Study on initiation characteristics of rotating detonation by auto-initiation and pre-detonation method with high-temperature hydrogen gas
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Equivalence ratio
Deflagration
Equivalence ratio
Detonation velocity
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Deflagration
Equivalence ratio
Detonation velocity
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Abstract The explosives with various molecular‐atomic structures substantially differ by their detonation velocities and brisance but often are similar by the expansion of their detonation products (DP's) which mainly consist of the same molecules. Such explosives referred to as “usual” show the relationship between ϱD and brisance determined by different methods. There are linear correlation relations between the results obtained. This relationship is not observed with the “unusual” explosives which differ from the “usual” ones by the chemistry of detonation processes. These explosives include liquid explosives, explosive‐oxidants. CNO‐ and HNO‐explosives and also CHNOF‐explosives. Their calculation of thc detonation parameters and brisance from the same criterions which characterize the chemical composition of the explosives and the detonation products, results in some errors. Taking these differences into account it is possible in some cases markedly to increase the accuracy of the detonation parameters. As an example is the calculation of the detonation pressure to within 3% based on the linear correlation relation between the pressure (P J ) and the relative detonation impulse (I rel ) which characterizes the charge ability to do work at the initial stages of thc expansion of the detonation products: The relative impulse, in its turn, may be calculated both for “usual” and “unusual” explosives from the atomic composition of an explosive, its density and the enthalpy of the formation with the error that does not exceed the experimental (2%).
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Abstract It was shown by Kamlet and Jacobs that an explosive's detonation velocity D and detonation pressure P D are governed largely by (a) the loading density of the explosive, and (b) a factor φ that depends upon the number and masses of gaseous detonation products and the accompanying heat release. For a series of different explosives, we show that the density and φ are both important in determining D and P D . For a given explosive, however, φ is approximately constant and so D and P D correlate quite well with the density, as has long been known. We propose that φ be interpreted as a measure of the intrinsic detonation potential of an explosive, that is independent of the external factors that affect the loading density. Comparison of φ values for different explosives can provide useful insights into features that promote high detonation velocities and detonation pressures. The parameter φ is related to a property introduced earlier, explosive power, but φ takes into account the fact that part of the carbon content of an explosive typically remains as a residue after the detonation process.
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The speed of strong detonation and its driving abilities in multiple stage explosive/flyer system have been studied by both analysis and experiments.The wedge test method is employed to record the detonation front ,s track for both TNT/RDX(40/60) and JO 9159 explosives.The abilities of strongly detonating explosive slab in driving metallic flyers to high speed are shown in our calculation model.Calculated results agree with experimental results.The performances of strong detonation are illustrated.
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In this paper, two dimensional detonation propagation in partially prevaporized n-heptane sprays is studied by using Eulerian/Lagrangian methods. The effects of droplet preevaporation on the detonation propagation are investigated. The general features and detailed structures of two-phase detonations are well captured with the present numerical methods. The results show that the detonation propagation speed and detonation structures are significantly affected by the preevaporated gas equivalence ratio. The numerical soot foils are used to characterize the influence of preevaporated gas equivalence ratio on the detonation propagation. Regular detonation cellular structures are observed for large preevaporated gas equivalence ratios, but when decreasing the preevaporated gas equivalence ratio, the detonation cellular structures become much more unstable and the average cell width also increases. It is also found that the preevaporated gas equivalence ratio has little effects on the volume averaged heat release when the detonation propagates stably. Moreover, the results also suggest that the detonation can propagate in the two-phase heptane and air mixture without preevaporation, but the detonation would be first quenched and then re-ignited when the preevaporated gas equivalence ratio is small or equal to zero.
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On the common circumstances the detonation of explosives has a steady propagation rate and can be satisfactorily explained by Chapman-Jouguet's theory on this phenomenon. Hence, this type of detonation is more frequently called the Chapman- Jouguet (C-J) detonation. The detonation properties such as pressure, density, and temperature, of the detonation products are often characterized as the C-J values of the explosive that represent the corresponding maximums of the variables in the detonation products. However, when an explosive is initiated in some special ways, for instance, high velocity impact of a flyer plate, a strong detonation with properties higher than C-J values will be induced in the explosive. This strong detonation is what we called the overdriven detonation of explosive. The use of overdriven detonation expects to provide much more work to the surrounding matter than does the common C-J detonation. In order to have a basic knowledge of this detonation phenomenon, we designate an experimental set- up for the purpose of acquiring the overdriven detonation in high explosive. The set-up uses a circular metal plate accelerated by a piece of cylinder explosive (donor) to impact another cylinder explosive (acceptor), inducing a detonation wave in the acceptor explosive. The donor explosive used is PBX (85%wt HMX and 15%wt binder) explosive cylinder that has the detonation velocity of 7.84 km/s and the detonation pressure of 25.24 GPa and the acceptor explosive cylinder is SEP (65%wt PETN and 35%wt paraffin) with the detonation velocity of 6.97 km/s and the detonation pressure of 15.9 GPa. The impactor is the copper disc with the same diameter of the donor explosive and 1 mm and 2 mm thicknesses respectively. The detonations occurred in the acceptor explosive from the impact of copper flyer were recorded by the high-speed camera (IMACON 790). The photographs make us possible to estimate the detonation velocities from the distance and time data on them. In addition, we also make a numerical visualization on this phenomenon using a 2-D Lagrangian hydrodynamic code. The calculation, to somewhat extent, reproduces the consequences of the current experimental results.
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The shocking-to-detonation transition(SDT) of insensitive high explosives(IHE) including LX-17 and ultrafine TATB was studied by using Hybrid reaction rate model and modified JWL equation of state(EOS),and phenomena of colliding diverging detonation was numerically simulated.The calculated shocking-to-detonation transition(SDT) of insensitive high explosives is in agreement with the experimental result,and the calculated peak pressure in colliding diverging detonation increases 10%.
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An experimental study of detonation was carried out for mixtures of blended fuels (H2/CH4 or H2/C3H8) and air. The detonation tube length is 7m and its inner diameter is 10mm. Fast deflagration and detonation speeds were measured by means of photodiodes, which are fitted with the tube by a special technique and detect light emitted from the reaction zone. The effects of mixing ratio of fuels on the behavior of deflagration to detonation, detonation speed and detonability limits were investigated. There exists a deflagration speed at the exit of the spiral that establishes detonation, and a reproducible pulsating deflagration speed can be seen near the limit of detonation. Detonation velocity increases monotonically with equivalence ratio or the ratio of hydrogen in blended fuels.
Deflagration
Equivalence ratio
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Abstract A new explosive ink based on 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) was designed and prepared. The explosive ink was deposited into micro‐size grooves by using direct ink writing (DIW) technology and its detonation properties in an explosive network were explored. The properties of impact sensitivity, detonation velocity and critical size of detonation were determined and analyzed. The results show that this explosive has a good impact safety. When the LLM‐105 content is 88 % and the density is 95 % TMD, the detonation velocity and critical size of detonation values are 7,771 m/s and 0.5×0.5 mm respectively. Moreover detonation velocity results indicated the explosive ink in micro‐size grooves loaded by DIW was uniform.
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