Ignition Control in the Hcci Combustion Engine System Fuelled with Methanol-reformed Gases

Homogeneous charge compression ignition (HCCI) combustion enables higher thermal efficiency and lower NOx emission to be achieved in internal combustion engines compared to conventional combustion systems. A new concept HCCI engine system fueled with dimethyl ether (DME) with a high cetane number and methanol-reformed gas (MRG) with high anti-knock properties has been proposed by the author et al. In the system, both DME and MRG are to be produced from methanol by onboard reformers utilizing the engine exhaust heat. It has been shown that adjusting the fraction of the two fuels effectively controls the duration of the low-temperature oxidation and the onset of the high-temperature oxidation in HCCI. The ignition control expands the operable range of equivalence ratio and engine load. Lean combustion by HCCI operation and a waste heat recovery by the fuel reforming utilizing engine exhaust heat achieve a high overall thermal efficiency. While MRG consists of hydrogen and carbon monoxide, the ignition control effect of MRG is attributed mostly to hydrogen. The current paper reviews the characteristics of the HCCI engine system fuelled with methanol reformed gases.