Finite Element Thermo-Structural Methodology for Investigating Diesel Engine Pistons with Thermal Barrier Coating
Abstract:
Traditionally, in combustion engine applications, metallic materials have been
widely employed due to their properties: castability and machinability with
accurate dimensional tolerances, good mechanical strength even at high
temperatures, wear resistance, and affordable price. However, the high thermal
conductivity of metallic materials is responsible for consistent losses of
thermal energy and has a strong influence on pollutant emission.
A possible approach for reducing the thermal exchange requires the use of thermal
barrier coating (TBC) made by materials with low thermal conductivity and good
thermo-mechanical strength.
In this work, the effects of a ceramic coating for thermal insulation of the
piston crown of a car diesel engine are investigated through a numerical
methodology based on finite element analysis. The study is developed by
considering firstly a thermal analysis and then a thermo-structural analysis of
the component. The loads acting on the piston are considered both separately and
combined to achieve a better understanding of their mutual interaction and of
the coating effect on the stress state.
The thermal analysis pointed out a decrease of temperature up to 40°C in the
upper part of the piston for the coated model. Despite the lower deformations
induced by the reduced thermal load, the stiffening effect provided by the TBC
results in higher peak stress. However, the lower temperature field inside the
piston compensates by allowing higher yielding stresses for the component and
reducing the impact on the safety factor.
The methodology is validated by comparison of the model results with numerical
data available from the literature; limitations and potential future
improvements are also discussed.