Ignition and transition to detonation under chain-branching kinetics

氢是一种有吸引力的汽车燃料，因为它燃烧时不会释放二氧化碳或其他温室气体，而且它是燃料电池的首选燃料。水力发电或风能产生的氢气是碳中性的。然而，由于氢气与碳氢化合物燃料相比具有明显不同的行为，因此在允许广泛的氢气储存和分配设施与人口稠密地区密切接触之前，需要解决重大的安全问题。同样，在隧道和公共车库的车辆中储存氢气也存在安全问题。由于氢气非常轻且浮力强，因此只要确保在不允许公众进入的地方周围有足够的距离，就可以确保户外装置的安全。然而，在封闭的环境中，仍然存在严重的问题，主要与爆炸的风险有关，氢气比其他燃料更容易发生爆炸。爆轰是最猛烈的燃烧形式，在这种燃烧中，燃烧依靠它所支持的冲击波。因此，只要遇到可燃混合物，爆震波就会以超声速传播，并引起通常几十个大气压的压力增加，这是非常具有破坏性的，可能导致比最近勃朗峰隧道事故更严重的事故。不幸的是，导致爆炸的机制仍然存在很大的不确定性，即使是氢，它的化学性质比其他更复杂的燃料更为人所知，至少在相对较低的压力下。此外，有可靠的实验证据表明，高压氢气突然释放到大气中可能会自燃，其机制也不太清楚。当前工作的目标是澄清氢化学的特定特征与爆炸和自发喷射点火的外观之间的关系。为此，数值模拟和数学分析将对一系列情景进行，从相对简单的情景到越来越复杂和现实的情景。

Hydrogen is an attractive automotive fuel because it burns without releasing CO2 or other greenhouse gases, and because it is the fuel of choice for fuel cells. Hydrogen production from hydro power or wind energy is carbon-neutral. However, because hydrogen has a markedly different behaviour when compared with hydrocarbon fuels, there are significant safety issues that need to be resolved before widespread hydrogen storage and distribution facilities are allowed in close contact with populated areas. Likewise, there are safety issues associated with hydrogen storage in vehicles in tunnels and public garages. Because hydrogen is very light and buoyant, outdoors installations can be made safe by ensuring that there is enough distance around where the public is not allowed. However, in enclosed environments, serious issues remain, mostly associated with the risk of detonation, which hydrogen is much more prone to than other fuels. Detonation is the most violent form of combustion, in which combustion rides on a shock wave which it also supports. Thus detonation waves travel at high supersonic speeds as long as they encounter combustible mixture, and they entail a pressure increase usually in the tens of atmospheres, which is quite destructive and could result in accidents more serious than for instant the recent Mont-Blanc tunnel accident. Unfortunately, major uncertainties remain on the mechanisms leading to detonation, even for hydrogen, the chemistry of which is better known than other more complex fuels, at least at relatively low pressures. In addition, there is reliable experimental evidence showing that a sudden release of high pressure hydrogen into the atmosphere may ignite spontaneously, under a mechanism that is not well understood either. The goal of the current work is to clarify the relationship between specific features of hydrogen chemistry and both appearance of a detonation and spontaneous jet ignition. To that effect, numerical simulation and mathematical analysis will be performed for a hierarchy of scenarios, starting from relatively simple ones to increasingly more complex and realistic ones.