scholarly journals Numerical Studies on Propagation Mechanisms of Gaseous Detonations in the Inhomogeneous Medium

2020 ◽  
Vol 10 (13) ◽  
pp. 4585
Author(s):  
Jianguo Ning ◽  
Da Chen ◽  
Jian Li
Keyword(s):  
Inhomogeneous Medium ◽  
Transverse Wave ◽  
Early Stage ◽  
Detonation Front ◽  
Homogeneous Medium ◽  
Wave Structure ◽  
Reaction Model ◽  
Propagation Mechanism ◽  
Gaseous Detonations ◽  
Cellular Detonation

Numerical simulation of propagation mechanisms of gaseous detonations in the inhomogeneous medium is studied by using the reactive Euler equations coupled with a two-step chemical reaction model. The inhomogeneity is generated by placing artificial temperature perturbations with different wavelengths and amplitudes. The motivation is to investigate the effect of artificial perturbations on the evolution or amplification of cellular instability. The results show that, without artificial perturbations, a planar ZND detonation can evolve into a fully-developed cellular detonation after a distance because of the amplification of the cellular instability. With the artificial perturbations evolved in, at the early stage, the artificial perturbations control the transverse wave spacing by suppressing the amplification of the cellular instability. However, after a steady-state, the cellular instability starts to amplify itself again and eventually transits to a fully-developed cellular detonation. It is demonstrated that the presence of the artificial perturbations delays the formation of the cellular detonation, and the increase of instability factor can slow down this delay. It is also found that, if the wavelength of the artificial perturbations is close to the transverse wave spacing of the cellular detonation in the homogeneous medium, synchronization of these two factors occurs, and hence a cellular detonation with extremely regular cell pattern is immediately formed. The temperature discontinuity causes the front to be more turbulent with the presence of weak triple-wave structure locally besides the natural transverse waves. The artificial perturbations can increase the intrinsic instability, and hence changes the propagation mechanism of the detonation front. In contrast, large artificial perturbations could prohibit the propagation but reduce cellular instability. It is concluded that the competition of artificial perturbations with intrinsic detonation instability dominates the evolution of cellular structures of the detonation front.

Propagation Mechanism of Cylindrical Cellular Detonation

2012 ◽  
Vol 29 (10) ◽  
pp. 108201 ◽  
Author(s):  
Wen-Hu Han ◽  
Cheng Wang ◽  
Jian-Guo Ning
Keyword(s):  
Propagation Mechanism ◽  
Cellular Detonation

Experimental and numerical investigation of propagation mechanism of gaseous detonations in channels with porous walls

2015 ◽  
Vol 162 (6) ◽  
pp. 2638-2659 ◽  
Author(s):  
Kiumars Mazaheri ◽  
Yasser Mahmoudi ◽  
Majid Sabzpooshani ◽  
Matei I. Radulescu
Keyword(s):  
Numerical Investigation ◽  
Propagation Mechanism ◽  
Gaseous Detonations ◽  
Porous Walls

PROPAGATION OF GASEOUS DETONATIONS IN PLANAR CURVED RECTANGULAR CHANNELS

2020 ◽  
Author(s):  
M. L. FOTIA ◽  
◽  
J. HOKE ◽  
A. J. OLSON ◽  
S. A. SCHUMAKER ◽  
...  
Keyword(s):  
Failure Mechanisms ◽  
Engineering Applications ◽  
Gaseous Detonations ◽  
Curved Channels ◽  
Rectangular Channels ◽  
Cellular Detonation ◽  
Practical Engineering ◽  
Rotating Detonation Engines ◽  
Rotating Detonation

The propagation of gaseous detonations through curved channels has a number of practical engineering applications that range from combustion initiation concepts to informing the design of rotating detonation engines. Understanding the failure mechanisms that do not allow a steadily propagating cellular detonation to traverse a curved segment of channel leads directly into these applications.

Numerical modelling of detonation performance

1992 ◽  
Vol 339 (1654) ◽  
pp. 419-429 ◽  
Keyword(s):  
Steady State ◽  
Reaction Zone ◽  
Fluid Dynamic ◽  
Detonation Front ◽  
Wave Structure ◽  
Detonation Performance ◽  
Primary Data ◽  
Reactive Flow ◽  
Temperature Dependent ◽  
Flow Models

Detonation performance is defined in terms of the steady state wave structure of the detonation front, and the initiation behaviour of the explosive. Some common techniques for modelling detonation performance are described, based on semi-analytic hydrodynamic and computational fluid dynamic reactive flow models. Accurate modelling of detonation performance is shown to require resolution of the reaction zone in the explosive, for non-ideal and for intrinsically unreactive systems. The ability of detonation models to predict steady state and initiation performance is discussed. Examples of resolve reaction zone models of explosives of varying degrees of ideality are presented. The sensitivity of predictions to primary data is examined for steady state reaction zone modelling of the insensitive explosive PBX W115, and Composition B3. Future directions for development of reactive flow models are examined. Particular emphasis is drawn to the need for more detailed temperature dependent kinetic schemes, and the inclusion of more detailed reaction geometries in such flow models.

Transverse wave structure in detonations

1967 ◽  
Vol 11 (1) ◽  
pp. 683-692 ◽  
Author(s):  
R.A. Strehlow ◽  
R. Liaugminas ◽  
R.H. Watson ◽  
J.R. Eyman
Keyword(s):  
Transverse Wave ◽  
Wave Structure

Role of transversal concentration gradient in detonation propagation

2019 ◽  
Vol 865 ◽  
pp. 602-649 ◽  
Author(s):  
Wenhu Han ◽  
Cheng Wang ◽  
Chung K. Law
Keyword(s):  
Detonation Velocity ◽  
Concentration Gradient ◽  
Detonation Front ◽  
Propagation Mode ◽  
Detonation Propagation ◽  
Cellular Detonation ◽  
Detonation Instability ◽  
Homogeneous Media ◽  
Reaction Equilibrium

The role of a transversal concentration gradient in detonation propagation in a two-dimensional channel filled with an $\text{H}_{2}{-}\text{O}_{2}$ mixture is examined by high-resolution simulation. Results show that, compared to propagation in homogeneous media, a concentration gradient reduces the average detonation velocity because of the delay in reaching downstream reaction equilibrium, leading to a large amount of unreacted $\text{H}_{2}$ and hence significant species fluctuations. The transversal concentration gradient also enhances the cellular detonation instability. Steepening it reduces considerably the number of triple points on the front, lengthens the global detonation front structure on average and consequently increases the deficit of the average detonation velocity. It is further found that the interaction of the leading shock with the transversal concentration gradient influences the formation of local $\text{H}_{2}$ bump and thus the unreacted pocket behind the front, while the transverse wave causes mixing and burning of the residue fuel downstream. Nevertheless, for the steepened concentration gradient, a transverse detonation is present and consumes the fuel in the compressed and preheated zone by the leading shock; consequently, the detonation velocity deficit is not increased significantly for detonation with the single-head propagation mode close to the limit.

The role of global curvature on the structure and propagation of weakly unstable cylindrical detonations

2017 ◽  
Vol 813 ◽  
pp. 458-481 ◽  
Author(s):  
Wenhu Han ◽  
Wenjun Kong ◽  
Yang Gao ◽  
Chung K. Law
Keyword(s):  
Transverse Wave ◽  
Average Velocity ◽  
Detonation Front ◽  
Cellular Structures ◽  
Two Dimensional ◽  
Average Structure ◽  
Global Curvature ◽  
Propagation Velocities

The role of the global curvature on the structure and propagation of cylindrical detonations is studied allowing and without allowing the development of cellular structures through two-dimensional (2-D) and 1-D simulations, respectively. It is shown that as the detonation transitions from being overdriven to the Chapman–Jouguet (CJ) state, its structure evolves from no cell, to growing cells and then to diverging cells. Furthermore, the increased dimension of the average structure of the cellular cylindrical detonation, coupled with the curved transverse wave, leads to bulk un-reacted pockets as the cells grow, and consequently lower average propagation velocities as compared to those associated with smooth fronts. As the global detonation front expands and its curvature decreases, the extent of the un-reacted pockets diminishes and the average velocity of the cellular cylindrical detonation eventually degenerates to that of the smooth fronts. Consequently, the presence of cellular instability renders detonation more difficult to initiate for weakly unstable detonations.

Sign in / Sign up

Export Citation Format

Share Document