Three-dimensional turbulent optimization of vaned diffusers for centrifugal compressors based on metamodel-assisted genetic algorithms

摘要

In this work, the performance of an automotive turbocharger centrifugal compressor, to be used in a microturbine for combined heat and power applications, have been improved through a design optimization procedure for vaned diffusers. This methodology couples a genetic algorithm with a three-dimensional turbulent computational fluid dynamics code. The computational costs have been reduced by using a Kriging metamodel to assist the genetic algorithm. The simulations have been performed by considering both the impeller and vaned diffuser, in order to account for the turbulent, three-dimensional, and non-uniform flow conditions at the diffuser inlet. A multi-objective optimization problem has been solved by minimizing two objective functions, which depend on the compressor stage total-to-static pressure ratio and total-to-total isentropic efficiency. The design variables are the position and inclination of the diffuser vanes leading and trailing edges, the vane number, and the diffuser outlet radius. Three optimized geometries extrapolated from the Pareto front exhibit higher static pressure recovery than the vaneless diffuser, but only one has better efficiency. Nevertheless, the performance of the current compressor can be improved by substituting the vaneless diffuser with a vaned one.