h i g h l i g h t sCompression ignition engine fueled with manifold injected natural gas. Engine operated under dual fueling mode with diesel and RME examined as pilot fuels. Emissions maps presented for specific emissions of CO 2 , HC and NO X . Novel method of presentation for the comparison of data collected from dual fueled CI engine. Engine efficiency for a dual fueled engine examined across entire range of operation. a r t i c l e i n f o Keywords: Contours Performance maps Natural gas Diesel RME Combustion a b s t r a c t When natural gas is port/manifold injected into a compression ignition engine, the mixture of air and the natural gas is compressed during the compression stroke of the engine. Due to the difference in the values of specific heat capacity ratio between air and natural gas, the temperature and pressure at the time of pilot fuel injection are different when compared to a case where only air is compressed. Also, the presence of natural gas affects the peak in-cylinder (adiabatic flame) temperature. This significantly affects the performance as well as emissions characteristics of natural gas based dual fueling in CI engine. Natural gas has been extensively tested in a single cylinder compression ignition engine to obtain performance and emissions maps.Two pilot fuels, diesel and RME, have been used to pilot natural gas combustion. The performance of the two liquid fuels used as pilots has also been assessed and compared. Tests were conducted at 48 different operating conditions (six different speeds and eight different power output conditions for each speed) for single fueling cases. Both the diesel and RME based single fueling cases were used as baselines to compare the natural gas based dual fueling where data was collected at 36 operating conditions (six different speeds and six different power output conditions for each speed). Performance and emissions characteristics were mapped on speed vs brake power plots. The thermal efficiency values of the natural gas dual fueling were lower when compared to the respective pilot fuel based single fueling apart from the highest powers. The effect of engine speed on volumetric efficiency in case of the natural gas based dual fueling was significantly different from what was observed with the single fueling. Contours of specific NO X for diesel and RME based single fueling differ significantly when these fuels were used to pilot natural gas combustion. For both of the single fueling cases, maximum specific NO X were centered at the intersection of medium speeds and medium powers and they decrease in all directions from this region of maximum values. On the other hand, an opposite trend was observed with dual fueling cases where minimum specific NO X were observed at the center of the map and they increase in all direction from this region of minimum NO X . RME piloted specific NO X at the highest speeds were the only exception to this trend. Higher specific HC and lower specific CO 2 emissions were observed in case of natural gas based dual fueling...

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Natural gas and hydrogen have been extensively tested in dual fuel mode in a compression ignition engine.Many studies conclude that the emissions, especially those oxides of nitrogen (NO X ) are expected to form in the region around the pilot spray where high temperatures exist and the equivalence ratio is close to stoichiometric. The effect of changing the pilot fuel quantity has not been widely reported. This study investigates the effect of changing pilot fuel quantity, and type and the effect of this change on various combustion (ignition delay, in-cylinder pressure and rate of energy release) and emission (specific NO X and hydrocarbons) parameters. Dual fueling of natural gas and hydrogen exhibit an increased ignition delay compared to the ignition delay exhibited by the pilot fuel at similar operating conditions. For dual fueling cases, the ignition delay is reduced as the quantity of pilot fuel is increased.Keywords: combustion, emissions, dual fueling, RME, compression ignition, pilot fuels

h i g h l i g h t sFuel injection sprays have been examined using a focused shadowgraph system. Diesel and Diesel and water emulsions containing 10% and 20% water examined. Temporal evolution of the spray cone angle and tip penetration have been measured. Emulsification reduced the cone angle at injection pressure of 500 bar. Emulsification had no discernable influence on the tip penetration. t r a c tDiesel fuel and water emulsions have been shown to reduce emissions of NO x and PM from compression ignition engines. There is a lack of work examining the influence of emulsification on the sprays formed during injection. This work examines the spray cone angle and tip penetration of Diesel fuel and water emulsions, containing 10% and 20% water (by mass). All experiments were conducted under nonreacting, non-vaporizing conditions in a constant volume pressure chamber filled with nitrogen. A focused shadowgraph system, with high speed photography, coupled with a research, high current LED system was used. Differences in the spray cone angle suggest the emulsification did have an effect for the injections at a pressure of 500 bar. Emulsification had no discernible effect on the spray tip penetration. Spray tip penetration showed agreement with previous trends in terms of proportionality to time after start of injection however agreement with models found in the literature was not consistent.