Effects of bluff body shape on the flame stability in premixed micro-combustion of hydrogen–air mixture

Combustion characteristics and flame stability of lean premixed hydrogen–air mixture in a micro-combustor with different shapes of bluff body (circle, ellipse, diamond, semicircular, half ellipse, triangle, crescent, arrowhead and wall-blade) under various physical and chemical circumstances were investigated by solving two-dimensional governing equations. The blow-off limit of different bluff bodies, combustion efficiency, wall temperature and exhaust gas temperature of micro-combustor were examined. The results illustrate that in moderate equivalence ratio (∅ = 0.5) and low velocity (V = 10 m/s), the maximum flame temperature occurs when a wall-blade is applied as a bluff body. When the inlet mixture velocity increases from V1 = 10 m/s to V2 = 20 m/s, the flame temperature of the micro-combustion rises in all cases. Apart from the wall-blade, the maximum flame temperature was recorded at V2 = 20 m/s for all cases and when the inlet velocity of the mixture increased from 20 m/s to 30 m/s, the flame temperature reduced in all studied cases. Therefore, the flame of micro-combustor with wall-blade bluff body is more stable than other cases. Moreover, the mean wall temperature of the micro-combustor with wall-blade bluff body is highest. Emitter efficiency is very high in the micro-combustor with wall-blade bluff body in lower velocities.