Spontaneous ignition of high-pressure hydrogen and boundary layer characteristics in tubes.

Hydrogen is efficient and environmentally friendly, but the danger of self-ignition resulted from the leakage of high-pressure hydrogen cannot be ignored. In this work, the self-ignition of high-pressure hydrogen released through different conditions was studied. 700-mm-length tubes with different diameters were adopted in our experiments. It summarized the characteristics of shock waves' attenuation and evolution process of hydrogen jets in tubes. In addition, effects of the boundary layer on the leading shock waves, the contact surface, and expansion waves were discussed. Results indicate that minimum pressure when self-ignition occurs for 15-mm-diameter tube is similar to 10-mm-diameter. And they have closely velocity of shock waves. Simulations show that the greater the release pressure, the more ignition products of hydrogen. Higher release pressure and smaller diameter can create a thicker boundary layer in micro shock tubes, and the boundary layer can lead to a change in the velocity of shock waves' structures. • The minimum pressure when self-ignition occurs is similar in 700-mm-length tubes with different diameters. • Higher release pressure and smaller diameter tubes result in thicker boundary layer. • Boundary layer of micro shock tube affects shock-wave propagation and hydrogen self-ignition. [ABSTRACT FROM AUTHOR]