Analysis on Self-ignition hazards during discharge of high-pressure flammable gas

当高压氢气突然排放到空气中时，可能会自燃。近年来，人们对这一现象进行了大量的研究。在这些实验室规模的工作中，氢释放压力的最大值为14.7 MPa。为了研究70MPa氢气的行为，我们采用了抽真空扩大压比的新方法。结果表明，该方法仅适用于空气压力大于0.07MPa的情况。自燃的另一个主要因素是氢气和空气的混合。人们发现，在两种气体到达接触面之前，氢气混合到加热的空气中。我们还测试了强制气体混合的效果。氢气通过各种几何形状的管道排出。点火的起始压力低于氢气在直管中释放时的压力。提出了一种简单的方法来估计自燃的最小压力，并进行了验证。

When high-pressure hydrogen is suddenly discharged into air, it is possible to be spontaneously ignited. Many researches were carried out on this phenomenon recently. Among those lab-scale experimental works, the maximum value for hydrogen release pressure was 14.7 MPa. In order to investigate into the behavior of 70MPa hydrogen, we adopted a new method of enlarging pressure ratio by vacuuming the air. It was found that this method to imitate high pressure hydrogen release is only valid when the pressure of air is larger than 0.07 MPa. Another major contributing factor in self-ignition is the mixing of hydrogen and air. It was discovered that hydrogen blends into the heated air before the contact surface of two gases arrives. We also tested the effect of enforced gas mixing. Hydrogen was discharged through pipes with various geometries. The onset pressures for ignition were lower than the pressure when hydrogen was released in a straight pipe. A simple way to estimate the minimum pressure for self-ignition was proposed and validation was attempted.