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Ignition by Nanosecond Repetitively Pulsed Discharges (NRPD) at EXponential Increase of Minimum Ignition Energy (MIE-EXI) region under super lean SI engine conditions was studied. Fundamental experiments were conducted with a turbulent ignition test chamber with twin counter-rotating fans. The MIE-EXI region by arc discharge appeared over 6500 rpm of fan speed. In the MIE-EXI region (7000 rpm), successful ignition was achieved by establishing coupled ignition kernels with NRPD at 15 kHz although ignition was unsuccessful at 1 kHz. Results show that ignition by NRPD has potential advantages for lean burn applications. Preliminary engine test results with NRPD were also demonstrated.

This paper presents new methodology of ignition property measurements using a micro flow reactor with a controlled temperature profile, which is a spin-off methodology developed through microcombustion studies during the last decade. Stable multi-stage reaction zones were observed in low flow velocity regime for hydrocarbons and it was found that unsteady multi-stage oxidations of hydrocarbons were examined by stable multi-stage reaction zones termed as weak flames. This methodology has been further applied to various fuels. Effects of research octane number of primary reference fuels on weak flames were examined and it was shown that stabilized temperature levels and appearances of weak flames have apparent correlations with RON. Recent works using the micro flow reactor were also introduced.