Torsional analysis of High-Performance Multi-Cylinder engine in GT-SUITE

This master thesis has been developed at POWERTECH Engineering S.R.L., an engineering consulting company, specialized in the field of 1D and 3D CFD analysis, in collaboration with McLaren Automotive Ltd., high end performance car manufacturer. The subject of this thesis is a high specific output, V6, S.I. engine currently under development at McLaren Automotive Ltd., which will equip a future, high performance vehicles. Numerical simulation allows a significant reduction in the need for physical testing, which in turn reduces costs and cuts time to market. It has become an essential tool in the development and optimization of new engines. In this perspective, this project was developed using GT-SUITE, a 1D CFD software, which also includes extensive tools for mechanical simulation. The aim of the thesis is to develop an engine model that includes all internal mechanical components, to perform a sensitivity study in order to evaluate the impact of the different parameters and elements on simulated results and to carry out a calibration of the model in order to correlate the experimental measured data and simulated results. This study will also be used to develop methodology for torsional model that could be used for future projects. The starting point for the activity were the GT-ISE models and properties of the components and high-frequency data provided by McLaren Automotive Ltd. The first step consisted of integrating all standalone models together with the dynamometer modelling into a comprehensive model, defining boundary conditions, elaborating the experimental data and setting the model suitable for torsional analysis. As an intermediary step toward the calibration, a sensitivity study was performed in order to evaluate the impact of the each parameters on the analysis results. This study is essential for both calibration procedure and future torsional models development. In fact it helps to define the main parameters that affect the under-study phenomenon. The final step of the activity was the calibration of the model. The cranktrain model was calibrated over full load steady-state curve, this procedure was carried out by comparing instantaneous rotating speed profile and their amplitude spectrum during the entire engine cycle. The Fourier analysis was implemented into the model in order to study the impact of each frequency on the results. The Fourier analysis is essential to understand the impact of specific component on the result, since it is possible to associate each component to a specific speed oscillation order. The outcome of the activity was a complete engine model that is able to reproduce the main speed oscillation of the engine with a satisfactory level of accuracy. It could be then used to further investigate on the remaining differences observed, mainly related to the simplification presents into the current approach: in fact, the model was set to perform only a torsional analysis (bending is not allowed) and the torsional stiffness of the crank throw was automatically calculated with an empirical approach that does not take into account the actual shape of the component.