Ignition enhancement using a hybrid repetitive nanosecond and DC discharge is studied in CH₄/O₂/He mixtures at atmospheric pressure by using a hybrid ZDPlasKin-CHEMKIN method. Special attention is placed on the control of vibrational and electronic excitations of methane and oxygen using different electric field strengths. A plasma-ignition kinetic mechanism incorporating the reactions involving both vibrational and electronic excitations of CH₄ and O₂ as well as the low temperature methane oxidation pathways of O₂(a¹Δ_g) is developed and validated. The results show that the hybrid non-equilibrium plasma excitation is much more effective in ignition enhancement than thermal heating and the nanosecond discharge alone. O₂(a¹Δ_g) is generated more efficiently in the hybrid discharge and shortens the ignition delay time more effectively than O(¹D) and O produced in the nanosecond discharge. Vibrationally excited species CH₄(ν) and O₂(ν) are also produced but mainly contribute to ignition enhancement via energy relaxation and gas heating. The results also show that e + O₂ → e + O₂(a¹Δ_g) and e + O₂ → e + O + O(¹D) reactions compete with each other for oxygen consumption and play opposite roles in ignition enhancement in a hybrid NSD/DC discharge with a given plasma energy. For a given repetitive nanosecond discharge, there is an optimum DC electric field strength which has the minimum ignition delay time due to the selective production of excited species and the difference in electron density. This work provides fundamental understanding for the design of a hybrid discharge to optimize low temperature ignition enhancement and fuel reforming.

使用ZDPlasKin-CHEMKIN混合方法研究了在大气压下在CH ₄ / O ₂ / He混合物中使用混合重复纳秒和DC放电增强点火的性能。特别注意使用不同的电场强度控制甲烷和氧气的振动和电子激发。掺入涉及CH的两个振动和电子激发反应的等离子体点火动力机构₄和O ₂以及低温甲烷氧化途径Ô ₂（A ¹ Δ_克）的开发和验证。结果表明，混合非平衡等离子体激发在点火增强方面比单独的热加热和仅纳秒级放电有效得多。Ô ₂（A ¹ Δ_克）被更有效地在混合放电产生并更有效地缩短点火延迟时间比O（¹ d）和O在纳秒放电产生。还会产生振动激发的物质CH ₄（ν）和O ₂（ν ），但主要通过能量松弛和气体加热来增强点火。结果还表明，电子+ O ₂  →E +Ô ₂（A ¹ Δ_克）和e + O ₂ →e + O + O（¹ D）反应彼此竞争耗氧量，并且在给定等离子能量的混合NSD / DC放电中，在增强点火方面起相反的作用。对于给定的重复纳秒放电，由于有选择地产生受激物质和电子密度的差异，存在一个最佳的直流电场强度，该电场强度具有最小的点火延迟时间。这项工作为优化低温点火增强和燃料重整的混合动力排放的设计提供了基本的了解。