This paper presents comprehensive numerical simulations of evaporation of droplets constituted of two liquid fuels in high pressure nitrogen ambient under normal gravity condition. A transient, two-phase and axisymmetric numerical model has been used for the simulations. Transport processes in liquid- and vapor-phases have been solved along with interface coupling conditions. Gas-phase non-idealities, solubility of ambient gas in liquid-phase, and pressure and temperature based variable thermo-physical properties in both liquid- and vapor-phases are considered in the numerical model. Phase equilibrium has been estimated using fugacity coefficients of all species in both phases. The range of Weber number has been chosen such that droplet remains almost spherical throughout its lifetime. Simulations have been carried out until the droplet surface regresses to one-tenth of its initial value or when the critical state for the mixture is reached. The numerical model has been quantitatively validated against the experimental data available in literature. The validated model is used to systematically study the evaporation characteristics of suspended n-heptane-hexadecane droplets in nitrogen ambient. The effects of the pressure, temperature, initial liquid-phase composition and forced convection velocity on evaporation characteristics have been discussed in detail. © 2018 Elsevier Ltd

Vasudevan Raghavan

Department of Mechanical Engineering

Critical current density (superconductivity)

Drops

Evaporation

Heptane

Liquid fuels

Liquids

nitrogen

Numerical models

Phase equilibria

solubility

Droplet evaporation

Fugacity

Gas solubility

Real gas effects

Two-component

Phase interfaces

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

International Journal of Multiphase Flow

Understanding the transport processes during evaporation and combustion of isolated liquid fuel droplet is highly important in several applications involving sprays. Comprehensive numerical models assist in carrying out simulations involving interlinked transport processes in liquid and gas phases using proper interface coupling conditions. The predictions from such numerical models reveal flow, temperature and species fields, with which the evaporation, as well as combustion characteristics, can be thoroughly analyzed. In this article, a detailed review of numerical models used to simulate evaporation of isolated droplets under several operating conditions is presented. This includes evaporation in high-pressure conditions, where real gas effects and solubility of ambient gas into the liquid droplet, come into play. Subsequently, a review of droplet combustion models, which are comprehensive enough to reveal the burning characteristics of an isolated droplet, is presented. Importance of liquid phase motion on evaporation and combustion behavior and water absorption in the case of alcohol droplets are reported. This review also includes modeling concepts applied to multi-component droplets. © 2019, Indian Institute of Science.

Journal of the Indian Institute of Science

Numerical Modeling of Evaporation and Combustion of Isolated Liquid Fuel Droplets: a Review

The paper presents a two-phase numerical model to simulate transient vaporization of a spherical two-component liquid fuel droplet. The model considers variation of thermo-physical properties in both liquid- and vapor-phases, as functions of temperature and species concentrations. Multi-component diffusion and surface tension effects are also considered. The model has been validated using the experimental data available in literature. The validated model is used to study the vaporization characteristics of both suspended and moving methanol-ethanol blended droplets in an atmospheric pressure environment. Relative strengths of forced convection and Marangoni convection are studied and compared for both suspended and moving droplets. Results in terms of streamlines, isotherms and isopleths at different time instants are reported and discussed. For low relative velocities, solutal Marangoni effects are seen to be important. © 2013 Elsevier Ltd.

Two-phase modeling of evaporation characteristics of blended methanol-ethanol droplets

Evaporation of stagnant (zero relative velocity) as well as moving spherical droplets of n-dodecane in a zero-gravity and high pressure nitrogen environment is modeled. The non-ideal effects, solubility of ambient gas into the liquid-phase, variable thermo-physical properties, and gas- and liquid-phase transients are included in the model. The model is quantitatively validated using published experimental data. Numerical predictions show that, for stagnant droplets at sub-critical ambient temperatures, the droplet lifetime continuously increases with pressure, while at critical temperature, the lifetime initially increases and thereafter remains almost constant. At super-critical temperatures, the lifetime decreases continuously with increasing ambient pressure and the average evaporation constant shows a local maximum at a particular ambient pressure. In the case of moving droplets, at super-critical ambient temperature, the rate of increase of average evaporation constant with ambient pressure becomes significant as the initial droplet relative velocity increases. For low initial velocities (<1 m/s), the average evaporation constant gradually increases with ambient pressure and subsequently levels-off with further increase in ambient pressure. The droplet lifetime decreases with increase in ambient pressure or initial velocity. Penetration distance of the moving droplets decreases with ambient pressure and increases with initial droplet relative velocity. The mechanisms influencing the differences in evaporation under varying conditions of pressure and temperature are discussed. © 2011 American Institute of Physics.

Physics of Fluids

A numerical study of evaporation characteristics of spherical n-dodecane droplets in high pressure nitrogen environment

International Journal of Thermal Sciences

Effect of unsteadiness on droplet evaporation

Predicting the evaporation rate of stationary droplets with the VOF methodology for a wide range of ambient temperature conditions

A novel formulation of multi-component drop evaporation models for spray applications

Two-phase transient simulations of evaporation characteristics of two-component liquid fuel droplets at high pressures

Journal	Data powered by TypesetInternational Journal of Multiphase Flow
Publisher	Data powered by TypesetElsevier Ltd
ISSN	03019322
Open Access	No