Hydrogen combustion and exhaust emissions ignited with diesel oil in a dual fuel engine

Hydrogen is expected to be one of the most prominent fuels in the near future for solving greenhouse problem, protecting environment and saving petroleum. In this study, a dual fuel engine of hydrogen and diesel oil was investigated. Hydrogen was inducted in a intake port with air and diesel oil was injected into the cylinder. The injection timing was changed over extremely wide range. When the injection timing of diesel fuel into the cylinder is advanced, the diesel oil is well mixed with hydrogen-air mixture and the initial combustion becomes mild. NOx emissions decrease because of lean premixed combustion without the region of high temperature of burned gas. When hydrogen is mixed with inlet air, emissions of HC, CO and CO₂ decrease without exhausting smoke while brake thermal efficiency is slightly smaller than that in ordinary diesel combustion. In particular, both smoke and NOx are almost zero and HC is low when the injection timing is significantly advanced although the engine operation becomes unstable.