Development, Implementation, and Validation of a Fuel Impingement Model for Direct Injected Fuels with High Enthalpy of Vaporization

摘要

Due to their superior enthalpy of vaporization, the charge cooling benefits of oxygenated fuels have been widely reported in the literature. Spark Ignition Direct Injection (SIDI) engines have the opportunity to maximize this charge cooling effect by controlling the phasing of the in-cylinder fuel vaporization, thus increasing charge density and suppressing auto ignition. Existing fuel vaporization models often over-predicted this charge cooling effect for SIDI applications when heat transfer effects related to impingement of the liquid fuel on combustion chamber surfaces are not considered. The present subject describes the development, implementation, and validation of an analytical model that attempts to predict the volumetric efficiency gains and heat transfer reduction of a flex-fuel SIDI engine by considering impingement of the fuel spray on the combustion chamber surfaces. The model incorporates combustion chamber geometry, spray geometry, temporal fuel vaporization, surface impingement deposition, and the conductive heat transfer interaction of the fuel with the engine components. The model was integrated as a sub-module into a commercially available 1-dimensional (1D) engine simulation code to predict the overall performance of the engine system, and was correlated with empirical engine data over a range of engine operating conditions. This comparison indicated excellent agreement in both absolute magnitude and trends at low engine speeds but required additional content to accurately comprehend fuel/air interactions at elevated engine speeds.