TY - GEN
T1 - Development of an Optically Accessible Mach 3.5 Axisymmetric Direct Connect/Semi-Free Jet Supersonic Combustion Flowpath
AU - Lee, Gyu Sub
AU - Lim, Jie
AU - Gessman, Isabella C.
AU - Kato, Nozumo
AU - Paganini, Arthur
AU - D’Agostino, Mitchell A.
AU - Lee, Tonghun
N1 - This work was supported by U.S. Air Force Office of Scientific Research grant FA9550-21-1-0072 monitored by Dr. Chiping Li, and by the Office of Naval Research grant N00014-21-1-2475 monitored by Dr. Eric Marineau. This material is also based in part upon work supported by the Department of Energy, National Nuclear Security Administration, under Award Number DE-NA0003963. The authors gratefully acknowledge these sources of support.
PY - 2025
Y1 - 2025
N2 - An axisymmetric Mach 3.5 direct connect supersonic combustion flowpath has been developed at the University of Illinois Urbana-Champaign for use in fundamental studies on high-speed combustion stabilization, scram and ram combustion performance, and mode transition. The current work outlines the first two iterations of the flowpath design, along with accompanying validation and preliminary measurements conducted in the Arc-Heated Combustion Tunnel (ACT-II) at Mach 7 total enthalpy conditions with ethylene fueling. These measurements include static pressure measurements on the flowpath wall, pitot measurements at the combustor exit, and optical measurements including OH* and broadband chemiluminescence, isolator plasma luminescence, and OH PLIF of the combustor flowfield. To enhance the diagnostic potential of the flowpath, optical access is featured along 80% of the flowpath length. The earliest prototype of the flowpath exhibited poor combustion and flameholding characteristics, and an inability to engage mode transition. The fault was assessed to be the rapid geometric expansion at the flameholding station of the combustor and an attendant reduction in static pressure, resulting in adverse ignition performance and shortened combustor residence time. Based on these initial results, the flowpath was redesigned with a longer combustor, a deeper flameholding cavity with a 30° takeback ramp, and an additional stage of fuel injection. Early tests of this second flowpath show promising results for both ignition and flameholding performance and demonstrate the capability for mode transition. Pulsed injection-induced ignition was also successfully tested in this new geometry. A semifree jet flowpath was developed based on the revised direct connect model. Mach 4.5 high enthalpy free jet tests of this new geometry were conducted in the ACT-II. The results confirm full flowpath startability and inlet performance of the unfueled semi-free jet flowpath model.
AB - An axisymmetric Mach 3.5 direct connect supersonic combustion flowpath has been developed at the University of Illinois Urbana-Champaign for use in fundamental studies on high-speed combustion stabilization, scram and ram combustion performance, and mode transition. The current work outlines the first two iterations of the flowpath design, along with accompanying validation and preliminary measurements conducted in the Arc-Heated Combustion Tunnel (ACT-II) at Mach 7 total enthalpy conditions with ethylene fueling. These measurements include static pressure measurements on the flowpath wall, pitot measurements at the combustor exit, and optical measurements including OH* and broadband chemiluminescence, isolator plasma luminescence, and OH PLIF of the combustor flowfield. To enhance the diagnostic potential of the flowpath, optical access is featured along 80% of the flowpath length. The earliest prototype of the flowpath exhibited poor combustion and flameholding characteristics, and an inability to engage mode transition. The fault was assessed to be the rapid geometric expansion at the flameholding station of the combustor and an attendant reduction in static pressure, resulting in adverse ignition performance and shortened combustor residence time. Based on these initial results, the flowpath was redesigned with a longer combustor, a deeper flameholding cavity with a 30° takeback ramp, and an additional stage of fuel injection. Early tests of this second flowpath show promising results for both ignition and flameholding performance and demonstrate the capability for mode transition. Pulsed injection-induced ignition was also successfully tested in this new geometry. A semifree jet flowpath was developed based on the revised direct connect model. Mach 4.5 high enthalpy free jet tests of this new geometry were conducted in the ACT-II. The results confirm full flowpath startability and inlet performance of the unfueled semi-free jet flowpath model.
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U2 - 10.2514/6.2025-1723
DO - 10.2514/6.2025-1723
M3 - Conference contribution
AN - SCOPUS:86000189467
SN - 9781624107238
T3 - AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025
BT - AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025
PB - American Institute of Aeronautics and Astronautics Inc, AIAA
T2 - AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025
Y2 - 6 January 2025 through 10 January 2025
ER -