A semi-analytical variable property droplet combustion model

A multi-zone droplet burn model is developed to account for changes in the thermal and transport properties as a function of droplet radius. The formulation is semi-analytical - allowing for accurate and computationally efficient estimates of flame structure and burn-rates. Zonal thermal and transport properties are computed using the Cantera software and pre-tabulated for rapid evaluation during runtime. Model predictions are compared to experimental measurements of burning n-heptane, ethanol and methanol droplets. An adaptive zone refinement algorithm is developed that minimizes the number of zones required to provide accurate estimates of burn time without excess zones. A sensitivity study of burn-rate and flame stand-off with far-field oxygen concentration is conducted with comparisons to experimental data. Overall agreement to data is encouraging with errors typically less than 20% for predictions of burn-rates, stand-off ratio and flame temperature for the fuels considered.