Effect of backward facing step on radiation efficiency in a micro combustor

The present study investigates the effect of backward facing step in a micro combustor on blowout limit and outer wall temperature. Effect of equivalence ratio of hydrogen-air mixture and combustor material (i.e. conductive heat transfer coefficient) on emitter efficiency and radiation efficiency perused. In addition, the effect of step height and diameter of combustor are studied. The results show that the presence of backward facing step leads to increase blowout limit and mean wall temperature. Temperature distribution along external wall of micro combustor shows a uniform distribution. It is also observed that combustor with lower step height has higher (mean) wall temperature. Maximum mean wall temperature and radiation efficiency achieved when equivalence ratio is located in lean values. It has been also observed that the wall thermal conductivity has an optimum value to obtain maximum radiation efficiency.