For solving the problem of ineffective utilization of energy dissipation in the process of high-pressure hydrogen decompression,based on the relevant design experience of Pelton expander and the hydrogen supply system of hydrogen fuel cell ship “Lihu”,an impingement hydrogen expander composed of Laval nozzle and double circular arc blade impeller was proposed and designed to recover hydrogen pressure energy dissipation.In order to further study the internal flow field,vortex losses and energy output performance of the hydrogen expander,the performance of hydrogen expander under the operating conditions of the ship at full speed was simulated by using Fluent software,taking hydrogen inlet temperature and outlet back pressure as variables.The results show that the overall velocity and temperature gradient of the expander are large,there is a shock wave in the process of air injection and a pressure vacuum along the exit of the nozzle.The vortexes of different sizes are produced when the air flow hits the blade.When the inlet pressure of the hydrogen nozzle is 2 MPa and the mass flow rate is 1.311 g/s,the average output torque of the device is 0.136 85 N·m.With the increase of inlet temperature,the gas injection speed increases and the gas upward trend weakens.The changes of inlet air temperature and back pressure have little influence on torque and great influence on rotational speed.