Dynamics characteristics analysis of the oil-free scroll hydrogen recirculating pump based on multibody dynamics simulation

The hydrogen recirculating pump is the key equipment of the hydrogen recirculating system for the fuel cell vehicles. The scroll pump is one of the preferred types of hydrogen recirculating pumps because of its unique advantages of higher efficiency and lower noise. In order to provide valuable basis for improving the reliability and durability of hydrogen pumps under oil-free high-speed conditions, this paper carried out dynamics performance research based on the theoretical method. The gas force, force and torque of moving parts were calculated. Tangential gas force is about 100 N and axial gas force is about 200 N which are much smaller than the traditional scroll compressors due to lower designed pressure ratio of hydrogen pump. Due to the exist of bearing assembly tolerances of sub-crankshafts during practical operation, the actual contact forces and dynamics characteristics were further analyzed based on multibody dynamics simulation. It is found that the rotating speed and the actual assembly tolerance have significant influence on the dynamics characteristics. The radial and tangential forces can reach 3000 N at 6000 r·min⁻¹ which is three times than the value at 3000 r·min⁻¹. Furthermore, the service lives of bearings were analyzed. The contact force considering assembly tolerance presented the high-frequency oscillations. When the size of clearance is increasing, the oscillation frequency is reducing, but the contact force is enlarging. The radial force on a sub-crankshaft was 30 N without assembly tolerances. It increased to 150 N and 330 N, respectively, when the assembly clearances were designed separately as 2~−14 μm and −8~−24 μm, and the corresponding bearing service life decreased by 46% and 83%.