Wij hanteren het label Open Access voor onderzoek met een Creative Commons licentie. Door een CC-licentie toe te kennen, geeft de auteur toestemming aan anderen om zijn of haar werk te verspreiden, te delen of te bewerken. Voor meer informatie over wat de verschillende CC-licenties inhouden, klik op het CC-icoon. Alle rechten voorbehouden wordt gebruikt voor publicaties waar enkel de auteurswet op van toepassing is.
This report explains the development of an undertray diffuser for an electric Formula Student race car. The main goal of this graduation internship is designing an undertray diffuser. An undertray diffuser is just as the front and back wing of race cars an aerodynamic package that generates downforce. The hard part of designing an aerodynamic package for these cars is their top speed. The faster a car drives the more downforce is going to be generated. The Formula student race cars have a top speed around 130km/h. Due to this low top speed (Formula 1 cars reach top speeds of 370km/h), the wings of the car have to work with lower speeds and have to be larger. The undertray diffuser has to generate as much downforce as possible and as less drag as possible. This report will give the students who are going to build the actual undertray diffuser the design and recommendations to build a good working undertray diffuser.
The first chapter of this report gives an explanation of the Formula Student competition at which URE competes every year. By competing in Formula Student competitions students are challenged to design and build a single-seat formula racecar in order to compete with over 400 university teams from all over the world. These competitions exist out of static and dynamic events. In chapter 2 the working principle of the undertray diffuser is explained. The air under the undertray diffuser travels faster than on top of the undertray diffuser. When this happens a lower pressure is generated underneath the undertray diffuser and this lower pressure generates downforce. The set of requirements for the undertray diffuser is given in chapter 3. Willemsen  did 2D CFD simulations in order to find the best undertray diffuser geometry. The optimized undertray diffuser of Willemsen  is the foundation of this graduation internship and in chapter 4 is his optimized undertray diffuser compared with a 3D undertray diffuser with the same dimensions in Flow Simulation. The 2D ANSYS model of Willemsen  is transferred into 3D with Solidworks in chapter 5. This model is optimized to fit on the URE08 and is built out of MDF. Because ANSYS and Flow Simulation give different values for the downforce and drag the undertray diffuser prototype has to be tested. There are four possibilities to test an undertray diffuser: with small-scale wind tunnel tests, with full-scale wind tunnel tests, with tests on the road with the prototypes mounted on the car, and with tests on the road with a test setup. These possibilities are explained in chapter 6 and in chapter 7 are given the actual test. Due to some problems not everything progressed as planned. The tests were not done on a URE car and the drag is not tested. The test data is validated and compared with the simulations in chapter 8. The end of this report contains out of conclusions, recommendations and appendices.
At a speed of 80km/h the most generated downforce is 210N and the generated drag is 56N. At top speed the downforce can reach up to be 4 times as much. The best undertray diffuser for URE to build is the 70 undertray diffuser. This undertray diffuser must be adapted a little bit to make sure the drag will be as small as possible. The edges from the undertray diffuser have to be round and the length of the Gurney Flap has to be revaluated.