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A set of piston rings is used to form a dynamic gas seal between the piston and cylinder wall. Many physical phenomena are associated with the operation of the system piston-ring-cylinder (PRC), such as: inter-ring gas dynamics for the labyrinth seal, hydrodynamic lubrication and mixed friction in gaps between the rings and cylinder liner, oil flow and distribution of lubricant along the liner, twist motion of rings, liner temperature influence on the oil viscosity. The first part of the paper presents a comprehensive model of the PRC system developed by the author. Among own models it includes several models taken from literature, like: a model of viscous oil flow between rough gap surfaces formulated by Patir & Cheng and an elastic contact model of Greenwood & Tripp. The main parts of developed mathematical model and software have been experimentally verified during a research period of the author at the marine engine designing centre ”Wärtsilä” in Switzerland.

The temperature influences significantly the braking effectiveness. The paper describes consistency criterions of the brake thermal state in road braking conditions and on the roll-stand. As a result of the vehicle motion simulation, the time histories of the heat fluxes generated on the friction surface of the front and rear disc were determined. They were used as an input data for the model of the heat transfer process in disc brakes. The problem was solved by the use of the finite element method. Time histories of temperatures on the friction surfaces and in the material of the disc were calculated. As a preliminary consistency criterion of the brake thermal state in road and roll-stand braking conditions, a balance of the energy cumulated in the brake rotor was assumed. As the most reliable consistency criterion an equality of average temperatures of the friction surface was assumed.

This paper deals with the influence of a wall soot layer of varying thickness on the unsteady heat transfer between the fluid and the engine cylinder wall during a full cycle of a four-stroke Diesel engine operation. For that purpose a computational investigation has been carried out, using a one-dimensional model of a multi-layer solid wall for simulating the transient response within the confinement of the combustion chamber. The soot layer is thereby of varying thickness over time, depending on the relative rates of deposition and oxidation. Deposition is accounted for due to a thermophoretic mechanism, while oxidation is described by means of an Arrhenius type expression. Results of the computations obtained so far show that the substrate wall temperature has a significant effect on the soot layer dynamics and thus on the wall heat flux to the combustion chamber wall.