Aerodynamic Characteristics of Typical Operating Conditions and the Impact of Inlet Flow Non-Uniformity in a Multi-Stage Transonic Axial Compressor

Multi-stage axial compressors play a crucial role in aerospace propulsion systems, as their exit flow field characteristics directly impact engine performance and stability. This study conducted numerical simulations on the first 3.5 stages of the NASA 74A transonic multi-stage axial compressor to analyze the exit flow field characteristics under different typical operating conditions. The research primarily investigated airflow deflection angle, radial velocity distribution, and their variation patterns. Additionally, the effects of inlet airflow angle and pressure variations on the exit flow field under non-uniform inlet conditions were examined in detail. The results indicate that at 68% rotational speed, the exit flow field of the NASA 74A compressor deteriorates significantly, with noticeable changes in distribution patterns. For the other four operating conditions, as the rotational speed decreases, both velocity and airflow angle exhibit a positive correlation with rotational speed. Compared to the design condition, peak velocity decreases by 2%, 3.7%, and 7%, while airflow deflection angle changes remain within 3°. Under non-uniform inlet conditions, when the inlet airflow angle decreases from 90° to 70°, variations in peak and average exit velocities remain within 2%, and the changes in peak and average airflow deflection angles are within 1%. However, when the inlet airflow angle decreases from 90° to 70°, the curve of the airflow deflection angle exhibits a leftward shift, with a deviation of 2.6%. Meanwhile, changes in inlet pressure under non-uniform conditions have a relatively minor impact on the overall flow field but significantly affect local distributions. When the inlet pressure increases from 1 atm to 1.05 atm, peak velocity increases by 0.98%, and average velocity rises by 3%. The maximum velocity difference reaches 6%, while the average airflow deflection angle differs by 0.7%, with a maximum deviation of 1.9°. Overall, the compressor exit flow field undergoes significant variations under different operating conditions, with increased flow instability at lower rotational speeds leading to flow separation, low-energy fluid accumulation, and non-uniform pressure distribution. In contrast, non-uniform inlet conditions have a relatively minor effect on the overall flow field but induce noticeable local changes, providing theoretical insights for compressor design optimization and performance evaluation.