稀燃条件下甲烷-空气预混射流的着火特性

基于可控热氛围燃烧试验系统,探究射流当量比、射流速率和协流速率对甲烷-空气预混射流着火特性的影响。根据试验规律对天然气发动机稀薄燃烧的控制策略提出优化建议,以减少失火现象的发生。结果表明：随着协流温度的升高,甲烷-空气预混射流的稀燃极限降低而富燃极限升高,符合大多数碳氢燃料预混合气的着火界限分布规律。不同的射流速率和协流速率下均存在临界当量比,当低于临界当量比时,着火温度随射流当量比的升高而显著降低,当高于临界当量比时,着火温度趋于稳定。在较低的射流当量比工况（0.20 ~ 0.62）下,提高射流速率可以降低着火温度从而优化着火性能。

Lean-Burn Ignition Characteristics of Methane/Air Premixed Jet

The effects of jet equivalence ratio, jet velocity, and co-flow velocity on the ignition characteristics of methane/air premixed jet were investigated on a controllable thermal-atmosphere combustion experimental system. According to the experimental law, the optimization suggestions for the lean-burn control strategy of natural gas engines were proposed to reduce the occurrence of the misfire. The results show that the lean limit of methane/air premixed jet decreases and the rich limit increases as co-flow temperature rises, which is consistent with the distribution of ignition limits of most hydrocarbon fuel premixes. Besides, there are different critical equivalence ratios at different jet velocities and co-flow velocities, below which the ignition temperature decreases sharply with the increase of jet equivalence ratio. Moreover, at a lower jet equivalence ratio （0.20~0.62）, the improvement in jet velocity can reduce the ignition temperature and optimize the ignition characteristics.