Numerical Study on Combustion and Emission Characteristics of Homogeneous Charge Compression Ignition Engines Fueled with Biodiesel

Abstract

This paper describes a numerical study on the effect of the mixing ratio of biodiesel on combustion and emission characteristics of homogeneous charge compression ignition engines. The KIVA code coupled with Chemkin chemistry solver was used to simulated combustion and emission formation processes. A modified reduced methyl butanoate mechanism was used after combining with it reduced n-heptane mechanism to model ignition and combustion of biodiesel. The mixing ratio of biodiesel was varied from 0% (conventional diesel) to 100% (pure biodiesel). Operating ranges covered up to a 2.0 equivalence ratio. The fueling rate was fixed at 18 mg/cyc, which corresponds to a medium engine load. Results of the present study showed that the ignition delay of biodiesel is shorter than that of conventional diesel fuel because of the higher cetane number of biodiesel. Little differences of emission maps for CO and NOx emissions are found between biodiesel and conventional diesel. However, higher concentration regions for hydrocarbon (HC) and soot maps on the peak cycle temperature/equivalence ratio are reduced significantly using biodiesel instead of conventional diesel fuel.