Range extender engine with very high power density, suitable for the use in a hybrid propulsion system: Deep Miller Cycle optimization with advanced CFD 1D-3D virtual validation.

The thesis work started during an internship at Leonardo Engineers for Integration Srl. The study was focused on the development and the optimization of a range extender engine, suitable for the use in a hybrid propulsion system. To obtain acceptable results, the optimization has been achieved by the use of simulations. The task of this study is to determine an appropriate working condition of the engine because the problems that can occur are different and it's essential to avoid them. How was a proper engine configuration achieved? The engine, subject of the study, has been considered as a 1-D model using WAVE software developed by Ricardo Software. Using the software, it's possible to carry out the engine analysis and to visualize its performance such as efficiency, power, torque and even pollutant emission. However, using another software called HEEDS by Red Cedar Technology, it was possible to optimize the model and detect the best operating point to improve the model. To define the best operating point of the engine, it is necessary to consider different objectives. In fact, the optimization study of the model must lead to a solution that allows to obtain an engine with the lowest possible fuel consumption and that avoids the rising of high pressure in the cylinder, called PCP (Peak Cylinder Pressure) which is a function of knock. So in order to consider this objective, the values of overall BSFC (Brake Specific Fuel Consumption) and knock intensity index have been derived. There will be a brief introduction about the internal combustion engine, its history, its features and, above all, its criticalities. Then, an another theme, very important nowadays, will be faced: the hybrid vehicle. Its history, its development and its applications will be discussed. Finally, the results of the work and the conclusions will be exposed. Then, future application for future works will be shown.