Various solutions have been proposed for reducing the exhaust emissions and improve the well-known soot and nitrogen oxide (NO) trade-off in diesel engines, without making serious modifications to the engine, one of which is the use of natural gas as supplement to liquid diesel fuel. In these types of engines, referred to as fumigated, natural gas–diesel dual-fuel compression ignition (CI) engines, gaseous fuel is fumigated and premixed with the aspirated air during the induction stroke. Natural gas is a clean-burning fuel with a relatively high auto-ignition temperature, which is a serious advantage in dual-fuel combustion. Previous research studies have shown that the natural gas–diesel fuel dual-fuel combustion in a CI engine environment, compared with conventional diesel fuel operation, suffers from high specific fuel consumption and high carbon monoxide (CO) and unburned hydrocarbon (HC) emissions. Compression ratio (CR) and diesel fuel injection timing (IT) are two engine parameters that can...

Different combustion strategies and fuel sources are needed to deal with increasing fuel efficiency demands and emission restrictions. One possible strategy is dual fueling using readily available resources. Propane and natural gas are readily available with the current infrastructure and biodiesel is growing in popularity as a renewable fuel. This paper presents experimental results from dual fuel combustion of methane (as a surrogate for natural gas) and propane as primary fuels with biodiesel pilots in a 1.9 liter, turbocharged, 4-cylinder compression ignition engine at 1800 rev/min. Experiments were performed with different percentage energy substitutions (PES) of propane and methane and at different brake mean effective pressures (BMEP/bmep). Brake thermal efficiency (BTE) and emissions (NOx, HC, CO, CO2, O2 and smoke) were also measured. Maximum PES levels for B100-methane dual fueling were limited to 70% at 2.5 bars bmep and 48% at 10 bars bmep, and corresponding values for B100-propane dual fueling were 64% and 43%, respectively. Maximum PES was limited by misfire at 2.5 bars bmep and the onset of engine knock at 10 bars bmep. Dual fuel BTEs approached straight B100 values at 10 bars bmep while they were significantly lower than B100 values at 2.5 bars bmep. In general, dual fueling was beneficial in reducing NOx and smoke emissions by 33% and 50%, respectively, from baseline B100 levels; however, both CO and THC emissions were significantly higher than baseline B100 levels at all PES and loads.