Numerical Study on Fast Filling Process of Vehicle Liquid Hydrogen Cylinder

The vehicle liquid hydrogen cylinder is easy to be overfilled due to the fast filling speed and the small size of hydrogen cylinder during the filling process and safety accidents might be caused. A three-dimensional symmetric model is built for vehicle liquid hydrogen cylinder that is equipped with an ullage tank, and a numerical study using CFD simulation method is performed on the fast filling process of vehicle liquid hydrogen cylinder. The effects of hole sizes, filling rate, initial filling rate and volume of overfill prevention device on the performance of the overfill prevention devices are studied. The results have been obtained. The hole sizes have a significant effect on the performance of the overfill prevention device, which limits the flow capacity of liquid. When the hole size is 6mm and the initial filling rate is 50%, the cylinders will be overfilled at the end of filling, and the maximum filling rate can reach 98.4%. The use of large volume overfill prevention devices can reserve more phase for cylinders, but it will also lead to issues such as insufficient filling. When the volume of overfill prevention device is 100L, the final filling rate is only 77.2%.