Experimental study of shock wave propagation and its influence on the spontaneous ignition during high-pressure hydrogen release through a tube

Abstract

An experimental study of shock wave propagation and its influence on the spontaneous ignition during high-pressure hydrogen release through a tube are measured by pressure transducers and light sensors. Results show that the pressure behind a shock wave first increases, and subsequently remains near constant value with an increase of the propagation distance. That is, a certain propagation distance is required to form a stable shock wave in the tube. In the front of the tube, the minimum value of pressure behind the shock wave (Pshock) required for spontaneous ignition decreases with the increase in axial distance to the diaphragm. However, the minimum Pshock remains nearly a constant value in the rear part of the tube. Moreover, the critical values of shock Mach number (MS) for spontaneous ignition decrease with the increase in tube length. And the ignition delay time decreases with the increase of the MS. As the ignition kernel grows in size to a flame, it propagates downstream along the tube with velocity greater than the theoretical flow velocity of the hydrogen-air contact surface. The flame propagation velocity relative to tube wall increases with MS. When the self-sustained flame exits from the tube, a rapid non-premixed turbulent combustion is observed in the chamber. The combustion-wave overpressure increases with the increase of the MS.