Theoretical modelling of cavitation in piston ring lubrication

Abstract

Mathematical models of piston ring dynamics and lubrication are sensitive to the boundary conditions adopted to describe the cavitation occurring in the diverging outlet region of the lubricant film between the piston ring and cylinder wall. In this paper, such sensitivity is investigated by applying different models of gaseous cavitation, flow separation and fluid film reformation to the analysis of a single compression ring from a diesel engine. Significant differences are predicted in hydrodynamic pressure profiles, lubricant film boundaries, lubricant film thickness, oil flow and friction. Such indications of substantial differences in piston ring operating characteristics associated with the distinct cavitation boundary conditions considered highlights the need for further research in this field. However, the lack of detailed experimental data to validate the predictive models suggests that future progress must be based upon combined theoretical and experimental approaches to the problem. It is postulated that boundary conditions based upon Reynolds cavitation and fluid film reformation may be applicable at high loads, and fluid film separation of a form proposed by Coyne and Elrod at low loads.

Mathematical Model of Piston Ring Sealing in Combustion Engine

“…and, it was also assumed that pressure in the divergent part of the gap cannot drop below the saturation pressure: p oil ≥ p cavit (the so called Reynolds cavitation conditions [21]). …”

Cavitation Bubble Measurement in Tribological Contacts Using Digital Holographic Microscopy

“…It is noted that for the Elrod and Coyne model, a contact angle of p/2 is assumed and the ratio h=h 1 was calculated as a function of the capillary number N ¼ 3gU c 1=3 using curve fits produced by Priest et al [33] for the experimental work of Taylor [34].…”

Cavitation induced starvation for piston-ring/liner tribological conjunction

“…[2]. This condition is often encountered if the machine elements in relative motion are separated by a lubricating film [3] (e.g.…”

“…This leads to transition of fluid from liquid form to gas-liquid mixture [5]. Different aspects of the ring-liner cavity formation and the advantages of various predictive techniques are well explained by Priest et al [2]. Arcoumanis et al [6] and Dhunput et al [7] used an experimental test rig to investigate the transient behaviour of the cavitation streams as well as their development through the TDC position.…”