The assumption of axisymmetry, employed by most of studies on piston ring lubrication, probably gives a too idealistic model for the real situation. A theoretical model for a nonaxisymmetrical analysis of piston ring lubrication has been established in the present study. When a piston ring with an arbitrary free shape is fitted into the cylinder bore, the determination of ring deflection and contact load has been modeled mathematically as a Linear Complementary Problem (LCP). By combining LCP solution with lubrication analysis, the film thickness and contact load distribution over the circumference are obtained, leading to a more realistic simulation for piston ring lubrication. The friction force between piston ring and cylinder bore is predicted by the mixed lubrication model including the effects of surface roughness and asperity contact. The static distortion of cylinder bore, gas pressure variation, and lubricant starvation are also considered in the simulation. Results show that the contact pattern and film thickness between piston ring and cylinder bore are not exactly axisymmetrical. The main reason for the nonuniform contact is the asymmetry of ring elasticity, the static distortion and dynamic load created by the secondary movement of piston skirt.

This paper presents a mathematical model for piston skirts in mixed lubrication. It takes into account the effects of surface waviness, roughness, piston skirt surface profile, bulk elastic deformation and thermal distortion of both piston skirts and cylinder bore on piston motion, lubrication and friction. The corresponding computer program developed can be used to calculate the entire piston trajectory and the hydrodynamic and contact friction forces as functions of crack angle under engine running conditions. This paper is the first part of a series of two papers. It gives basic information and some preliminary results. The second part will include the major results and discussions, focused on the influences of elastic and thermal deformations.

This paper presents a mathematical model for piston skirts in mixed lubrication. It takes into account the effects of surface waviness, roughness, piston skirt surface profile, bulk elastic deformation and thermal distortion of both piston skirts and cylinder bore on piston motion, lubrication and friction. The corresponding computer program developed can be used to calculate the entire piston trajectory and the hydrodynamic and contact friction forces as functions of crank angle under engine running conditions. Complete distributions of the oil film thickness and elastic deformation as well as the hydrodynamic and contact pressures can also be given at any crank angle if needed. This paper is the second part of a series of two papers. The first part (Basic Modeling), presented earlier by Zhu et al. (1991), gave the basic formulation and some preliminary results without bulk deformation considerations. In the present part, the three-dimensional finite element method is used to calculate so-called influence coefficient matrices. These matrices are repeatedly used to compute bulk elastic deformations of piston skirts. Results for 12 different cases are presented, and discussions are given focusing on the influences of elastic and thermal deformations on piston motion, lubrication and friction. An attempt to compare the calculated friction with experimental data is made, and agreement appears good for the two available cases. The computer program presented should be a useful tool for piston design and development.

A ruthenium complex bearing a new phosphine­(η2-silane) chelate ligand connected by a xanthene backbone, Ru­{κ4(Si,H,O,P)- t Bu2xantSiP­(H)}­(H)­Cl­(PPh3) (2), was synthesized by a ligand substitution reaction of Ru­(H)­Cl­(PPh3)3 with 2,7-di-tert-butyl-4-dimethylsilyl-5-diphenylphosphino-9,9-dimethylxanthene (1, t Bu2xantSiP­(H)). Dehydrogenation reaction of 2 with styrene, a hydrogen acceptor, gave a 16-electron phosphine­(silyl) complex Ru­{κ3(Si,O,P)- t Bu2xantSiP}­Cl­(PPh3) (3) together with ethylbenzene. Complex 2 was reproduced quantitatively by exposure of 3 to H2 (1 atm) at room temperature. Thus, hydrido­(η2-silane) complex 2 and silyl complex 3 are interconvertible through alkene hydrogenation (from 2 to 3) and dihydrogen addition to the Ru–Si bond (from 3 to 2) in which t Bu2xantSiP functions as a nonspectator ligand by reversibly releasing and accommodating a hydrogen atom. Complex 2 was also found to catalyze hydrogenation of alkenes via this interconversion.

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