Abstract: Aimed at studying the effects of equivalence ratio on plasma assisted detonation initiation by alternating current dielectric barrier discharge (AC DBD) under lean burn condition，a loosely coupled method was used to simulate the detonation initiation process of a hydrogen-oxygen mixture in a detonation combustor under different equivalence ratios. Three equivalence ratios including 1.0，0.8，and 0.6 are selected in the study. The temporal and spatial distribution characteristics of discharge generated particles，profiles of the combustor flowfield parameters at several representative stages，deflagration to detonation transition (DDT) time and distance，and history of thrust wall pressure are studied in detail. It is found that the pattern of the temporal and spatial distribution of discharge products in one cycle does not change as equivalence ratio decreases，yet the number density of the key active particles increases while the increase amplitude declines. With the flow velocity of combustor increases，the effect of plasma on the flowfield structure becomes more and more notably，and every sub-process of the stable detonation wave forming process is accelerated. The DDT distance and time are both reduced by the plasma for all the cases. However，the reduction amplitude declines when lower the equivalence ratio. Also，it shows that the acceleration effect of plasma on the flowfield evolution weakens with equivalence ratio decreases from the dynamic analysis of the thrust wall pressure，yet the magnitude of pressure is independent of the plasma. The reasons for the phenomenon that the lower equivalence ratio is not conducive to the plasma to play a role in expediting the DDT process under the lean burn condition are as follows: the disadvantage effect brought by the decline of the percentage of fuel is stronger than the effect of plasma assisted combustion，and the discharge area is limited.

Key words: Alternating current dielectric barrier discharge；Plasma assisted detonation initiation；Lean burn；Equivalence ratio；Active radicals

摘要： 为研究贫燃条件下当量比对交流介质阻挡放电等离子体辅助起爆的影响，采用松耦合方法仿真求解了当量比分别为1.0，0.8及0.6三种条件下氢氧预混气体起爆过程，对比研究了放电产物时空分布特性、不同阶段爆震管内流场参数分布、起爆时间和距离以及推力壁动态历程。结果表明放电产物在同一周期内的时空分布形态不随当量比改变而变化，但随着当量比下降，各主要活性粒子的密度增大，增幅则降低。随着管内流速上升，等离子体对流场结构的改变更加明显，加速了形成稳定爆震波的各个子过程；不同工况下等离子体都缩短了起爆时间和距离，但当量比越低，缩短程度越小。对推力壁受力的动态分析也显示等离子体对流场演化的加速效果随当量比减小而减弱，不过其受力大小与等离子体无关。在本文贫燃条件下出现低当量比不利于等离子体发挥作用的原因包含两点，一是燃料占比降低带来的不利影响大于等离子体助燃的效果，二是放电区域尺寸有限。

关键词: 交流介质阻挡放电；等离子体辅助起爆；贫燃；当量比；活性基团