An Evaluation of a Two-Fluid Eulerian-Liquid Eulerian-Gas Model for Diesel Sprays

Abstract

A two fluid Eulerian-liquid Eulerian-gas (ELEG) model for diesel sprays is developed. It is employed to carry out computations for diesel sprays under a wide range of ambient and injection conditions. Computed and measured results are compared to assess the accuracy of the model in the far field, i.e., at axial distances greater than 300 orifice diameters, and in the near field, i.e., at axial distances less than 100 orifice diameters. In the far field, the comparisons are of drop mean velocities and drop fluctuation velocities and in the near field they are of entrainment velocities and entrainment constants. Adequate agreement is obtained quantitatively, within 30 percent, and qualitatively as parameters are changed. Unlike in traditional Lagrangian-drop Eulerian-fluid (LDEF) approaches that are employed for diesel spray computations, adequate resolution can be employed in the near field to achieve numerical grid independence when the two-fluid model is employed. A major source of uncertainty in the near field is in the modeling of liquid jet breakup and atomization.

Computational study of charge stratification in early-injection SCCI engines under light-load conditions

“…The spray is, however, modeled using a Lagrangian-drop Eulerian-fluid (LDEF) model that is commonly employed for RANS and large-eddy simulations (O'Rourke and Bracco, 1981). The author and his collaborators have shown during the last fifteen years that this approach to modeling sprays has severe constraints and can give rise to large errors when collisions/coalescence of drops are included (Aneja and Abraham, 1997;Abraham, 1997;Iyer and Abraham, 2003). For this reason, it is unlikely that the results presented in this work are quantitatively accurate.…”

“…There are known deficiencies in all the submodels (Abraham and Magi, 1997;Aumann et al, 2003). To add to such deficiencies, as is well-known, irrespective of the model selected, the transient spray results, especially close to the orifice, are sensitive to the grid resolution (Iyer and Abraham, 2003;Abraham, 1997). The grid resolution is kept unchanged in the simulations reported below in the hope that the changes identified are qualitatively indicative of physical changes.…”

“…The REC code Iyer and Abraham, 2003;Premnath and Abraham, 2002;Gopalakrishnan and Abraham, 2004) is employed for this study. Turbulence is modeled using a standard k-e model with the model constants that are widely employed in engine simulations (Wilcox, 1993;Abraham and Magi, 1997;Magi et al, 2001).…”

A study on the reduction of exhaust emissions through HCCI combustion by using a narrow spray angle and advanced injection timing in a DME engine

“…In addition, the case of advanced injection timing is greatly influenced by the size of the computational grid in the squish region. Therefore, the spray improvement model based on a gas jet theory [25] was applied for reducing grid-dependency by the effect of relative velocity in this study. This model showed improved gridindependency results by various investigations [26,27].…”

Modeling Collision Outcome in Moderately Dense Sprays

“…The second problem concerns the validity of the collision/coalescence models currently used to compute the evolution of the mean (or filtered) surface density in the dense zone. Indeed, the first class of models proposed by Vallet et al [11,17] and then by Iyer and Abraham [18] are based on droplet collisions. Therefore, these models are applied in the dense part of the spray where the droplets are not formed yet!…”