Research On The Optimization Of High Efficiency And Low Noise Compressor Impeller Structure

Turbocharger is one of the main parts of marine diesel combustion engine,which can significantly increase the output power of diesel engines,reduce fuel consumption and pollutant emissions.With the increased demand of low noise internal combustion engine,the noise control of turbochargers has become a hot topic.The compressor is the main noise source of a turbocharger.Thus the reduction of compressor noise can effectively reduce the noise level of the turbocharged engine.In this paper,a centrifugal compressor used in a marine diesel engine turbocharger is selected as the research object,the optimal design of compressor impeller is conducted to reduce compressor noise,which is a noise control method starting from noise source.The main purpose of this paper is to reduce the radiation noise at compressor inlet but keeps or improves compressor aerodynamic performance.The characteristics of the compressor internal flow and the radiated noise at compressor inlet are studied first.The compressor characteristic lines at three different rotating speeds are calculated using the CFD simulations.The internal flow field are analyzed with the distribution of temperature,pressure and velocity.The compressor aerodynamic noise is predicted using the hybrid CAA method at the operating points with highest efficiency of all three rotating speeds.The radiated noise distribution at compressor inlet and noise spectral characteristics are analyzed.The parameterized impeller model is obtained from a baseline compressor geometric model using reverse engineering method,the accuracy of the parameterized impeller model is validated against the baseline compressor.A series of numerical models are established based on the parameterized impeller model,in order to study the influence of five impeller parameters on compressor flow and noise.The impeller parameters including the impeller including tip clearance,the curvature of cut-off trailing edge,exit lean angle,inlet blade angle on shroud and inlet blade angle on hub.A comprehensive sensitivity analysis of the impeller parameters is conducted using the Morris method,it is found that the tip clearance and the inlet blade angle on shroud have a significant influence on compressor flow and noise.The Latin Hypercube Sampling(LHS)is used to generate the initial sampling points,and the compressor flow and noise under the operating conditions defined by the initial sampling points are subsequently calculated using the hybrid CAA method.The surrogate model and genetic algorithm are used to find the optimal solution of impeller parameters,the influence of different objective functions on the optimization are also discussed.The results indicate that the global optimal solution can be quickly found using the optimization method,and the optimization results are satisfactory.Among them,the impeller with the best optimization effect can increase the highest isentropic efficiency of the compressor by 2.069% and reduce the average sound pressure level of the noise emission at inlet by 3.0d B.