Piston ring lubrication in some types of low-speed 2-stroke marine diesel engines is completely different from those in medium-or high-speed diesel engines since the inner surface of cylinder liners are textured with circular grooves in macro-scale and honing texture in micro-scale. In this paper, a numerical model has been developed to study the potential of use of cylinder bore surface texturing, in the form of circumferential oil grooves with different dimensions and densities, and their efficiency to improve the tribological properties of piston ring-cylinder liner tribo-system. The average Reynolds equation has been employed in the area of micro-scale texture and the effect of macro-scale grooves has been incorporated to improve the currently lubrication model. The results showed that the cylinder liner oil grooves can efficiently be used to maintain hydrodynamic effect. It is also shown that optimum surface texturing may substantially reduce the friction losses between piston ring and cylinder liner.

In this paper fully flooded and starved lubrication models considering surface roughness are developed for the piston ring and cylinder bore lubrication. The effect of oil available in the inlet region of a top ring is studied by comparing predicted oil film thickness, asperity contact friction and power loss under different oil supply conditions. The simulation results show that the proper oil supply is important in controlling the piston ring frictional power loss. The influences of lubricant viscosity and composite roughness on frictional power loss of piston ring are also discussed.

An efficient method utilizing the concept of inverse heat conduction is presented for the thermal analysis of pistons based on application to the piston head of a marine diesel engine. An inverse heat conduction problem is established in the form of an optimization problem. In the optimization problem, the convection heat transfer coefficient（HTC）on the top side of the piston is defined as the design variable, while the error between the measured and analysed temperatures is defined as objective function. For the optimization, an axi-symmetrical finite element conduction model is presented. The optimum distribution of the HTC at the top side of piston is successfully determined through a numerical implementation. The temperature obtained via an analysis using the optimum HTC is compared with the measured temperature, and reasonable agreement is obtained. The present method can be effectively utilized to analyze the temperature distribution of engine pistons.

The present work mainly focuses on study the piston ring lubrication parameters, and the influence of viscosity index improvers onthese parameters. Mathematical model has been developed using average Reynolds equation considering fully flooded inlet condition. The oil characteristics used in the modeling is enhanced by a series of polyacrylates viscosity index improvers, in order to indicate the effect of them on the oil film thickness, friction force, and hydrodynamic power losses. The simulation results help to explain the mechanism of action of viscosity index improvers in the oil during running conditions.