Abstract
The leakage and transport of oil within secondary air system cavities is of interest in oil and air system design, for which CFD can be used as a predictive tool. This paper focuses on the leakage of oil from cracks into a high speed crossflow, idealised as round nozzles at Weber numbers and momentum flux ratios relevant to those in an aero-engine. Simulations were performed using the Euler-Lagrangian approach implemented in a commercial CFD code (FLUENT), including sub-models for breakup, deforming droplet drag, collisions/coalescence and turbulent dispersion. CFD predictions were compared with experimental data from two independent studies.
The calculated position of the centre-of-mass of the spray plume agreed well with experiment in all cases, but the penetration was found to be under-estimated. Differences in droplet sizes between experiments could not be explained by variations in the the gas Weber number alone, and a review of the literature has highlighted the importance of the liquid to gas viscosity ratio in determining droplet size trends. Experimental trends in droplet size with changing viscosity ratios were captured by CFD simulations, and droplet SMD was predicted within 20% of experiment. It is concluded that the sub-models used within an Euler-Lagrangian approach can be useful tools for the prediction of droplet size, although further improvements in breakup and coalescence modelling will be necessary if greater accuracy is required.