In recent years, many engine manufacturers have turned to downsizing and boosting of gasoline engines in order to meet the ever more stringent fuel economy and emissions regulations. With an increase in the number of turbocharged gasoline engines, solutions are required to manage knock under a range of operating conditions. The charge air cooler has been introduced to mitigate knock. Moreover, the engine is required to operate with spark retard and/or boost reduction to provide knock reduction leading to reduced fuel economy.
Under some operating conditions water can condense in the charge air cooler (CAC). Corrugated plate separators have been widely used in gas-water separation and oil-water separation in many industries including marine diesel engines. However, this sort of separator has not been applied to gasoline engines in vehicles to separate the condensation in the charged air. In this paper, a 1-D condensation model to estimate the potential amount of water condensation and entrainment from the charge air coolers is presented. An approach to designing a unit to separate condensation in the flow from the charge air cooler while maintaining a low pressure drop is described. The design approach provides correlations of separator geometries versus separation and pressure drop performance. The study is developed using a 3-D computational model for analyzing charge air and condensation flow. The model results of the 1-D condensation model and the 3-D computational model have been validated by experiments on an engine-dynamometer based test cell. The set-up incorporates a 4 cylinder gasoline direct injection (GDI) turbocharged engine. An air-to-air charge air cooler is mounted under the engine. The intake air for the engine is supplied using a combustion air unit which enables the operators to control the temperature and humidity.
Test conditions have been identified to demonstrate the phenomenon of CAC water condensation. Measurements of water condensation and motion through the system confirm the results of models. A separator has been designed that achieves high separation efficiency and low pressure drop.