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

A mired laminar and turbulent (MLT) model of heat transfer has been de veloped and implemented in the KIVA II code for describing impinging f uel 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 whet her or not a sliding film is determined to be present on the wall, res pectively. In the flooded condition, the heat flux between the liquid film and the wall is calculated by a laminar or turbulent model of hea t transfer, using the Reynolds number as a criterion. In the nonfloode d condition the heal flux is calculated using a heat transfer model of individual drops on a wall. The fuel spray development and the heal t ransfer characteristics of impinging diesel sprays in a rapid compress ion machine were investigated using the new model. The model predictio ns and the experimental results were generally in good agreement for c ases with different distances between the spray nozzle and the wall.