Excitation characteristics of lobe hydrogen circulating pump in polymer electrolyte membrane fuel cell under different clearances and pressure ratios

More specifications for the suction volume, hydrogen return volume, and pressure ratio of the hydrogen circu-lating system are needed with the development of high-power and high-efficiency vehicular polymer electrolyte membrane fuel cells (PEMFC). The working clearance and pressure ratio are essential in parameters such as pulsation characteristics, radial excitation force, leakage flow rate, and volumetric efficiency of hydrogen circulating pumps. These parameters are closely related to the noise level, reliability, and service life of the fuel cell. Transient numerical simulations of lobe hydrogen circulating pump for fuel cell vehicles (FCVs) based on CFD and dynamic mesh method were employed. The effects of four working clearances on the pulsation char-acteristics, flow field distribution, and radial excitation force were studied. The relationship between different pressure ratios on internal flow characteristics and volumetric efficiency was analyzed. The results showed that the pressure pulsation in the pump chamber and the radial excitation force on the lobe rotor have distinct periodicity. The radial force pulsation is minimized when the rotor-rotor clearance zeta L is 0.18 mm, and the rotor -casing clearance zeta r is 0.21 mm. It was found that the increase of the working clearance helps to reduce the amplitude. Moreover, as the pressure ratio rises, the pressure pulsation amplitude at the rotor-casing clearance and the leakage flow rate increase, while the volumetric efficiency decreases. The pressure ratio is the main factor affecting exhaust temperature rise.