Improvement in combustion characteristics of biodiesel by reforming with cross-metathesis reaction

The boiling point curve of FAME, so called biodiesel fuel can be adapted to that of diesel fuel by breaking it down to low-molecular structure using cross-metathesis reaction with short chain olefin. Metathesis biodiesel mainly consists of medium-chain olefins and fatty acid methyl esters. In this study, the engine performance and exhaust emissions from metathesis biodiesel was investigated through engine bench tests. Surrogate fuels made from typical chemical components of metathesis biodiesel were used to clarify the effect of respective component on 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, calorific value of reformed biodiesel of waste cooking oil (WME). A single cylinder diesel engine equipped with common-rail type injection system was used. In-cylinder pressure, fuel consumption, and exhaust emissions were measured. Obtained results show that the high flammability of metathesis biodiesel improve the combustion efficiency of pilot-injection fuel. Advanced and higher heat release rate from pilot-injection fuel were obtained by using metathesis biodiesel compared to conventional WME especially under low load condition. Then, the emissions of unburned hydrocarbon and carbon monoxide were reduced. In addition, the effect of respective chemical component in metathesis biodiesel on combustion and exhaust emission were examined. The result shows that 1-decene in particular brings higher efficiency to pilot-combustion under low load condition due to its high volatility and ignition quality.