Studies of multi-channel spark ignition of lean n-pentane/air mixtures in a spherical chamber

A novel ignition strategy using multi-channel sparks was developed in this paper. Compared with the typical single spark, the three-channel spark ignition technique enables three spatially separated and temporally synchronized discharges to increase the ignition kernel size while maintaining the same total ignition energy. The three-channel discharge characteristics, ignition kernel development, and ignition probability of lean n-pentane/air mixtures were studied and compared with those of single-channel spark in a spherical combustion chamber with different discharge distances, pressures, and CO₂ dilution levels. The experimental results show that the three-channel sparks increase the ignition probability and dramatically extend the fuel-lean ignition limits compared to the single-channel discharge under all tested conditions. Moreover, ignition enhancement effects of multi-channel sparks increase with the decrease of pressure, reduction of discharge gap, and increase of CO₂ dilution. One-dimensional numerical simulation was performed by using a detailed n-pentane kinetic model (Bugler et al., 2017) and the results revealed that the increase of fuel lean ignition probability and the decrease of the minimum ignition energy by using multi-channel sparks were the outcome of increased ignition kernel size compared to the minimum critical ignition radius. This present study confirms the advantages of using multi-channel sparks on advanced fuel-lean combustion engines.