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Journal ArticleDOI

Behavior of detonation propagation in mixtures with concentration gradients

28 Jul 2007-Shock Waves (Springer-Verlag)-Vol. 17, Iss: 1, pp 95-102
TL;DR: In this article, the behavior of detonation waves in mixtures with concentration gradients normal to the propagation direction was studied experimentally, where a stoichiometric hydrogen-oxygen mixture was charged in the detonation chamber, while oxygen or nitrogen was filled in the diffusion gas chamber.
Abstract: Behavior of detonation waves in mixtures with concentration gradients normal to the propagation direction was studied experimentally. Mixtures with various concentration gradients were formed by sliding the separation plate which divides a detonation chamber from a diffusion chamber in which a diffusion gas was initially introduced. A stoichiometric hydrogen–oxygen mixture was charged in the detonation chamber, while oxygen or nitrogen was filled in the diffusion gas chamber. Temporal concentration measurement was conducted by the infrared absorption method using ethane as alternate of oxygen. Smoked foil records show a deformation of regular diamond cells to parallelogram ones, which well corresponds to local mixture concentration. Schlieren photographs reveal the tilted wave front whose angle is consistent with the deflection angle of the detonation front obtained from trajectories of the triple point. The local deflection angle increases with increase in local concentration gradient. Calculation of wave trajectory based on the ray tracing theory predicts formation of the tilted wave front from an initial planar front.
Citations
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Journal ArticleDOI
TL;DR: In this article, the detonations propagating through the annular channel of an optically accessible rotating detonation engine (RDE) operating on hydrogen-air are visualized using OH* chemiluminescence imaging.

274 citations

Journal ArticleDOI
01 Jan 2009
TL;DR: In this paper, the authors review recent progress in gaseous detonation experiment, modeling, and simulation and discuss the implications of this for detonation propagation and dynamic behavior such as diffraction, initiation, and quenching or failure.
Abstract: We review recent progress in gaseous detonation experiment, modeling, and simulation. We focus on the propagating detonation wave as a fundamental combustion process. The picture that is emerging is that although all propagating detonations are unstable, there is a wide range of behavior with one extreme being nearly laminar but unsteady periodic flow and the other chaotic instability with highly turbulent flow. We discuss the implications of this for detonation propagation and dynamic behavior such as diffraction, initiation, and quenching or failure.

244 citations

Journal ArticleDOI
TL;DR: In this article, rotating detonation engines are compared to pulsed detonation engine and they are shown to produce thrust with fuel efficiencies similar to those associated with pulsed engines while operating on gaseous hydrocarbon fuels.
Abstract: Recent accomplishments related to the performance, application, and analysis of rotating detonation engine technologies are discussed. The pioneering development of optically accessible rotating detonation engines coupled with the application of established diagnostic techniques is enabling a new research direction. In particular, OH* chemiluminescence images of detonations propagating through the annular channel of a rotating detonation engine are reported and appear remarkably similar to computational fluid dynamic results of rotating detonation engines published in the literature. Specific impulse measurements of rotating detonation engines and pulsed detonation engines are shown to be quantitatively similar for engines operating on hydrogen/air and ethylene/air mixtures. The encouraging results indicate that rotating detonation engines are capable of producing thrust with fuel efficiencies that are similar to those associated with pulsed detonation engines while operating on gaseous hydrocarbon fuels....

157 citations

Journal ArticleDOI
TL;DR: In this article, an injection mechanism was developed that produces vertical fuel concentration gradients inside a horizontal channel with large aspect ratio, equipped with obstacles to enhance flame acceleration, and Schlieren measurements were conducted to track gas mixing behind the obstacles and to track the formation of the detonation.
Abstract: The hazardous potential of hydrogen/air mixtures has intensively been studied assuming a perfect mixture of fuel and oxidant. However, comprehensive risk assessment studies have shown that an inhomogeneous mixture with a vertical concentration gradient is much more likely to be generated in a real accident scenario. From a safety point of view, an open question is whether established criteria such as the 7λ criterion for the determination of the deflagration-to-detonation transition (DDT) limits can be applied to inhomogeneous mixtures as well. For the experimental investigation of DDT in such mixtures an injection mechanism has been developed that produces vertical fuel concentration gradients inside a horizontal channel with large aspect ratio. The channel is equipped with obstacles to enhance flame acceleration. Photodiodes and pressure transducers measure flame and shock arrival times. Schlieren measurements are conducted to track gas mixing behind the obstacles and to track the formation of the deton...

75 citations


Cites background from "Behavior of detonation propagation ..."

  • ...Ishii and Kojima (2007) studied detonations in mixtures with a concentration gradient perpendicular to the propagation direction of the detonation....

    [...]

Journal ArticleDOI
TL;DR: In this paper, the influence of transverse concentration gradients on detonation propagation was investigated experimentally in a wide parameter range, and significant amounts of mixture seem to be consumed by turbulent deflagration behind the leading detonation.
Abstract: The influence of transverse concentration gradients on detonation propagation in $$\hbox {H}_2$$ –air mixtures is investigated experimentally in a wide parameter range. Detonation fronts are characterized by means of high-speed shadowgraphy, OH* imaging, pressure measurements, and soot foils. Steep concentration gradients at low average $$\hbox {H}_2$$ concentrations lead to single-headed detonations. A maximum velocity deficit compared to the Chapman–Jouguet velocity of 9 % is observed. Significant amounts of mixture seem to be consumed by turbulent deflagration behind the leading detonation. Wall pressure measurements show high local pressure peaks due to strong transverse waves caused by the concentration gradients. Higher average $$\hbox {H}_2$$ concentrations or weaker gradients allow for multi-headed detonation propagation.

70 citations

References
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Book
01 Jun 1989
TL;DR: Pierces as mentioned in this paper is a classic text on acoustics with a rich history and development of the field of sound and acoustical engineering. But he organizes it superbly and writes intelligently with a wonderful way of integrating the history and evolution of the science and the graphics are exceptionally clear and communicative.
Abstract: My Personal Review: Texts on acoustics approach the subject from many different angles and at many different levels. Pierce's text is classic, rigorous and complete. It should serve the needs of serious students of acoustics for a variety of purposes musical acoustics and sound are my particular perspective.Some writers cater their approach to electrical engineers or to mechanical engineers, assuming that by tieing everything to those disciplines they will make the effort easier for their readers. This may serve well those who come from those disciplines, but may not serve others well and may not serve all applications of acoustics equally well either. Pierce does not do so. His approach is rigorously mathematical and pure, going to the heart of the matter, rather than one of attempting to cut corners by making analogies to other fields that you may or may not know.The book is not for the faint of heart or the mildly curious, it is deep and demanding. But he organizes it superbly and writes intelligently with a wonderful way of integrating the history and development of the science, and the graphics are exceptionally clear and communicative.Highly recommended for the very serious about this subject. My favorite among the books I have consulted.

2,235 citations


"Behavior of detonation propagation ..." refers background or methods in this paper

  • ...In the present work the formation of the wave front is calculated using the ray tracing theory [ 16 ]....

    [...]

  • ...Instead of dealing with n directly, a wave slowness vector s(xp) =∇ τ( xp) [ 16 ] which is parallel to n can be introduced by the following equation...

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Journal ArticleDOI
TL;DR: In this article, two detonation tubes were used to study detonation propagation in concentration gradients, and it was shown that the mechanism of detonation initiation in a weaker mixture by an incident detonation propagated across a concentration gradient differs from that in a homogeneous mixture in that a secondary shock is formed as an intermediate stage.

55 citations


"Behavior of detonation propagation ..." refers methods in this paper

  • ...Transmission of detonation from one mixture to the other through an area of continuously changing concentration was experimentally studied using circular detonation tubes [ 5 ,6]....

    [...]

Journal ArticleDOI
01 Jan 1998
TL;DR: In this paper, a detonation tube of 174 mm id. was used to test the effect of the gradient on the transmission process of a single detonation wave in non-uniform mixtures.
Abstract: Experiments on the behavior of detonation waves in nonuniform mixtures are presented. The situation studied was the propagation of a detonation wave from a driver mixture of variable length through a concentration gradient of variable width into a less reactive acceptor mixture. The effect of the gradient on the transmission process were studied. A detonation tube of 174 mm id. was used. The tube was initially divided by a fast-opening, stretched rubber diaphragm. Stoichiometric hydrogen/air mixture was used in the driver section. Hydrogen/air mixtures (14.0–19.0% H 2 ) were used as acceptor mixtures. Natural diffusion was used to create a concentration gradient between two mixtures. It was shown that the behavior of detonations at concentration gradients depends significantly on the sharpness of the gradient. For relatively sharp gradients a detonation always decays in the nonuniform region. It can be reinitiated downstream in the acceptor mixture, if the driver length is large enough for a particular acceptor mixture. For relatively smooth gradients, detonation is able to propagate through without decay. The boundary between these cases is defined only by the value of sensitivity gradient for a particular pair of driver and acceptor mixtures. The critical value of the gradient depends strongly on the difference in energy content of driver and acceptor mixtures. The more overdriven is the detonation in the driver mixture compared to that in the acceptor, the sharper gradient is necessary for detonation decay. The order of magnitude of critical values of the gradient shows that evolution of the cellular structure may play a role effecting conditions for detonation decay at concentration gradients.

53 citations


"Behavior of detonation propagation ..." refers methods in this paper

  • ...Transmission of detonation from one mixture to the other through an area of continuously changing concentration was experimentally studied using circular detonation tubes [5, 6 ]....

    [...]

01 Sep 1991
TL;DR: In this article, a complex, dynamic shock-detonation structure formed by the glancing interaction of a primary detonation with a secondary explosive is studied by using time-dependent two-dimensional simulations and related experiments.
Abstract: The complex, dynamic shock-detonation structure formed by the glancing interaction of a primary detonation with a secondary explosive is studied by using time-dependent two-dimensional simulations and related experiments. The materials considered in the simulations are stoichiometric and lean mixtures of hydrogen and oxygen diluted with argon. Related experiments have used undiluted hydrogen and oxygen as well as other gases. For the conditions simulated: (a) the primary mixture is stoichiometric and the secondary inert; (b) both the primary and secondary mixtures are the same and stoichiometric; (c) the primary mixture is lean and the secondary is stoichiometric; and (d) the primary mixture is stoichiometric and the secondary is lean. In addition, for cases (b) and (d) , comparisons are made between simulations in which the primary mixture is overdriven and when it is a Chapman-Jouguet detonation. For the overdriven stoichiometric primary detonation interacting with the lean mixture, a complex detonation structure forms and quickly asymptotes to the detonation velocity of the primary mixture. For this same case, but when the primary detonation is initially at Chapman-Jouguet velocity, the detonation appears to die but then reignites due to a series of shock reflections and then propagates as a complex structure. The lowest velocity of the complex structure is always greater than the Chapman-Jouguet velocity of the lean mixture and it increases in time, appearing to approach the Chapman-Jouguet velocity of the stoichiometric mixture. The dynamics of this decay and reignition process are described and discussed in detail.

44 citations

Journal ArticleDOI
TL;DR: In this article, a complex, dynamic shock-detonation structure formed by the glancing interaction of a primary detonation with a secondary explosive is studied by using time-dependent two-dimensional simulations and related experiments.
Abstract: The complex, dynamic shock-detonation structure formed by the glancing interaction of a primary detonation with a secondary explosive is studied by using time-dependent two-dimensional simulations and related experiments. The materials considered in the simulations are stoichiometric and lean mixtures of hydrogen and oxygen diluted with argon. Related experiments have used undiluted hydrogen and oxygen as well as other gases. For the conditions simulated: (a) the primary mixture is stoichiometric and the secondary inert; (b) both the primary and secondary mixtures are the same and stoichiometric; (c) the primary mixture is lean and the secondary is stoichiometric; and (d) the primary mixture is stoichiometric and the secondary is lean. In addition, for cases (b) and (d) , comparisons are made between simulations in which the primary mixture is overdriven and when it is a Chapman-Jouguet detonation. For the overdriven stoichiometric primary detonation interacting with the lean mixture, a complex detonation structure forms and quickly asymptotes to the detonation velocity of the primary mixture. For this same case, but when the primary detonation is initially at Chapman-Jouguet velocity, the detonation appears to die but then reignites due to a series of shock reflections and then propagates as a complex structure. The lowest velocity of the complex structure is always greater than the Chapman-Jouguet velocity of the lean mixture and it increases in time, appearing to approach the Chapman-Jouguet velocity of the stoichiometric mixture. The dynamics of this decay and reignition process are described and discussed in detail.

35 citations