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

Abstract

Operational, efficiency, safety, and economic issues may arise from the formation and accumulation of sludge, varnish, and coke deposits that result from the degradation of engine lubricants through oxidation or thermal breakdown processes. Having a good understanding of the limits of lubricant performance may be useful in determining the best way to protect the engines. To this end, experiments were conducted using Mobil DTE 732, a turbine lubricant, that is aerated using a coarse gas dispersion tube. The oil then flows through a heated test section with a known axial temperature distribution. The inlet and outlet bulk oil temperature measurements are collected and used to determine the amount of time required for deposit formation and buildup. The induction times were determined for various surface temperatures, up to 236 °C. It was found that increased temperatures shortened induction times, and exposure to oxygen increased the rate at which deposits accumulate, but the nature of the deposits, soft and easily removed, was different from those formed during higher-temperature experiments completed in an inert environment in previous studies. Oil samples collected during the test were analyzed with Fourier transform infrared (FTIR) spectroscopy, with no significant changes detected.