Development of Flamelet Combustion Model with Reaction Progress Variable for Applying in Direct Injection Engines

Abstract

This research investigates on the development of a spray combustion model for diesel engineapplications. This spray model is based on the spray droplet number size distribution moments approach.These moments relate to volume, surface area, radius and number of droplets, respectively. The source termsof sub-models including droplet breakup, collision, evaporation, and the interactions between the liquidphase and the gas phase are derived in term of these droplet moments. The governing equations for boththe gas and liquid phases are developed based on the moment-average quantities and solved by the finitevolume method on an Eulerian framework. For combustion analysis, Steady Flamelet approach is employedhere combining with reaction progress variable in order to indicate the reaction level. The skeleton chemicalkinetic mechanisms consisting of 43 chemical components and 185 reactions are solved in order to createthe Flamelet library. The thermo-chemical variables in this library including flame temperature, speciesmass fraction, density, and reaction rate are averaged by a probability density function averaging approach.The simulation results predicted by developed Steady Flamelet model are compared with the experimentaldata. The comparison results are relatively satisfactory. In addition, the lifted-off length predicted is alsocomparable with the flame luminosity as well.

Keywords : Auto-ignition / Combustion / Diesel Engine / Modelling / Spray