MODELLAZIONE CAD PARAMETRICA E ANALISI STRUTTURALE FEM DEL ROTORE DI UN MOTORE WANKEL

This thesis deals with the geometric reconstruction, parametric CAD modelling and structural analysis of a Wankel engine rotor. The aim is not to reproduce a specific commercial component with metrological accuracy, but to develop a geometrically and functionally consistent model while clearly distinguishing literature-based data, calculated quantities and dimensions introduced as modelling assumptions. The rotor profile was generated using a mathematical formulation of the conjugate envelope and discretised with an angular step of 0.5°, resulting in 361 points that were subsequently imported into Autodesk Inventor. The main functional features were then added to the basic solid, including the central bore, combustion recesses, apex-seal slots, a simplified internal gear and the grooves associated with the sealing system. A second, simplified geometry was prepared for the global finite element analysis. The material assigned to the model was the “Iron, Ductile” material available in the Inventor library. Two combustion-pressure levels, 5 and 7 MPa, were considered. Two additional equivalent static configurations were analysed by combining the 7 MPa pressure load with inertial effects associated with a reference eccentric-shaft speed of 8500 rpm. A mesh- sensitivity study was also carried out in order to assess the stability of the numerical response. For the 5 MPa case, the maximum von Mises equivalent stress was 34.101 MPa, increasing to 47.742 MPa at 7 MPa. The most severe inertial configuration among those investigated was obtained with the equivalent orbital acceleration directed along the negative X direction: in this case the maximum von Mises stress reached 102.224 MPa, the maximum displacement was 0.013556 mm and the minimum safety factor was 7.93. Within the assumptions of the model, the rotor therefore remains well inside the elastic range. At the same time, the analysis highlights the importance of boundary conditions, mesh refinement and the instantaneous direction of inertial loads when interpreting the structural response of a Wankel rotor.