Effects of inter-pulse coupling on nanosecond pulsed high frequency discharge ignition in a flowing mixture
Effects of inter-pulse coupling on nanosecond pulsed high frequency discharge ignition in a flowing mixture
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DOI：
10.1016/j.proci.2022.06.018
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发表时间：
2022-07
影响因子：
3.4
通讯作者：
Xingqian Mao;Hongtao Zhong;Ziyu Wang;T. Ombrello;Y. Ju
中科院分区：
文献类型：
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作者：
Xingqian Mao;Hongtao Zhong;Ziyu Wang;T. Ombrello;Y. Ju
这项工作数值研究了非平衡纳秒等离子体放电脉冲重复频率，脉冲数和流速对临界点火体积，最小点火能量和化学在等离子体辅助H2/空气流在300 K和1大气压使用多尺度自适应减少化学求解等离子体辅助燃烧（MARCS-PAC）的影响。研究了脉冲序列中跨解耦、部分耦合和完全耦合状态的放电/点火核之间的相互作用。对于单脉冲放电，由于对流热损失和火焰拉伸的增加，增加的流速增加了所需的最小点火能量。结果表明，临界点火核体积处的最小点火核传播速度随流速的增大而增大。最小临界点火体积随等离子体放电能量的增加而减小。对于连续的两个脉冲放电，点火失败，在解耦和部分耦合制度，即使当总的放电能量高于最小点火能量，但成功的完全耦合制度在一个较短的脉冲间时间。OH自由基池的重叠之间的顺序的两个脉冲放电和化学效应的增加，由于在完全耦合制度的减少电场的增加有助于点火增强。此外，对于在完全耦合的放电制度中的两个脉冲放电，混合物可以在低于具有相同流动条件的单个脉冲的最小点火能量的总能量下被点燃。此外，对于一个给定的总放电能量与多脉冲放电，点火内核体积的增强有一个非单调的依赖于放电频率和脉冲数。通过选择最佳的脉冲重复频率和脉冲数，可以有效地增强点火。这项工作提供了一个新的理解的机制，重复等离子体点火和见解的等离子体点火在反应流中的优化。
This work numerically investigates the effects of non-equilibrium nanosecond plasma discharge pulse repetition frequency, pulse number, and flow velocity on the critical ignition volume, minimum ignition energy, and chemistry in a plasma-assisted H2/air flow at 300 K and 1 atm using a multi-scale adaptive reduced chemistry solver for plasma assisted combustion (MARCS-PAC). The interactions between discharges/ignition kernels spanning decoupled, partially-coupled and fully-coupled regimes in a pulse train are studied. For a single pulse discharge, increased flow velocity increases the minimum ignition energy required due to the increase of convective heat loss and flame stretch. The results show that the minimum ignition kernel propagation speed at the critical ignition kernel volume increases with the flow velocity. The minimum critical ignition volume decreases with the increase of plasma discharge energy. For sequential two-pulse discharges, ignition fails at both decoupled and partially-coupled regimes even when the total discharge energy is above the minimum ignition energy, but succeeds only in the fully-coupled regime at a shorter inter-pulse time. Overlap of the OH radical pool between the sequential two-pulse discharges and the increase of the chemistry effect due to the increase of reduced electric field in the fully-coupled regime contribute to the ignition enhancement. In addition, for two-pulse discharges in the fully-coupled discharge regime, the mixture can be ignited at a total energy below the minimum ignition energy of a single pulse with the same flow conditions. Moreover, for a given total discharge energy with multiple pulsed discharges, the enhancement of the ignition kernel volume has a non-monotonic dependence on discharge frequency and pulse number. The effective ignition enhancement can be achieved with an optimal pulse repetition frequency and pulse number. This work provides a new understanding of the mechanism for repetitive plasma ignition and insights for the optimization of plasma ignition in a reactive flow.