Analysis On Aerodynamic Noise Of Turbocharger Compressor And Optimization Of Casing Structure

Modern ships are developing towards large scale and high speed.In order to meet this trend,diesel engine needs to further improve its dynamic performance.As an important part of marine diesel engine,turbocharger should develop towards higher supercharging,higher speed,higher efficiency and wider operation range.However,with the increase of supercharger speed,the air flow speed in the compressor is greatly accelerated,resulting in turbulence pulsation,which becomes the main noise source of the supercharger,and the compressor aerodynamic noise becomes an urgent problem to be solved.Therefore,it is of great significance to study the flow field,sound field and noise control of compressor for improving its aerodynamic and acoustic performance.The research emphases of this thesis are as follows:In this thesis,the three-dimensional model of each part of the compressor is established and meshed,and the steady flow field of the compressor is simulated by using the SST Turbulence model.By comparing the simulation and experimental data,it is proved that the simulation is consistent with the experiment.The flow field characteristics of the internal meridional plane,impeller,diffuser and volute of the compressor are analyzed in detail,and the flow field characteristics of the compressor are revealed.The results show that: in the compressor passage,a large part of the entropy loss at the impeller comes from the loss of the impeller flange.The shock wave makes a large number of low-energy fluid masses form on both sides of the splitter blade,causing blockage.The flow produces vortex motion in some regions of the diffuser,and wake vortex appears at the end,which affects the compressor performance.Based on the study of steady flow field,broadband noise model and acoustic analogy model are used to calculate and analyze the aerodynamic noise distribution of compressor components.The results show that the sound power at the impeller is the largest in the whole compressor,and the highest value at the trailing edge of the impeller is 184.5db.The sound power of diffuser decreases gradually along the gas flow direction,and the sound power level of volute throat and diffuser outlet area is larger.The noise of the impeller is mainly concentrated in the middle and high frequency band.The noise peak value of the impeller is between 2000 and 2500 Hz,where is the first-order blade frequency of the impeller.The noise at the compressor inlet and the radiated noise on the compressor surface are experimentally studied on the turbocharger test bench.The main noise sources and the noise spectrum characteristics of the turbocharger are revealed based on the simulation analysis.At different speeds,the maximum inlet noise appears at the first-order blade frequency;With the increase of speed,the sound pressure level at the compressor inlet increases obviously.The noise of supercharger is mainly composed of discrete single tone noise and broadband noise.The main noise frequency is distributed in medium and high frequency.With the increase of harmonic number,the amplitude of compressor blade frequency discrete spectrum and continuous spectrum noise decreases.The speed of supercharger is proportional to the noise value,and the broadband noise frequency band becomes wider gradually.The orthogonal test method and response surface method are used to optimize the structure of the self circulation gearbox with the isentropic efficiency of the design point as the objective.The optimal parameter combination of the compressor self circulation gearbox is obtained.The flow field and sound field of the optimal parameter combination model and the original model are analyzed.The most significant influence on isentropic efficiency is the intake angle,the second is the width of the slot and the position of the slot,and the blade distance has the least influence on the isentropic efficiency of the compressor.Through the optimization of the self circulation gearbox,the isentropic efficiency of the compressor design point is increased by 5.23%,and the inlet flow rate is increased by 1.9%.Through the research of this thesis,we have a comprehensive understanding of the flow characteristics,noise characteristics and generation mechanism in the compressor.The structural parameters of the self circulation casing are optimized.The influence of the self circulation casing with different geometric parameters on the compressor performance is analyzed,and the optimization scheme is obtained.It can be used for reference to improve compressor performance and control compressor aerodynamic noise source.