A New Cavitation Algorithm to Support the Interpretation of LIF Measurements of Piston Rings

Fabian H. Ruch, Georg Wachtmeister

Research output: Contribution to journalConference articlepeer-review

Abstract

Laser induced fluorescence (LIF) is used to investigate oil transport mechanisms under real engine conditions. The engine oil is mixed with a dye that can be induced by a laser. The emitted light intensity from the dye correlates with the residual oil at the sensor position and the resulting oil film thicknesses can be precisely determined for each crank angle. However, the general expectation is not always achieved, e.g. an exact representation of piston ring barrel shapes. In order to investigate the responsible lubrication effects of this behavior, a new cavitation algorithm for the Reynolds equation has been developed. The solution retains the mass conservation and does not use any switch function in its mathematical approach. In contrast to common approaches, no vapor-liquid ratio is used, but one or several bigger bubbles are approximated, as have been observed in other experiments already. As a result, not only the known boundary conditions for the Reynolds equation become unnecessary, but the solution also gives a clearer idea as to the shape of the cavitation bubble. The combination of simulated oil film thicknesses, the resulting cavitation bubbles and the fixed field of view from the LIF sensor allows a reproduction of the measurement signal. The comparison of measurement and simulation exhibits a high correlation, and thus enables a deeper knowledge and understanding of the real conditions inside a combustion engine. On the other hand, it can be seen that effects such as a decrease in the LIF signal in the cavitation area is much lower than would be expected according to the literature.

Original languageEnglish
JournalSAE Technical Papers
Volume2020-April
Issue numberApril
DOIs
StatePublished - 14 Apr 2020
EventSAE 2020 World Congress Experience, WCX 2020 - Detroit, United States
Duration: 21 Apr 202023 Apr 2020

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