Stress Analysis and Design Optimisation of Carbon Piston

This work was carried out as a part of a European project coordinated by Daimler Benz. The aim of this research programme was to reduce HC emissions of a petrol engine by using a newly designed carbon piston. The Mercedes-Benz mid-series four-valve petrol engine (M111, 2.2 litre) was used as the demonstration engine. A number of finite element (FE) analyses were carried out to predict thermal and mechanical stresses in the piston and optimise its shape. The original design of the piston was fully analysed under full load and maximum torque conditions. Results showed two critical areas in the piston with very high stresses and very low safety factors. A parametric study of various design features / dimensions was conducted to strengthen the design and improve its safety. Several specific features of the original design such as the crown thickness and pin hole profile, were modified to reduce stresses in the critical areas of the piston. As the result of this work, the overall design of the carbon piston was optimised and its structural integrity and safety factor were improved.