Influence of CH4/air injection location on non-premixed flame blow-off limits in a novel micro-combustor.

Stable flame is still one of the challenging issues in the micro-combustors. Besides, the premixed flame may flash back under the large equivalence ratio, and the non-premixed combustion is an effective way to avoid the flame flash-back issue. In this work, a novel non-premixed CH 4 /air micro-combustor with the flame holder, the backward-facing steps and the separated preheating channels is developed to avoid the flame flash-back issue and extend the flame blow-off limits. This paper investigates the influence of two different CH 4 /air injection locations on the flame blow-off limits numerically and profoundly reveals the mechanisms in this micro-combustor. Results show that this novel configuration can considerably anchor the flame without the flame flash-back issue and significantly extend flammability owning to the flow & heat recirculations. Compared with the "Air (out) /CH 4(in) " injection location, the "Air (in) /CH 4(out) " injection location exhibits a comparatively larger size of recirculation, causing a more vital anchorage ability. In addition, after the preheating in the preheating channels, the CH 4 /air mixture of the "Air (in) /CH 4(out) " injection location presents a higher temperature level than that of the "Air (out) /CH 4(in) " injection location. Consequently, compared to the "Air (out) /CH 4(in) " injection location, the larger blow-off limits are attained for the "Air (in) /CH 4(out) " injection location. These results provide new insights into the stable non-premixed flame and give valuable guidance for designing the similar non-premixed micro-combustor. [Display omitted] • A novel CH 4 /air non-premixed micro-combustor is developed. • This novel configuration can anchor the flame without the flame flash-back issue. • Influence of CH 4 /air injection locations on flame blow-off limits is studied. • "Air (in) /CH 4(out) " presents larger recirculation & better heat recirculation. • "Air (in) /CH 4(out) " attains larger blow-off limits than "Air (out) /CH 4(in) ". [ABSTRACT FROM AUTHOR]