Electric centrifugal air compressor is one of the most important auxiliary components for the fuel cell engine, which has great impacts on the system efficiency, cost and compactness. However, the centrifugal compressor works at an ultra-high speed for a long time, which poses a great challenge to the lives of motor, bearing and seal. Therefore, reducing the rotating speed of the impeller and maintaining high pressure ratio and high efficiency are important issues for aerodynamic design of the compressor.
In this paper, a centrifugal compressor rotor for a 100kW fuel cell system is designed. Aiming at reducing the rotating speed, the influences of three key structural parameters including inlet blade angle, outlet blade angle and blade outlet radius on performance are investigated. The aerodynamic performance of the compressor is predicted using the Reynolds-averaged Navier-Stokes (RANS) equations with computational fluid dynamic (CFD) tools. The numerical simulation and experiment showed good agreement. Results show that the inlet blade angle has little impact on the pressure ratio. However, it significantly influences the compressor operation range. Impeller with a smaller inlet blade angle is more suitable for a fuel cell system. At the design point, the pressure ratio and isentropic efficiency are increased by 3.30% and 5.56% respectively with reduced inlet blade angle. Both the outlet blade angle and radius have great impacts on the pressure ratio. With increased outlet blade angle and radius, the rotating speed of the impeller can be reduced by 27.83% at the design pressure ratio, while the efficiency is almost kept the same.