The air compressor is a key component in the polymer electrolyte membrane (PEM) fuel cell system and its performance has great impact on the electric power output from the system. Here, analysis was conducted firstly on the Roots-type compressor with fixed internal compression based on the volume reduction created by helical rotors. The built-in volume ratio variations with the wrap angle and the lobe numbers were calculated and discussed. Then a prototype of the Roots-type air compressor with 6 lobes was developed according to the outcomes of the research. The volumetric and isentropic efficiency of the prototype were measured under the discharge pressures from 0.11 MPa to 0.25 MPa while the rotation speeds from 10000 to 14000 rpm. Under the design conditions, the volumetric efficiency and isentropic efficiency of the Roots-type air compressor were 75.8% and 53.9% respectively. It was concluded that this kind of Roots-type air compressor is especially suitable for the fuel cell systems applied in the range extended electric vehicles.

空气压缩机是聚合物电解质膜（PEM）燃料电池系统的关键部件，其性能对系统的电力输出有很大影响。在这里，首先对基于螺旋转子产生的容积减少的具有固定内部压缩的罗茨式压缩机进行了分析。计算和讨论了内建体积比随包角和瓣数的变化。然后根据研究成果研制了6叶罗茨式空压机样机。在排气压力为 0.11 MPa 至 0.25 MPa 和转速为 10000 至 14000 rpm 的条件下测量原型的体积效率和等熵效率。在设计条件下，罗茨式空压机的容积效率和等熵效率分别为75.8%和53.9%。结果表明，这种罗茨式空气压缩机特别适用于增程式电动汽车的燃料电池系统。