The Numerical Investigation of Physical and Geometrical Conditions of Combustor and Mixture on Flame Stability in Micro Burner and Their Effects on Radiation Efficiency

The present numerical study investigates the effects of a step in a micro scale combustor on blow out limit and outer wall temperature. Also, the effects of the equivalence ratio of hydrogen-air mixture and combustion material on the emitter efficiency are scrutinized. The effects of the step in combustor is studied from two viewpoints: first the existence of the step, and second the step height and combustor diameter. The results showed that blow out limit is increased when using a step at the entrance of the combustion chamber. Besides, the mean wall temperature increases, while the flame temperature in the micro burner shows a more uniform behavior. It was observed, by comparing combustor 2 and 3, that the combustor with the lowest step height had higher (mean) wall temperature. On the other hand, the combustor with larger diameter achieves higher mean wall temperature. In this study, the effects of the equivalence ratio and conduction heat transfer coefficient on radiation efficiency of the micro burner are also investigated. It was observed that the maximum emitter efficiency of the micro burner is achieved for lean mixture. It was also observed that the conduction heat transfer coefficient has an optimum value.