Flow Field Analysis Of Turbocharged Compressor And Study Of Aerodynamic Optimization Of Impeller

Turbocharged technology,which is a milestone in the development of internal combustion engines,can improve the working condition of the engine,so as to meet the high standards of emission requirements.Being the core part of turbocharged technology,the turbocharger is composed primarily of compressor and turbine.The working principle of the turbocharger is that engine exhaust gas makes the turbine rotate at high speed.As the compressor and turbine connected by a shaft,so the turbine drives the compressor impeller rotating at high speed too.And then air is compressed into the engine by the compressor.The state of compressor has a great impact on the performance of the whole pressurization system.Therefore,it is of great theoretical and practical significance to analyze and optimize the turbocharged compressor.Based on a certain type of turbocharged compressor as the research object,the author is aimed to conduct numerical simulation on compressor and explore the mechanism of flow loss of compressor impeller.On this basis,the aerodynamic optimization design of the impeller is made,so as to improve the efficiency and compression ratio of the impeller and the performance of the compressor.Firstly,reverse engineering technology is employed to remodel the impeller and volute of the compressor.Three-dimensional scanning,a non-contact measurement method,is used to measure the impeller and volute.The reverse modeling of them is done then,after completing the measurement and getting the cloud data of the impeller and volute.Secondly,NUMECA software is adopted to conduct numerical simulation study of the compressor with the Reynolds-averaged N-S equation and turbulence model of Spalart-Allmaras.The computing results of the flow field are obtained by numerical simulation of the compressor at three different speed rates that are 92,000r/min,116,000r/min and 130,000r/min,and the characteristic curve of the compressor is drawn according to the computing results of the flow field.On this basis,the author analyzes the performance of the compressor.And then the internal flow field of the compressor at the maximum efficiency point(mass flow 0.103 kg/s)at the speed of116,000r/min is analyzed,and the flow loss mechanism inside the impeller is studiedemphatically.It is concluded that: the flow loss of the impeller mainly includes leading edge impact disturbance loss,tip leakage loss and wake flow loss,etc.Finally,Artificial neural network and genetic algorithm are employed to make the aerodynamic optimization of the impeller by the optimizing goal of efficiency and pressure ratio with the optimization platform of Fine/Design3 D.And then the optimization results are compared with that of original impeller.The results indicate that the blade profile is basically the same as that of the original model after optimization,but there are some small changes appearing at the root of the blade,such as the blade angle of splitter blade slightly increasing,the blade angle of leading edge of main blade reducing,opposite for the blade angle of trailing edge and the whole body of the blade profile shifting to the trailing edge with the blade chord length unchanged.At the tip of the blade,the main blade is basically the same as the original blade,while the blade shape of the splitter blade changes greatly.The blade profile of splitter blade is extended to both the leading edge and trailing edge,with the chord length of the blade increasing.After optimization,the blade load of main blade and splitter blade are both increased,but the pressure distribution at the leading edge of them becomes uniform.The flow state at the exit of the impeller is improved.And the flow loss is reduced.The efficiency and pressure ratio of the optimized impeller are increased and the comprehensive stability margin is also improved.The isentropic efficiency of the impeller is 2.03% higher than that of the original model at the optimization point,and the pressure ratio is increased by 0.11.This research can provide some theoretical reference for the modeling,analysis and optimization of turbocharged compressor,which is of great significance in the advancement of turbocharged technology.