Modeling of hydrogen leakage and dispersion from a hydrogen fuel cell vehicle

Hydrogen fuel cell vehicles (HFCVs) operate with zero emissions and can be refueled quickly, making them a promising alternative to traditional gasoline vehicles in the future. However, hydrogen is a highly flammable and explosive gas, and leakage from the onboard high-pressure hydrogen storage tanks in hydrogen fuel cell vehicles can easily result in hydrogen explosion accidents. Therefore, the characteristics of hydrogen leakage and dispersion in HFCVs should be carefully studied to ensure the safety in large-scale deployments of HFCVs. This study used the FLACS software to simulate the hydrogen leakage and dispersion from a hydrogen fuel cell vehicle for different operating conditions to investigate the effects of driving speed and leakage direction on the development of combustible clouds. The results show that when the vehicle is stationary and the leakage direction is perpendicular to the ground, the hydrogen gas impacts the ground after leakage and the combustible cloud quickly spreads around the vehicle. Subsequently, the combustible cloud begins to rise due to buoyancy and surrounds the vehicle within 9 s after the leakage. The flow rate of leakage slows down as the amount of hydrogen in the storage tank decreases, and the combustible cloud gradually dissipates. When hydrogen leaks forward at an angle of 45°, the combustible cloud does not encircle the bodywork and spreads mainly towards the front of the vehicle, and the volume of the combustible cloud decreases and dissipates faster. The airflow around the vehicle body significantly affects the hydrogen dispersion when the vehicle is moving. The leaked hydrogen spreads in the opposite direction to the vehicle's movement, forming a long and narrow hydrogen cloud. The hydrogen cloud dissipates more quickly than the stationary case due to the counter airflow. The rate of dissipation of hydrogen leaking vertically downwards is accelerated due to the counter airflow, but it is slowed down for hydrogen leaking forwards at an angle of 45°.These results can provide references for the structural design of hydrogen fuel cell vehicles and the formulation of emergency response plans.