Evaporation of volatile droplets subjected to flame-like conditions

TL;DR

This study evaluates various Lagrangian droplet evaporation models used in spray combustion, highlighting the importance of Stefan flow effects and identifying the Abramzon-Sirignano model as the most comprehensive and relevant for high-temperature evaporation.

Contribution

It compares multiple evaporation models, assesses their validity, and recommends the Abramzon-Sirignano model as the most suitable for spray combustion simulations.

Findings

Models ignoring Stefan flow are invalid under studied conditions.

Langmuir-Knudsen model is inadequate for high-temperature evaporation.

Abramzon-Sirignano model effectively captures key phenomena and is recommended.

Abstract

This work assesses Lagrangian droplet evaporation models frequently used in spray combustion simulations, with the purpose of identifying the influence of modeling decisions on the single droplet behavior. Besides more simplistic models, the evaluated strategies include a simple method to incorporate Stefan flow effects in the heat transfer (Bird's correction), a method to consider the interaction of Stefan flow with the heat and mass transfer films (Abramzon-Sirignano model), and a method to incorporate non-equilibrium thermodynamics (Langmuir-Knudsen model). The importance of each phenomena is quantified analytically and numerically under various conditions. Evaporation models ignoring Stefan flow are found to be invalid under the studied conditions. The Langmuir-Knudsen model is also deemed inadequate for high temperature evaporation, while Bird's correction and the Abramzon-Sirignano model are identified as the most relevant for numerical studies of spray combustion systems. Latter is the most elaborate model studied here, as it considers Reynolds number effects beyond the empirical correlation of Ranz and Marshall derived for low-transfer rates. Thus, the Abramzon-Sirignano model is identified as the state of the art alternative in the scope of this study.