Recirculation-groove coupled casing treatment for a transonic axial compressor

Abstract

This paper investigates a novel casing treatment for an axial compressor that combines a circumferential casing groove with flow recirculation channels. This casing treatment is located in the rotor's tip region and comprises a single shallow circumferential groove with 36 recirculation channels that are distributed equally around the annulus. The effects of the casing treatment on the stability and aerodynamic performance were evaluated numerically on a NASA Stage 37 single-stage transonic axial compressor. The results show that the addition of the recirculation channels improved the gain in stall margin while mitigating the penalty in the adiabatic efficiency and pressure rise compared to a casing groove without recirculation channels. Six geometric parameters were examined in a parametric study. The maximum increase in stall margin was 42.5% with small reductions in the efficiency and pressure ratio. To maximize the stall margin and minimize efficiency loss, two design variables were selected to perform a multi-objective optimization using a multi-objective genetic algorithm coupled with surrogate models using a radial basis neural network. The optimization successfully improved both the objective functions for all representative designs compared to the reference design.