On the running-in behavior of rough surface of piston rings in mixed lubrication regime

Abstract

Purpose -The purpose of this paper is to study the real-time change of surface roughness at different small regions of piston rings during running-in process. Meanwhile, the effects of real-time change of the rough surface topography on the lubrication and friction of piston rings are investigated. Design/methodology/approach -An uneven wear model has been developed to research the running-in behavior at the different small regions of piston rings. The model is verified by comparing the simulation results with the experimental results on a reciprocating friction and wear test rig. Findings -This research shows that the wear process of piston ring surface is uneven during running-in. At most time of the operating cycle except the vicinity of top dead center and bottom dead center, the minimum oil film thickness ratio increases while the friction force and power loss decrease after the running-in period. Originality/value -Through this research, the running-in behavior of piston rings is investigated in detail. The interaction between the running-in and the lubrication and friction of piston rings is understood more deeply.

Numerical analysis of textured piston compression ring conjunction using two-dimensional-computational fluid dynamics and Reynolds methods

“…In this research, the oil temperature is assumed to be equivalent to the liner temperature at the same position, and the difference in the whole region is ignored. According to the temperature distribution along the liner, the oil temperature can be calculated by 36 T…”

“…On account of the hydrodynamic lubrication and asperity contact, the friction is generated between the conjunction surfaces, consisting of the hydrodynamic friction and asperity contact friction. These two friction forces can be obtained as follows 36,39…”

“…In this research, the oil temperature is assumed to be equivalent to the liner temperature at the same position, and the difference in the whole region is ignored. According to the temperature distribution along the liner, the oil temperature can be calculated by 36 where S is the stroke; s is the distance to the top dead center (TDC); and Ttdc, Tmid, and Tbdc are the temperature at TDC, the middle of stroke, and the bottom dead center (BDC), respectively. As shown in Table 1, the detailed values of the necessary parameters are given for the corresponding calculation.…”

“…On account of the hydrodynamic lubrication and asperity contact, the friction is generated between the conjunction surfaces, consisting of the hydrodynamic friction and asperity contact friction. These two friction forces can be obtained as follows 36,39 where Øf, Øfs are the shear flow factors, Vr is the variance ratio, τ0 is the shear stress constant, Ac is the cumulative area of asperity tips, and α1 is the boundary friction coefficient. Thus, the total friction force, total friction loss, and friction mean effective pressure (FMEP) can be calculated by 39 where Vd is the displaced volume of the cylinder and T1 is the period of one engine operating cycle.…”

An extended Elrod-Adams model to account for backpressure and blow-by inception

“…A particular characteristic of the PRL operating conditions is that gas leakage can take place through the gaps between piston and ring and/or between ring and liner. This undesirable effect is known as blow-by and is associated to power-loss and air pollution [26]. Performing two-dimensional simulations it is shown here that the extended model can be used to predict blow-by inception, which manifests itself as the development of channels of gas/vapor through the gap between the ring and the liner.…”