Analyses of effects of molecukar structures and ingredients in biodiesel fuels on chemical and physical phases of diesel combustion

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Biodiesel fuels are the mixtures of fatty acid methyl esters. Computations using detailed chemical kinetic models indicate that for gas-phase fuels, the ignition delay times of fatty acid methyl esters are much shorter than those of alkanes with initial temperatures over 1000 K. On the contrary, engine operation tests indicate that for fuel sprays, the ignition delay times of alkanes are shorter than those of fatty acid methyl esters. The better ignition characteristics but the worse atomization and vaporization characteristics are a restriction against the improvement in combustion and exhaust-gas characteristics for diesel combustion using biodiesel fuels. Fuel design concepts should aim at improving the atomization and vaporization characteristics without deteriorating the ignition characteristics.