Design And Optimization Of Centrifugal Compressor Impeller Of Electric Assisted Turbocharger

In recent years,increasingly stringent environment and energy issues have led to the development of automotive engines toward miniaturization,high power density and low emissions.Corresponding to this,the traditional exhaust gas turbocharger has become increasingly unable to meet the new regulatory requirements,so electric assisted turbocharger comes into being.In this paper,the electric assisted two-stage turbocharger system is used to solve the problem of low-speed performance deterioration of diesel engine with turbocharger.In the low-speed and start-up conditions of engine,the series of electric assisted compressor and exhaust turbocharger work together to achieve rapid response,adequate intake,good economic requirements.The work of this paper focuses on the design of an electrical assisted compressor impeller that meets the above electrical assisted turbocharger system,making the centrifugal impeller designed work with good performance in the system.Firstly,based on the performance requirements of the exhaust gas turbocharged engine,this paper matches and calculates the compressor of the two-stage electrical assisted turbocharger system.The mass flow,pressure ratio,speed and other design parameters at the design point of the compressor are determined.Combined with the design principle of the electrical assisted compressor,the preliminary design and calculation of the compressor impeller and volute are carried out and the basic geometry of the impeller and volute are determined.Starting from the geometrical parameters of the impeller optimization design through the Concepts-NREC software,one-dimensional preliminary design of the electrical assisted compressor is performed and the initial geometric parameters and performance parameters of the electrical assisted compressor are determined.Secondly,based on the one-dimensional design,3D design and geometric modeling of the electrical assisted compressor impeller is carried out.The performance requirements and design features of electrical assisted compressor in electric assisted turbocharger system are analyzed.By analyzing two impellers for different applications,one is used for ordinary turbocharger centrifugal compressor called J90,another is used for motor-driven compressor called JE90.Comparing and analyzing the differences of the profile of the meridian flow channel,the distribution of the blade angle and the blade load of the two kinds of impellers,the design rules and strategies of the electric assisted compressor impeller are got.Based on this,a redesign is carried out to obtain an efficient compressor design impeller that can operate at a low speed range.At last,the compressor impeller is numerically calculated by FINE / Turbo CFD analysis software.The compressor impeller meeting the design requirements is obtained.Finally,three-dimensional aerodynamic multi-objective optimization of the designed centrifugal impeller is performed using NUMECA’s FINE / Design3 D software package.The genetic algorithm optimized sample library is obtained by using super Latin sampling method.Multi-objective optimization uses the approximate model of artificial neural network and the performance of the centrifugal impeller has been improved.Optimization results show that: The isentropic efficiency of the impeller increases from 0.8293 before optimization to 0.841 with an increase of 1.4% at the design point.The total pressure ratio increases from 1.274 before optimization to 1.277 with an increase of 0.24%.Multi-objective optimization changes the width of the outlet of the meridian flow channel,which is the most important reason for the change of impeller performance.