Numerical Study on Spray Combustion Processes in n-Heptane and Dimethyl Ether Fueled Diesel Engines

The present study numerically investigates the distinctive differences of dimethyl ether (DME) spray combustion processes compared to conventional hydrocarbon liquid fuels in direct-injection diesel engines. To realistically represent the physical processes involved in the spray combustion, this study employs the hybrid breakup model, the stochastic droplet tracking model, collision model, high-pressure evaporation model, and transient flamelet model with detailed chemistry. The present representative interaction flamelet model with the vaporization effects on turbulent combustion has been validated against measurements for a Cummins N-14 diesel engine. The sequence of the comparative analysis has been made to understand the overall spray combustion characteristics of DME fuel as well as to identify the distinctive differences of DME combustion processes in direct-injection diesel engines, compared to n-heptane liquid fuel. On the basis of numerical results, the detailed discussions are also made in terms of the spray dynamics, evaporation, turbulent mixing, autoignition, spray flame structure, turbulence-chemistry interaction, and pollutant (soot, NOx) formation in the n-heptane and DME fueled diesel engines.This work was supported by the CEFV (Center for Environmentally Friendly Vehicle) of the Eco-STAR project from MOE (Ministry of Environment, Republic of Korea)