Improvement in Combustion Characteristics of Biodiesel by Reforming with Cross-Metathesis Reaction 2021-01-1205
The boiling point curve of fatty acid methyl esters (FAME), or biodiesel fuel, can be adapted to that of diesel fuel by breaking FAME down into a low-molecular structure using a cross-metathesis reaction with a short-chain olefin. Reformulated FAME by a metathesis reaction consists mainly of medium-chain olefins and fatty acid methyl esters. In the present study, the engine performance and exhaust emissions from reformulated FAME were investigated through engine bench tests. Surrogate fuels made from typical chemical components of reformulated FAME were used to clarify the effects of respective components upon combustion. Surrogate fuels were made by mixing 1-decene, 1-tetradecene, methyl laurate, methyl palmitate, and methyl oleate to simulate the boiling point, oxygen mass concentration, and calorific value of reformed biodiesel of waste cooking oil methyl ester (WME). A single-cylinder diesel engine equipped with common-rail-type injection system was used. The in-cylinder pressure, fuel consumption, and exhaust emissions were measured. The obtained results show that the high flammability of reformulated FAME improves the combustion efficiency of pilot injection fuel. The advanced ignition timing and the higher heat release rate of pilot injection fuel were obtained by using reformulated FAME, as compared to conventional WME, especially under a low-load condition. Moreover, emissions of unburned hydrocarbons and carbon monoxide were reduced. In addition, the effects of respective chemical components in reformulated FAME upon combustion and exhaust emissions were examined. The results show that 1-decene, in particular, has a higher efficiency for pilot combustion under a low-load condition due to its high volatility and ignition quality.