Effect of pilot fuel quantity and type on performance and emissions of natural gas and hydrogen based combustion in a compression ignition engine

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.