Comparative study on the influence of inlet configurations on compressor performance in compressed air energy storage systems

This study combines numerical simulation and experimental testing to systematically evaluate the influence of radial and axial inlet configurations on the performance of a mixed-flow compressor for compressed air energy storage (CAES) systems. Comparative analyses were carried out using an inlet volute for radial intake and a straight inlet pipe for axial intake. The investigation encompasses overall compressor performance, including outlet flow field distortion and total pressure loss in the inlet volute, static pressure distribution along the blade tip, and circumferential static pressure distribution in the outlet volute. Results demonstrate that under design conditions, the axial intake compressor attains a total pressure ratio of 1.7 and an isentropic efficiency of 83.72%, representing relative increases of 1.19% in total pressure ratio and 4.8% in isentropic efficiency compared with the radial intake configuration. Furthermore, the stable operating range of the axial intake compressor is 9.7 % wider than that of the radial intake variant. Through variable speed regulation, this range can be further extended to 45.14%. In contrast, the radial intake configuration exhibits pronounced outlet flow distortion and elevated total pressure loss attributable to the inlet volute geometry. These effects are especially marked under high speed and high mass flow conditions, where both the distortion coefficient and total pressure loss increase substantially. The resulting non-uniformity in the impeller inlet flow field leads to a deterioration in overall compressor performance. The study confirms good consistency between numerical predictions and experimental measurements, thereby providing a theoretical basis and technical support for the optimization of inlet structures and the enhancement of variable condition operation in high-efficiency, wide-operating range compressors for CAES applications.