Numerical investigation of deformation and evaporation of a volatile ethanol droplet under high-temperature conditions

Angwani, Vikas (2017) Numerical investigation of deformation and evaporation of a volatile ethanol droplet under high-temperature conditions. Masters thesis, Indian Institute of Technology Hyderabad.

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Abstract

Secondary atomization of a liquid fuel droplet is an important phenomenon observed in all spray related engin es. M inute fragments formed because of secondary breakup dictate the evaporation rates and hence the engine performance. Secondary droplet atomization is primarily governed by the ambient gas phase conditions, which are grouped into a non - dimensional number called as Weber Number , We . In the present stud y, an attempt has been made to capture the droplet deformation and evaporation of a volatile ethanol droplet for different We , ambient gas phase temperature and initial droplet temperature conditions. Commercial software, ANSYS FLUENT 13.0 is used which is first validated with several benchmark cases relating to droplet dynamics studies. Various parameters viz. drag coefficient, instantaneous droplet velocity , and deformation shapes, depicting the aerodynamic behavior of the droplet are analyzed with respec t to time. Droplet evaporation phenomenon is captured after developing a model based on kinetic theory, which is implemented by writing a User Defined Function. Thermal behavior of the droplet is then depicted by analyzing the evaporation rate evolution. F inally, a comparative study is presented for the droplet breakup time for isothermal and evaporating cases. Adaptive Mesh Refinement technique is implemented in all the cases to achieve high grid resolution near the vicinity of the droplet interface, thus precisely capturing various phenomena involved in the deformation process at minimal computational cost.

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