Multizone Model Study for DI Diesel Engine Running on Diesel-Ethanol-Biodiesel Blends of High Ethanol Fraction
A multizone combustion model for closed cycle of a DI diesel engine is developed to interpret the experimental investigations on the utilization of diesel-ethanol-biodiesel blends of high ethanol fraction (DEB blends). A computer-based programming for engine process simulation is developed in MATLAB. The model is validated with the experimental values of cylinder pressure and heat release rate. Important information related to fuel injection and combustion inside the combustion chamber, is revealed through the model prediction which is normally difficult to get from the experiments. Model prediction shows that the rate of fuel evaporation is higher for DEB blends, than diesel fuel at any instant of time. The fuel combustion is started late for DEB blends compared to diesel fuel, however, once the combustion is started the burning rate is higher than the diesel fuel. The droplet size (Sauter mean diameter) is decreased for DEB blends which indicate improved fuel atomization. The mean temperature in the zone is significantly lower for DEB blends compared to diesel fuel. The equivalence ratio in the zone is decreased for DEB blends proving that engine runs leaner. The equivalence ratio trend is not uniform as it depends on the combination of the rate of fuel evaporation, rate of air entrainment and rate of burning. Soot density is remarkably decreased, and NOx formation is also drastically reduced for DEB blends at different instant of time. The predictions help to interpret the experimental results for DEB blends and its comparison with diesel fuel.
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