Session: 36-04 Water, Icing, and Lubricant Deposition

Paper Number: 81178

81178 - Characterization of an Apparatus to Study Solid Deposit Formation in Lubricating Oils at High Temperatures 

Improvements in gas turbine efficiencies have caused higher operating temperatures throughout the entire system. When exposed to excessively high temperatures, the lubricating oils in the turbines undergo extreme oxidation and thermal degradation processes that eventually result in the formation of solid deposits within the oil. These deposits cause operational problems like reduced cooling effects, decreased oil flow rates, and plugged orifices, among others. This paper describes the testing and characterization process of a newly constructed test rig that studies the propensity of lubricants to form solid deposits when exposed to high temperatures. In the test rig, the lubricant flows through a heated tube, thermally degrades or oxidizes, and forms solid deposits that adhere to the heated surface. The test rig can be pressurized to better simulate oil conditions in a turbine. It also allows for the control of the surface temperatures to which the oil is exposed and of the oil flow rate which is related to its residence time. The induction time is determined from bulk oil temperature measurements. The pressure rating of the assembly was confirmed through pneumatic tests. In addition, because the oil flow rate and the heated surface temperature have important effects on the solid-deposit-formation process, accurately knowing their values is a critical aspect of a well-controlled experiment. Hence, the ability to precisely control the oil’s flow rate through the system was verified, and the steady-state temperature distribution within the heated test section was experimentally measured and analytically modeled. The model predicts the oil temperature at a given radial and axial position by modeling the heat transfer in the entrance region of a pipe with uniform wall heat flux and laminar flow. It reveals the thermal conditions in the heated test section without the need of extensive measurements in every test. Future work involves the testing of a wide range of turbine lubricants with different compositions under carefully controlled, high-temperature conditions. This testing will allow for more-educated decisions to be made in the field regarding lubrication practices at the edges of the temperature envelope.

Presenting Author: Raquel Juarez Texas A&M University

Presenting Author Biography: Raquel Juarez graduated in May of 2017, summa cum laude, from Minnesota State University, Mankato with a Bachelor of Science in Mechanical Engineering. Her interest in further education and research was sparked while she worked as an undergraduate research assistant in a project involving vertical axis wind turbine performance. She then attended graduate school and joined Dr. Eric L. Petersen’s combustion research group at the Turbomachinery Laboratory at Texas A&M University where she received a master’s in mechanical engineering in May of 2021 and is now working towards a Ph.D. Her current work involves studying the oxidation and thermal degradation of lubricants at high temperatures.

Authors:

Raquel Juarez Texas A&M University
Noble Gutierrez Texas A&M University
Eric L. Petersen Texas A&M University