Impact of plasma length on flame kernel development under flow condition 2020-01-1114
Advanced ignition systems with enhanced discharge current level have been extensively investigated in research, since they are highly regarded to have potentials to overcome challenges arisen when spark-ignition engines are running under lean or EGR diluted conditions. Local flow field is also of particularly importance to improve the ignitability of the ignition system as spark plasma channel is stretched under flow conditions, leading to more thermal spark energy distribution to the air-fuel mixture in the vicinity of the spark plug. Research results have shown that a constantly high discharge current is considered to be effective to maintain stable discharge with less restrikes and longer plasma holding period. However, with the further increase of the discharge current, plasma channel becomes thicker, and the stretched plasma length becomes shorter under certain flow speed, which may suppress the advantages of the presence of air flow.
In this work, the interaction between discharge current level and plasma length under flow conditions is investigated. Whether a thick but short plasma or a thin but stretched long plasma are more effective for the flame kernel formation is discussed to provide an insight into the influence of the plasma length on flame initiation. An optical combustion chamber platform with a cross flow generation system is used to study the plasma channel behavior; an in-house developed current management module is used to vary the discharge current level to a wide range and to decouple the effects of discharge duration on combustion initiation by controlling the discharge process within a very short duration.
Hua Zhu, Qingyuan Tan, Xiao Yu, Zhenyi Yang, Li Liang, Ming Zheng, Graham Reader, Jin Qian
University of Windsor, Zhuzhou Torch Spark Plug Co., Ltd.