Parametric Analysis of Piston Assembly Focusing on Friction Losses Reduction and Fuel Consumption

This paper presents a parametric analysis of the piston assembly of an Otto cycle engine, focusing on mechanical efficiency and fuel consumption through the implementation of a numerical model of the piston secondary motion. This model considers a mixed lubrication between the cylinder liner and the piston skirt as well as the piston skirt profile and surface waviness, being able to calculate the hydrodynamic and contact friction forces and the entire piston trajectory through the course of the cylinder. The studied parameters include the connecting rod length, the piston skirt waviness and the piston off-set. A comparative analysis is finally made using the results piston secondary motion inside the cylinder bore, the hydrodynamics and contact forces as well as the friction force between the piston skirt and the cylinder liner as a function of the crankshaft angle.