Crankshaft misalignment effect on bearing tribo-dynamics under multi-clearance lubrication

Existing dynamic models of the crank-connecting rod mechanism (CRM) primarily focus on single clearance lubrication in piston engines, making it difficult to analyze the coupled effects of crankshaft misalignment and mixed lubrication of bearings under multi-clearance collaboration. This study proposes a novel dynamic model that integrates multi-clearance lubrication. Based on the generalized coordinates of the crank and connecting rod, including misalignment angles in two directions, the dynamic boundary conditions of the three-dimensional lubrication fields of the big-end and main bearings are calculated synchronously, and incorporated into a mixed elasto-hydrodynamic lubrication (MEHD) model to evaluate the friction performance. The motion equations are derived using the Lagrange method with a variable-step fourth-order Runge-Kutta (VRK4) method to address numerical instability under multi-clearance misalignment. Furthermore, the coupled effects of operating parameters and misalignment on the friction and wear characteristics of the bearings are examined. The results show that crankshaft misalignment significantly increases the volumetric wear rate and friction power loss, with more pronounced effects under low-speed, high-load conditions. Appropriate bearing clearance and lubrication viscosity can help mitigate the adverse effects of misalignment. This study provides a high-precision simulation framework for analyzing and designing piston engine bearings and elucidates the misalignment fault mechanisms.