Instability of Premixed Flame and its Turbulent Combustion Properties under High Pressure

本文研究了压力对预混火焰传播的影响。在过去的一年里，我们发现火焰伸展对层流燃烧速度的影响可以很好地用Markstein长度来评价，并且它随着压力的变化而变化。当混合气的Markstein长度较小时，球形层流火焰表面会产生一些裂纹。稀薄甲烷和富丙烷混合物表现出这种特性。对于本研究中考察的所有混合物，马克斯坦长度随着压力的增加而变小。随着压力的增加，裂纹在扩展的早期阶段形成。对于马尔可斯坦长度较小的混合气，火焰上覆盖着泡孔。随着Markstein长度的减小，这种从层流火焰向胞状火焰转变的时间变得更早。随着压力的增大和Markstein长度的减小，晶胞尺寸也变小。

In this study, the effects of pressure on the premixed flame propagation was investigated. In the last year, we had shown that the effects of flame stretch on the laminar burning velocity could be evaluated well by the Markstein Length and it varied according to the pressure.In this year, our study found that the flame instability was notable when the Markstein Length was small. When the Markstein Length of the mixture was small, some cracks were formed on the surface of the spherical laminar flame. Lean methane and rich propane mixtures showed this properties.For all the mixtures examined in this study, Markstein Length became small according to the pressure. Cracks were formed in the early stage of the propagation with increasing the pressure. For some mixture with small Markstein Length, flame was covered with cells. The timing of this transition to cellular flame from laminar flame became earlier as the Markstein Length was smaller. The size of cell also became small with increasing the pressure and decreasing the Markstein Length.