Extinction of Hydrogen Premixed Flames by Turbulence

氢是未来很有前途的燃料。利用逆流燃烧器研究了氢-空气预混火焰的特性。在可燃性范围内的氢-空气混合物从多孔圆筒中喷射出来。从底部向转换喷嘴输送具有相同当量比和均匀速度分布的氢气-空气混合物。在碰撞流场的停滞区产生稳定的双火焰。本文通过对等效比的计算，研究了层流氢气-空气火焰的熄灭机理，以及湍流对熄灭现象的影响。结果表明，仅用火焰拉伸法扑灭氢-空气火焰需要大量的氢气。因此，氢燃料被氮气稀释，并构建了供氮系统，在少量氢气的情况下扑灭氢-空气火焰。首先，用氮气将燃料稀释85%。结果表明，在倾斜侧，火焰熄灭极限随着等效比的增大而增大，在等效比为1.0时达到最大值。由于燃烧不完全和热损失，上下火焰距离减小，出现熄灭极限。另一方面，对于丰富的火焰，熄灭极限再次降低。即使在熄灭状态下，两个火焰之间的距离也很远，熄灭只是由于火焰的伸展。因此，路易斯数是火焰熄灭的重要参数。我们打算考虑湍流对火焰熄灭的影响。但是，氢、氮供给系统和流量控制系统的建设非常耗时。因此，湍流对火焰熄灭的影响在目前的研究中无法测量。然而，我们已经建立了危险的氢气-空气混合物的实验程序。少

Hydrogen is the promising fuel for future. The characteristic feature of he hydrogen-air premixed flame was investigated using the counterflow burner. The hydrogen-air mixtures within the inflammability limits were ejected from the porous cylinder. The hydrogen-air mixture of same equivalence ratio and uniform velocity distribution from the conversing nozzle was supplied from the bottom. The stable double flame was produced in the stagnation region of the impinging flowfield. In the present study, the flame produced in the counterflow were investigated the extinction mechanism of laminar hydrogen-air flame by varuing the equivalence ratio and the effect of the turbulence on the extinction phenomenon.It was made clear that the large amount of the hydrogen is needed to extinguish the hydrogen-air flame by flame stretch only. Therefore the hydrogen fuel is diluted by the nitrogen and we constructed the nitrogen supply system to extinguish the hydrogen-air flame at small amount of the hydr … More ogen. Firstly, the fuel was diluted by 85% with nitrogen. As a result, on the lean side the extinction limit at which the flame was extinguished increases with the equivalence ratio and the maximum appeared at the equivalence ratio of 1.0. The distance of the upper and lower flame decreased and extinction limit appears due to the incomplete combustion and heat loss. On the other hand, for the rich flames the extinction limit decreases again. The distance between two flames is far even at the state of extinction and extinction occurs only due to flame stretch. Therefore the Lewis number is the important parameter for flame extinction.We were intended to involve the effect of turbulence on flame extinction. However, it was very time consuming to construct the hydrogen and nitrogen supply system and flow controlling system. So the effect of turbulence on the flame extinction could not measure in the present study. However, we have establised the procedure of experiments of dangerous hydrogen-air mixture. Less