstract

The application provides a method for weakening pressure fluctuation of a rotor pump inlet and outlet, comprising the following steps: step 1, a rotor pump and pipeline calculation model is established; step 2, a point to be weakened pressure fluctuation upstream and downstream of the rotor pump is set and data is monitored; step 3, a pressure fluctuation law function is fitted; step 4, a boundary change pressure is backstepped; and step 5, a change pressure boundary is applied. Compared with the prior art, the application has the following advantages: the applied pressure is a supposed sinusoidal pressure wave, can be used for fitting the pressure fluctuation law caused by the rotation of the rotor pump, is simple and easy to operate; the sinusoidal pressure fluctuation can be applied at any position of the pipeline, is suitable for any fluid medium, and only the pressure fluctuation period and amplitude caused by the rotor pump need to be found out.

Description

Technical Field

[0001] This invention relates to the technical field of fluid machinery, and more particularly to a method for reducing pressure fluctuations in a rotor pump. Background Technology

[0002] A rotary pump consists of a rotor and a pump casing. The periodic and rapid changes in the cavity volume create a pressure difference, thereby driving the liquid transport. Rotary pumps generate noise during operation, primarily due to flow pulsations and pressure fluctuations during fluid transport. These factors reduce the operational stability of the rotary pump, leading to vibration and making it more susceptible to wear, thus affecting its lifespan.

[0003] Existing research on the optimization of rotor pump operation includes the following aspects: (1) Optimizing the rotor shape, analyzing issues such as the rotor pump's volume and displacement. (2) Optimizing the rotor pump's transmission mechanism, such as changing gear transmission to toothed belt transmission. (3) Optimizing the rotor profile pressure angle, such as increasing the rotor pressure angle to reduce flow pulsation and pressure pulsation. (4) Optimizing the number of rotor pump blades, such as increasing the number of blades to effectively reduce internal pressure pulsation.

[0004] Existing methods, including theoretical analysis, CFD numerical simulation, and model testing, mostly focus on optimizing the rotor pump itself, such as blade profile, number of blades, and other components, to improve its operational stability and reduce flow pulsation, pressure fluctuations, and flow separation. However, few methods have been found to improve rotor pump characteristics from the perspective of fluid control. Summary of the Invention

[0005] When conducting numerical simulations of the flow regime of a rotor pump, the inventors discovered that this deficiency in the prior art stemmed from a lack of consideration for pressure fluctuations at the inlet and outlet pipes of the rotor pump. Through research involving the application of sinusoidal pressure fluctuations to the boundaries of the extended inlet and outlet pipes of the rotor pump, the inventors found that the phase difference in pressure could mitigate some of the pressure fluctuations caused by the rotor pump.

[0006] The purpose of this invention is to propose a method to reduce the pressure fluctuations at the inlet and outlet of a rotor pump, based on the inventor's research, in order to solve the problem of large pressure pulsation fluctuations at the inlet and outlet of the rotor pump in the prior art.

[0007] Therefore, the present invention adopts the following technical solution:

[0008] A simulation calculation method for reducing pressure fluctuations at the inlet and outlet of a rotary pump, characterized by comprising the following steps:

[0009] Step 1: Establishment of a computational model for the rotary pump and piping.

[0010] A 3D model of the rotor pump and its connected upstream and downstream pipelines is performed, with the length of the upstream and downstream pipelines L ≥ 3 times the rotor diameter. To enable the rotor pump to rotate during the calculation, the rotor pump region is divided into an unstructured mesh, and dynamic mesh technology is used to update the mesh at every moment during the rotation of the rotor pump. The pipeline section is divided into a structured mesh to reflect the flow state and pressure fluctuations. Given the rotor speed ω, a fixed pressure P1 is set at the pipeline inlet, and a fixed pressure P2 is set at the pipeline outlet.

[0011] Step 2: Setting and monitoring of pressure fluctuation points to be reduced upstream and downstream of the rotor pump.

[0012] A pressure monitoring point Point-1 is set upstream of the rotor pump, and a pressure monitoring point Point-2 is set downstream of the rotor pump. Point-1 and Point-2 are at the same distance from the center of the rotor pump. The data results of Point-1 and Point-2 are set to be output, and the calculation source file is saved at a fixed time interval.

[0013] Step 3, Fitting the Pressure Fluctuation Pattern Function

[0014] Based on the output of step 2, a stable operating time period is selected, and the pressure fluctuation pattern is fitted using a function. The upstream fitting pressure function is P_1, and the downstream fitting function is P_2. The time period is from time T1 to time T2, and the calculation file is saved at time T1.

[0015] Step 4, back-calculation of boundary change pressure

[0016] Based on the function curve obtained in step 3, according to the principle of fluctuation superposition and cancellation, the varying pressure is applied at the pipeline boundary to counteract the pressure fluctuation at the monitoring point; where the upstream fitting pressure function is P_x1 and the downstream fitting function is P_x2.

[0017] Step 5: Calculation of varying pressure applied during the time period T1 to T2

[0018] Based on the calculation program file saved at time T1 in step 3, the fixed pressures P1 and P2 at the original pipeline boundary are changed to the variable pressures P_x1 and P_x2 in step 4, respectively. The other conditions remain unchanged, and the calculation is performed again to obtain the upstream and downstream measuring point pressures P_11 and P_22, which tend to fluctuate more gently, and P_11 and P_22 exhibit slight sinusoidal fluctuations.

[0019] As a further preferred embodiment, step 3 is specifically implemented as follows:

[0020] (1) Assume that the pressure fluctuation patterns of the output Point-1 and Point-2 conform to the law of sine function transformation; and satisfy the following formulas (1) and (2):

[0021] P_1 = A_1 * sin (B_1 * t + C_1) + D_1 (1)

[0022] P_2 = A_2 * sin (B_2 * t + C_2) + D_2 (2)

[0023] (2) Extract the pressure fluctuation amplitudes A_1, A_2, periods 1 / B_1, 1 / B_2, initial phase displacements C_1, C_2 and longitudinal displacements D_1, D_2 of Point-1 and Point-2 according to the fluctuation law.

[0024] As a further preferred embodiment, step 4 is specifically implemented as follows:

[0025] Assume that the transformed pressure applied at the boundary and the pressure fluctuation caused by the original rotor pump are functions with opposite phase, approximately the same amplitude, and the same period, i.e., sinusoidal function waves. The cancellation function P_x1 of P_1 and the cancellation function P_x2 of P_2 are obtained, as shown in formulas (3) and (4).

[0026] P_x1 = -A_1 * sin (B_1 * t + C_1) + D_1 (3)

[0027] P_x2 = -A_2 * sin (B_2 * t + C_2) + D_2 (4)

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (i) The applied pressure is assumed to be a sinusoidal pressure wave. The rotor pump rotates at a fixed speed, and the resulting pressure fluctuations are periodic. The sinusoidal function is also periodic and can be used to fit the pressure fluctuation pattern caused by the rotation of the rotor pump. It is simple and easy to implement.

[0030] (ii) Sinusoidal pressure fluctuations can be applied at any location in the pipeline, with a phase difference or negligible phase difference between the pressure application point and the rotor pump. There is a distance between the upstream and downstream pressure measuring points of the rotor pump and the pressure application point. By considering the wave velocity in the liquid, there is a phase difference between the pressure wave given at the pressure application point and the pressure wave caused by the rotor pump, ensuring that the pressure wave given at the pressure application point cancels out the pressure wave caused by the rotor pump when it propagates to the measuring point. When the distance between the measuring point and the pressure application point is extremely short, the phase difference can be ignored.

[0031] (iii) The method of the present invention is applicable to any fluid medium, and it is only necessary to find the pressure fluctuation period and amplitude caused by the rotor pump. Attached Figure Description

[0032] Figure 1This is a schematic diagram of the computational region grid of the present invention;

[0033] Figure 2 This is a schematic diagram showing the location of the pressure measuring points in this invention;

[0034] Figure 3 This refers to the pressure fluctuation at the measuring point under the original boundary conditions of this invention.

[0035] Figure 4 This invention addresses pressure fluctuations at measurement points under applied pressure boundary conditions.

[0036] Figure 5 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0038] Referring to the accompanying drawings, the present invention provides a simulation calculation method for reducing pressure fluctuations at the inlet and outlet of a rotor pump, comprising the following steps:

[0039] Step 1: Establishment of Calculation Model for Rotary Pump and Piping

[0040] A 3D model of the rotor pump and its connected upstream and downstream pipelines was created, with the pipeline length L ≥ 3 times the rotor diameter. To ensure the rotor pump could rotate during calculation, the rotor pump region was divided into an unstructured mesh, and dynamic meshing technology was used to update the mesh at every moment during the rotor pump's rotation. The pipeline section was divided into a structured mesh to reflect flow patterns and pressure fluctuations. The rotor speed was set to 1000 r / min, the pipeline inlet pressure was set to a fixed 0 Pa (i.e., 0 m water pressure), and the pipeline outlet pressure was set to a fixed 48,961.71 Pa (i.e., 5 m water pressure).

[0041] Step 2: Setting and monitoring of pressure fluctuation points to be reduced upstream and downstream of the rotor pump

[0042] A pressure monitoring point, Point-1, is installed upstream of the rotor pump, and a pressure monitoring point, Point-2, is installed downstream of the rotor pump. Point-1 and Point-2 are both 0.05m away from the center of the rotor pump. (See attached diagram.) Figure 2 Set the output to include the data for Point-1 and Point-2, and set a fixed time interval to save the original calculation file. The calculation results are attached. Figure 3 As shown.

[0043] Step 3: Fitting the pressure fluctuation law function

[0044] Based on the output of step 2, a stable operating time period (0.1s) is selected. The initial time of the selected time period is redefined as 0s, and the calculation file for the current time is saved. The pressure change curve is shown in the attached figure. Figure 3 As shown. The applied pressure is assumed to be a sinusoidal pressure wave. Based on this, the approximate amplitudes of the pressure fluctuations at Point-1 and Point-2 are extracted to be 22500 and 25000, respectively; the periods are both 0.03s; the initial phase displacements are 0.7 and 1.08, respectively; and the longitudinal displacements are -10000 and 47500, respectively. According to the direction of the sinusoidal wave, the functions of P_1 and P_2 are as follows:

[0045] P_1 = 22500 * sin (2*3.14159 / 0.03 * t +0.7) -10000 (1)

[0046] P_2 = -25000 * sin (2*3.14159 / 0.03 * t + 1.08) + 47500 (2)

[0047] Step 4: Back-calculation of boundary change pressure

[0048] Based on the function curve obtained in step 3, according to the principle of superposition and cancellation of sinusoidal wave fluctuations, the varying pressure applied at the pipeline boundary is deduced to cancel the pressure fluctuation at the monitoring point. The sinusoidal pressure wave applied at the boundary and the pressure fluctuation caused by the original rotor pump are two functions with opposite phase, approximately the same amplitude, and the same period. The cancellation function P_x1 of P_1 and the cancellation function P_x2 of P_2 are obtained, as shown in formulas (3) and (4).

[0049] P_x1 = -22500 * sin (2*3.14159 / 0.03 * t +0.7) -10000 (3)

[0050] P_x2 =25000 * sin (2*3.14159 / 0.03 * t + 1.08) + 47500 (4)

[0051] Step 5: Calculation of varying pressure applied within a time period of 0.1s

[0052] Based on the calculation program file saved at time T1 in step 3, the fixed pressures P1 and P2 at the original pipeline boundary are changed to the variable pressures P_x1 and P_x2 in step 4, respectively, while keeping the other conditions unchanged. The calculation is then performed again, and the results are shown in the appendix. Figure 4 As shown, the pressure at the upstream and downstream measuring points exhibits a slight sinusoidal fluctuation, and the fluctuation amplitude is much smaller than that of the adjacent points. Figure 3 The value in.

[0053] Any equivalent changes or modifications made to the technical solution based on the technical concept proposed in this invention shall still fall within the scope of protection of this invention.

[0054] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A simulation calculation method for reducing pressure fluctuations at the inlet and outlet of a rotary pump, characterized in that, Includes the following steps: Step 1: Establishment of a computational model for the rotary pump and piping. A 3D model of the rotor pump and its connected upstream and downstream pipelines is performed, with the length of the upstream and downstream pipelines L ≥ 3 times the rotor diameter. To enable the rotor pump to rotate during the calculation, the rotor pump region is divided into an unstructured mesh, and dynamic mesh technology is used to update the mesh at every moment during the rotation of the rotor pump. The pipeline section is divided into a structured mesh to reflect the flow state and pressure fluctuations. Given the rotor speed ω, a fixed pressure P1 is set at the pipeline inlet, and a fixed pressure P2 is set at the pipeline outlet. Step 2: Setting and monitoring of pressure fluctuation points to be reduced upstream and downstream of the rotor pump. A pressure monitoring point Point-1 is set upstream of the rotor pump, and a pressure monitoring point Point-2 is set downstream of the rotor pump. Point-1 and Point-2 are at the same distance from the center of the rotor pump. The data results of Point-1 and Point-2 are set to be output, and the calculation source file is saved at a fixed time interval. Step 3, Fitting the Pressure Fluctuation Pattern Function Based on the output of step 2, a stable operating time period is selected, and the pressure fluctuation pattern is fitted using a function. The upstream fitting pressure function is P_1, and the downstream fitting function is P_2. The time period is from time T1 to time T2, and the calculation file is saved at time T1. Step 4, back-calculation of boundary change pressure Based on the function curve obtained in step 3, according to the principle of fluctuation superposition and cancellation, the varying pressure is applied at the pipeline boundary to counteract the pressure fluctuation at the monitoring point; where the upstream fitting pressure function is P_x1 and the downstream fitting function is P_x2. Step 5: Calculation of varying pressure applied during the time period T1 to T2 Based on the calculation program file saved at time T1 in step 3, the fixed pressures P1 and P2 at the original pipeline boundary are changed to the variable pressures P_x1 and P_x2 in step 4, respectively. The other conditions remain unchanged, and the calculation is performed again to obtain the upstream and downstream measuring point pressures P_11 and P_22, which tend to fluctuate more gently, and P_11 and P_22 exhibit slight sinusoidal fluctuations.

2. The simulation calculation method for reducing pressure fluctuations at the inlet and outlet of a rotor pump as described in claim 1, characterized in that, In step 3, the specific method is as follows: (1) Assume that the pressure fluctuation patterns of the output Point-1 and Point-2 conform to the sinusoidal function transformation law and satisfy the following formulas (1) and (2): P_1 = A_1 * sin (B_1 * t + C_1) + D_1 (1) P_2 = A_2 * sin (B_2 * t + C_2) + D_2 (2) (2) Extract the pressure fluctuation amplitudes A_1, A_2, periods 1 / B_1, 1 / B_2, initial phase displacements C_1, C_2 and longitudinal displacements D_1, D_2 of Point-1 and Point-2 according to the fluctuation law.

3. The simulation calculation method for reducing pressure fluctuations at the inlet and outlet of a rotor pump as described in claim 1, characterized in that, In step 4, the specific method is as follows: Assuming that the transformed pressure applied at the boundary and the pressure fluctuation caused by the original rotor pump are functions with opposite phase, approximately the same amplitude, and the same period, i.e., sinusoidal function waves; the cancellation function P_x1 of P_1 and the cancellation function P_x2 of P_2 are obtained, as shown in formulas (3) and (4); P_x1 = -A_1 * sin (B_1 * t + C_1) + D_1 (3) P_x2 = -A_2 * sin (B_2 * t + C_2) + D_2 (4)。

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