当量比对甲烷预混低旋流燃烧的影响

Effect of Equivalence Ratio on Methane Pre-mixed Low-Swirl Combustion

通过实验和数值模拟的方法研究了甲烷/空气预混低旋流燃烧的流场结构及当量比对甲烷低旋流燃烧的影响．结果表明，甲烷/空气预混低旋流气流在喷嘴出口处扩张，形成有利于燃烧稳定的低速区；预混火焰“悬浮”于喷嘴上方，在剪切区的内侧，火焰呈 W 型；富燃时，随着当量比的增加，火焰的推举高度略有增加；甲烷/空气预混低旋流流场具有自相似性，无量纲轴向速度的径向分布几乎不受当量比的影响．同时，燃烧室出口的温度随着当量比的增加而增加，并且在当量比为0.8～1.4时变化较为明显，当量比超过1.4后，增加趋势变缓．

The flow structure of CH4/air pre-mixed low-swirl combustion is experimentally and numerically studied. The effect of equivalence ratio on methane pre-mixed low-swirl combustion is also analyzed. Results show that the flow divergent at nozzle exit in the CH4/air pre-mixed low-swirl flow field,forming a low velocity zone favors flame stabilitization. The flame lifts up at nozzle exit having shape of “W” in the inner shear layer,and the height where flame stands increases slightly with the increase of equivalence ratio when the equivalence ratio exceeds 1. The low-swirl burner shows self-similarity features and the dimensionless axial velocity seems not to be influenced by the variation of equivalence ratio. Meanwhile,it is indicated that the exhaust temperature increases with increasing equivalence ratio,and that the increment is comparatively obvious when the equivalence ratio ranges from 0.8,to 1.4,while it slows down when the equivalence ratio exceeds 1.4.