The impact of the piston bearing surface stepped profile microgeometry on friction losses in the supercharged combustion engine
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Publication date: 2016-05-01
Combustion Engines 2016,165(2), 54–59
The currently designed engines are usually supercharged and are characterized by high values of the boost pressure. As a result high values of maximum combustion pressure are obtained. This in turn leads to the occurrence of high mechanical loads and thermal stresses on elements of the crank mechanism. The piston is the most mechanically and thermally loaded engine component. Geometry of the gap between piston bearing surface and cylinder liner significantly affects the total friction losses of the internal combustion engine. On the basis of previous research it appears that friction losses depend more on the area of the piston bearing surface which is covered with the oil film than on the thickness of the oil layer separating collaborating parts. Properly designed barrel shape of the piston bearing surface is a way to reduce the oil film cover area. Another shape which could lead to reduce the oil film cover area is the stepped profile. The stepped profile, contrary to the barrel shape, can be obtained by covering the cylindrical or tapered piston bearing surface with a thin layer of graphite. In this paper the results of simulation for the stepped piston bearing surface are presented.