CFD Simulation of Oil Jets for Piston Cooling Applications Comparing the Level Set and the Volume of Fluid Method 2019-01-0155
A new CFD simulation model and methodology for oil jet piston cooling has been developed using the modern level set approach. In contrast to the widely used volume of fluid method, the level set approach explicitly tracks the interface surface between oil and air by an additional field equation. The new method has been extensively tested on two- and three-dimensional examples using results from literature for comparison. Furthermore, several applications of oil jet piston cooling on Ford engines have been investigated and demonstrated. For example, three-dimensional simulations of piston cooling nozzle jets of a Diesel engine have been calculated and compared to test-rig measurements. Laminar jets as well as jets with droplets and fully atomized jets have been simulated using realistic material properties, surface tension, and gravity. Simulations of cooling jets on the undercrown of a gasoline piston as well as on a moving piston with a cooling gallery have been investigated and compared to test-rig measurements. Results of a simplified model with the CFD software STAR-CCM+ used in the Ford CAE workflow have been compared to the new level set method. Although using different computational approaches (level set versus volume of fluid method), the results are quite similar for laminar jets. Larger differences occur for semi-turbulent and atomized oil jets with many droplets, which need highly resolved meshes. All in all, the modern CFD tools are powerful to investigate active cooling strategies for pistons to improve the efficiency of internal combustion engines and to reduce emissions.
Loic Wendling, Marek Behr PhD, Anselm Hopf, Frank Kraemer, Carsten Weber, Paul Turner cEng
RWTH Aachen University, Ford Motor Company