Effect of the leak port area and tube length on suppression of spontaneous ignition of high-pressure hydrogen

Suppression of high-pressure hydrogen spontaneous combustion is essential for the sustainable development of hydrogen energy. Previous studies have shown that suppressing hydrogen spontaneous combustion by reducing the area of the leak port is a feasible method. However, the effect of some factors, such as tube length, on this suppression method has not received attention. Therefore, the effect of leakage port areas of 10 mm, 8 mm, 6.6 mm, and 4.5 mm on the suppression of hydrogen spontaneous combustion was investigated experimentally and simulated for different pipe lengths. The results show that reducing the leak port area increases the hydrogen-air mixing path, which raises the combustible concentration. However, by reducing the leak port area, the intensity of shock waves and the maximum temperature in the tube decreased significantly, and the possibility of hydrogen spontaneous combustion decreased. This indicates that reducing the leak port area can inhibit hydrogen spontaneous combustion. In addition, within a certain leak area, increasing the tube length weakens the performance of this inhibition method. However, the effect of tube length on this method disappears as the leak area decreases. Finally, the leakage port area is reduced, changing the flow field at the nozzle, so that the spontaneous combustion flame in the near field of the nozzle undergoes extinguishment and re-ignition. The results show that reducing the area of the leakage port can effectively inhibit hydrogen self-ignition and is not affected by the length of the tube, providing a way to inhibit hydrogen self-ignition.