Analytical modeling and performance improvement of an electric two-stage centrifugal compressor for fuel cell vehicles

Abstract

The integrated two-stage electric centrifugal compressors are most widely used in the present fuel cell vehicles. Air compressors influence the efficiency of fuel cell systems significantly, so it is crucial to improve the energy efficiency of centrifugal compressors. However, there is a lack of centrifugal compressor performance models that can reflect the thermodynamic characteristics of two-stage compression system, which is the main focus of this paper. In this paper, an analytical model of two-stage centrifugal compressor performance considering the thermodynamic characteristics of two-stage compression was first derived and experimentally validated. The single-stage centrifugal compressor model (SSCCM) can be treated as a lumped parameter model of the two-stage centrifugal compressor to predict the compressor performance. Therefore, the SSCCM and the two-stage centrifugal compressor model (TSCCM) were compared. The results show that the TSCCM is more accurate and robust. Furthermore, a novel compressor structure equipped with an intercooler in the inter-stage piping was proposed to improve the energy efficiency of the centrifugal compressor. Based on this novel structure, the TSCCM was modified. Finally, a quantitative analysis was performed to study the effect of an inter-stage intercooler on compressor efficiency. Compared to the original compressor without the inter-stage intercooler, the efficiency improvement by the inter-stage intercooler can be in the range of 3.29–3.97%, with power savings of 0.332–0.635 kW. The study can be used to support engineers and researchers in fast identifying effective solutions in terms of design for the next generation of centrifugal compressors.