Abstract
For different operating conditions of an internal combustion engine, the piston–ring–liner compartment represents one of the largest sources of friction and power losses. The aim of this article is to evaluate the effect of the compression ring profile on the main tribological performance of the lubricant in a four-stroke diesel engine. A one-dimensional analysis was developed for the hydrodynamic lubrication between the compression piston ring and the cylinder wall. A numerical method was applied to analyze the influence of different ring geometrical designs during the working cycle on oil film thickness, frictional force, and power losses. Our predicted results were validated with the Takiguchi data of a previous study, and they have shown a good agreement. The results in the current analysis demonstrated that the ring geometry profile, the engine speed, and load have a remarkable effect on oil film thickness, friction force, and friction power losses between the top ring and cylinder liner. Therefore, it would help in reducing friction as well as making a contribution to the improvement of engine performance such as torque, efficiency, and fuel consumption.
Highlights
The optimization of the piston rings as important components of combustion engines can contribute to the engine friction reduction since about 20%–40% of the friction losses of the engine are due to the piston ring assembly
Piston ring lift is due to piston acceleration, which is the derivative of the piston speed equation (Figure 6)
The theoretical results obtained with the numerical model developed to prove that the engine speed, load, (a) and profile of the compression rings have an important effect on the tribological behavior of the system piston ring–cylinder liner
Summary
The optimization of the piston rings as important components of combustion engines can contribute to the engine friction reduction since about 20%–40% of the friction losses of the engine are due to the piston ring assembly. The main functions of the piston rings are the sealing between the combustion chamber and the engine crankcase, the support for the heat transfer from the piston to the cylinder wall, and the control of the engine oil consumption. Radakovic and Khonsari[1] presented the governing equations and the appropriate numerical solution method to treat thermohydrodynamic problems implying thin-film flows in the presence of transversal compression and shear thinning. They analyzed thermal and shear effects of oil film on ring performance.
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