Formula SAE: How to optimize a fuel tank in motorsports?
Formula SAE is a student design competition created by SAE International. The aim of this competition is to give to the participants the chance to experience working in a motorsport team. They have to design, manufacture, test, and drive a Formula-style race car respecting the different rules established by Formula SAE. There are events all around the world where students from universities of every country can compete on different aspects, such as speed, design, cost, and more.
Fuel Tank Design in Formula SAE Competition
One of the main problems we can find in motorsport is the design of a fuel tank. This issue is also very important in Formula SAE, as the fuel tank is a core part of the car and needs to be absolutely secure, with no leak and with the lowest possible weight. To reduce weight, each team has to study the consumption of its car and design the fuel tank to contain the necessary fuel to finish The Endurance (the longest event of the competition).
At the end of the race, car handling is massively changing, since most of the fuel gets consumed and the tank is nearly empty. This result is a phenomenon called sloshing which means that the fuel in the cell is pulled by inertia forces towards the corners of the fuel cell. This is a massive problem because the engine can stop if it doesn’t receive fuel soon and it can provoke the retirement of the team.
Computational Fluid Dynamics (CFD) can be used to avoid this problem. It is possible to simulate several designs of fuel tank to analyze the behavior of fuel inside it and study if the circuit where we are going to compete will provoke that effect. For that, it is necessary to make an in-depth study of the circuit, analyzing forces on corners and preparing a sequence of them.
This requires a huge effort because it is necessary to estimate the velocity on each corner (analyzing, if it’s possible, other years’ performance) and calculate for each corner the force over the car. This task is critical because it will be the base of the simulation, so we will create a file with all important parameters which will be the boundary conditions of our simulation.
Next step is to create several designs of the fuel tank, adapting it to the shape of the car and taking into account the other components of the engine. On a motorsport car, there is very little space, so it’s essential to design the different components as a block, to be able to introduce and manipulate every part.
As we have seen, fuel moves from one side to the other of the fuel tank while the pilot is driving, so it’s necessary to find some solutions to stabilize it and ensure that the injection valve always has fuel. The most common solution is to introduce some breakwaters in the fuel tank which prevent fuel to “dance” from one side to the other. For this project, we designed several types of breakwaters to analyze through CFD analyses.
Based on the simulation results, we could decide which was the best design for the circuit of the competition (Hockenheim in this case) and we developed a test fuel tank to prove it. Tests showed that without breakwaters, fuel took 5 seconds to be stabilized while with breakwaters, it only took 1 second.
Finally, the design was developed, and the fuel tank was manufactured using aramid (essential to ensure that the fuel tank will not burn).
This method is used in all motorsport competitions, even the most elitist one, the F1, where teams use this kind of simulation method to develop their cars. The teams design the fuel tank and oil sump with this technique to avoid problems of lack of lubrication on the engine. For those cases, they simulate the forces over the car at Eau Rouge — the most difficult corner of the World Championship —, because there are huge G forces combined with altitude changes.
With more than 30 years of engineering experience in the automotive industry, Carlsson Autotechnik GmbH provides engineering services for companies like Mercedes-Benz, Citroen, Peugeot, Honda, Toyota and SsangYoung. This case study shows how the engineers from Carlsson used SimScale to test the aerodynamics behavior of their sports car.