Evaluation of Soot Production Near a Cold Surface for an Impinged Diesel Spray Combustion

Spray impingement in internal combustion engines has received great attentions. Such a phenomenon is especially important for diesel spray because the spray and combustion characteristics are significantly altered by the impingement. In this study, numerical investigations of impinged reacting spray jets in a constant volume combustion chamber were performed to understand the spray and flame structure under high pressure and high temperature conditions. The 3-D computational fluid dynamics (CFD) CONVERGE code was selected as the numerical tool to perform Large-eddy simulations (LES) to understand the process of spray combustion-wall interaction. CFD models were validated against experimental results in terms of spray penetration and ignition delay at inert and reacting spray conditions. The temperature and soot mass fraction profiles near the impinging plate were investigated for 900 and 1000 K ambient conditions. It was found that soot mass fraction is generally increased near the impinging plate as the temperature is decreased. The heat transfer from the flame to the plate makes the temperature close to the wall more favorable for soot formation. A dense soot core was observed at the leading edge when the injection was still happening because the vortex there took the opportunity from existing burned gas to new fuel to meet the ambient air. A soot layer was observed stick on the wall as the air was hard to entrain the flame all the way to the plate side.