ANALYSIS OF N-DODECANE SPRAY COMBUSTION BASED ON PROPER ORTHOGONAL DECOMPOSITION

Liquid fuel spray combustion is a complex multiple physical-chemical coupling phenomenon. Gaining an insight into this phenomenon is important to develop advanced internal combustion engines or gas turbines. In this paper, large eddy simulation (LES) is adopted for investigation of the n-dodecane spray combustion process. To study the spray and combustion characteristics of n-dodecane, the corresponding velocity field and concentration field are analyzed by using proper orthogonal decomposition (POD). The results show that the increase of initial ambient temperature can enhance the convective heat transfer between the fuel and surrounding gas, accelerate liquid droplets breakup, and promote evaporation. Thus, large-scale structures of the spray concentration field are significantly correlated with the spatial distribution of the local vortices, and the temporal evolutions of energy/intensity of the two fields are similar. POD analysis can reveal the correlation of flow field and concentration field at different scales. In the combustion state, increasing the initial ambient temperature can change the ignition conditions and promote the temperature rise in the fuel-rich region, thus advancing the ignition delay time, decreasing the flame lift-off length, increasing the high temperature reaction region area, promoting the reaction activity. In addition, POD analysis can also reflect that the correlation between the unstable flame structure and the turbulent flow field.