Research On Inflow Distortion Characteristics And Flow Induced Noise Optimization Of Pipeline Pump

Pipeline pumps are widely used in pipeline pressurization,and their noise reduction is of great significance to people’s daily life and industrial production.In this paper,the nonuniform outflow of the elbow suction chamber of the pipeline pump was studied.The RNG k-εturbulence model in CFX software was used to simulate the internal flow field of the pipeline pump,and the Lighthill acoustic analogy method was used to calculate the internal and external flow induced noise sound fields of the pump.Flow induced noise includes dipole flow noise,dipole flow noise considering structural vibration and flow induced vibration noise.On the basis of the numerical simulation results,the disturbance law of the nonuniform outflow of the elbow suction chamber on the flow field in the pipeline pump was explored,and the radiation characteristics of the internal and external noise of the pipeline pump were analyzed,and this provided the theoretical basis for the optimization of pipeline pump noise reduction.The main research work and results of this study are as follows:(1)The CFX software was used to simulate the internal flow characteristics of the pipeline pump.The distortion and formation mechanism of outflow of the elbow suction chamber were analyzed,and verified by experiments.Analysis of the flow field calculations revealed that the curvature difference between the upper and lower line of the elbow suction chamber induces distortion flow,which includes mainly the flat wake vortex at the lower line,the secondary vortex at the left and right walls,and the recirculation zone at the upper line(high curvature).The distortion flow disturbs the impeller inflow field,and the reverse vortex of the secondary vortex evolves into a large-scale extended separation vortex in the impeller,which happens at the inlet edge of the suction surface of the blade 3 and 6.During the circumferential propagation of the large-scale extended separation vortex,part of the flow path is blocked and new flow separation is induced,which aggravating the pressure pulsation at the impeller inlet and the tongue.(2)Furthermore,the LMS Virtualab was used to simulate the sound fields inside and outside of the pipeline pump.The results showed that the sound pressure level curve of the dipole flow noise is similar to the dipole flow noise considering the structural vibration.The sound pressure is weakened due to the damping effect of the pump wall surface.The former sound pressure level is generally higher than the latter,but the pump resonance phenomenon aggravates the sound pressure level at the double blade-passing frequency of the latter.In the external sound field,the sound energy of the flow induced vibration noise is mainly concentrated in the motor bracket and the flanges of pump inlet and outlet.The flow induced vibration noise intensity of the pump is much lower than the dipole flow noise.The low-frequency part of the dipole flow noise(0 to295 Hz)has little difference in sound energy near the pump inlet and outlet,while the intermediate frequency(295 Hz to 2360 Hz)sound energy is more concentrated in the pump outlet direction.(3)Based on the design of the eight factors two-level orthogonal experiment with IV precision,the length1,Radial1 and Radial4 were selected as the key factors in the structural parameters of the elbow suction chamber.Then,with the key factor as the independent variable,sound pressure level of dipole flow noise at P2 monitoring point and the nonuniformity of suction chamber outflow surface were selected as the response variables.This was supplemented by the design of central combination experiment,and the quadratic regression response surface equations of two response variables were constructed.Based on the regression response,the optimal solution was obtained,which was verified by simulation.The results confirmed that the P2 sound pressure level is positively correlated with the nonuniformity of the elbow suction chamber.At the design condition,the outflow nonuniformity of the elbow suction chamber is reduced from 0.327 to 0.119.The maximum drop of the pressure pulsation of the suction surface,pressure surface and tongue is 24.5%,40.2%and 35%,respectively;the conditions of 0.8Q_d,1.0Q_d and 1.2Q_d,at which the P2 sound pressure level decreases by 1.66dB,3.65dB and 2.3dB,respectively.The corresponding sound power reduction is 2.2dB,3.69dB and 3.31dB,respectively.