Jet-jet interaction in diesel engine combustion

This paper presents numerical and experimental investigation of flame lift-off and stabilization mechanisms in heavy-duty diesel engines. The injection strategy, employing different nozzle configurations, allows quantification of the impact of varying inter-jet angle spacing in the presence of swirl. For this purpose, two different inter-jet angles are chosen in this study, 45°?and 135°. Large-eddy simulations are performed, utilizing a detailed kinetic mechanism for n-heptane to resolve the turbulent fuel and air mixing and to capture the important species surrounding the ignition and flame-fronts to describe the flame stabilization process. Measurements are carried out for OH chemiluminescence to identify the flame lift-off position in an optical accessible engine. With decreasing inter-jet angle, it is shown that the impact of transportation of hot products from adjacent jets becomes more prominent. Hot reservoirs surrounding the lift-off length increase the local ambient temperature and augment the auto-ignition process by mixing of the cold injected fuel and hot air. When the inter-jet angle decreases, this effect becomes less important.