Effect of Viscosity and Speed on Oil Cavitation Development in a Single Piston-Ring Lubricant Assembly

Abstract

A high-speed camera has been used to produce unique time-resolved images of high quality to describe the dynamics of the lubricant flow and cavitation characteristics in a sliding optical liner over a fixed single piston-ring lubricant assembly for three lubricants with different viscosities to establish their impact on cavitation formation and development. The images were obtained at two cranking speeds (or liner sliding velocity) of 300 rpm (0–0.36 m/s) and 600 rpm (0–0.72 m/s), at a lubricant temperature of 70 °C and a supply lubricant rate of 0.05 L/min. A special MATLAB programme has been developed to analyse the cavitation characteristics quantitatively. The dynamic process of cavities initiation was demonstrated by time-resolved images from fern cavity formation to fissure cavities and then their development to the sheet and strings cavities at a liner sliding velocity of around 0.17 m/s. The results for both up- and down-stroke motions showed that the cavities reach their fully developed state downstream of the contact point when the liner velocity reaches its highest velocity and that they start to collapse around TDC and BDC when the liner comes to rest. Within the measured range, viscosity had a great influence on length of cavities so that a decrease in viscosity (from Lubricant A to C) caused a reduction in length of cavities of up to 35% for Lubricant C. On the other hand, an increase in speed, from 300 rpm to 600 rpm, have increased the number of string cavities and also increased the length of cavities due to thicker oil film thickness with the higher speed. Overall, the agreement between the processed data by MATLAB and visualisation measurements were good, but further thresholds refinement is required to improve the accuracy.

Piston ring performance II: measurement of cavitation shapes in different operating conditions and their link to lubricant properties

“…As a final conclusion, and in combination with previous findings in Nouri et al (2019), the results showed that viscosity plays a major role in the breakup process of the cavities so that lubricants with higher viscosity resist more cavity disintegration. Composition of lubricants will also play a major role in cavities formation, development and collapse and also related information on lubricants' properties, with the major one being their surface tension, which plays a major role in cavities' breakup.…”

“…As a final conclusion, and in combination with previous findings in Nouri et al. (2019), the results showed that viscosity plays a major role in the breakup process of the cavities so that lubricants with higher viscosity resist more cavity disintegration.…”

“…The dynamic process of cavities initiation was demonstrated by time-resolved images from fern cavity formation to fissure cavities and then their development to the sheet and strings cavities at a liner sliding velocity of around 0.17 m/s. When speed increases from 300 to 600 rpm, the number of string cavities have increased as well as the length of cavities due to thicker oil film that is accompanied with the higher speed (Nouri et al. , 2019).…”

Water-Based Lubricants: Development, Properties, and Performances

“…Viscosity is a measurable physical property that can translate information about the liquid's hydration, solvation, the shape of the infused particles, and the forces acting between the particles [64]. It can also be defined as the internal resistance that a fluid has to flow.…”

Cavitation between cylinder-liner and piston-ring in a new designed optical IC engine

“…Extensive reviews of all previous works in piston-ring lubricant assembly have been given by Vasilakos, 4 Ostovar, 12 Dhunput, 13 who also used different techniques like high-speed visualisation, LIF, capacitance and pressure transducers to visualise the oil film flow and cavitation formation, to measure the oil film thickness, the friction and the pressure distribution within the contact point between the rings and the liner. The recent experimental work 14 used the high-speed visualisation and a specially written MATLAB programme to quantify the effect of speed and lubricant viscosity on cavitation development. They showed fully the dynamic process of cavities development by time-resolved images from fern cavity formation to fissure cavities and then their development to the sheet and strings cavities at finally their collapse.…”