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Upcoming regulations and new technologies are challenging the internal combustion engine and increasing the pressure on car manufacturers to further reduce powertrain emissions. Indeed, RDE pushes engineering to keep low emissions not only at the bottom left of the engine map, but in the complete range of load and engine speeds. This means for gasoline engines that the strategy used to increase the low end torque and power by moving out of lambda one conditions is no longer sustainable. For instance scavenging, which helps to increase the enthalpy of the turbine at low engine speed cannot be applied and thus leads to a reduction in low-end torque. Similarly, enrichment to keep the exhaust temperature sustainable in the exhaust tract components cannot be applied any more. The proposed study aims to provide a solution to keep the low end torque while maintaining lambda at 1. The tuning of the air intake system helps to improve the volumetric efficiency using resonance charging effects.

This paper focuses on the numerical simulations of flow around a realistic generic car model called the DrivAer body. This new open-source model is based on the geometries of two medium sized cars, the Audi A4 and the BMW 3 series, and possesses more representative car features as the well-known generic Ahmed body. In this paper, only the fastback geometry is investigated. The flow solver used is ISIS-CFD developed by CNRS and Ecole Centrale de Nantes. This solver is based on a finite-volume method, and two turbulence modelizations are used: the Explicit Algebraic Reynolds Stress Model (EARSM) and a Detached Eddy Simulation (DES). Two meshes are used. For one, the walls are described with a wall function and the mesh contains 19 million cells. This mesh is called “Mesh 1”. For the second mesh, a low-Reynolds number turbulence model for the walls is used. In this case, the mesh contains 39 million cells, and is called “Mesh 2”.

One of the main advantage of a hybrid thermal-electric vehicle is that the internal combustion engine (ICE) can be shut down when not needed anymore (Stop&Start system, propulsion with full-electric mode), thus reducing fuel consumption. But this use of the ICE impacts its thermal behavior because of a lack of heat source and thermal losses. Furthermore, the ICE is sometimes used with higher load in order to charge the batteries that increases the total heating power produced by the combustion. Therefore, the simulation of hybrid vehicles becomes really interesting to evaluate the effect of different control strategies (energy repartition between the engine and the electric motor) on the fuel consumption. However, in most of actual hybrid vehicles simulation tools, for calculation speed reasons, the thermal phenomena are either not taken into account, or their calculation is not based on physical equations (empirical formulas). Their predictive capability is then limited.