Numerical simulation of detonation initiation in a contoured tube (original) (raw)
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Initiation of detonation in a tube with parabolic contraction and conic expansion
Doklady Physics. – 2010. – Vol. 55, No. 3. – P. 150 – 154., 2010
On the basis of results of two and three dimen sional numerical simulation, we proposed for the first time to use the profiling of axisymmetric tube walls in the shape of parabolic contraction and conic expan sion for initiating the detonation by means of a rela tively weak shock wave. The detonation initiation mechanism is revealed, and its basic stages are ana lyzed. For simulating the propane-air mixture, we found the parabolic contraction shape and selected the conic expansion parameters providing the initia tion of detonation for the Mach number of an original shock wave equal to 2.65.
Numerical and experimental investigation of detonation initiation in profiled tubes
Combustion Science and Technology. – 2010. – V. 182, № 11 – 12. – P. 1735 – 1746., 2010
Detonation initiation in a tube with parabolic contraction and conical expansion was investigated numerically and experimentally. The optimized geometry of conical expansion with sine-shaped wall is proposed. The generalized diagram in the form of detonation curves at the contraction slope angle versus incident shock Mach number plane is presented. For solving the governing Euler equations, the numerical method based on finite volume approach with Godunov flux approximation adapted for multiprocessor systems is used. It has been shown experimentally that the parabolic contraction and conical expansion ensure shock-to-detonation transition in a stoichiometric propane-air mixture under normal conditions at a very low minimal incident shock wave velocity of 680 AE 20 m/s, which approximately corresponds to a Mach number of 2. This result is important for novel jet propulsion systems with detonative burning of fuel-pulse detonation engines.
Science and Technology of Energetic Materials. – 2011. – Vol. 72, No. 4. – P. 116 – 122., 2011
The mathematical model, the numerical method and the parallelization technique are presented for the problems of detonation initiation by means of comparatively weak shock wave and propagation of detonation waves in threedimensional tubes of complex shapes. The mechanisms of detonation initiation in a tube with parabolic contraction and cone expansion and in a helical tube are analyzed. The results obtained are of interest both for basic research contributing to understanding of the mechanism of detonation initiation in tubes with curved walls and for applications from point of view of predictive modeling of accidents in chemical industry.
Physics of Fluids, 2020
In the present work, using a high-resolution three-dimensional numerical analysis the initiation and propagation mechanism of a detonation wave is studied in a circular tube with a hot jet initiation. The reactive Euler equations with a one-step two-species chemistry model are solved based on the structured adaptive mesh refinement technique. Influences of both a single hot jet and impinging double hot jets on the formation of the detonation wave are studied. For each case, the objective is to investigate the role of the tube wall on the initiation and propagation of the detonation wave. The result for both cases shows that the hot jet-induced bow shock forms a complex reflection structure in the circular tube. The reflection effect of the circular wall strengthens the shock and facilitates the formation of the Mach stem, which leads to the formation of the detonation wave. However, when the hot jet condition and the total area of jet hole remain the same, for the case of initiation using double hot jets, the reflection strength of the bow shocks weakens when the diameters of the hot jets become smaller. When using a single hot jet, the initiated detonation is overdriven and propagates in the twoheaded mode. In this initiation mode, by increasing the inflow Mach number, a four-headed mode detonation front is formed. While in the case of impinging double hot jets, a four-headed mode detonation front is initiated directly.
Detonation propagation from a cylindrical tube into a diverging cone
Journal of Thermal Science and Technology, 2020
The characteristics of the propagation of a detonation from a cylindrical tube of constant cross section into a diverging cone were experimentally investigated using the smoked-foil technique for three explosive gas mixtures: C2H2+2.5O2, 2H2+O2+4.5Ar, and C2H4+3O2+0.44N2. The initial pressure and the cone enlargement angle were varied as governing parameters. The results were summarized in terms of the ratio between the inner diameter of the cylindrical tube through which a detonation initially propagated and the detonation cell width d and of the cone enlargement half angle . Four patterns of detonation propagation were observed in the diverging cone: continuous propagation, re-initiation on the cone wall, re-initiation apart from the cone wall, and failure. The obtained results were qualitatively consistent with past experimental results reported by other researchers. However, quantitatively, the obtained results were dependent on the explosive gas mixtures, particularly on the so...
Transient dynamic response of tubes to internal detonation loading
Journal of Sound and Vibration, 2006
This paper reports the analytical and numerical modeling of transient-dynamic response of tubes to internal detonation loading. Since gaseous detonation involves loads that propagate at high speeds, the excitations of flexural waves in the tube wall become significant. Flexural waves can result in high strains, which may exceed the equivalent static strains by up to a factor of 4. The presented analytical model, which considers the effects of transverse shear and rotary inertia, provides a very good simulation of the structural response of cylindrical tubes with finite length to internal detonation loading. It is shown that the predictions provided by this model are in better agreement with the experimental results, as compared to the existing analytical models. In the numerical part of this study, several finite element analyses are carried out to obtain the structural response of the tube to pressure loads moving at different speeds. The results of the analytical and numerical simulations are compared with experimental results reported in the literature. r
Three-dimensional numerical simulation of detonations in coaxial tubes
Shock Waves, 2008
Three-dimensional numerical simulation of detonations in both a circular tube and a coaxial tube are simulated to reveal characteristics of single spinning and twoheaded detonations. The numerical results show a feature of a single spinning detonation which was discovered in 1926. Transverse detonations are observed in both tubes, however, the single spinning mode maintains the complex Mach reflection whereas the two-headed mode develops periodically from the single Mach reflection to the complex one. The calculated cell aspect ratio for the two-headed mode changes from 1.09 to 1.34 as the radius of axial insert increases from r 1 /R = 0.1 to 0.9. The calculated cell aspect ratio for r 1 /R = 0.1 is close to the experimental results without an axial insert. The formation of an unreacted gas pocket behind the detonation front was not observed in the single spinning mode; however, the two-headed mode has unreacted gas pocket behind the front near the axial insert.
Initiation of cylindrical detonation by rapid energy deposition along a line
Symposium (International) on …, 1998
Initiation of gaseous detonation in hydrogen, ethylene, and acetylene-air mixtures by a line source of condensed explosives (detonating cord) is investigated experimentally. Initiation in the cylindrical geometry is important in validating a general theory of initiation and has particular significance to the interaction of high-velocity projectiles with combustible gas. The flowfields generated by the detonating cord resemble the flows observed around blunt hypersonic projectiles in combustible gas, with oblique detonation being observed in good agreement with theoretical predictions. When the energy of the detonating cord greatly exceeds the critical energy per unit length to initiate a cylindrical detonation, the blast wave generated by the cord decays monotonically to the Chapman-Jouguet (CJ) detonation speed. As the source energy approaches the critical energy predicted by theoretical models of initiation, the results become increasingly complex. In these cases, the blast wave and combustion front first decay to sub-CJ velocity, then exhibit oscillations before the final onset of detonation. The initiation of gaseous detonation is also no longer sequential along the length of the cord and is instead associated with discrete explosion centers. This phenomenon is similar to what has been previously observed in spherical initiation, suggesting a universal mechanism of detonation initiation.