Introduction

Formula Student Germany is a student engineering design competition in which student teams design, manufacture, test and race their own formula style race-car. In 2022, the competition added a driverless event in which teams had to implement self-driving capabilities on their race-car. This project was a part of working for the team - Orion Racing India.

The event has many dynamic events which the teams have to complete successfully. The vehicle has to navigate around the track by itself using inbuilt sensors and computers.

Goals

The primary objective for the 2021 season for the aerodynamics system was to improve upon the previous year's package to improve skid-pad lap time's by 0.2 seconds. This required the car to have more grip and thus an increase in Cl and Cd both.

In order to mitigate the negative effects of this, the goal of the Drag Reduction System (DRS) project was to develop a system for the race-car that could switch between high downforce and low drag configurations.

Work Done

Initial task was airfoil selection. The S1223 is a high lift coefficient, low reynolds number airfoil which makes it an ideal candidate for racecar application. But before actually using it for the wing, we need to find out the angle of attack that is optimal for our use case. We do this by plotting the coefficients of lift and drag v/s the angle of attack. From this we obtained the angles required to make the low drag and high lift/downforce configurations.

After a preliminary result was obtained, based on the angles found, a complete CFD simulation of the vehicle was performed. This simulation helps to determine how the airfoil wings interact with the rest of the car and provide a more realistic representation of the performance of the wings. Flow separation and tire wake also give vital insights into the aerodynamic interaction of the vehicle.

A basic control algorithm was made for the actuation of the wing elements. The idea was that in straight paths, the vehicle would have a high speed, hence it would make sense to have the low drag configuration when vehicle speed is more. So the driver can read the speed and press the button to activate the Drag Reduction System (DRS). An arduino testbed was used to test the system if it worked or not before implementing it on the actual vehicle.

Results

After extensive CFD simulations and taking help from the multi wing theory, the following configuration (A) was fixed for the rear winglets arrangement. A three wing configuration was used. And the wings have angles of 0°, 21°, 52° respectively. This helps achieve maximum downforce. But it also produces a lot of drag. Because of which, another CFD based optimization by changing winglet angles was performed to optimize for reduction in drag value. And configuration (B) was obtained with winglet angles close to 0°, -5°, -3°. Drag was found to be significantly reduced when configuration (B) was used over configuration (A) although it meant there wasn’t enough downforce.

The DRS system can be actuated either via a pneumatic system, hydraulic system, an electro mechanical system or simply a servo based electronic system. In this project we implemented it via servos that will be used in combination with a control board to help with the functioning of the DRS system. A linkage based actuation mechanism is attached along the endplates which will be operated by the servo motors. That will eventually tilt the winglets along a fixed hinge on the chord of the airfoil, thus helping achieve the required angles for the DRS system.

Introduction

Goals

Work Done

Results

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