Large Eddy Simulation of Air Entrainment and Mixing in Reacting and Non-Reacting Diesel Sprays

摘要

Large eddy simulation is performed to investigate air entrainment and mixing in diesel sprays with and without combustion. The Spray A case of the Engine Combustion Network (ECN) is considered in the study, in which liquid n-Dodecane is injected at 1500 bar through a nozzle of 90 μm into a constant volume vessel with an ambient density of 22.8 kg/m~3 and an ambient temperature of 900 K. Primary and secondary breakup processes of the liquid fuel are taken into account. The gas and liquid phases are modeled using Eulerian/ Lagrangian coupling approach. Detailed chemical kinetics for n-Dodecane is employed to simulate the ignition process and the lifted flames. A chemistry coordinate mapping approach is used for speeding up the calculations. The effect of low temperature ignition (cool flame) on the evaporation process and on the liquid penetration length is analyzed. The effect of combustion heat release from the lifted flames on the vapor spreading in the radial direction and on the vapor transport in the streamwise direction (vapor penetration) is investigated.