Clearance Impact on Hydrogen Recirculation Pump Applied in Proton Exchange Membrane Fuel Cell Systems

The clearance between the impeller and pump head is a critical parameter of the hydrogen recirculation pump used in proton exchange membrane fuel cell (PEMFC) systems, and it significantly affects performance, efficiency, and reliability. This study investigates the impact of clearance on the performance of a hydrogen recirculation pump applied in PEMFC systems. Both numerical simulation and experimental methods are employed to systematically evaluate the effects of symmetric circular clearances ranging from 0 to 0.4 mm, as well as asymmetric clearance configurations representative of manufacturing tolerances and assembly deviations. According to the research results, the pressure rise increases with the clearance decreasing under a given flow rate, and a smaller clearance would show a stronger capability to cover a larger flow rate range. The clearance impact on the performance of the hydrogen recirculation pump is found to be in the lower flow rate zone. In addition, the pressure distribution inside the hydrogen recirculation pump shows that the pressure would increase from the inlet to the outlet and increase along the circumferential direction of the impeller. The flow pressure at the inlet side is different from the flow pressure at the outlet side, which results in asymmetric clearance. And this brings a negative impact on the flow performance of the hydrogen recirculation pump. The flow performance capability of the hydrogen recirculation pump with the asymmetric clearance condition is not as good as that with a base clearance of 0.2 mm, and it is better than that with a clearance of 0.3 mm. When the flow rate is higher than 450 LPM, the clearance impact and the asymmetric clearance impact on the performance become insignificant. Based on a combined assessment of hydraulic performance and pressure stability, a clearance of approximately 0.2 mm is suggested as a potential optimal design target based on simulation results and observed trends. The simulation results show good agreement with experimental data, with deviations within 10% across the investigated operating conditions.