Self-organized generation of transverse waves in diverging cylindrical detonations

Jiang, Zonglin; Han, Guilai; Chun, Wu; Zhang, Fan

doi:10.1016/j.combustflame.2009.02.012

Cited by 31 publications

(13 citation statements)

References 17 publications

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“…When the distance becomes too large between adjacent transverse waves, new transverse waves are easy to form, especially in the case with high activation energy. This phenomenon is also observed in diverging detonations whose surface becomes larger and larger, related with the curvature effects [27,30]. Generally, the merging and splitting of transverse waves appear to be equivalent to those observed in normal detonations, which thus demonstrate that the transition mechanism is due to the inherent instability of detonations.…”

Section: Transition Of the Two Kinds Of Cellular Structurementioning

confidence: 66%

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Evolution of cellular structures on oblique detonation surfaces

Teng

et al. 2015

Combustion and Flame

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115

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a b s t r a c tIn this study, numerical simulations using the inviscid Euler equations with one-step Arrhenius chemistry model are carried out to investigate the effects of activation energy and wedge angle on the stability of oblique detonation surfaces. Two kinds of cellular structure are studied, one is featured by a single group of transverse waves traveling upstream, referred to as LRTW (left-running transverse waves), and the other is featured by additional RRTW (right-running transverse waves). The present computational simulation reveals the formation of un-reacted gas pockets behind the cellular oblique detonation. Numerical smoked foil records are produced to show the emergence of the two types of transverse waves and the evolution of the unstable cellular structure of the oblique detonation. The transverse wave dynamics, including the colliding, emerging and splitting types, are found to be similar to the normal detonation propagation, demonstrating the instability mechanism is originated from the inherent instability of cellular detonations. Statistical analysis on the cellular structure is carried out to observe quantitatively the influences of activation energy and wedge angle. Results from the parametric study show that high activation energy and low wedge angle are favorable to the LRTW formation. However, the condition for the RRTW formation is more complex. In the case of low activation energy, small wedge angle is beneficial to the RRTW formation, as to the LRTW formation. In contrary, for high activation energy, there appears one moderate wedge angle favoring the RRTW formation and giving the shortest length between the onset of both LR and RR transverse waves. For quantitative comparison, we analyze the variation of two distances with the wedge angle, one is between the detonation initiation and LRTW formation points, and the other between LRTW and RRTW formation points. Results show the latter is relatively less pronounced than the former, indicating the RRTW formation depends mainly on the activation energy and the generation of LRTW.

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Section: Transition Of the Two Kinds Of Cellular Structurementioning

confidence: 66%

“…The surface evolution of oblique detonations appears to be similar to that for normal detonations [24][25][26][27][28][29]. With the ZND structure as an initial condition, a spectrum of instability modes induces many weak transverse waves on the detonation surface initially.…”

Section: Transition Of the Two Kinds Of Cellular Structurementioning

confidence: 99%

Evolution of cellular structures on oblique detonation surfaces

Teng

et al. 2015

Combustion and Flame

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115

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“…The most well-known theories describing detonation are the Chapman-Jouguet (CJ) theory and the Zeldovich-von Neuman-Doring (ZND) model. Detonation waves have special selforganized micro-structures, which occur due to the detonation instability such as the movement of the transverse waves in the detonation front and the cellular structure recorded after the detonation propagation [5][6][7][8] . An excellent experimental study on cellular detonation was made by Pintgen et al [9] , which revealed clear transverse waves in the detonation front by use of planar laser-induced fluorescence (PLIF).…”

Section: Introductionmentioning

confidence: 99%

Theoretical approach to one-dimensional detonation instability

Chun

Jiang

Han

2016

Appl. Math. Mech.-Engl. Ed.

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Detonation instability is a fundamental problem for understanding the microbehavior of a detonation front. With the theoretical approach of shock dynamics, detonation instability can be mathematically described as a second-order ordinary difference equation. A one-dimensional detonation wave can be modelled as a type of oscillators. There are two different physical mechanisms controlling the behaviors of a detonation. If the shock Mach number is smaller than the equilibrium Mach number, the fluid will reach the sonic speed before the end of the chemical reaction. Then, thermal chock occurs, and the leading shock becomes stronger. If the shock Mach number is larger than the equilibrium Mach number, the fluid will be subsonic at the end of the chemical reaction. Then, the downstream rarefaction waves propagate upstream, and weaken the leading shock. The above two mechanisms are the basic recovery forces toward the equilibrium state for detonation sustenance and propagation. The detonation oscillator concept is helpful for understanding the oscillating and periodic behaviors of detonation waves. The shock dynamics theory of detonation instability gives a description of the feedback regime of the chemical reaction, which causes variations of the leading shock of the detonation.

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“…However, it is also found that detonation can also be formed in unconfined regions in the absence of wall 10 . Jiang et al's study showed that detonation can be sustained in a diverging cylindrical detonation via the generation of new transverse waves 11 . In these unconfined detonations, wall friction is not considered.…”

Section: Introductionmentioning

confidence: 99%

Computational Study of Deflagration to Detonation Transition in a Straight Duct: Effect of Energy Release

Dou

Khoo

2012

Int. J. Mod. Phys. Conf. Ser.

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Numerical simulation based on the Euler equation and one-step reaction model is carried out to investigate the process of deflagration to detonation transition (DDT) occurring in a straight duct. The numerical method used includes a high resolution fifth-order weighted essentially nonoscillatory scheme for spatial discretization, coupled with a third order total variation diminishing Runge-Kutta time stepping method. In particular, effect of energy release on the DDT process is studied. The model parameters used are the heat release at q =50, 30, 25, 20, 15, 10 and 5, the specific heat ratio at 1.2, and the activation temperature at Ti =15, respectively. For all the cases, the initial energy in the spark is about the same compared to the detonation energy at the Chapman-Jouguet (CJ) state. It is found from the simulation that the DDT occurrence strongly depends on the magnitude of the energy release. The run-up distance of DDT occurrence decreases with the increase of the energy release for q =50~20, and increases with the increase of the energy release for q =50~20. It is concluded from the simulations that the interaction of the shock wave and the flame front is the main reason for leading to DDT.

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Self-organized generation of transverse waves in diverging cylindrical detonations

Cited by 31 publications

References 17 publications

Evolution of cellular structures on oblique detonation surfaces

Evolution of cellular structures on oblique detonation surfaces

Theoretical approach to one-dimensional detonation instability

Computational Study of Deflagration to Detonation Transition in a Straight Duct: Effect of Energy Release

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