Effects of Internal Heat Transfer Models on the Ignition of a Fuel Droplet

The purpose of this study is to examine the effects of different liquid-phase heat transfer models on the ignition characteristics of a pure fuel droplet. An existing gas-phase ignition criterion is employed and the effects of infinite-conductivity model, conduction-limit model and vortex model on droplet ignition are studied. It is shown that the ignition delay times as predicted by different models are significantly different in the droplet-heating-controlled regime. These differences persist over a wide range of pressures, droplet sizes and fuel volatility. The differences also exist in the cold environment or kinetically-controlled regime, but are relatively less important because of the strong influence of pressure and kinetics parameters and also because of uncertainties in the values of these parameters. The present results also show good qualitative agreement with the experiments. The quantitative differences are discussed.