Enhancing the Durability of Connecting Rod of a Heavy-Duty Diesel Engine

Abstract

This paper investigates the mechanical loads resulting from the combustion pressure and dynamic inertia and their effects on the connecting rod of a direct injection turbocharged diesel engine. The main purpose is to enhance the durability of the connecting rod in order to withstand more engine power increase. The distribution of the axial (compressive/tensile) stress, deformation, and safety factors are calculated in order to predict any possible mechanical failure. The finite element routine is used by ANSYS Workbench to analyse the loading on the connecting rod model. The current study is applied to the connecting rod of a 300 hp diesel engine in order to increase the engine power by 17%. The connecting rod operates safely and withstands the applied loads until the power increase reaches 72%. The most stressed points are at the connecting rod shank, while less stressed are experienced at the big end. Calculations show that introducing some changes to the connecting rod geometry may result in decreasing the excessive stresses. These changes include increasing the thickness of the shank cross-section, increasing the fillets radii and slightly reducing the dimensions of the big end in order to maintain the same mass. The new geometry could significantly reduce the maximum stress by 25.5% with an insignificant reduction in the total mass of the connecting rod.