Performance and specific emissions contours throughout the operating range of hydrogen-fueled compression ignition engine with diesel and RME pilot fuels

This paper presents the performance and emissions contours of a hydrogen dual fueled compression ignition (CI) engine with two pilot fuels (diesel and rapeseed methyl ester), and compares the performance and emissions iso-contours of diesel and rapeseed methyl ester (RME) single fueling with diesel and RME piloted hydrogen dual fueling throughout the engines operating speed and power range. The collected data have been used to produce iso-contours of thermal efficiency, volumetric efficiency, specific oxides of nitrogen (NOX), specific hydrocarbons (HC) and specific carbon dioxide (CO2) on a power-speed plane. The performance and emission maps are experimentally investigated, compared, and critically discussed. Apart from medium loads at lower and medium speeds with diesel piloted hydrogen combustion, dual fueling produced lower thermal efficiency everywhere across the map. For diesel and RME single fueling the maximum specific NOX emissions are centered at the mid speed, mid power region. Hydrogen dual fueling produced higher specific NOX with both pilot fuels as compared to their respective single fueling operations. The range, location and trends of specific NOX varied significantly when compared to single fueling cases. The volumetric efficiency is discussed in detail with the implications of manifold injection of hydrogen analyzed with the conclusions drawn.