Enhancing Cabin Comfort

TotalSim began by running simulations at a low vehicle speed to mimic a street circuit. Its typical slower speeds and heavy braking would represent the ‘worst case’ scenario for cooling that the cars see all season. The runs were set at a slow corner entry braking configuration using a full model of the racecar that included over 11 different solid material types; modeling hundreds of solid parts in the car such as:

• Exhaust assembly including inconel, stainless steel and insulation mats
• Reflective films for thermal radiation management
• Carbon fiber panels and their core materials
• Stainless steel and mild steel for frame components
• Foam blocks used for crash protection materials around door panels

All the components were included to accurately track the conductive heat transfer through varying materials, the conjugate and convective heat transfer from the solids to the air and the radiative heat from the very hot exhaust and engine to other components of the vehicle. 

Prior to the simulation, NASCAR was able to collect Forward Looking Infrared (FLIR) data from a track test that was used to correlate and validate the simulations. Almost identical hotspots were shown between the FLIR track data and the simulation baseline data. This gave TotalSim and NASCAR the confidence to move forward with modeling the new concepts

Once all of the data had been collected, and the baseline had been completed and validated, TotalSim began testing NASCAR ideas and concepts to increase cabin comfort for NASCAR drivers. The car already had cooling air supplied directly to the original exhaust design but due to the muffler’s position, much of the cooling air flow would recirculate the exhaust heat back into the engine bay. This left an inadequately cooled exhaust pipe right next to the steel chassis structure which then in turn, conducted that heat into the cabin. 

To combat this, NASCAR created a short exhaust design which carried a shorter muffler and exited earlier on the car. The panels around the short exhaust were redesigned to increase the air volume around the exhaust and muffler to better allow the cooling air to convect heat away. The chassis was further protected by an additional sealing panel that was used to prevent hot air from propagating down the chassis sides. 

All of these options were created first in CAD, and then modeled in CFD simulations. Each part or design option was able to be tested and quantified by monitoring the temperatures in the critical cabin areas. The short exhaust design simulations showed that it was able to accomplish much of the cooling desired. NASCAR and TotalSim also tested several additional design options that could be added or track tested in the future as needed.