Session: 03-04 Advancements in Turboprop and Turboshaft Engine Technologies

Paper Number: 152962

Report on Incidental Findings of Cyclic O-Ring Behavior During Fuel/Elastomer Compatibility Testing 

A recent investigation into elastomer O-ring compatibility with conventional and sustainable jet fuels has revealed a cyclic phenomenon of elastomer behavior that cannot be accounted for with normal swelling reactions to aromatic content percentage of the fuel. The investigation was conducted with a novel fuel/elastomer compatibility test rig designed to measure the changes of O-ring molecular stresses to physical, chemical, and/or thermal influence. Furthermore, the test rig seal assembly contains a gland where an installed O-ring can be compressed while also allowing fuel to wet the internal portion of the O-ring. The compression assembly includes four load cells independently measuring O-ring counterforces which are termed as swelling/shrinking behaviors. O-ring swell, fuel temperature, and ambient laboratory temperature data, including date/time stamps, were recorded at 1-second intervals continually for the duration of each test. Experiments were conducted with different types of O-rings exposed to fuels with varying amounts of aromatic species (0% - 25%) for periods up to 500 hours. These experiments were designed to study O-ring swelling as an expected result of O-rings wetted with fuels containing certain components such as aromatics and paraffins. The results of the O-ring behavior with these fuels aligned with other peer studies. Other trends not discussed in literature were found within the data that required a closer inspection. These trends were noticed to correspond with daily solar cycles. During hours of unobstructed daylight, O-rings exhibited increased swelling behavior while decreasing after sunset. The swell forces began to increase near sunrise and reached an apex when the amount of solar radiation was greatest. This cycle continued apart from days with cloud coverage with the rate of the daytime O-ring swell dissipating as the percentage of cloud coverage increased. A thorough literature review was conducted to identify the 24-cycle. The review revealed that these 24-cycles were embedded in the graphs of other published studies with no discussion of the cycle beyond a mere mention and an assumption that laboratory temperature fluctuations might be the cause of the swell. This paper provides an in-depth discussion of the potential mechanisms that could explain these 24-hour cycles. A path to detecting causation is identification of the correlations and then testing each individually.

Presenting Author: Bhupendra Khandelwal University of Alabama

Presenting Author Biography: Dr. Bhupendra Khandelwal joined The University of Alabama as an associate professor for fuels and
combustion. He is working on combustion, emissions and performance of alternative fuel to be used in
gas turbine engines and other combustion sources. Prior to this position, Khandelwal held a position of
assistant professor and lecturer at the University of Sheffield in the Low Carbon Combustion Centre. He
was leading combustion and emissions research areas at LCCC. Khandelwal is working closely with a
large range of industries, government organizations and universities, including U.S. DOE, FAA, Siemens,
Rolls-Royce, UK MOD and Dstl. He is an American Institute of Aeronautics and Astronautics Associate
Fellow; Royal Aeronautical Society Member; American Society of Mechanical Engineers Combustion,
Fuels and Emissions committee member; and AIAA Terrestrial Energy Systems Technical Committee
Member. He is also recipient of a Royal Aeronautical Society Centennial Scholar, ASME IGTI Student
Scholar for two consecutive years in 2011 and 2012, and the IMechE Grant. Khandelwal serves as the
technical area organizer for AIAA conferences and as a reviewer for different scientific journals and U.S.
DOE/European Commission for alternative fuels related projects. He was point of contact for ASME
Turbo Expo 2020 on behalf of the alternative fuels technical committee. His research on fuels, emissions,
combustion and combustors is widely published in journals and conferences, with a total of close to 100
publications. He has delivered several invited talks at prestigious conferences and meetings including UK
fuels standards committee, Aviation Fuels Committee 2018, Aero India, and Coordinating Research
Council. He has also delivered tutorials at international conferences.

Authors:

Jerry Hamilton The University of Alabama
Bhupendra Khandelwal University of Alabama