This presentation describes the methodology developed by Simerics Inc to model the piston cooling process as part of an engine thermal modelling strategy.
The methodology covers for the multiphase flow analysis (oil + air) with heat transfer and for the actual solid piston heat transfer analysis; it’s based on two models:
Transient thermo-fluid multiphase model including squirter, cylinder, gallery and piston passages.
Steady State solid piston model
Coupling between the two models is implemented via a mapping procedure that exports local temperatures and heat transfer coefficients on the piston and gallery walls.
The main reason to adopt such a cycling scheme is in the very different timescales for the fluid and the solid: it’s estimated, in fact, that more than 1000 revolutions (on average and depending on the piston geometry and the engine working conditions) are needed to achieve thermal stability on the piston solid. This is why a steady state simulation is adopted and coupled with a fluid simulation covering 1 piston revolution.
Between 10 and 20 cycles are needed to bring the methodology to convergence.