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Advanced combustion engines dominate all automotive applications. Future high efficiency clean combustion engines can contribute significantly to sustainable transportation. Effective ignition strategies are studied to enable lean and diluted combustion under considerably high-density mixture and strong turbulences, for improving the efficiency and emissions of future combustion engines. Continuous discharge and multi-site ignition strategies have been proved to be effective to stabilize the combustion process under lean and EGR diluted conditions. Continuous discharge strategy uses a traditional sparkplug with a single spark gap and multiple ignition coil packs. The ignition coil packs operate under a specific time offset to realize a continuous discharge process with a prolonged discharge duration. Multi-site ignition strategy also uses multiple ignition coil packs.

An experimental investigation of low temperature combustion (LTC) cycles is conducted with diesel and ethanol fuels on a high compression ratio (18.2:1), common-rail diesel engine. Two LTC modes are studied; near-TDC injection of diesel with up to 60% exhaust gas recirculation (EGR), and port injected ethanol ignited by direct injection of diesel with moderate EGR (30-45%). Indicated mean effective pressures up to 10 bar in the diesel LTC mode and 17.6 bar in the dual-fuel LTC mode have been realized. While the NOx and smoke emissions are significantly reduced, a thermal efficiency penalty is observed from the test results. In this work, the efficiency penalty is attributed to increased HC and CO emissions and a non-conventional heat release pattern. The influence of heat release phasing, duration, and shape, on the indicated performance is explained with the help of parametric engine cycle simulations.