On the Transient Three-Dimensional Tribodynamics of Internal Combustion Engine Top Compression Ring

Abstract

There are increasing pressures upon the automotive industry to reduce harmful emissions as well as meeting the key objective of enhanced fuel efficiency, while improving or retaining the engine output power. The losses in an internal combustion (IC) engine can be divided into thermal and parasitic as well as due to gas leakage because of untoward compression ring motions. Frictional losses are particularly of concern at low engine speeds, assuming a greater share of the overall losses. Piston–cylinder system accounts for nearly half of all the frictional losses. Loss of sealing functionality of the ring pack can also contribute significantly to power losses as well as exacerbating harmful emissions. The dynamics of compression ring is inexorably linked to its tribological performance, a link which has not been made in many reported analyses. A fundamental understanding of the interplay between the top compression ring three-dimensional elastodynamic behavior, its sealing function and contribution to the overall frictional losses is long overdue. This paper provides a comprehensive integrated transient elastotribodynamic analysis of the compression ring to cylinder liner and its retaining piston groove lands' conjunctions, an approach not hitherto reported in the literature. The methodology presented aims to aid the piston ring design evaluation processes. Realistic engine running conditions are used which constitute international drive cycle testing conditions.

Numerical analysis of the effects of compression ring wear and cylinder liner deformation on the thermal mixed lubrication performance of ring-liner system

“…In this study, the hydrodynamic pressure of oil film in CRCL considering the variable density and viscosity in the x, y, and z directions can be described by the generalized Reynolds equation. Moreover, the surface roughness affects greatly the lubrication performance of CRCL, especially under the mixed/boundary lubrication regime [9]. In order to simulate the effects of surface roughness on the lubrication performance, two different methods (i.e., the direct/deterministic method and the indirect/stochastic method) are usually adopted [32,33].…”

“…For PRCL in working conditions, various regimes of lubrication (hydrodynamic, mixed, and boundary) will be encountered in an engine cycle because of the rapidly changing velocity, highly fluctuating thermal and structural loads [8]. Generally, the PRCL is under hydrodynamic regime in the majority of the engine cycle, and under mixed or boundary regimes at piston dead centers [9]. In consideration of the dominant lubrication regime of hydrodynamic in the engine cycle of PRCL, Jeng et al [10] conducted a one-dimensional lubrication analysis for PRCL by solving Reynolds equation.…”

Lubrication Performance of Engine Commercial Oils with Different Performance Levels: The Effect of Engine Synthetic Oil Aging on Piston Ring Tribology under Real Engine Conditions

“…With regard to the thin nature of the piston ring, analytical and experimental reports were also presented on ring tribology for different engine conditions. Numerical predictions and experimental measurements of the piston ring-liner mechanism were presented by Rahmani et al [17], Baker et al [18], and Zavos et al [19]. It was found that the elastodynamics thin ring performance showed thinner lubricant films and higher friction values when hot engine conditions were expected.…”

In-Plane and Out-of-Plane Elastodynamics of Thin Rings and Seals

“…A disproportionate 5% of the total engine losses can be attributed to the piston compression ring [1], especially when considering its small size. The thinness of the ring constitutes high modal density, exciting a plethora of responses during the engine cycle, resulting in a number of undesired phenomena such as ring flutter, ring jump, twist, and rotation [2][3][4][5][6][7][8][9], as well as promoting blow-by [10].…”

“…In turn, a tribological study of the conjunction provides important input for a ring dynamic analysis [4][5][6]16] such as the generated contact pressures, load carrying capacity, and friction. Furthermore, the ring's dynamic behavior determines important parameters within a gas flow analysis through the ring pack in an IC engine [2,3,7,8]. This is utilized for the prediction of the phenomena underlying gas blow-by, loss of sealing and power loss, as well as lubricant degradation.…”