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Automotive manufacturers are facing stronger and stronger pressure to optimize all aspects related to fuel consumption of cars, and aerodynamic drag makes no exception, due to increasing government enforcing rules for the reduction of the emissions and the increasing influence of aerodynamic performance on fuel consumption with WLTC and RDE driving cycles. Nowadays, CFD simulation is a common tool across automotive industries for the assessment and the optimization of vehicle resistance in the design phase. The full power of these numerical methods of studying many design variants in advance of experimental testing, however, can be fully exploited when coupled with optimization techniques, always keeping into account constraints and aesthetical demands. On the other hand, a massive use of CFD optimization can lead to unaffordable computational efforts or a limitation of the design exploration space.

The aim of this work has been to develop an advanced methodology to model the car cabin cool down test. It has been decided to focus the attention on the fluid dynamics and thermal dynamics aspects of the phenomenon, trying to catch the correct heat transfer between the outside environment and the internal cabin with a thermal tool, together with an internal flows CFD simulation. To start with, an experimental cool down test was conducted in the FCA Italy climatic wind tunnel on a L0 segment vehicle, to get the correlation data and the boundary conditions required for the simulation: panel ducts air transient temperatures, wind tunnel air temperature and velocity, solar array load. The simulation was divided into two steps: steady state soak with a finite difference based thermal solver and transient cool down, coupling the thermal solver with a CFD one. In particular an advanced CFD/thermal coupled approach has been applied, using STAR-CCM+® and TAITherm® tools.

The clutch is that mechanical part located in an internal combustion engine vehicle which allows the torque transmission from the shaft to the wheels, permitting at the same time gear shifting and supporting engine revolutions while the car is idling. This component exploits friction as working principle, therefore heat generation is in its own nature. The comprehension of all the critical issues related to thermal emission, and also of the principal physical parameters driving the phenomena are a must in design phases. The subject of this paper is the elaboration of an accurate, but also easy to use and easily replicable, methodology to simulate thermal behavior of a clutch operating inside its usual environment. The present methodology allows to prevent corrective actions in the last phase of the projects (real testing), such as changes in gear ratios, that likely worsen CO2 emissions, permitting to achieve the wished thermal performance of the clutch avoiding late changes.