A numerical model for calculating the vaporization rate of a fuel droplet exposed to a convective turbulent airflow

Abstract

Purpose -The purpose of this paper is to develop a three-dimensional (3D) numerical model capable of predicting the vaporization rate of a liquid fuel droplet exposed to a convective turbulent airflow at ambient room temperature and atmospheric pressure conditions. Design/methodology/approach -The 3D Reynolds-Averaged Navier-Stokes equations, together with the mass, species, and energy conservation equations were solved in Cartesian coordinates. Closure for the turbulence stress terms for turbulent flow was accomplished by testing two different turbulence closure models; the low-Reynolds number (LRN) k-1 and shear-stress transport (SST). Numerical solution of the resulted set of equations was achieved by using blocked-off technique with finite volume method. Findings -The present predictions showed good agreement with published turbulent experimental data when using the SST turbulence closure model. However, the LRN k-1 model produced poor predictions. In addition, the simple numerical approach employed in the present code demonstrated its worth.Research limitations/implications -The present study is limited to ambient room temperature and atmospheric pressure conditions. However, in most practical spray flow applications droplets evaporate under ambient high-pressure and a hot turbulent environment. Therefore, an extension of this study to evaluate the effects of pressure and temperature will make it more practical. Originality/value -It is believed that the numerical code developed is of great importance to scientists and engineers working in the field of spray combustion. This paper also demonstrated for the first time that the simple blocked-off technique can be successfully used for treating a droplet in the flow calculation domain.

A numerical study of the effect of turbulence on mass transfer from a single fuel droplet evaporating in a hot convective flow

“…where a P , a E , a W , a N , a S , a T , a B , and b Φ are coefficients and their expressions are reported elsewhere [21,23]. S P and S C are the two terms of the linearized source term S Φ .…”

“…For the liquid phase, the conservation equations of mass, momentum and energy are used. The set of governing equations for the gas and the liquid phases can conveniently be written in a general transport equation having the following form [21].…”

“…Four eddy-viscosity turbulence closure models (i.e. low-Reynolds number k-ε, low-Reynolds number k-ω, Baseline k-ω and SST) were tested for predicting the effect of freestream turbulence intensity on sphere drag coefficient [21]. It was found that the SST and k-ε models predicted the best and worse results, respectively, compared to their counterpart's experimental published data.…”

“…[27] and references cited therein. A recent attempt is made to test this technique for determining the characteristics of laminar and turbulent flows over a sphere [23], and the evaporation of a droplet in a turbulent convective flow [21]. The Cartesian grid-based blocked-off treatment of a droplet immersed in the computational domain is schematically shown in Fig.…”

“…The numerical model validation is reported in [21], therefore, it is not presented in this paper. The numerical data reported in [21] are used here to verify the vaporization Damköhler number correlation proposed in [14,18,19]. Fig.…”