Experimental investigation of the performance and surge approaching characteristics of a two-stage centrifugal air compressor for a fuel cell system

The air centrifugal compressor used in fuel cell systems often faces the challenge of variable operating conditions and the need to operate near the surge boundary. Understanding its performance characteristics within the operating range and the surge approaching process is crucial for enhancing the safety of the fuel cell system. This study conducts detailed tests on the staging characteristics and surge development process of a two-stage centrifugal air compressor for a fuel cell system under typical low-speed operating conditions. The stage performance and dynamic pressure traces are obtained with high-response sensors under various working conditions, from stable to surge. It is found that the vibration under surge conditions is not highly destructive for the small compressor. The high-pressure stage of the compressor is more prone to surge due to the interactions of the two stages. A special process, named self-recovering surge progression, is found where significant pressure fluctuations occur, but could revert to a relatively stable state as the surge approaches. At 60 000 rpm, a low-frequency peak of 15.73 Hz is observed during self-recovering surge progression, close to the Helmholtz frequency and the surge frequency of the compressor system. It is suggested that the self-recovering surge progression could be regarded as a precursor to surge. This study can provide experimental references for the analysis of the surge development characteristics and surge detection of the small multi-stage centrifugal compressor used in the air supply system for fuel cells.