Research and analysis of a thermal optimisation design method for aluminium alloy pistons in diesel engines

Abstract

To further improve the thermal state of the piston for better thermal design, a multi-objective optimisation algorithm was used in this paper to find the best combination of design variables. The results show that thermal barrier coating (TBC) can effectively prevent heat transfer to the piston, and the thicker the ceramic layer, the better the thermal insulation effect. The maximum temperature and maximum thermal stress of the optimised piston matrix can be reduced by a maximum of 55.54 °C and 43.94 MPa, with a reduction of 15.08 % and 25.43 %, respectively, compared with that of the aluminium alloy piston of 368.39 °C and 172.76 MPa. Moreover, the thermal stress at the bottom of the combustion chamber, a larger cross-sectional area of the cooling gallery can dissipate more heat, which can have a more significant impact compared to the thickness of the ceramic layer. The large temperature gradient causes the maximum thermal stresses of the TBC piston to occur on the surface where the metal bonding layer contacts the piston matrix. Such high thermal stress is the main cause of coating delamination. The findings of this study can provide a reference for improving the thermal state of the piston and enhancing the engine performance.

Keywords

• Diesel engine
• Piston
• Thermal barrier coating
• Design method
• Thermal optimisation