A one-dimensional ring-pack lubrication model developed at MIT is applied to simulate the oil film behavior during the warm-up period of a Kohler spark ignition engine. This is done by making assumptions for the evolution of the ail temperatures during warm-up and that the oil control ring during downstrokes is fully, flooded. The ring-pack lubrication model includes features such as three different lubrication regimes, i.e., pure hydro-dynamic lubrication, boundary lubrication and pure asperity contact, nonsteady wetting of both inlet and outlet of the piston ring, capability to use all ring face profiles that can be approximated by piece-wise polynomials, and, finally, the ability to model the rheology of multigrade oils. Not surprisingly the simulations show that by Snr the most important parameter is the temperature dependence of the oil viscosity.
Frølund, K., Schramm, J., Tian, T., Wong, V., & Hochgreb, S. (2001). Analysis of the piston ring/liner oil film development during warm-up for an SI-engine. Journal of Engineering for Gas Turbines and Power, 123(1), 109-116. https://doi.org/10.1115/1.1341206