Study On Characteristic Relevance Between Flow Feature And Flow-induced Noise In The Vortex Pump

With the development of economy and industry,noise pollution has increasingly become a hot issue of concern to society.At present,the research on centrifugal pump noise focuses on improving the hydraulic design to reduce the non-ideal flow in the pump,so as to reduce the noise intensity.However,there are few researches on the characteristic relevance between flow and flow-induced noise.Therefore,in this paper,the self-designed vortex pump is used as the research object.The RNG k-? model is used to obtain the static pressure diagrams and velocity cloud diagrams.Without initialization,the large eddy simulation is used for unsteady calculation.When the calculation is stable again,the velocity field data and flow field data are outputted simultaneously.And the velocity field is only exported with stationary domain,which is taken as the source field.Then the noise numerical simulation software ACTRAN is used to perform noise numerical simulation.Finally,the frequency domain information of the pressure fluctuation of the flow field and the sound pressure level of the sound field is extracted for relevance analysis.Through the comparison of several numerical simulation results under different conditions,the flow characteristics and noise vocalization characteristics of the no-blade cavity are studied separately.The results are as follows.For the flow field,the flow field is quietly different in the no-blade cavity of vortex pump.With flow rate changing,there are significant differences,which directly determine the flow pattern in the pump.Then the unsteady calculation results show that there are two types of vortex system with distinct boundaries in the no-blade cavity.For the sound field,the total sound pressure level of the noise is related to the flow intensity.Along the sound propagation direction,the characteristic of the plane wave with interval peaks appears.The impeller-rotating frequency and its frequency multiplication are the main frequency bands for sound propagation.The noise at one-fold blade passing frequency and its frequency multiplication rarely participates in the noise propagation process.The sound pressure levels of flow-induced noise at different frequencies in the no-blade cavity have obvious directionality.Based on the above mentioned flow field characteristics,the pressure pulsation is extracted as the eigenvalue of the flow field.It can be seen from the analysis that at the cross-section of the no-blade cavity,the pressure fluctuation's amplitude is the highest at impeller-rotating frequency and its frequency multiplication,and the second highest amplitude is at the blade passing frequency,meanwhile at other frequency,the amplitude of pressure pulsation is almost small.So the relationship between the pressure fluctuation of the flow field and the characteristics of the flow-induced noise can be analyzed.Under the design condition,the extremum points of the curves of the pressure fluctuation coefficient and the sound pressure level between the one-fold impeller-passing frequency and its frequency multiplication are shifted by one impeller-rotating frequency,while the tendency of these two curves at the blade-passing frequency and its frequency multiplication are similar,indicating that in this frequency range,the pressure fluctuation can accurately predict the phonation of the flow-induced noise.What's more,under off-design conditions,the tendency of curves of the pressure fluctuation coefficient and the sound pressure level between one-fold impeller-rotating frequency to two-fold blade-passing frequency are inconsistent,indicating that the incentive effect of noise caused by pressure fluctuation is limited.