Excitation Of Detonation Research Articles

ОБРАЗОВАНИЕ ПЕРВИЧНЫХ ОЧАГОВ ВОСПЛАМЕНЕНИЯ ПРИ УДАРНОМ ИНИЦИИРОВАНИИ ВЗРЫВЧАТЫХ ВЕЩЕСТВ

In the article, an attempt was made to develop a theory of formation of primary decomposition sources in energy-saturated materials. Meanwhile, probabilistic values are used: relative speed of primary decomposition "sources" occurrence and the quantity of those sources. A special role in the initiation is given to the occurrence of so-called clusters of primary sources, which sizes exceed the critical one, which is determined by the charge size and the conditions of initiation. The proposed model defines the optimal initiation speed leading to guaranteed detonation excitation and becomes a prerequisite for blasting explosives probabilistic initiation theory development.

ANALYSIS OF THE POSSIBILITY OF USING SMALL CUMULATIVE CHARGES TO NEUTRALIZE AMMUNITION

The article presents the results of a study of the possibilities of using small cumulative charges to neutralize (destroy) ammunition during demining operations or during their disposal. The relevance of research is proved and the efficiency of using small cumulative charges as liquidators' charges for neutralization (destruction) of ammunition during demining works or during their utilization is confirmed. The authors analyzed research and publications on explosive technologies, which cover the issues of blasting in construction, mining and military field. The basic principles of theoretical substantiation of the behavior of explosive charges at the established penetration of a cumulative jet, determination of critical characteristics of a cumulative jet necessary for initiation of detonation and estimation of mass of the reacted explosive at penetration of a cumulative jet into a charge without initiation of detonation are given. The composition and construction of small cumulative charges "MKZ-1", "MKZ-2", "MKZ-3" developed by OOO "Vognyana Varta" are considered. The results of field experiments during which the behavior of explosive charges under the influence of cumulative jet was studied. The use of cumulative charges as liquidators for explosive destruction of structures and devices equipped with loaded explosives without excitation of detonation are proposed and substantiated. According to the results of research, the effectiveness of the use of MKZ for neutralization (destruction) of ammunition during demining works or during their utilization is confirmed. It is proved that the developed MKZ meet the requirements for modern means of ammunition disposal and have satisfactory prospects for further improvement in reducing the mass of the explosive while increasing the effectiveness of the application.

Diffraction of waves in combustible mixtures

The results of investigations of combustion and detonation wave diffraction, including the nonstationary regimes of combustion–detonation transition, are presented. A wide variety of transient regimes upon diffraction have been revealed. On the basis of diffraction investigations, a criterion of detonation excitation is proposed and formulas for estimating the critical energy of initiation of plane, cylindrical, and spherical waves have been obtained. The calculated values are in good agreement with the experiment.

Distinctive features of galloping detonation in a supersonic combustible-mixture flow under an inert gas layer

The problem of detonation initiation in a supersonic flow of a stoichiometric propane-air mixture occupying partially or completely the cross-section of a plane channel is considered. The initiation in the flow is produced by a step or a wall completely cutting off the flow. The study is conducted within the framework of one-stage combustion kinetics. A numerical method based on the Godunov scheme is employed. The critical conditions for detonation formation are determined in terms of the oncoming flow velocity. A previously unknown mechanism of detonation propagation is found; it is related with the presence of the combustible mixture in the wall layer under an inert gas layer. It is due to the formation of a complicated wave structure of the flow characterized by the penetration of a shock wave formed in the inert gas layer into a combustible mixture layer ahead of the detonation wave with the result that the latter layer is heated and ignited. The process as a whole is periodic in nature, as distinct from the conventional cellular detonation in a homogeneous fluid. Many problems arise in connection with the use of detonation in engines and other power plants. The most important among them are detonation excitation and stabilization in combustion chambers. The detonation initiation within a layer under conditions of unbounded space and a fluid at rest was experimentally investigated in [1]. In the case of a combustion chamber bounded in the transverse direction, some new effects accompanying the detonation might be expected.

Numerical Simulation of Detonation Excitation at Shock Wave Interaction with Dust Cloud in Channel

Numerical Simulation of Detonation Excitation at Shock Wave Interaction with Dust Cloud in Channel

Use of pulsed radiography in studies of shock wave initiation of TATB

Pulsed radiography is used to study the excitation of detonation in plasticized TATB. Conditions are determined for setting up experiments in which the outcome of shock loading is nonunique. Experiments in which desensitization and sensitization of TATB occur with preliminary loading of the samples are described.

Diffraction estimate of the critical energy for initiation of gaseous detonation

A criterion for the excitation of detonation is proposed: the critical initiation energy equals the work performed by the expanding detonation products along a path length equal to the longitudinal dimension of a cell. The initial radius of the layer is chosen to be equal to the radius of the detonation wave diffracted at 90° edge at the time the axial rarefaction wave converges on the axis of the gaseous charge. Formulas are obtained for estimating the critical energy for initiation of plane, cylindrical, and spherical detonation waves. The calculated values are in good agreement with experiment.

Critical conditions of the excitation of detonation by a thermal mechanism

The authors take into account the dynamics of temperature variation in the bridge when an electric current flows. The system of differential equations describing the dynamics of temperature variation in the bridge and in the surrounding layers of explosives is presented, and the critical ignition conditions are determined by numerical and analytical methods. Analytical dependences are obtained which allow the critical conditions for ignition of explosive from an incandescent bridge to be calculated, and the theoretical results are compared with experimental data. The theoretical curves describe the experimental results with satisfactory accuracy.

Self-sustaining detonation in liquids with bubbles of explosive gas

The authors have the goal of explaining the properties and conditions of excitation of detonation in relation to the value of beta and the physiochemical composition of the bubble medium. It was shown that a detonation wave propogates in the above-examined bubble systems by the mechanism of microexplosions: bubbles compressed in the pressure field expolde and send out shock waves to the surrounding liquid. These shock waves in turn compress and ignite bubbles located upstream. A similar mechanism was examined previously to describe the excitation of low-velocity detonation in liquid explosives.

Transient processes in the impact initiation of TNT

As well as experimental methods, the method of mathematical modeling is now used in investigating processes of detonation excitation in condensed explosives. In constructing a mathematical model of the initiation of heterogeneous explosives, the material in the chemical-reaction region behind the shock-wave front is represented, as a rule, in the form of a mixture of unreacted explosives and detonation products (DP). Modern experimental methods do not allow measurements of the gasdynamic and thermodynamic parameters of the individual components in the reaction region to be made and, therefore, in developing the model, it is necessary to use certain assumptions regarding the evolution of the initiation process. The most common for all models, in practice, are the assumptions that the reaction develops from individual sources (hot points) and that the mass velocities and pressures of the individual components in the reaction region are equal. In [I, 2], the temperatures were also assumed to be equal.

Shock initiation of detonation in nitroglycerin

So far the problem of the conditions of excitation of detonation in nitroglycerin (NG) has received little attention. It is known that NG is capable of exploding under the impact of a hammer, but sometimes does not explode under the impact of a bullet [1] or under the action of a shock wave produced by an explosive charge [2]. The processes associated with the initiation of NG may be affected by several factors: the time and nature of the shock loading, the dimensions and material of the vessel , etc.