“Fast Running” and “Real Time” Model Creation and Calibration of a High Performance S.I. Engine

This master course thesis has been developed at POWERTECH Engineering S.R.L., an important engineering consulting company, specialized in the field of 1D and 3D CFD analysis, in collaboration with Aston Martin Lagonda, a renowned high end performance car manufacturer. Computational fluid dynamics has become a fundamental tool in the development and optimization of new engines, by allowing a significant reduction in the need for physical testing, which in turn reduces costs and cuts time to market. This is why this project was developed using GT-POWER, a leading edge 1D CFD software, which also includes extensive tools for vehicle simulation. The subject of this thesis is a high specific output, V6, turbocharged, S.I. engine currently under development at Aston Martin Lagonda, which will equip a future, high performance hybrid vehicle. One peculiarity of this engine is that it includes an electrically assisted turbocharger. This is an important feature as it allows, not only to improve the transient performance of the engine, but also to generate power that can be used in the electric portion of the hybrid powertrain. The starting point of this project was the detailed model of the aforementioned engine and the main objective was the reduction of this model to a real time model that could be integrated into its respective vehicle model. Vehicle models commonly use map based engine models, which can run simulations very fast but lack predictive capability, thus delivering potentially less accurate results when the vehicle is tested in many different operating conditions. Integrating a detailed engine model into the vehicle model would significantly improve model predictivity and accuracy but at the cost of increasing its run time to unacceptable levels. Hence the need for a real time model which trades a small amount of accuracy for a reduced real time factor, providing the optimal compromise. As an intermediary step towards RT reduction, the initial detailed model was first reduced to a fast running model, both for the purposes of being a reference point with respect to accuracy versus RTF, and because it was requested by AML for use in standalone performance analyses. Finally, the reduced and calibrated real time model was setup to run transient simulations. In particular, it was tested on the WLTC and an equivalent lap of the Nurburgring. This step was carried-out to ensure the model would be able to perform driving cycle simulations, once integrated into the vehicle model.