Performance analysis of the two-stage axial compressor with 90-degree bend inlet conditions

Abstract

The 90-degree bend is one of the basic connection components applied in industrial flowing systems. This bend influences the aerodynamic performance of the downstream connecting equipment. In this study, the performance of a two-stage axial compressor with a 90-degree bend inlet was numerically and experimentally analyzed under low rotating speed. The testing results show that the outflow of the bend was numerically non-uniform in the circumferential and radial directions. To analyze the performance influence of the bend on the downstream compressor, a full passage compressor model with and without the inlet bend was simulated. The size of the distortion region gradually spread to the entire cascade, and the intensity of the distortion obviously dropped after the first stage as the compressor ran with the bend. The deterioration of the compressor performance, especially in the first stage, was verified numerically and experimentally. The total pressure coefficient and isentropic efficiency decreased by 2.6 % and 1.13 %, respectively. To save simulation cost, a model with a downstream single blade passage and cylindrical inlet was proposed, and the distorted flow was set as the inlet boundary condition. In addition, the unsteady numerical simulation was performed with the rotating inlet distortion region. Compared with the full blade passage model, the unsteady single blade passage model obtained the downstream spread characteristic of the distortion and performance deterioration. The latter can therefore be suggested as a compromised approach for obtaining the propagation characteristics of the inlet distortion with acceptable accuracy and low computational cost.