Effect of Heterogeneity of Surrounding Gas on the Diesel Combustion

概要

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In order to clarify the effect of heterogeneity of distributions of temperature and oxygen concentration in a combustion chamber on the soot and NO emissions from the diesel engine, the combustion characteristics and emissions of diesel spray flame achieved in a rapid compression and expansion machine (RCEM) at various patterns of temperature and oxygen concentration distributions in the chamber are investigated. The single-hole nozzle and multi-hole nozzle are used for the experiments. Results indicate that the NO and soot emissions from diesel combustion with single-hole nozzle are governed mainly by the amounts of oxygen and enthalpy entrained into the spray upstream the ignition region, when the temperature distribution and oxygen concentration distribution in a chamber are changed. In the case of multi-hole nozzle, NO emission is affected strongly by the amounts of oxygen and enthalpy entrained into the spray upstream the ignition region similarly to the results of the case of single-hole nozzle. However, the soot emission from the diesel flame with multi-hole nozzle is not affected by the heterogeneity of surrounding gas because the soot oxidation during late phase of combustion is governed mainly by the efficiency of utilization of air in a chamber which is affected significantly by the number of holes of the nozzle.