Discharge current management for lean or diluted combustion under forced flow conditions 2020-01-1118
Lean or diluted combustion with enhanced gas motion is effective in improving the efficiency of spark ignition engines. However, it is getting more difficult to generate an ignition process under this circumstance. Enhanced spark discharge energy is required to initiate the combustion. Moreover, the discharge process should also be carefully controlled to improve the effectiveness of the high energy spark. In this study, spark ignition systems with boosted discharge energy are used to ignite lean or diluted air-fuel mixture under forced flow conditions. The impacts of discharge current profile on the ignition is investigated in detail using shadowgraph imaging. It is evident from the result that higher discharge current is beneficial for the flame kernel formation. However, when the spark energy is the same, there is a trade-off between the increased discharge current and the reduced discharge duration. When the discharge duration is reduced to a certain extent, the high current discharge loses its advantage in the ignition process. The matching among the discharge current level, the discharge duration, and the flow velocity should be taken into consideration in designing the spark ignition strategies. The impacts of increased discharge energy level on the ignition of the lean or diluted mixture under forced flow conditions are also reported in the study. There seems to be a limit in the discharge energy level, beyond which further increased discharge energy does not provide any significant benefit in the ignition process.
Zhenyi Yang, Linyan Wang, Navjot S. Sandhu, Xiao Yu, Ming Zheng