Effect of Piston Profile on Piston Motion and Liner Bore Polishing

One of the popular development trends in diesel engine piston assembly is higher reliability and life of components. These can be ensured by actual engine testing and comparing the appearance of piston assembly. However, testing multiple iterations involves significant cost and development which can be avoided by using software for piston-assembly performance parameters simulation. This paper contains a detailed study conducted using commercially available piston secondary dynamics simulation software and actual testing on a 4-cylinder diesel engine. In this study, the effect of piston profile and clearance on piston secondary dynamics parameters and piston-liner appearance are studied. In this study, three piston skirt profiles are designed by varying piston axial profile (barrel shape), radial profile (oval shape), and nominal clearances. The simulation results are studied in which piston profile 2 has shown minimum piston tilting, radial displacement, radial velocity, tilting velocity, radial acceleration, tilting acceleration, pressure, and force at TS and ATS. Testing and component merit rating for liner bores and piston skirts were also conducted in which piston profile 2 has shown significantly less liner bore polishing. A good correlation was observed between piston secondary motion parameters obtained from simulation and piston and liner bore observations after testing.