A COMPARATIVE STUDY OF DIRECT NUMERICAL SIMULATION AND EXPERIMENTAL RESULTS ON A PREFILMING AIRBLAST ATOMIZATION CONFIGURATION

Liquid injection systems play a key role in the control of flame stability and reduction of pollutant emissions in aircraft engines. However, the disintegration process of the liquid fuel is not completely understood. In that context, direct numerical simulations can be helpful but tend to be very costly. Indeed, they require high spatial resolution to accurately capture complex phenomena such as liquid-gas interface instabilities and primary atomization process with liquid bags, ligaments, and droplets formation. This paper presents a computational study of a prefilming atomizer where relevant dimensionless parameters are chosen to reproduce realistic conditions while limiting CPU cost. The experiment under study is an academic configuration from KIT-ITS in which a liquid film is injected along a prefilmer plate surrounded by high-speed air flow. The simulation has been performed with the in-compressible solver NGA using a volume of fluid method coupled with a piecewise linear interface calculation technique for interface reconstruction. Qualitative and quantitative analyses are carried out and show very good agreement between simulation and experiment. The main physical phenomena such as film instabilities, liquid accumulation process at the prefilmer edge, and primary breakup mechanisms are well recovered by the simulation and in agreement with the experiment. A consistent method to compare both the experiment and the numerical simulation based on frame analysis is developed to extract the droplet diameter distribution. The resulting size distribution evaluated from simulation is shown to be in good agreement with experimental data validating our proposed methodology to reduce computational cost.