Partially premixed low temperature combustion using dimethyl carbonate (DMC) in a DI diesel engine for favorable smoke/NOx emissions

This study investigates the potential use of dimethyl carbonate (DMC), a green, non-toxic and low-reactive biofuel to enable partially premixed low temperature combustion (PPLTC) mode in a DI diesel engine. PPLTC is an intermediate combustion strategy between conventional diesel combustion and homogenous charge compression ignition (HCCI) combustion which provides sufficiently long ignition delay for fuel/air to pre-mix inside the cylinder and to eventually restrain harmful smoke and NOx emissions. The engine was fueled with 15% by vol. of DMC/diesel blend (DMC15) and the combustion, performance and emission characteristics were examined under high loads with charge-dilution and combustion-phasing controlled by employing EGR (0-30%) and adjusting the injection timing (25-21°CA bTDC). Experimental results revealed that DMC15 exhibited better performance when the injection timing is advanced from 21° to 25°CA bTDC at the expense of emissions. Nevertheless DMC15 injected at 21°CA bTDC under 30% EGR experienced longest ignition delay and lowest peaks in pressure and heat release rate (HRR) to achieve a maximum simultaneous reduction of NOx emissions (▾46.1%) and smoke opacity (▾64.7%) respectively with a small drop in performance (▾11.8%). Both total hydrocarbons (THC) and carbon-monoxide (CO) emissions increased at intensified EGR rates.