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.