Ethanol fuel blends with gasoline for spark ignition (SI) internal combustion engines are widely used on account of their advantages in terms of fuel economy and emissions reduction potential. The focus of this paper is to study the effects of these blends on combustion characteristics such as in-cylinder pressure profiles, gas-phase emissions (e.g., unburned hydrocarbons, NOx) and particulates (e.g., particulate matter and particle number) using both measurement campaigns and digital engineering workflows.
Nineteen load-speed operating points in a 1L 3-cylinder GDI SI engine were measured and modelled. The measurements for in-cylinder pressure and emissions were repeated at each operating point for three types of fuel: gasoline (E0, 0% by volume of ethanol blend), E10 (10 % by volume of ethanol blend) and E20 (20% by volume of ethanol blend). A digital engineering workflow combining high-fidelity physico-chemical modelling with advanced machine learning techniques was adopted to cover the entire load-speed operating window of the engine within practical computational times. Model parameter estimation and validation against measurements were performed with respect to the in-cylinder pressure profiles and emissions. Subsequently, the validated model was applied for further investigations.
The study demonstrates that the digital engineering workflow is capable of accurately simulating the effects of ethanol blended fuels on in-cylinder pressure profiles and trends in emissions, by simply modifying the chemical fuel composition to reflect the ethanol content in the blended fuel. Secondly, the calibrated model parameters behave well over the entire operating window, which is useful in simulating in-cylinder pressure profiles and emissions at new load-speed operating points, thus demonstrating the capability of the digital workflow to populate data and thus augment measurements. Finally, it was observed that the effects of ethanol content vary according to the operating conditions, e.g., particle number (PN) was found to decrease with increasing ethanol percentages for most of the engine operating points except at high engine load.