Session: 33-02 Experiments of particle deposition in engine components

Paper Number: 128396

128396 - Temperature Dependence of Aerated Turbine Lubricating Oil Degradation From a Lab-Scale Test Rig 

The higher turbine operating temperatures that result from efficiency improvements and advanced engine materials, coupled with the extension of the periods between engine maintenance, result in the thermal degradation of the lubricants in the system. Several issues arise from oil degradation. First, exposure to overly high temperatures may result in the eventual formation of solid, coke deposits that attach to the high temperature surfaces. Second, in certain oils, much faster breakdown reactions can occur that lead to the precipitation of lubricant components that still move about the system. Third, exposure to oxygen, even at moderate temperatures, gradually deteriorates the oils, changing their properties and eventually leading to sludge and varnish formation. Coke deposits, precipitates, sludge, and varnish may cause various operational issues such as reduced cooling effects and plugged oil lines and filters and are difficult and costly to remove from the system. Despite oil degradation and deposits being an issue for decades now, only a few studies can be found in the literature in which the degradation mechanisms and the factors that affect them under turbine operating conditions are systematically studied. This study explores the effect of surface temperature, oil composition and exposure to oxygen on the breakdown at elevated temperatures via the three mechanisms described above. New tests were conducted using an experimental apparatus in which the flowing oil is exposed to a heated surface, thermally degrades or oxidizes, and consequently forms deposits that either attach to the high-temperature surface or are collected for later study. The data presented were obtained using multiple, off-the-shelf turbine oils. The study of their induction time (time required for deposits to form and accumulate) as a function of surface temperature allows a comparison of their thermal stabilities, for the extrapolation of the temperature dependence to lower temperature ranges, and for insight on the effect of oxygen on deposit formation. This work will expand on previous studies that have examined the effect that surface temperature alone has on coke formation by exploring other methods of lubricant failure and the effect of oxygen on their stability.

Presenting Author: Raquel Juarez Texas A&M University

Presenting Author Biography: Raquel Juarez is currently a Ph.D. candidate in the J. Mike Walker ’66 Department of Mechanical Engineering at Texas A&M University. She joined Dr. Eric L. Petersen’s combustion research group at the Texas A&M Turbomachinery Laboratory in 2019 where she has worked on studying the oxidation and thermal degradation of lubricants at high temperatures.

Authors:

Raquel Juarez Texas A&M University
Barry Creighton Texas A&M University
Eric L. Petersen Texas A&M University