Abstract

When exposed to excessively high temperatures, the lubricating oils in turbines undergo extreme oxidation and thermal degradation processes that eventually result in the formation of solid deposits that can, in turn, cause operational problems. This work describes the testing and characterization process of a newly constructed test rig that studies the propensity of lubricants to form such deposits. 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. An oil flow rate calibration curve as a function of pump speed was developed using two oils, Castrol GTX 20W-50 and Mobil DTE 732. The steady-state axial temperature distribution along the heated tube was measured for temperature settings of up to 475 °C and flow rates of 10.4, 12.2, and 13.9 mL/min using Mobil DTE 732. The results showed that the surface temperature is not uniform, but that it varies axially as is expected from the heat transfer in the thermal entrance region of a pipe with laminar flow. Examples of the results of tests performed with the apparatus using Mobil DTE 732 and Castrol GTX 20W-50 flowing at 10.4 mL/min with surface temperatures between 328 and 489 °C are presented. Based on these tests, it is clear that the induction time for solid-deposit formation can be unambiguously determined using the experimental apparatus. The induction times of the sample tests described were found to be 638 ± 10 min and 86 ± 10 min for Mobil DTE 732 and Castrol GTX 20W-50, respectively.

References

1.
Rowland
,
R. G.
,
Dong
,
J.
, and
Migdal
,
C. A.
,
2009
, “Antioxidants,”
Lubricant Additives Chemistry and Applications
,
L. R.
Rudnick
, ed.,
CRC Press
,
Boca Raton, FL
, pp.
3
50
.
2.
Kauffman
,
R. E.
,
Feng
,
A.
, and
Karasek
,
K. R.
,
2000
, “
Coke Formation From Aircraft Turbine Engine Oils: Part I—Deposit Analysis and Development of Laboratory Oil Coking Test
,”
Tribol. Trans.
,
43
(
4
), pp.
823
829
.
3.
Novotny-Farkas
,
F.
,
Baumann
,
K.
, and
Leimeter
,
T.
,
2008
, “
Optimizing the Thermo-Oxidation Stability of Gas Turbine Oils
,”
Goriva I Maziva
,
47
(
3
), pp.
209
231
.
4.
Bardasz
,
E. A.
, and
Lamb
,
G. D.
,
2009
, “Additives for Crankcase Lubricant Applications,”
Lubricant Additives Chemistry and Applications
,
L. R.
Rudnick
, ed.,
CRC Press
,
Boca Raton, FL
, pp.
457
492
.
5.
Snyder
,
C. E.
,
Gschwender
,
L. J.
, and
Sharms
,
S. K.
,
2009
, “Long-Term Additive Trends in Aerospace Applications,”
Lubricant Additives Chemistry and Applications
,
L. R.
Rudnick
, ed.,
CRC Press
,
Boca Raton, FL
, pp.
637
645
.
6.
Gschwender
,
L. J.
,
Snyder
,
C. E.
,
Nelson
,
L.
,
Fultz
,
G. W.
, and
Saba
,
C. S.
,
2001
, “Advanced High-Temperature Air Force Turbine Engine Oil Program,”
Turbine Lubrication in the 21st Century
,
W. R.
Herguth
, and
T. M.
Warne
, eds.,
ASTM International
,
West Conshohocken, PA
, pp.
17
24
.
7.
“Tech Topic: Coking,” ExxonMobil Corporation, last modified November 15, 2016, https://www.exxonmobil.com/en/aviation/knowledge-library/resources/engine-oil-coking.
8.
Pawlak
,
Z.
,
2003
,
Tribochemistry of Lubricating Oils
,
Elsevier
,
Amsterdam
.
9.
Gatto
,
V. J.
,
Moehle
,
W. E.
,
Cobb
,
T. W.
, and
Schneller
,
E. R.
,
2006
, “
Oxidation Fundamentals and Its Application to Turbine Oil Testing
,”
J. ASTM Int.
,
3
(
4
), pp.
1
20
.
10.
Wiehe
,
I.
,
2008
,
Process Chemistry of Petroleum Macromolecules
,
CRC Press
,
Boca Raton, FL
.
11.
Kauffman
,
R. E.
,
Feng
,
A. S.
, and
Karasek
,
K. R.
,
2000
, “
Coke Formation From Aircraft Engine Oils: Part II—Effects of Oil Formulation and Surface Composition
,”
Tribol. Trans.
,
43
(
4
), pp.
677
680
.
12.
Juarez
,
R.
,
Gutierrez
,
N.
, and
Petersen
,
E. L.
,
2021
, “
Pyrolysis of Motor Oil in Contact With High-Temperature Surfaces Leading to Solid Deposit Formation
,”
Proceedings of the 12th U. S. National Combustion Meeting
,
College Station, TX
,
May 24–26
.
13.
Juarez
,
R.
,
2021
, “
Development of a Test Rig to Study the Lubricating Oil Degradation and Solid Deposit Formation Process at High Temperatures
,”
M.S. thesis
,
Mechanical Engineering, Texas A&M University
,
College Station, TX
.
14.
Weigand
,
B.
,
Kanzamar
,
M.
, and
Beer
,
H.
,
2001
, “
The Extended Graetz Problem With Piecewise Constant Wall Heat Flux for Pipe and Channel Flows
,”
Int. J. Heat Mass Transfer
,
44
(
20
), pp.
3941
3952
.
You do not currently have access to this content.