A Body with Active Aerodynamics for a D-I-S Race Car

Abstract

This thesis regards the design of a vehicle body with active aerodynamics for a DIS1 racecar, as well as the evaluation of the design. The key focus of the design is the active rear wing of the car, for which support brackets and actuation mechanism are designed. The motivation behind this is incorporation of electro-mechanical system design in the development of aerodynamic components, as well as demonstrating multidisciplinary expertise. The project is done in collaboration with D-I-S, which provided with a car model and data used for the design and evaluation in question of the project. Since aerodynamics have a meaningful impact on a vehicle’s performance, as well as oftentimes downforce needs to be compromised if low drag is desired and vice-versa; active aerodynamics should yield a solution where a vehicle’s performance is substantially improved with minimal compromises. Each design phase of the design consists of applicable simulations and/or calculations to ensure that the designed component is capable of delivering the expected performance. The design starts with developing the car body based on the premise that it should exhibit minimal drag and airflow disruptions, effectively having negligible effects on later incorporated active aerodynamic elements on it. The car body underwent two iterations, as the iterative process stopped when a satisfactory result was obtained. Thereafter, the rear wing is designed so it can generate sufficient downforce for the car to handle at least as much lateral acceleration as the current Nurburgring lap-record holder likely did at its peak during the record breaking lap, which is presumed to occur at the compression part of the ’Foxhole’ corner at the track. As a part of the wing design, simulations for NACA 4412 airfoil based wing are performed to attain relations between lift and drag coefficients and angle of attack. The obtained aerodynamic coefficients differ from the ones used to initially determine the wing size, which leads a reiteration of the wing design. A ’Scorpion Tail’ wing bracket is invented for the purpose of supporting the wing, as this bracket type exhibits desirable criteria to be incorporated in the design. It was chosen to be implemented after numerous structural and aerodynamic simulations, that compared it to two other wing bracket types; swan neck and reverse swan neck brackets. The actuation of the rear wing consists of a servo-motor, flexible shaft and a worm drive, which set in motion the shaft mechanically coupled with the wing. This solution is considered superior to conventional wing actuation techniques for this application, as this is a compact and light solution, that is able to adjust to the designed geometry. A simple control scheme is developed, presenting how the active aerodynamics should be controlled. The scheme uses steering wheel angle and vehicle velocity as inputs; suspension compression to determine the error to be corrected; and servo motor position as the output. When benchmarking, optimistic results are obtained suggesting that achieving the goals set for the car by DIS is plausible. Some simulations exhibit a negative drag acting on the rear wing, it is concluded that it is probably related to the downwards curvature at the rear of the car, yet the root cause remains unidentified, which is presumed to be related to the simulation settings. In the end, the overall objective of the project is considered to be realized, as the design and evaluation of the car body with active aerodynamics is deemed complete within the specified project scope.

A master thesis from Aalborg University

A Body with Active Aerodynamics for a D-I-S Race Car