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

The laser-induced fluorescence technique is based on the excitation of molecules of a fluorescent material by a light source. The main advantage of this technique is that it has the potential to quantify the lubricant film thickness throughout the cycle. Similar to all the other optical techniques, it has this major advantage compared to the electrical techniques where the oil film can be measured only under the piston rings. In this work, experimental data from a simulating single-ring test rig are presented and further parametric analysis is given regarding cavitation in lubricants that was, at first, in the case of the single-ring test rig, evident in laser-induced fluorescence measurements. Different lubricants are used for the laser-induced fluorescence experiments and the different laser-induced fluorescence signals are analysed and interpreted compared to their physical and chemical properties and, furthermore, with the aid of imaging through a glass liner, a clearer picture is given regarding the cavitation shapes together with the respective laser-induced fluorescence measurements and cavitation initiation.