7.1.1 Full Vehicle Modelling
The full vehicle model described here, includes all external surfaces, under-body and underhood details. No geometry clean up is required for front end air flow analysis and underhood thermal cooling analysis. The underhood thermal effects are studied including the full under-body geometry, with a fast simulation set up time. In Simerics-MP+, the template ensures the good quality of mesh to capture all features of the geometry, with cells efficiently distributed in the regions of interest using predefined refinement zones. The template also allows to retain internal mesh for specific solid or fluid components (Example: Exhaust manifold, after treatment system) and solve conjugate heat transfer.
The underhood compartment in vehicle is made of complex aerothermal phenomena, especially convection and radiation, with complicated airflow paths. The coolant air is guided through the grilles and guided towards heat exchangers. Some vehicles use fans to guide the air to the thermal components in the under hood. The cooling air is released into the wheel houses or into the under-floor regions. This may result in some interference effects and flow losses.
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Figure 7.2 - Vehicle geometry |
Figure 7.3 - Underhood layout |
The major components of the underhood thermal systems are:
- Grille: The coolant air is guided through these vents. The openings of grille can be adjusted to reduce or increase the air flow. Adequate care needs to be taken in modelling the grille to ensure that the proper amount of cooling air is let into the under hood compartment through the grille. The grille structure is as shown in Figure 7.4.
- Fan: The cooling of the thermal components happens through convection. The fan (see Figure 7.5) enhances the rate of heat transfer to the coolant air through forced convection.
- Condenser: The hot compressed refrigerant liquid is cooled by air in this heat exchanger before reaching the evaporator. The condenser (see, Figure 7.6) can be modelled as an actual model or a resistance model. The resistance model requires the parametric values derived from pressure drop vs velocity (DP-V) plot.
- Radiator: This heat exchanger pumps the liquid coolant to channels running through the engine and cylinder head. After the liquid cools the engine components, the hot liquid coolant is passed through many small tubes equipped with fins. The coolant air which flows through the grille passes through these fins and cools the hot engine liquid. The radiator (see, Figure 7.7) can be modelled as an actual model or a resistance model. The resistance model requires the parametric values derived from pressure drop vs velocity (DP-V) plot.
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Figure 7.6 - Condenser1 https://grabcad.com/library/condenser-heat-exchanger-1 |
Figure 7.7 - Radiator2https://grabcad.com/library/radiator-complete |
The full vehicle modelling consists of following sections: