A two-fluid model is employed to model vaporizing non-combusting sprays under high injection pressure Diesel conditions. A ìocally homogeneous flow approximation is considered where the two phases have the same velocity at a given spatial location and time. Two approaches are used to model vaporization. In the first approach, thermodynamic equilibrium is assumed between the two phases. In the second approach, non-equilibrium effects are included by employing the D2-law for dropìet vaporization. The computed liquid penetration is compared with constant volume measurements made under Diesel conditions at the Sandia National Laboratories. The variation of the liquid penetration with droplet size, injection velocity and ambient density is studied. It is shown that non-equilibrium effects are not important when the dropìets are relatively small. The process of vaporization is controlled only by turbulent mixing under such conditions. The effect of drop size becomes important when the injected drop sizes are large. Such conditions are likely to occur at low ambient densities where the non-equilibrium model predicts better agreement of trends with the measurements.

Evaluation of Equilibrium and Non-Equilibrium Vaporization Effects in Diesel Sprays Using a Two-Fluid Model

MAGI, Vinicio
2000

Abstract

A two-fluid model is employed to model vaporizing non-combusting sprays under high injection pressure Diesel conditions. A ìocally homogeneous flow approximation is considered where the two phases have the same velocity at a given spatial location and time. Two approaches are used to model vaporization. In the first approach, thermodynamic equilibrium is assumed between the two phases. In the second approach, non-equilibrium effects are included by employing the D2-law for dropìet vaporization. The computed liquid penetration is compared with constant volume measurements made under Diesel conditions at the Sandia National Laboratories. The variation of the liquid penetration with droplet size, injection velocity and ambient density is studied. It is shown that non-equilibrium effects are not important when the dropìets are relatively small. The process of vaporization is controlled only by turbulent mixing under such conditions. The effect of drop size becomes important when the injected drop sizes are large. Such conditions are likely to occur at low ambient densities where the non-equilibrium model predicts better agreement of trends with the measurements.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11563/14459
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