Design optimization of vaned diffusers for centrifugal compressors using genetic algorithms

Abstract

This paper describes a three-dimensional design optimization procedure of vaned diffusers for centrifugal compressors, based on the coupling of a Genetic Algorithm (GA) and the CFD code TASCflow. The aim of the optimization is to find the combination of the geometrical parameters of the diffuser that assures, for a given operating condition of the impeller, the maximum pressure recovery with the minimum amount of thermodynamic losses. Physical quantities involved in the fitness functions of the optimization are calculated by means of steady state simulations using the CFD code. The Genetic Algorithm is a multi-objective in-house optimization code based on the canonical genetic and Pareto ranking operators. The method presented in this paper is virtually independent from the operating conditions of the machine, and therefore can be used as a general tool to search for optimal configurations for any mass flow rate and pressure-ratio of the impeller. Moreover, it is useful to investigate the behavior of a single optimal solution as a function of the operating range of the compressor. The effectiveness of the method is demonstrated by comparing the performances of a real vaned diffuser with those of a series of optimized diffusers for both efficiency and pressure recovery.