Multicomponent and single-component fuel droplet evaporation under high pressure conditions

Abstract

The current spray models used for predicting two-phase flows in gas' turbine combustors are based on a single-component droplet vaporization submodel, although it is well known that gas turbine fuels are mixtures of many compounds with a broad distillation curve. Consequently, it is important to identify conditions under which the vaporization behavior of a multicomponent fuel droplet can be represented by a surrogate single-component droplet. In this study, a quasi-steady droplet vaporization model is employed to examine the vaporization behavior of a bicomponent fuel droplet and an equivalent single-component droplet at different pressures. The infinite-diffusion and diffusion-limit models are used to represent the transient liquid-phase transport in the droplet interior. In addition, a high-pressure, quasi-steady, droplet vaporization model is developed. The model includes the nonideal gas behavior, liquid-phase solubility of gases, and dependence of thermotransport properties on pressure. The Peng-Robinson equation of state is employed to represent the gas nonidealities, and to compute the liquid-phase equilibrium at the droplet surface. Results concerning the comparison of bicomponent and singlecomponent droplets indicate that the representation of a bicomponent fuel droplet by an equivalent single-component becomes increasingly better as the pressure is increased. In fact, the predicted vaporization behavior is much more sensitive to the droplet heating model rather than to the liquid fuel composition. This can be attributed to a significant increase in droplet heatup time, and a reduction in the relative volatility differential between the constituent fuels at higher pressures. Predictions of the high-pressure droplet model show good agreement with the available experimental data over a wide range of pressures. * Copyright @ 1998 by S. K. Aggarwal. Published by the American Institute of Aeronautics and Astronautics, Inc.