A parametric study on oil film pressure measurements in a single piston-ring configuration

Abstract

Oil film pressure, the driving force behind piston-ring lubrication phenomena, is measured in a single piston-ring simulating rig after the successful installation of a miniature pressure transducer. The partition of overall load-carrying capacity between direct surface interaction and hydrodynamic action is clearly of some significance if the characteristics of the piston seal are to be understood and predicted with any confidence. It is therefore important that the contribution of the fluid film lubrication to load support be adequately represented. This study presents an extensive load, speed, temperature and piston-ring curvature parametric study on how the measured pressure profile at mid-stroke is affected in terms of peak pressure, magnitude and shift in the trailing edge of the piston ring, taking into account cavitation appearance and lubricant viscosity variation.

Laser-induced fluorescence measurements in a single-ring test rig: Evidence of cavitation and the effect of different operating conditions and lubricants in cavitation patterns and initiation

“…It is already shown that a difference in the cavitation area can affect the load-carrying capacity of the piston ring. 33 Hence, lubricant formulation and chemistry can play an important role, as specific lubricants can be formed to perform in an optimized manner in terms of cavitation and load-carrying capacity of the piston ring. In addition, an uneven development of cavitation, such as in the case of changing between different cavitation patterns, results in an uneven distribution of the load, raising load sustainability issues.…”

“…The test rig structure introduces easy access to the ring–liner interface and thus provides a better understanding of the lubrication and the lubricant characteristics. Measurements of OFT in the test rig can be accomplished with both capacitance and LIF, whereas at the same time the installation of an ultra-miniature pressure transducer provides valuable oil film pressure data that, with the aid of a glass liner dedicated to imaging only, were able to complement on the cavitation imaging, 28,29,33,34 eliminating the many uncertainties that follow the engine experiments. In Figures 1 and 2, the photo and schematic of the simulation test rig are shown.…”

“…30 Calibrated weights could be hung from the end of the assembly to increase the cyclic load acting on the ring. 28,33,34…”

“…The 2-mm-diameter transducer is fitted in the moving liner specimen and the lubricant goes through a very thin slot of 0.1 mm total width to provide the pressure reading. 28,33…”

“…32 It is, therefore, important to consider different lubricants for engine lubrication subsystems with a subsystem dedicated to piston ring lubrication. Since the variation of the LIF cavitation pattern that appears under the piston ring for specific oil formulations is taken into account and load capacity of the piston ring is affected due to cavitation, 33,34 the lubricant behaviour at the interface between the piston ring and the liner should be optimized for addressing the cavitation issues without compromising the load capacity of the piston ring.…”