Insights into the impact of polluted moist air on transonic condensation flow to enhance compressor performance: experimental and numerical investigation

Non-equilibrium condensation in transonic moist air flows can significantly affect the aerodynamic performance and operational reliability of compressed air energy storage (CAES) compressors. Considering the non-equilibrium phase-change processes induced by strongly varying temperature and pressure conditions at the compressor inlet, the present study investigates moist air condensation through a combined experimental and numerical approach based on transonic Laval nozzle flows. A new droplet growth model is employed to predict non-equilibrium condensation processes of particulate-laden moist air in both a transonic Laval nozzle and compressor blade passages relevant to CAES systems. An integrated research approach combining experimental measurements and numerical simulations is adopted, enabling reliable prediction of condensation-induced shock structures and pressure variations under humid operating conditions. This study develops a comprehensive mathematical and physical framework and proposes a blended condensation model to capture the complex interplay between vapor condensation and particle-induced nucleation. The proposed model is validated against experimental and numerical results obtained in a transonic Laval nozzle, demonstrating reliable predictive capability. Building upon this validation, the model is further applied to investigate the flow structure and condensation behavior within compressor rotor passages under moist air conditions. The influences of inlet air temperature ranging from 282.05 to 303.15 K and relative humidity varying between 20% and 83.7% on condensation behavior and compressor-relevant performance parameters are systematically analyzed. The results show that increasing inlet relative humidity leads to an earlier onset of condensation and increases total pressure loss by approximately 6–10%, accompanied by a reduction in isentropic efficiency of up to 3%. In contrast, moderate inlet air preheating effectively suppresses premature condensation and reduces condensation-induced pressure losses by about 7–9% under high-humidity conditions. Furthermore, condensation-related irreversibility is found to intensify with decreasing inlet temperature and increasing humidity, highlighting its non-negligible impact on CAES compressor performance. These findings provide quantitative insights into condensation-driven efficiency degradation and highlight the necessity of controlling inlet humidity to ensure stable and efficient operation of CAES systems.