Engine Lubrication System Model for Sump Oil Temperature Prediction

A flow and heat transfer model of an engine lubrication system has been developed in order to predict sump oil temperature and study heat transfer mechanisms within the lubricating oil circuit. The objective was to develop the capability of simulating all the energy transfers between the oil and the combustion process, the engine coolant, and the engine bay air. The model developed in this study simulates a V8 spark ignited engine. Included in this simulation is a bearing model for friction heat generation, a combustion heat input model, and component models for each key heat transfer site in the lubricating oil circuit. The model predicts sump oil temperatures under different engine operating conditions and simulation results were compared to test data with good agreement. The sensitivity of oil temperature to engine speed, engine load, coolant temperature, piston friction, bearing heat energy generation, piston design, water jacket depth, and oil flow rate(s) was studied. The assumptions made during modeling are discussed along with an estimate of their significance. Further, all of the significant heat transfer mechanisms in the oil circuit are discussed. This study shows that a lubricating oil circuit model is a useful tool for engine concept design, as well as providing an understanding of the mechanisms that effect sump oil temperatures.