Piston Ring Lubrication and Cylinder Bore Wear Analysis, Part I—Theory

Abstract

An analytical method developed for determining the bore wear pattern for a reciprocating piston engine over a complete running cycle is presented. The method includes the considerations of the hydrodynamic lubrication theory between the ring and the cylinder bore wall, piston ring geometric and elastic characteristics, blowby through the piston ring pack, minimum film thickness permitting film lubrication, piston side thrust load and Archard’s wear relation. Since the method is general, it also can be applied to other reciprocating piston devices, such as gas compressor, Rankine cycle engine or Stirling engine. Wear factor data, however, must be available in order to make quantitative predictions of wear. The verification of the present theory is given in a subsequent paper (Part II) which shows good agreement between the predicted bore wear curves and measured ones for actual engines.

Analysis of ring pack lubrication

“…Exhaust gas pressure distribution in the ring pack is obtained by a simplified method which takes into consideration the gas flow as the flow of an ideal gas, which has a constant discharge coefficient through the square edge orifices (Ting and Mayer, 1973). However, the way to determine the hydrodynamic pressure profile at the interface and an effective width has not been fully verified.…”

“…The gas flow through the ring gap is assumed to be of an ideal gas with a constant discharge coefficient in one-dimensional flow passing through the square edge orifices (Ting and Mayer, 1973). The resultant pressure distribution in the ring pack and inertia of the ring are considered to determine ring position.…”

Effect of Compression Ring Elastodynamics Behaviour upon Blowby and Power Loss

“…Regarding blowby, Ting and Mayer [26] considered labyrinth passages made by piston rings for the flow of gas from combustion chamber to the crank case. They assumed the ring end gaps are the only openings for the flow of gas.…”

Wear Analysis of Top Piston Ring to Reduce Top Ring Reversal Bore Wear

“…(3) according to the explicit Euler integration scheme [25]. The wear depth at node number i after the j th simulation step is then: (4) where hi,j−1 is the wear depth after the (j−1) th step, Δhi,j is the incremental nodal wear depth during the j th step, computed based on the nodal pressure pi,j and the incremental nodal sliding distance Δsi,j according to: (5) Due to large pressures at TDC, higher temperature exposed over the rings, change in viscosity with respect to temperature and boundary lubrication causes high wear rates between ring and liner. As shown in Fig.…”

“…Another important study on lubricant film thickness was given by Elion and Saunders [3]. Ting and Mayer [4,5] developed an analytical model for determining the ring-bore wear mechanism for a reciprocating piston engine over a complete running cycle. The model used RESEARCH hydrodynamic lubrication theory to analyze the flow between ring and cylinder bore.…”