Experimental Study on Low Temperature Combustion Dual Fuel Biodiesel/Natural Gas Engine

Low Temperature combustion (LTC) strategies are capable of simultaneous reduction in NOx and particulate matter (PM) emissions. However, this combustion process generally leads to higher HC and CO emissions together with more cyclic variation (unstable combustion) especially at light engine loads. These emissions could drastically be reduced using certain alternative fuels like natural gas and biodiesel in LTC or PCI combustion engines. In the present research, a single cylinder compression ignition engine has been modified to operate in dual fuel mode with natural gas injection into the intake manifold as the main fuel and biodiesel as the pilot fuel to ignite the gas/air mixture. The combustion characteristics, engine performance and exhaust emissions of the reactivity controlled compression ignition (RCCI) dual fueled CNG/biodiesel engine are investigated and compared with the conventional diesel engine mode at various load conditions. The analysis of the results revealed that biodiesel as the high reactivity fuel in RCCI mode leads to higher in-cylinder pressure together with shorter heat release rate duration, compared to the common diesel engine. Experimental results indicated that combining the low temperature combustion concept and alternative fuels (e.g. biodiesel and naturals gas) causes lower levels of unburned hydrocarbon (UHC) and carbon monoxide (CO) as well as nitrogen oxide (NOx) emissions.