Effect of dimethyl ether addition on flame stability of premixed methane/air in a micro-planar quartz combustor

Abstract

Blended combustion has a potential to promote flame stability under micro-scale condition. For this, the effect of dimethyl ether (DME) addition on the flame stability of premixed methane/air confined within a quartz combustor is explored through experimental approach. Seven flame propagation modes are observed for pure methane-air combustion. Experimental results indicate that flame stability could be remarkably enhanced, especially under fuel-lean conditions, and the flame is able to sustain stable combustion for some extreme circumstances with DME addition. To further understand the underlying mechanism of enhanced flame stability, detailed analyses regarding flame shape range and flame transition point as a function of blended ratio are also conducted. The existence range of various flame shapes can be generally broadened to some degree as increasing blended ratio, which is due to the increased value of flame transition point. Furthermore, it is found that variation frequency of weak flame decreases with an increase in blended ratio and inlet velocity. For sufficiently high blended ratio under fuel-lean condition, oscillating flame disappears, which indicates that flame is much more stable in this case. The reason for enhanced flame stability could be related to the increased flame speed and large extinction strain rate with DME addition.