MODELING FUEL SPRAY IMPINGEMENT AND HEAT TRANSFER BETWEEN SPRAY AND WALL IN DIRECT INJECTION DIESEL ENGINES

Abstract

A mixed laminar and turbulent (MLT) model of heat transfer has been developed and implemented in the KIVA II code for describing impinging fuel sprays in direct injection diesel engines. The model accounts for various wall impingement regimes, including rebounding drops and drops sliding along the wall, using the drop's Weber number as a criterion. The model identifies flooded and nonflooded regimes depending on whether or not a sliding film is determined to be present on the wall, respectively. In the flooded condition, the heat flux between the liquid film and the wall is calculated by a laminar or turbulent model of heat transfer, using the Reynolds number as a criterion. In the nonflooded condition the heat flux is calculated using a heat transfer model of individual drops on a wall. The fuel spray development and the heat transfer characteristics of impinging diesel sprays in a rapid compression machine were investigated using the new model. The model predictions and the experimental results were generally in good agreement for cases with different distances between the spray nozzle and the wall.