TY - JOUR
T1 - Flame acceleration and the transition to detonation of stoichiometric ethylene/oxygen in microscale tubes
AU - Wu, Ming Hsun
AU - Burke, M. P.
AU - Son, S. F.
AU - Yetter, R. A.
N1 - Funding Information:
This work was supported by the Air Force Office of Scientific Research under contract AFOSR F49620-01-1-0376. The authors gratefully acknowledge the support from Dr. Mitat Birkan, contract monitor, of the program. SFS is supported by Los Alamos National Laboratory (LANL), which is operated by the University of California for the U.S. Department of Energy under contract W-7405-ENG-36. The authors acknowledge Dr. Grant Risha for his assistance on the experimental setup as well as discussions. The informative input from Dr. Scott Jackson at LANL is especially appreciated.
PY - 2007
Y1 - 2007
N2 - Flame propagation in capillary tubes with smooth circular cross-sections and diameters of 0.5, 1.0, and 2.0 mm are investigated using high-speed photography. Flames were found to propagate and accelerate to detonation speed in stoichiometric ethylene and oxygen mixtures initially at room temperature in all three tube diameters. Ignition occurs at the midpoint along the length of the tube. We observe for the first time transition to detonation in micro-tubes. Detonation was observed with both spark and hot-wire ignition. Tubes with larger diameters take longer to transition to detonation. In fact, transition distance scales with the diameter in our 1.0 and 2.0 mm cases with spark ignition. Flame structures are observed for various stages of the process. Three types of flame propagation modes were observed in the 0.5 mm tube with spark ignition: (a) acceleration to Chapman-Jouguet (CJ) detonation speed followed by constant CJ wave propagation, (b) acceleration to CJ speed, followed by the detonation wave failure, and (c) flame acceleration to a constant speed below the CJ speed of approximately 1600 m/s. The current detonation mechanism observed in capillary tubes is applicable to predetonators for pulsed detonation, micro propulsion devices, safety issues, and addresses fundamental issues raised by recent theoretical and numerical analyses.
AB - Flame propagation in capillary tubes with smooth circular cross-sections and diameters of 0.5, 1.0, and 2.0 mm are investigated using high-speed photography. Flames were found to propagate and accelerate to detonation speed in stoichiometric ethylene and oxygen mixtures initially at room temperature in all three tube diameters. Ignition occurs at the midpoint along the length of the tube. We observe for the first time transition to detonation in micro-tubes. Detonation was observed with both spark and hot-wire ignition. Tubes with larger diameters take longer to transition to detonation. In fact, transition distance scales with the diameter in our 1.0 and 2.0 mm cases with spark ignition. Flame structures are observed for various stages of the process. Three types of flame propagation modes were observed in the 0.5 mm tube with spark ignition: (a) acceleration to Chapman-Jouguet (CJ) detonation speed followed by constant CJ wave propagation, (b) acceleration to CJ speed, followed by the detonation wave failure, and (c) flame acceleration to a constant speed below the CJ speed of approximately 1600 m/s. The current detonation mechanism observed in capillary tubes is applicable to predetonators for pulsed detonation, micro propulsion devices, safety issues, and addresses fundamental issues raised by recent theoretical and numerical analyses.
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U2 - 10.1016/j.proci.2006.08.098
DO - 10.1016/j.proci.2006.08.098
M3 - Conference article
AN - SCOPUS:34548783737
SN - 1540-7489
VL - 31 II
SP - 2429
EP - 2436
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
T2 - 31st International Symposium on Combustion
Y2 - 5 August 2006 through 11 August 2006
ER -