Development of a One-Dimensional Engine Thermal Management Model to Predict Piston and Oil Temperatures 2011-01-0647

A new, 1-D analytical engine thermal management tool was developed to model piston, oil and coolant temperatures in the Ford 3.5L engine family. The model includes: a detailed lubrication system, including piston oil-squirters, which accurately represents oil flow rates, pressure drops and component heat transfer rates under non-isothermal conditions; a detailed coolant system, which accurately represents coolant flow rates, pressure drops and component heat transfer rates; a turbocharger model, which includes thermal interactions with coolant, oil, intake air and exhaust gases (modeled as air), and heat transfer to the surroundings; and lumped thermal models for engine components such as block, heads, pistons, turbochargers, oil cooler and cooling tower. The model was preliminarily calibrated for the 3.5L EcoBoost™ engine, across the speed range from 1500 to 5500 rpm, using wide-open-throttle data taken from an early heat rejection study.

The model accurately predicts oil sump temperatures, coolant engine-out temperatures and peak piston temperatures for steady-state, WOT conditions, across the speed range. Also, the model predicts warm-up oil sump temperatures within the experimental test data variation, and predicts warm-up coolant temperatures within ± 5°F. With further calibration, it is expected that this model may provide design guidance to determine the effects of piston squirter oil flow rates on piston temperature and on cold-start oil warm-up temperatures.

The current model uses experimental coolant energy to estimate the combustion energy input. To enhance the predictive capability, this model should be further calibrated using data from additional engine configurations and from piston heat transfer engine or bench tests. Additionally, an in-cylinder heat release model should be included as a replacement for the experimental coolant energy input.