ID 352

Numerical investigation of droplet evaporation modeling in combustion environment

 

Abstract:

Great part of the available droplet evaporation models in the literature have been developed focusing on spray combustion processes. However, the validation of such models is typically performed in non-reactive or environments with strongly simplified thermo-chemical properties. It is the purpose of this work to investigate the influence of such simplifications in the evaporation modeling and their subsequent impact on combustion processes. Therefore, a systematic study about different procedures used to address thermo-chemical properties in two of the most employed evaporation models in CFD (Computational Fluid Dynamics) applications is conducted in a numerical context. Both are the infinite liquid conductivity versions of Abramzon-Sirignano and Miller et al. models. In a first part, investigations are addressed in a single droplet framework for different fuels (i.e. ethanol, hexane, and decane). Various approaches used to compute the vapor-liquid equilibrium (VLE) are investigated. In a second part, the different modeling strategies are compared in the framework of flames propagating in droplet mists of ethanol including a detailed description of the chemistry. Different methods used to derive thermo-chemical properties for the evaporation modeling are also tested. Namely, the actual representation of the gas mixture and its simplification as pure air at the same temperature and pressure. The representation of the combustion process as a freely propagating flame facilitates the observation of the impacts caused by evaporation in terms of the flame speed. Results show good agreement with available experimental data in non-reactive atmospheres and can demonstrate the relevance of the investigated features in combustion environment.