Characterization of compact gas turbine combustors for alternative fuel integration

Wood, Eric James

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https://hdl.handle.net/2142/121339 Copy

Description

Title

Characterization of compact gas turbine combustors for alternative fuel integration

Author(s)

Wood, Eric James

Issue Date

2023-07-06

Director of Research (if dissertation) or Advisor (if thesis)

Lee, Tonghun

Doctoral Committee Chair(s)

Lee, Tonghun

Committee Member(s)

• Chamorro, Leonardo
• Allen, Cody
• Temme, Jacob

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Gas turbine combustion
• Alternative fuels
• Sustainable Aviation Fuel
• Liquid fuel spray
• Liquid atomization
• X-ray diagnostics
• Phase contrast imaging
• Laser diagnostics
• Planar laser-induced fluorescence
• Particle image velocimetry

Abstract

Decarbonizing the worldwide transportation sector is one of the major goals of modern society, and the aviation industry is no exception. The United States government and other nations around the world have set goals to achieve a carbon neutral aviation industry by the year 2050. Achieving this goal requires the development and use of alternatively-derived sustainable aviation fuels that can operate in existing aircraft, gas turbine engines, and ground infrastructure in a drop-in capacity, while offering a significant reduction in lifecycle carbon emissions. The ability to use alternatively-derived domestically produced fuels in existing equipment also offers advantages in providing greater economic security and energy independence. To ensure alternatively-derived fuels operate well in all existing equipment, they must undergo an intensive certification process that is lengthy and requires large volumes of the test fuel. This process is necessary to ensure no operational issues arise with the new fuel even under unusual or extreme conditions. Developing a better understanding of combustion behavior using low fuel volumes can aid in this process by providing additional confidence about how systems will perform with a new fuel or allowing for preliminary testing using significantly less fuel. The goal of this work is to improve the fundamental understanding of compact gas turbine combustion systems to aid in the effort to simplify fuel certification and to inform future, more efficient or higher performance, engine designs. To perform this investigation, a compact research combustor, the Army Research Combustor - Medium (ARC-M1), is tested in a variety of critical operating scenarios. This combustor is a liquid-fueled gas turbine combustor designed to replicate combustion behavior from modern engines while offering ample optical access for characterizing the system with advanced diagnostic tools. In order to study effects of liquid fuel properties on the combustion performance, four jet fuels are selected for testing that each offer unique properties spanning extremes that may be encountered with future alternatively derived fuels. These fuels are used to understand how specific fuel properties impact local and global combustion performance. The first area of focus for this work is studying the combustor performance, liquid spray, and flame dynamics near combustor lean blowout (LBO). LBO is a condition where the flame in the combustor unexpectedly blows out, often following rapid drops in throttle. Characterizing the LBO performance of the combustor shows a strong dependence on fuel properties governing the liquid atomization and vaporization, motivating further detailed study of the liquid spray. To do this, high-speed x-ray phase contrast imaging is conducted at 90,517 Hz to visualize the liquid fuel leaving the fuel spray nozzle in the operating combustor. Spray imaging is conducted across different fuel flowrates, inlet air conditions, and fuels to capture how each of these aspects impacts the liquid spray physics. Comparisons are first made qualitatively; then, a custom algorithm is developed for determining droplet size and velocity, enabling quantitative comparisons between the measured conditions. To augment these x-ray liquid spray measurements, additional laser-based diagnostic techniques are used to study the broader airflow and combustion dynamics at comparable near blowout conditions. High-speed (10,000 Hz) OH PLIF and PIV are performed simultaneously on the combustor, allowing visualization of the product zones and airflow motion within the flame. Together, these three diagnostic tools provide incredibly detailed information on the key physics taking place near lean blowout in a compact gas turbine combustor. The second major focus of this work is characterizing the performance of the ARC-M1 combustor at cold-start and altitude relight conditions. Should LBO occur in a combustor in flight, it is critical that it can be quickly reignited, even though the low ambient air temperature and pressure make ignition challenging. Using an altitude chamber facility, measurements of the combustor's ignition performance are made at multiple inlet air conditions, including cold start measurements down to -35°C and at 10,000 ft equivalent altitude relight conditions. The results from these measurements suggest that the liquid fuel spray is again critical to combustion performance in the system, prompting the use of additional diagnostics to characterize the liquid fuel spray under these unfavorable ignition conditions. High-speed x-ray phase contrast imaging is again performed to visualize the liquid fuel spray in the vicinity of the spark, and the spark's ability to vaporize nearby liquid droplets is directly visualized. Droplet size distributions before and after the spark are also quantified using the same algorithm as in the LBO case. Additional diagnostics are used to characterize the heat release from the flame after successful and unsuccessful sparks, showing the evolution of early flame kernels into successful widespread combustion. By performing this suite of measurements to characterize the ignition event, the interaction between the liquid fuel spray and the early flame kernel is captured in great detail, helping to improve the understanding of how sparks produce successful combustor ignition in these compact environments. As a whole, this work serves to investigate the combustion behavior of compact gas turbine combustors using a collection of advanced diagnostic techniques at relevant conditions for these two critical scenarios. All together, the knowledge gained from this work aims to improve the collective understanding of lean blowout and ignition behavior in compact gas turbine combustors, which will help aid in the certification process for alternative fuels and help in developing future combustors with greater efficiency and performance.

Graduation Semester

2023-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/121339

Copyright and License Information

Copyright 2023 Eric James Wood

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