Finite Element-Based Optimisation of Two-Stroke Marine Diesel Piston: A structural reliability and weight reduction study

Two-stroke marine diesel engines are pivotal in propelling ocean-going vessels, owing to their remarkable efficiency and durability. Within these engines, the piston is subjected to extreme mechanical and thermal loads, positioning it as a critical component for structural optimisation. This study presents a simulation-driven design optimisation of a marine two-stroke piston to enhance mechanical performance while reducing component weight. A parametric model was developed using SolidWorks, and the Taguchi method was applied to investigate the effects of piston height, crown thickness, and pin diameter on displacement, von Mises stress, factor of safety (FOS), and overall mass. Finite element analysis (FEA) was conducted under a peak combustion pressure of 15.3 MPa, with model validation achieved through a Grid Convergence Index (GCI)-based mesh independence study. The analysis indicated crown thickness was the most influential factor affecting piston stiffness and stress behaviour. The optimised design, featuring a height of 1000 mm, crown thickness of 120 mm, and pin diameter of 300 mm in alloy steel, achieved a 25.7% reduction in weight while maintaining a maximum von Mises stress of 2.94 × 10⁸ N/m² and an FOS of 6.05. These results illustrate the effectiveness of combining parametric modelling with statistical optimisation to achieve lightweight and structurally resilient piston designs suitable for high-load marine diesel applications.