Effect of rotational speed on unstable characteristics of lobe hydrogen circulating pump in fuel cell system

The hydrogen circulating pump is an essential component of hydrogen fuel cell systems. It plays a vital role in improving hydrogen utilization efficiency and optimizing hydrothermal control capabilities. Due to its compact design, high efficiency, and outstanding low-temperature adaption performance, the lobe hydrogen circulating pump has excellent potential for hydrogen recirculation in fuel cell vehicles (FCVs). This paper investigated the internal flow characteristics of a lobe hydrogen pump for FCV under different rotational speeds by experiments and computational fluid dynamics (CFD). Moreover, the lobe rotor domain was calculated using the dynamic mesh method. The effects of different rotating speeds on transient pressure pulsation, exhaust flow rate, external noise, and vibration were studied. The result reveals that the volumetric efficiency improves with the increased lobe rotor speed when the pressure ratio remains constant. The vibration acceleration level (VAL) and the external noise also increase. The vibration is most significant at the pump casing outlet and tends to decrease as the frequency increases. The sound pressure level spectrum has a discrete character in the low-frequency band, with peaks mainly concentrated at the rotating fundamental frequency and harmonics. The middle and high frequency bands have prominent broadband characteristics, and the energy is relatively concentrated.