Abstract
In the paper a comprehensive model of a piston ring pack motion on an oil film has been presented. The local thickness of the oil film can be compared to height of the combined surface roughness of a cylinder liner and piston rings. Equations describing the mixed lubrication problem based on the empirical mathematical model formulated in works of Patir, Cheng and Greenwood, Tripp have been combined and used in this paper. In addition a model of gas flow through the labyrinth seal of piston rings has been developed. The main parts of the model and software have been experimentally verified abroad by the author at the marine engine designing centre. For the selected two-stroke marine engine, the influence of the number of piston rings used and the type of the top ring lock (straight or overlapped) on blowby to piston underside and on friction losses of the piston-ring-cylinder (PRC) system have been investigated. The developed model and software can be useful for optimization of the PRC system design
Highlights
Piston rings are important part of internal combustion engines
The purpose of this paper is to present numerical calculations concerning an influence of the number of piston rings used and the type of the top ring lock on blowby to piston underside and on friction power losses of the PRC system
The experimental verification of the model of gas flow through the labyrinth seal of piston rings was carried out using measurements of unsteady gas pressure in the cylinder, between the piston rings and under piston performed by piezoelectric sensors mounted in the piston
Summary
A set of piston rings is used to form a dynamic gas seal between the piston and cylinder wall [5, 6, 13]. The sliding motion of the piston forms a thin oil film between the ring land and cylinder wall, which lubricates the sliding components [2, 4, 11]. The use of modern oil of low viscosity, working at a high temperature causes the existence of a very thin oil film thickness comparable to the value of the liner surface roughness. In such conditions, the possibility of direct contact between the ring and cylinder liner surface exists. The purpose of this paper is to present numerical calculations concerning an influence of the number of piston rings used and the type of the top ring lock (straight or overlapped) on blowby to piston underside and on friction power losses of the PRC system
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