Investigation of the Stability Criterion for Axial Compressor under Circumferential Total Pressure Distortion

Abstract

The distorted inlet flow that is a widespread flow phenomenon in compressors not only reduces the compressor performance but more seriously deteriorates the compressor stability, thus threatening flight safety. However, quantitatively determining the stability boundary is challenging due to the complexity of the distorted inlet flow. The effective static-pressure-rise coefficient in the stability criterion from Koch, a stability analysis method under clean inlet flow, was applied to explore the compressor stability under circumferential total pressure distortion. Using a series of single-stage axial compressor experiments for aspect ratio and solidity, this study investigated the influence of the distortion index on compressor stability. Subsequently, based on the analysis method under clean inlet flow, a new stability criterion under circumferential total pressure distortion was established to determine quantitatively the stability boundary. In addition, the stability criterion for determining the stability boundary was combined with the body force model for calculating the compressor performance to simulate a five-stage axial compressor under 120° total pressure distortion, and the results were in agreement with the experimental data to verify the stability criterion. Numerical simulation was used to show the internal flow field in the compressor, analyze the load at each stage, and identify the instability stage that induces stall, which can provide a reasonable solution for determining the stability boundary of a multistage axial compressor under circumferential total pressure distortion. The combination can serve as a convenient preliminary design tool to evaluate compressor stability using fewer computational resources. Most stability investigations adopt simple methods such as numerical divergence and specified parameters under circumferential total pressure distortion, which makes the stability boundary inaccurate. Since the stability analysis methods under clean inlet flow have been studied more deeply so far compared to that under distorted inlet flow, a new stability analysis method under circumferential total pressure distortion is established to quantitatively determine the stability boundary based on the stability analysis method under clean inlet flow. Therefore, in the preliminary design phase, the stability analysis method is combined with the model for calculating the compressor performance to scientifically evaluate the stability of the multi-stage axial compressor under circumferential total pressure distortion. Also, the combination simply requires fewer computational resources than the millions of grids in commercial software.