Research On Flow Induced Noise Simulation Of Pipeline Pump And Bionic Noise Reduction

In order to solve the problem of LPP-390-2 vertical pipeline pump running noise,the CFD and Lighthill sound analogy theory was adopted to figure out its internal flow and acoustic field.Based on the analysis of its internal flow field,the indirect mixing method was used to figure out its internal and external sound fields.The causes of flow noise and the sound field characteristics were explored,and the interaction between the flow field and the sound field was analyzed.The main noise of the pipeline pump was found and the internal flow induced noise propagation law was explored to provide theoretical basis and ideas for reducing vibration and noise of this type of pump.On this basis,the bionic blade model was established by similarity criteria reference to the goshawk wings,the orthogonal experiment was designed to optimize the noise reduction of multiple targets,and the performances of the flow field and sound field before and after optimization were compared.Orthogonal experiments were designed to optimize the noise of the pipeline pump,and the flow field and the model with excellent noise and hydraulic performance were obtained.The main content and results of this paper are as follows:1)The CFX was used to solve the internal flow field of the pipeline pump.The characteristics of its internal flow field were obtained by the steady and unsteady calculations.The flow field was diagnosed by the regularized helicity,and the internal pressure loss and the energy mutation were analyzed.The analysis found that the energy loss at the inlet of the impeller,the impeller outlet and the tongue,which could easily induce noise source.The pulsation amplitude is mainly concentrated in the blade passing frequency and the tongue is the concentration of pulse energy.2)Based on the calculation of the flow field,The LMS Virtual.Lab was used to solve the internal and external acoustic fields of the pipeline pump to find the main noise source,the sound source characteristics and acoustic propagation characteristics were analyzed,the influence of the flow field on the sound field was explored.The result shows that the sound source is mainly concentrated at the tongue of the volute and the section near the outlet of the volute,the tongue is the main gathering area of the noise source,and the static and dynamic interference between the impeller and the tongue is the main reason causing the pipeline pump to generate flow noise.The noise of blade passing frequency is the largest,and the noise gradually decreases with increasing frequency.At the low frequencies less than the blade passing frequency,the acoustic wave propagates mainly along the inlet and outlet pipelines in the hydraulic near field,as the frequency increases,the sound source begins to radiate outward through the pump casing.and the greater the flow rate,the greater the sound pressure of the external sound field.3)The similarity criterion was used to established the bionic blade model with reference to the structure characteristics of the wings of the goshawk.Three parameters include tooth width,tooth pitch and tooth width were constructed to control the geometry of the bionic blade.Orthogonal experiments were designed,and intuitive analysis and linear weighted analysis were used to determine the optimal noise reduction model.Analysis of the characteristics and noise of the pump revealed that there is a linear relationship between the head and the three parameters under the design conditions,which increases with the increase of the tooth width and decreases with the increase of the tooth pitch and tooth height.The efficiency increases with the increase of tooth pitch,and decreases with the increase of tooth width and tooth height.There is no strict linear relationship between noise and three factors,but the overall trend is increasing.4)The flow field and sound field characteristics of the prototype and optimization model were compared.It was show that the bionic saw-tooth impeller is approximately equal to the prototype head under design conditions,and has lower noise and better efficiency.The bionic saw structure can inhibit the generation of vortex,reduce the eddy accumulation on the suction surface of the blade,reduce the jet-wake structure in the outlet of the impeller and he pressure pulsation at the tongue of the pipeline pump,and reduce the hydrodynamic noise.The bionic sawtooth blade reduces the internal sound pressure intensity and distribution of the pipeline pump especially in the tongue.Under the design condition,the sound pressure level of outlet point of the pump is reduced by 7.9 dB,the noise reduction effect is obvious.This structure is mainly to control the noise of the pipeline pump by suppressing the low frequency noise such as the blade passing frequency,2 times blade passing frequency to achieve the purpose of noise reduction.Noise reduction is obvious in design conditions and large flow conditions,and small flow rate have little effect on noise.