On the Mechanism of Rapid Flame Propagation in a Rotating Flow

从旋涡爆燃机理上解释了旋转气流中火焰的快速传播，认为低密度的热燃烧气体被强制卷入高密度的未燃烧气体混合物中。第一年考察了火焰速度与旋转气体速度之间的关系，指出该理论不能定量地解释结果。第二年，验证了假设火焰前面的压力低于火焰后面的压力的理论，这是因为在低密度的热燃烧气体中离心力较弱，因此旋转轴上的压力不能与环境压力相比降低太多，而在高密度的未燃烧气体中离心力较强，因此，在低密度的热燃烧气体中，离心力较弱，因此，在高密度的未燃烧气体中，离心力较强。旋转轴上的压力变得比环境压力低得多。利用高响应微差分压力计和瞬时存储器，测量了旋转混合气中火焰传播的压力分布。为了进行比较，还测量了火焰在静止可燃混合物和非旋转混合流中传播的压力分布。结果表明，正如理论预测的那样，火焰前方的压力低于火焰后的压力。结果表明，火焰进气速度仅为预计速度的1/2或1/3。今年的附加实验证实了这一点。第一年的成果已发表在《宇航与航空进展》上，最后一年的成果将发表在《燃烧科学与技术》上。

The rapid flame propagation in a rotating flow is explained on the vortex bursting mechanism, in which it is considered that the hot burned gas of low density is forcibly involved into the unburned gas mixture of high density. In the first year, the relation between the flame speed and the rotating gas speed was examined and it was pointed out that quantitatively the theory could not explain the results.In the next year, the pressure distribution across the flame front was exaimed to substantiate the theory in which the pressure ahead of the flame is assumed to be lower than that behind the flame, because the centrifugal force is weak in the hot burned gas of low density, and hence, the pressure on the axis of rotation cannot be decreased much as compared with the ambient pressure, whereas the centrifugal force is strong in the unburned gas of high density, and hence, the pressure on the axis of rotation becomes much lower than the ambient pressure. Resultingly, the pressure behind the flame becomes higher than the pressure ahead of the flame.Using a high-response, micro-diffential manometer and a transient memory, the pressure distribution was measured for the flame propagating in a rotating mixture. For comparison, the pressure distribution was also measured for the flames propagating in a quiescent combustible mixture and in a non-rotating mixture stream. The results show that, as the theory predicts, the predicts, the pressure ahead of the flame is lower than the pressure behind the flame. However, it is shown that the flame apeed is only one half or one third the predicted speed. This is confirmed by the additonal experiments this year. The results obtained in the first year have been published in Progress in Astronautics and Aeronautics, and those in the last year will appear in Combustion Science and Technolgy.