Predicting Unburned Hydrocarbons in the Thermal Boundary Layer Close to the Combustion-chamber Wall in a Gasoline Engine Using a 1-D Model

The purpose of this study was to develop a one-dimensional (1-D) model for predicting the amount of unburned hydrocarbons (UHC) due to flame extinction by quenching close to the combustion chamber wall in a gasoline engine. The local Reynolds number was used to predict the thickness of the thermal boundary layer developed by in-cylinder flow caused by high speed charge passing through the intake valves. The effect of different intake port geometries, including moderate- and high-tumble types, on the thickness of the thermal boundary layer was examined. The flame extinction model was integrated into a 1-D gasoline engine model. The amount of UHC predicted by the model was compared with experimental results by using a single-cylinder gasoline engine under various engine operating conditions. The numerical values were found to be in reasonable agreement with the measured data. A methodology for controlling UHC was also proposed in the final section.