Abstract
To meet the increasingly stringent constraints on mobile and point emissions in the wake of the dwindling fortunes of fossil fuels, evaluation of hybrid fuels for application in combustion engines has become an imperative, especially in the third world countries. This paper presents, modeling of atomization characteristics of gasoline-ethanol fuel blends. Fuel breakup models and correlations between flow patterns and droplet characteristics were adopted and implemented in OpenFOAM Computational Fluid Dynamics (CFD) modeling suite for direct gasoline injector using a simple cylindrical mesh structure at constant volume. The Rosin Rammler distribution model was used to generate the number of spray particles injected into the cylinder. The spray modeling and atomization employed the use of blob sheet model and Kelvin-Helmholtz-Rayleigh-Taylor (KH-RT) model while the numerical technique for simulating atomization process by CFD included the use of governing equations such as Eulerian for gas phase, Lagrangian for disperse phase and turbulence modeling. The effects of fuel blends, injection pressure, ambient gas pressure and spray cone angle were evaluated on the axial spray tip penetration, spray width, and overall Sauter Mean Diameter (SMD). The SMD was seen to be affected by varying the degree of injection cone angle. The spray tip penetration lengths were larger for higher injection cone angles while higher penetration lengths were obtained at higher injection pressures. One salient conclusion drawn from the modeling is that as the number of particle increased, the density of clusters became smaller.
Highlights
Atomization is a phenomenon that entails the repeated breakup of bulk liquid into an ensemble of droplets, with the attendant effect of increasing the volume to surface area ratio
Atomizers are used for effecting atomization and several variants, including the air-assisted and pressure atomizers are employed in various fields such as agricultural irrigation pesticides application, fluid catalytic cracking, spray drying waste fuel reuse and medical applications
Relative to studies on diesel and bio-ethanol, much less attention has been given to atomization and spray modeling of gasoline-ethanol fuel blends
Summary
Atomization is a phenomenon that entails the repeated breakup of bulk liquid into an ensemble of droplets, (sprays) with the attendant effect of increasing the volume to surface area ratio. Relative to studies on diesel and bio-ethanol, much less attention has been given to atomization and spray modeling of gasoline-ethanol fuel blends. The existing breakup and spray models center around Kelvin-Helmholtz (k-H), Rayleigh-Taylor (RT) instability, Raynolds -Averaged - Navier-Stokes, Taylor-Analog breakup, wave breakup and modified forms Such modifications where they are introduced are local to the fuel and the atomizer that is studied. The use of spray distribution functions, no consensus has been reached on the most reliable one; the purpose of this paper is to apply models to the study of breakup and atomization characteristics of blends of gasoline and ethanol fuels, using Openfoam and MatLab as computational and spray visualization platforms. Wel l ru are gas and liquid Weber numbers, respectively and urel velocity of liquid droplet relation to stationary gas phase (Beale and Reitz, 1999)
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