Optimization of high speed centrifugal compressor for a micro gas turbine based on CFD and FEM analysis

The centrifugal compressor impeller plays a significant role in the micro gas turbine. Its aerodynamic performance and structural reliability has great impact on the gas turbine system. Its aerodynamic performance and structural reliability are determined by blade design parameters and impeller back face design parameters. This paper presents a process of optimizing a centrifugal compressor impeller during the development of 100kW class micro gas turbine. Predicted by a 3D Navier-Stokes solver the aerodynamic performance is mainly affected by meridian contour and blade angle β distribution. The stress is calculated by means of a finite element analysis method and controlled by blade angle β distribution and thickness distribution at the hub. The requirement of high efficiency is met by using genetic algorithm and artificial neural network. Then the impeller back face profile is parameterized and optimized to decrease the stress of the impeller. The isentropic efficiency of the compressor is increased by 1% and the blade stress is reduced by 10% as compared with the original design. The results show that it is possible to reduce the centrifugal stress in the impeller without penalizing the aerodynamic performance through the optimization method.