3D printed heat exchangers push the E-Stall Formula Student race car

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Using additive manufacturing technology, the Formula Student Racing Team E-Stall at Esslingen University of Applied Sciences in Germany improved the cooling of the electric drivetrain and power electronics. Printed with the highest precision on the EP-M260 by Eplus3D, the aluminum parts could easily dissipate the heat generated and thus improve the performance of the racing car.

The E-Stall racing team at Esslingen University of Applied Sciences designs and builds an electric racing car to compete in the Formula Student competition. With EPlus3D, three components have been significantly improved, including two heat exchangers.

Germany Student Formula

In Formula Student, a team of students builds a single-seater racing car to compete against other teams around the world. The competition is not won solely by the team with the fastest car, but rather by the team with the best overall package of design, performance and financial planning.

The Formula Student challenges team members to go the extra mile in their training by incorporating intensive construction and manufacturing experience as well as considering the economics of the automotive industry. Teams assume that they are a manufacturer developing a prototype to be evaluated for production. The target audience is the non-professional Weekend-Racer. The racing car must show very good driving characteristics such as acceleration, braking and handling. It should be offered at a very reasonable cost and be reliable and trustworthy. Additionally, the market value of the car increases through other factors such as aesthetics, comfort, and the use of readily available off-the-shelf purchase components.

The challenge teams face is to put together a complete package consisting of a well-built race car and a sales plan that best fits these given criteria. The decision is made by a panel of experts from the motorsport, automotive and supplier industries. The judging panel will judge each team’s car and sales plan based on construction, cost planning and sales presentation. The rest of the judging will take place on the track, where students will demonstrate in a number of performance tests how well their self-built race cars perform in their real environment.

Electric motor cooling

E-Stall has been a regular and proven competitor in Formula Student for many years. Based on findings from past racing seasons, they wanted to improve the cooling system of their electric racing car in terms of reliability. The previous cooling jacket used by the E-Stall team was made of a temperature-resistant polymer, which was mounted directly around the electric drive, consisting of two shells. The purpose of the cooling jacket is to regulate the temperature of the drive and prevent overheating. Without sufficient cooling, the risk of engine damage is quite high. Over the season of use of the polymer cooling jacket, a two-component solution has been shown to be prone to leaks and therefore problems.

In an all-wheel-drive electric racing car, the high-performance electric motors need to be cooled. Since these motors have a high power density of 10 kW/kg, they would overheat under full load without cooling. There are two cooling circuits, one for each side. The four motors are cooled as well as the corresponding inverters. Using EPlus3D’s design for additive manufacturing expertise and their latest EP-M260 Dual-Laser metal powder bed fusion solution, the cooling component leakage problem could be solved and the performance could be increased by significantly.

Thanks to the versatility of metal 3D printing technology, the E.Stall team was able to test new shapes, which was not possible with traditional methods until now. At the same time, the entire surface of the cooling jacket can be used for heat dissipation due to the nature of the aluminum material.

“The 3D printed cooling jacket will be an efficient and reliable product. We were able to create complex structures, which is unthinkable in a conventional way. Thanks to the EPlus3D and the latest additive manufacturing technologies, we were able to reduce the thickness of the walls thanks to the high precision of the 3D printer and therefore reduce the overall size of the parts.

Besides the cooling jacket, EPlus 3D supported E-Stall with a cooling pad for their inverters and a steering component. Both also inherited functional integration of multiple components, lightweight design, and overall performance improvements.

Inverter cooling.

Performance improvement

With the functional integration of cooling system, connectors, and mounting, assembly steps are saved and the fail-safe design is no longer prone to leaks. The minimum wall thickness of the part helps reduce the overall diameter and therefore creates more space for other suspension components based around the electric motor.

The high quality of the prints is crucial for their function. For inverters, a well-fitting and pressed cooling jacket was as important as the straightness of the cooling plate. Both parts could perform their functions well and keep the motors and inverters below 65°C, which the team says is an “incredibly good result”. Compared to last season, when the engines regularly hit 120°C, the advantage of the EPlus3D manufacturing process, which allows design integration, is clearly demonstrated.

Cooling jacket flow simulation.

The design of the cooling jacket allowed a simulated cooling capacity of 3.8 kW. Due to the lower temperature of the components, they can operate more efficiently, which leads to longer range of the overall car as well as improved acceleration.

Thanks to the high-level engineering of components and overall parts and the dedication of the entire E-stall team, they have achieved 4e place in technical design competitions at FS Czech and FS Alpe Adria. According to Felix Wenzelburger, Powertrain & Vehicle Dynamics project manager, “this discipline is the most important of all the static disciplines and assesses the technical knowledge of the team and the processes they use to design the car”.

In Croatia, they completed the endurance test and achieved first place in the efficiency category. The endurance test tests the reliability of the car and of each component. In addition, most points are awarded for this discipline. This is why a successful endurance event is the main goal of every Formula Student team and therefore a milestone for them. This endurance event shows the high reliability and functionality of heat exchangers made in metal additive manufacturing. In the future, we will see an increasing demand for such applications in areas where lightness and performance are crucial.

E-Stall Formula Student Team Improves Performance with 3D Printed Heat Exchangers Supported by Eplus3D Metal Additive Manufacturing Technology
The steering gear housing was also 3D printed by EPlus3D.

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