Abstract
The article describes the results of simulations of the approved variations of sliding surfaces of ring seals in relation to a reference symmetrical barrel profile which is most often used in piston internal combustion engines. In particular the paper discusses the impact of the five assumed variants of sliding profiles of ring seals onto the thickness of oil film left on the cylinder face by a bottom and upper ring seal, the distribution of internal friction force in oil film between the ring seal set and the cylinder face, finally the oil film cover on a sliding surface of the upper ring seal. The results presented in the article show a close relationship between the sliding surface profile of ring seals and a unit oil consumption. A relationship between these parameters for the elements lying in the movement plane of a wrist pin axis was proven, as well as for the one lying in the plane perpendicular to it. Exemplary parameters of oil film and friction losses were presented while assuming a constant total axial values of the height and depth of circumferential grooves. The shapes of these grooves on the sliding surface of the ring seals in free state can be made with electroerosion microprocessing or ablative laser microprocessing.
Highlights
Determining the share of friction losses in overall mechanical losses has been the subject of many theoretical and experimental papers [1, 2, 7, 8, 9, 11,12,13,14,15]
The friction resistance of ring seals depend among others on: – the height and shape of the profile of ring sliding surface, – the characteristics of materials applied, – the distribution of piston compression ring pressure against the cylinder face, which are determined by ring elasticity and the operation of external forces, – limiting errors of macroshapes of cylinder aperture, – profiles of piston grooves, – thermal strain of the piston and cylinder, – oil dynamic viscosity – the temperature of the components of the piston-cylinder set
Meeting the conditions which favour fluid friction in all the range of crankshaft rotation angle, regardless of engine load and its operation conditions is the main condition to justify the method of shaping the geometry of a profile of a sliding surface of the lower and upper ring seal while limiting friction losses in the piston-cylinder assembly
Summary
Determining the share of friction losses in overall mechanical losses has been the subject of many theoretical and experimental papers [1, 2, 7, 8, 9, 11,12,13,14,15]. The friction resistance of ring seals depend among others on: – the height and shape of the profile of ring sliding surface, – the characteristics of materials applied, – the distribution of piston compression ring pressure against the cylinder face, which are determined by ring elasticity and the operation of external forces, – limiting errors of macroshapes of cylinder aperture (its roundness, straightness or concentricity), – profiles of piston grooves, – thermal strain of the piston and cylinder, – oil dynamic viscosity – the temperature of the components of the piston-cylinder set. The technologies of precise processing of various materials used to produce piston rings and the opportunities to shape the profiles of sliding surfaces very accurately require more detailed simulation studies, as well as experimental studies of possibilities to reduce friction losses of ring seals
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