Predicting Flow Dynamics of an Entire Engine Cooling System Using 3D CFD

Abstract: A combustion engine generates a lot of heat which need to be cooled to prevent damages to the engine and the surrounding parts. If the cooling system can not provide enough cooling to keep the engine in a well defined range of temperatures performance and durability will decrease and emissions increase. It is also important that the cooling system do not over-cool the engine, since this may result in rough running, increased engine friction and an overall negative performance. The aim of this thesis work is to create a complete 3D digital model of the cooling system for the first generation VED4 HP with CFD in STAR-CCM+. The simulated results are compared to available experimental data for validation. Today the entire system is being modeled with 1D CFD. One of the selected components in the cooling system being model in 3D at Volvo Cars is the water jacket. The 3D CFD model depends on the 1D CFD model for the boundary conditions which is an ineffective and time consuming process, sending data back and forth between the models when making changes. A 3D CFD model is not only more accurate than the 1D CFD model, since it capture the 3D flow phenomenas but it also allows parts or areas to be studied in detail. A study of four different turbulence models is conducted on the water jacket and on an arbitrary pipe in the cooling system. A mesh study is carried on the water jacket, the same arbitrary pipe and on the thermostat, both for the opened and closed thermostat. These studies are done with regard to pressure drop only. The study yields a low Reynolds model with the k-ε v2f turbulence model gave the best results. There is a discrepancy between the simulated results and the experiments. Main reasons to this may be the difference in the geometry used in this thesis for the digital model and the geometry used for the experiments together with the inaccuracies in the experimental data. The overall deviation is larger for a case with closed thermostat than for a case with an open thermostat. With the correct geometry and more accurate experimental data the simulations should be a close representation of reality.