One of the fundamental mechanisms for detonation initiation is deflagration-to-detonation transition (DDT). This research experimentally explores the runaway condition for highly turbulent fast flames before DDT, which are characterized by extremely high turbulent flame speeds. Such fast turbulent flames experience increased effects of compressibility and may develop a runaway acceleration combined with a pressure buildup that leads to a turbulence-induced DDT (tDDT) mechanism that has been recently reported. The flame dynamics and the associated reacting flow field are characterized using simultaneous high-speed particle image velocimetry, OH*chemiluminescence, pressure measurements, and schlieren imaging. We study the flow-field conditions for runaway acceleration of fast turbulent flames and effects of compressibility on the evolution of these flames. The locally measured turbulent flame speed is found to be greater than that of a Chapman–Jouguet deflagration speed, which places the flame in the runaway transition regime that would eventually lead to a detonation.
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Design Considerations and Imaging Setup for Liquid Fuel Droplet Experiments
Design considerations for a new detonation tube are presented to further improve detonation wave interaction research. The new structure consists of four independent portions: the deflagration to detonation initiation section, the transition expansion section, the operating test section, and the dump section. The initiation, transition, and test sections are designed to operate within a temperature limit of 150 °C and a maximum detonation pressure of 100 bar. The test section is comprised of interchangeable 155 cm 316 stainless steel plates assembled to create a 10x10 cm square hollow structure, sealed with longitudinal O-rings between plates and lateral O-rings between flanges and plate ends. The ports and windows are all sealed with O-rings. The current assembly has 30 circular ports for pressure measurements and ion gauge measurements. These same circular ports will also be used for laser spectroscopy measurements through 1.27 cm diameter circular windows. Two axial rectangular windows of 16.51 x 5.74 cm and two of 16.51 x 2.54 cm, with centers 52 cm from the downstream end of the test section, are used for various diagnostics and imaging techniques. Hydrostatic droplet release, piezo-actuated droplet release, and vibration-induced droplet release have been designed and discussed.
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- Award ID(s):
- 2244324
- PAR ID:
- 10591085
- Publisher / Repository:
- American Institute of Aeronautics and Astronautics
- Date Published:
- ISBN:
- 978-1-62410-711-5
- Format(s):
- Medium: X
- Location:
- Orlando, FL
- Sponsoring Org:
- National Science Foundation
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