Numerical study on the dynamic process of reciprocating liquid hydrogen pumps for hydrogen refueling stations

Abstract

Reciprocating liquid hydrogen pump operates under alternating pressure, temperature, and flowrate with dramatic changes in the thermodynamic states of liquid hydrogen. The thermodynamic state in the pump is influenced by the dynamic interactions between fluid flow, heat transfer, piston motion, and valve dynamics. This paper presents a numerical study for reciprocating liquid hydrogen pumps based on a coupled simulation of the dynamic processes between the alternating flow, unsteady heat transfer, and valve dynamics with a given piston motion as the input. A pump for hydrogen refueling stations with a nominal flowrate and delivery pressure of 50 kg/h and 87.6 MPa is selected as the research object. The appropriate design parameters of the pump and its valves are determined to avoid cavitation in the cylinder and oscillation of the valves. The effects of the frequency and delivery pressure on the valve motion and pump performance are further analyzed. Finally, the in-cylinder heat transfer leads to an extra evaporation loss of 0.012 kg/day, and the isentropic and volumetric efficiencies of the liquid hydrogen pump are 97.30% and 90.76% respectively. The work presented here would be beneficial for the design and optimization of reciprocating liquid hydrogen pumps.