Modern engines with increasing power densities have put additional demands on pistons to perform in incrementally challenging thermal environments. Piston cooling is therefore of paramount importance for engine component manufacturers. The objective of this CFD study is to identify the effect of a given piston cooling nozzle (PCN) geometry on the cooling oil jet fanning (spreading) phenomenon.
The scope of this study is to develop a numerical set-up using the open-source CFD tool OpenFOAM® for measuring the magnitude of oil jet fanning and comparing it to experimental results. Large eddy simulation (LES) turbulence modeling is used to capture the flow physics that strongly affects the inherently unsteady jet break-up phenomenon. The oil jet fanning width is the primary metric used for comparing the numerical and experimental results. The results of simulation are validated for the correct applicability of LES by evaluating the quality metric (according to Pope [1]) at various probe locations and also by performing turbulent kinetic energy (TKE) spectral analysis.
CFD results appear promising since they correspond to the experimental data within a tolerance (of ±10%) deemed satisfactory for the purpose of this study. Further generalization of the set-up is underway, towards developing a tool that predicts the aforementioned metric — thereby evaluating the effect of nozzle geometry on jet fanning and hence on the oil catching efficiency (CE) of the piston cooling gallery. Such a tool would act as an intermediate step in defining the boundary conditions for determining the filling ratio (FR) and subsequently the heat transfer coefficients (HTCs) in the piston cooling gallery.
Large-eddy simulation of an air-assisted liquid jet under a high-frequency transverse acoustic forcing