In this paper, direct numerical simulations are performed in order to investigate whether an ignition will happen when a small hole is opened suddenly on the wall of an extremely high pressure hydrogen tank and a hydrogen jet is ejected out of the tank into the air. Two-dimensional axisymmetric Euler equations with a full chemical mechanism of hydrogen-air mixture are employed, where the detailed chemical mechanism consists of 9 species and 18 elementary reactions. Mass diffusion and heat conduction terms are included in the governing equations. The diameter of the hole is 1 mm. Three cases of tank pressures, 10, 40 and 70 MPa, are simulated. The results show that a local combustion occurs at the tip region of the contact surface at 10 µs after hydrogen jetting out from the hole for the 40 and 70 MPa tank pressure cases. This local combustion is caused by the strong shock wave which heats up the air in front of the hydrogen jet to a very high temperature. However, as the jet propagates away from the tank wall, its strength drops off and the local combustion is quenched quickly. The results demonstrate that the local combustion is blown off and it can not develop into a stable jet flame under the pressure and the diameter of the hole being examined in this study.
Hydrogen jet, Auto-ignition, Shock wave, High pressure, Numerical simulation