| A large percentage of the frictional losses in internal combustion engines have been attributed to the piston-assembly. The current study focuses on examining the piston secondary motions and the relationships with which they interact with the lubricating oil film. Both tilting and lateral motions of the piston were accounted for in this work. The instantaneous position and orientation of the piston inside the cylinder have been determined herein by using a detailed model of the piston-assembly/connecting-rod/crankshaft mechanism. The formulation takes into consideration the torsional vibration and the out-of-plane transverse deformation of the crankshaft. Moreover, it accounts for the out-of-plane transverse deformation of the connecting-rod. The crank-slider mechanism model was developed herein to have a variable structure. The rationale is to allow the degrees of freedom of the system to vary based on the nature of contact between the piston-assembly and the cylinder liner. Single-point, double-point and line-contact between the piston and the liner were considered in this study. The current formulation uses the instantaneous piston position and orientation to determine the oil film thickness. Furthermore, the 3-D Reynolds' equation is solved by the finite difference method to yield the oil film pressure distribution over the piston surface.;The effect of the oil film on the piston motion is reflected in the derivation by the hydrodynamic friction force as well as by the normal force induced by the oil pressure. The proposed dynamic model has been used herein as a test bed to yield the instantaneous oil film thickness, the hydrodynamic friction force and the piston secondary motions. Furthermore, the digital simulations results serve to assess the effects of structural deformations of the crank-slider mechanism, the oil viscosity along with the motoring and firing engine operating conditions on the oil film and the piston secondary motions. |
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