Hydrogen-Assisted Renewable Fuels RME and HVO in the Compression-Ignition Engine

The article presents the research results on performance, thermodynamic parameters, and toxic exhaust emissions from the combustion in a compression-ignition engine fueled by the hydrotreated vegetable oil (HVO) or the rapeseed methyl ester (RME), both with hydrogen addition. Furthermore, regular diesel fuel was used to obtain the reference data for comparing HVO, RME, and diesel fuel. Hydrogen was injected into the intake manifold of a CI engine with a compression ratio of 17. Typically, diesel fuel combustion in a CI engine initiates through its self-ignition, usually simultaneously occurring at many points across the engine cylinder. Hydrogen, as a very chemically reactive substance, can promote pre-ignition reactions and accelerate flame kernel formation, shortening the ignition lag. This is crucial in the case of the smooth running of the compression-ignition engine. Hydrogen was added at amounts not exceeding 7% by volume as regards air sucked into the engine cylinder. The heat release rate was analyzed, the basic combustion phases were identified, and a correlation was made with the hydrogen energy share. It was found that hydrogen added at small amounts does not form the so-called knock originating from hydrogen rapid combustion regardless of the diesel knock.