Experimental study on control of flame inclination in a thermal flow reversal reactor with extra lean premixed methane/air intake

Combustion instability is a basic obstacle to the wide application of porous media combustion devices in industry. However, the investigation about it with extremely dilute gas fuel is sorely lacking due to the limitation of laboratory test conditions. In this study, inclinational instability of extra lean-premixed flame (with volume fraction below 1%) in a thermal flow-reversal reactor with honeycomb ceramic packings is investigated experimentally. The effects of inlet methane concentration on the flame inclination are studied. Then the flame inclination is restrained through electronically controlled adjustment on the valve opening and switch time. The experimental results show that the intake methane concentration has a remarkable effect on the flame inclination angle variation in each semi cycle. When the intake concentration decreases from 0.6 vol% to 0.2 vol% and the flow direction is downward, the growth of the flame inclination angle in each semi cycle gets lower. The adjustment on the scale of the high temperature zones in two half parts of the packed bed through the valve opening has a great influence on the flame front position and flame inclination angle. The setting of asymmetric switch time for the reverse flow also has obvious effect on the evolution of the flame inclination. Finally, the flame inclination angle drops firmly for approach of the two high temperature zones in size and height. The synchronous adjustment of valve opening and switch time fastens the convergence of the two high temperature zones in two half parts of the packed bed. This work is beneficial to the development of thermal flow-reversal reactor technique for better dealing with ventilation air methane and other lean gaseous fuel streams.