Compressible turbulent flame speeds of highly turbulent standing flames

Sosa, Jonathan; Chambers, Jessica; Ahmed, Kareem A.; Poludnenko, Alexei; Gamezo, Vadim N.

doi:10.1016/j.proci.2018.07.039

Cited by 27 publications

(4 citation statements)

References 25 publications

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“…5B, which is higher than the static temperature of the fuel-air mixture in the experiments, and was required for ODW initiation in the simulations. In this way, the enthalpy of the incoming fuel-air mixture in the simulations is enhanced beyond that of the experimental facility in order to compensate for the inability of the simulations to reproduce the experiment's turbulence, which has been shown to assist in mixture ignition through the generation of eddy shocklets and local compressibility effects (36). The inflow Mach number is 5 (Mach number generated in the experimental facility after full expansion of an incoming airflow), and the static pressure matches that of the experiments.…”

Section: Numerical Simulationsmentioning

confidence: 99%

Stabilized detonation for hypersonic propulsion

Rosato

Thornton

Sosa

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Future terrestrial and interplanetary travel will require high-speed flight and reentry in planetary atmospheres by way of robust, controllable means. This, in large part, hinges on having reliable propulsion systems for hypersonic and supersonic flight. Given the availability of fuels as propellants, we likely will rely on some form of chemical or nuclear propulsion, which means using various forms of exothermic reactions and therefore combustion waves. Such waves may be deflagrations, which are subsonic reaction waves, or detonations, which are ultrahigh-speed supersonic reaction waves. Detonations are an extremely efficient, highly energetic mode of reaction generally associated with intense blast explosions and supernovas. Detonation-based propulsion systems are now of considerable interest because of their potential use for greater propulsion power compared to deflagration-based systems. An understanding of the ignition, propagation, and stability of detonation waves is critical to harnessing their propulsive potential and depends on our ability to study them in a laboratory setting. Here we present a unique experimental configuration, a hypersonic high-enthalpy reaction facility that produces a detonation that is fixed in space, which is crucial for controlling and harnessing the reaction power. A standing oblique detonation wave, stabilized on a ramp, is created in a hypersonic flow of hydrogen and air. Flow diagnostics, such as high-speed shadowgraph and chemiluminescence imaging, show detonation initiation and stabilization and are corroborated through comparison to simulations. This breakthrough in experimental analysis allows for a possible pathway to develop and integrate ultra-high-speed detonation technology enabling hypersonic propulsion and advanced power systems.

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Section: Numerical Simulationsmentioning

confidence: 99%

Stabilized detonation for hypersonic propulsion

Rosato

Thornton

Sosa

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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“…The geometric configuration employed allows us to survey the flame regimes of interest and focus on the conditions for tDDT. Extensive experimental testing of the design and arrangement of perforated plates has been performed to ensure that desired turbulence conditions are achieved, specifically in terms of the amplitude of turbulent velocity fluctuations (63)(64)(65).…”

Section: Experimental Studymentioning

confidence: 99%

“…Values of the turbulent integral scale, l, were 1.45 cm (average), 3.17 cm (maximum), 0.19 cm (minimum), and 0.45 cm (standard deviation). Procedures for determining these turbulent characteristics in the TST facility have been described elsewhere (65). The pressure and temperature of the reacting mixture in the compressed region ahead of the flame are 6.92 atm and 627 K, respectively.…”

Section: Experimental Studymentioning

confidence: 99%

A unified mechanism for unconfined deflagration-to-detonation transition in terrestrial chemical systems and type Ia supernovae

Poludnenko

Chambers

Ahmed

et al. 2019

Science

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110

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A general theory of the deflagration-to-detonation transition is presented along with its experimental and numerical confirmation, as well as its application to Type Ia supernovae.The nature of type Ia supernovae (SNIa) -thermonuclear explosions of white dwarf stars -is an open question in astrophysics. Virtually all existing theoretical models of normal, bright SNIa require the explosion to produce a detonation in order to consume all of stellar material, but the mechanism for the deflagration-to-detonation transition (DDT) remains unclear. We present a unified theory of turbulence-induced DDT that describes the mechanism and conditions for initiating detonation both in unconfined chemical and thermonuclear explosions. The model is validated using experiments with chemical flames and numerical simulations of thermonuclear flames. We use the 1 arXiv:1911.00050v1 [astro-ph.HE]

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“…Experiments to test the predictions for purely turbulence-induced DDT described above have been started at several laboratories (See, for example, [28]). Currently there is an indication that it is, in fact, a valid and actual mechanism.…”

Section: Ddt In a Turbulent Flame (Unconfined No Congestion)mentioning

confidence: 99%

Mechanisms and Occurrence of Detonations in Vapor Cloud Explosions

Oran¹

2019

Preprint

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Not all accidental releases of ﬂammable gases and vapors create explosions. Most releases do not ﬁnd an ignition source, and of those that do ignite, most of them result in deﬂagrations that generate low or moderate overpressures. Under some circumstances, however, it is possible for deﬂagration-to-detonation transition (DDT) to occur, and this can be followed by a propagating detonation that quickly consumes the remaining detonable cloud. In a detonable cloud, a detonation creates the worst accident that can happen. Because detonation overpressures are much higher than those in a deﬂagration and continue through the entire detonable cloud, the damage from a DDT event is more severe.This paper ﬁrst provides a brief summary of our knowledge to date of the fundamental mechanisms of ﬂame acceleration and DDT. This information is then contrasted to and combined with evidence of detonations (detonation markers) obtained from large-scale tests and actual large vapor cloud explosions (VCEs), including events at Bunceﬁeld (UK), Jaipur (India), CAPECO (Puerto Rico), and Port Hudson (US). The major conclusion from this review is that detonations did occur in prior VCEs in at least part of the VCE accidents. Finally, actions are suggested that could be taken to minimize detonation hazards.

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Compressible turbulent flame speeds of highly turbulent standing flames

Cited by 27 publications

References 25 publications

Stabilized detonation for hypersonic propulsion

Stabilized detonation for hypersonic propulsion

A unified mechanism for unconfined deflagration-to-detonation transition in terrestrial chemical systems and type Ia supernovae

Mechanisms and Occurrence of Detonations in Vapor Cloud Explosions

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