Modelling of wall films formed by impinging diesel sprays

Abstract

The aim of this article is in modeling and application of wall films resulting from the impinging diesel sprays. The mass and momentum equations of the film are derived in an integral form for film thickness on the basis of the incompressible boundary layer approximations. The major physical processes affecting the liquid film include mass and momentum contributions to the film due to spray impingement, splashing effect, shear forces on the film and dynamic pressure effects. After integrating in the cross-film direction, the three-dimensional film equations can be reduced to 2D flow equations and solved by the predictor-corrector step using the Euler method as a predictor. With the present film model, the new model published earlier (Lee and Ryou, 2000a) is used for spray/wall interactions. Assessment of the spray/wall interaction model and the film model is performed for the non-evaporative diesel sprays by comparing their predictions against several sources of experimental data. The computational model for spray/wall interactions is in fairly good agreement with experimental data for both spray radius and height. The film model suggested in the present work is better than the static film model presented previously, indicating that the dynamic effects of film motion should be considered for wall films. It may be thought that the present film model is acceptable for prediction of the film radius and thickness. Copyright © 2001 SAE International and Messe Düsseldorf.