Experiments in Dual Fuelling a Compression Ignition Engine by Injecting Di-Methyl Ether as a Pilot Fuel to Ignite Varying Quantities of Natural Gas

Biodiesel, emulsified biodiesel and dimethyl ether as pilot fuels for natural gas fuelled engines

“…It has been shown that reductions in the targeted emissions (smoke and NO x ) can be achieved using the dual-fuel mode [25][26][27]. In fact they can be reduced by P 90% and 20% respectively, depending on the type of pilot fuel employed.…”

“…The low smoke emissions are due primarily to the higher hydrogen to carbon ratio of the high-octane fuel (compared to conventional high-cetane fuels) and a higher residence time for the fuel-air mixture to lean out after fuel injection [36]. NO x reduction is due to lower combustion temperatures of dual-fuel operation, which stem from the slower burning velocity of natural gas [25,26]. However, dual-fuelling operation has significantly increased HC and CO emissions (by about 80% and 60% respectively) [25,26].…”

“…However, dual-fuelling operation has significantly increased HC and CO emissions (by about 80% and 60% respectively) [25,26]. The pilot fuel ignition delay was also extended by about 3% as a result of a lower oxygen concentration in the intake charge as well as a higher specific heat capacity [25,26]. Emissions of HC and CO in particular indicate that ignition of the natural gas-air charge can be much improved, leading to more complete combustion.…”

“…Dual-fuelling in CI engines would allow the reduction of smoke and NO x emissions common in conventional CI engine exhaust while maintaining the characteristically high CI engine thermal efficiencies. Different main (high-octane) fuels have been used, with natural gas and hydrogen gas in particular having been researched extensively [24][25][26][27][28][29][30][31][32][33][34][35]. These fuels were selected for their high octane number compared to gasoline (around 120 RON and 95 RON respectively).…”

“…NO x reduction is due to lower combustion temperatures of dual-fuel operation, which stem from the slower burning velocity of natural gas [25,26]. However, dual-fuelling operation has significantly increased HC and CO emissions (by about 80% and 60% respectively) [25,26]. The pilot fuel ignition delay was also extended by about 3% as a result of a lower oxygen concentration in the intake charge as well as a higher specific heat capacity [25,26].…”