Research On Noise Reduction Of Centrifugal Pump Based On Bionics

The research of this paper is carried out under the support of Zhenjiang Key Research and Development Plan?GY2017001?.Flow noise which is a significant part of centrifugal pump noise is harmful to the environment.Bionic non-smooth structure is a long-term method to reduce flow noise in the field of aeroacoustics,and it is expected to be successfully applied in centrifugal pump.In addition,the different bionic forms make a distinction between the noise reduction performance and mechanism of different bionics.Therefore,it is of great value to study the application of different bionics in centrifugal pumps.In this paper,theoretical analysis,numerical calculation and experimental test are combined to study the optimization design of the bionic pit structure,the noise reduction effect and law of different bionics and their coupling effects.The purpose of this paper is to propose an optimization method for the bionic pits used for noise reduction of the twist blade of centrifugal pump,and master the noise reduction mechanism of the bionic pit and serrated structures.The main research work and results are as follows:1.Systematically summarize the causes of flow noise induced by centrifugal pump and the methods of noise reduction,the research status of noise reduction with bionic structure is summarized,and the applications of artificial neural network and particle swarm optimization algorithm in the field of centrifugal pump are analyzed.2.Present a bionic optimization method for the pits used for noise reduction of the twisted-blade centrifugal pump,the optimization variables are selected from many parameters that affect the effect of the bionics,the range and objective of the optimization variables are determined,the network error is weighed against the requirements of the number of samples,the sample database is established by the uniform design method,and finally the neural network algorithm is used for fitting,and the particle swarm optimization algorithm is used for optimization.In order to adapt to the strong three-dimensional configuration of the twisted blade,a new layout method of bionic pit structure is proposed based on the earth's longitude and latitude division method.To increase the optimization dimension,the pit texture is divided into three groups with different flow direction parameters like diameters named d₁,d₂,d₃.Meanwhile,the artificial supervision is added to avoid that the fitting result has met the actual needs,but the optimal solution found is close to the optimal sample.The results show that the optimization result obtained by taking the total sound pressure level as the optimization objective has a 1.66dB noise reduction,the suppression of wideband noise is more obvious than that of discrete noise.3.Based on the calculation method of total sound pressure level,the weight of high amplitude noise is reduced,and a index TOSPL reflecting the ability of broadband noise reduction is proposed;then the optimization work is carried out,and the relationship between the noise reduction effect and the pit diameter is explored.It is found that the broadband noise suppression ability of the optimized pits is significantly improved,and the TOSPL value is decreased 0.94dB.The optimal variables of high wideband noise reduction samples meet the aggregation rules of d₁?d₂,d₃?1-d₂ and d₁?d₃ at the same time;if all samples conform to this rule,the proportion of samples whose tospl drop is more than 0.5dB is 40%,otherwise only 21%;if all samples conform to the law,the upper limit of pit diameter d₂ and d₃ will significantly affect the expectation of noise reduction of broadband noise,when the upper limit of pit diameter d₃ is not higher than 0.3,the TOSPL drop of almost all samples is higher than 0.5dB.Whether all samples conform to the aggregation rule or not,the expectation of noise reduction decreases with the decrease of the upper limit of pit diameter d₁.4.The effects of the concave bionic structure and the serrated bionic structure on the performance parameters and amplitude frequency characteristics of centrifugal pump are compared and analyzed,The effect and law of noise reduction under the coupling effect of two characteristics are explored.The results show that bionics have little effect on the hydraulic efficiency of centrifugal pump,the serrated bionics will reduce the head and torque of centrifugal pump greatly;the noise reduction effect of the pits is mainly reflected in the wide-band part of the centrifugal pump noise,while the serrated bionics is mainly reflected in the discrete part of the leaf frequency and its double frequency.The wideband noise reduction ability of the pit comes from the prevention or absorption of the micro scale vortex and disturbance wave,as well as the change of the phase difference between the upstream scattered sound wave and the disturbance wave.The noise reduction ability of the serrated structure comes from the weakening of the rotor-stator interaction.The performance of the coupled bionic model is similar to that of the sawtooth bionic model,and the coupled bionic structure fails to simultaneously suppress the discrete and wideband noise of the centrifugal pump.Because the boundary layer or the unstable disturbance wave at different span positions contact the serrated structure at different positions from the tooth tip to the tooth root,the unstable disturbance wave is amplified and the flow noise in the centrifugal pump increases.