Detonation Wave propagation

Figure 7-53. Detonation velocity, V, static pressure, Pg, and reflected pressure, Pp developed by detonation wave propagating through hydrogen-oxygen mixtures in a cylindrical tube at atmospheric pressure at 18°C. By permission, U.S. Bureau of Mines, Bulletin 627 [43].

The extent to which a detonation will propagate from one experimental configuration into another determines the dynamic parameter called critical tube diameter. It has been found that if a planar detonation wave propagating in a circular tube emerges suddenly into an unconfined volume containing the same mixture, the planar wave will transform into a spherical wave if the tube diameter d exceeds a certain critical value dc (i.e., d > dc). II d < d.. the expansion waves will decouple the reaction zone from the shock, and a spherical deflagration wave results [6],... 

Fig. 9.1 Detonation wave propagation initiated by a point-source.

Following is a resume of paper by Fickett (Ref 2) If a cylinder of explosive is suddenly heated or struck at one end, a detonation wave propagates down the length of the charge with approximately constant velocity. This phenomenon is often treated by the model of von Neumann-Zel dovich. Transport properties are neglected, and the wave consists of a plane shock followed by a short reaction zone of constant length in which the explosive material is rapidly transformed into decomposition or detonation products. 

CA 49, 11285-86 (1955) (Detonation wave propagation in cartridges of small diameter) 33a) N. Manson, "Formation and Velocity of Spherical... 

Detonations. The magnitude of the decrease in vclocit r which occurs across a detonation wave may be more easily visualized in terms of the Mach number of the detonation wave, since the Mach number behind the wave is one, for the Chapman-Jouguct case, usually encountered in practice. For a given initial pressure and temperature, the velocity with which a supersonic detonation wave propagates itself through an unburned mixture is a function of the initial mixture composition. Figure 5 presents some experimental (32) Mach numbers of detonation waves as a function of initial mixture composition. Breton (7), Laffitte and Breton (23), Bone and Fraser (4), Bone, Fraser... 

A critical characteristic of energetic materials is the Chapman-Jouguet (CJ) state. This describes the chemical equilibrium of the products at the end of the reaction zone of the detonation wave before the isentropic expansion. In the classical ZePdovich-Neumann-Doring (ZND) detonation model, the detonation wave propagates at constant velocity. This velocity is the same as at the CJ point which characterizes the state of reaction products in which the local speed of sound decreases to the detonation velocity as the product gases expand. 

FIGURE 6.6. Schematic illustration of the velocity profile behind a detonation wave propagating in a tube all velocities in the - x direction. 

Figure 7. Instantaneous configuration of a detonation wave propagating in a 3D cylinder of radius 150 A. Atoms are colored according to their potential energy (yellow for unreacted AB material, blue for and B2 detonation products).

Figure 12. LX-17 detonation wave propagating between brass (left side) and beryllium (right side).

Since detonative explosives are kept in various types of vessels used for different objectives such as warheads, bombs, and industrial mines and civil engineering, the performance of the explosives is dependent not only on the chemicals and mass of explosives but also the physical shape of explosives. When a detonation is initiated at a point in an explosive charge, the detonation wave propagates spherically in all directions. When a detonation is initiated at a point at one end of an explosive charge, the detonation wave propagates semi-spherically in the charge. Thus, the... 

A recent review of detonation theory is given elsewhere [12]. Models of the phenomenon envisage a detonation wave propagating into unreacted material with a sharp discontinuity in temperature and pressure at the detonation front. A reaction zone of a millimeter or smaller dimensions and yielding the equilibrium quantities of reaction products at high temperature and pressure abuts the up-stream side of the front. Using macroscopic hydrodynamic-thermodynamic theory, the energy released, and an equation of state for the assumed products, detonation velocities, pressures, and temperatures may be calculated in certain cases. 

In a steady detonation wave propagating along the length of a cylindrical charge of a condensed explosive at 4-9 km/sec, it is assumed the product species exist momentarily at high pressures and temperatures of the order of 100-500 kbar, and 2000-5000°K, respectively. It is further assumed that ... 

Radial losses of mass, momentum, and energy through the lateral surface of the cylinder do not occur. The detonation wave propagates along the axis of the cylindrical charge and is confined laterally by the infinite diameter explosive (the minimum diameter which can support hydrodynamic detonation at its maximum steady-state rate). 

Detonating explosives syn. high explosives are unstable chemicals or mixtures that react almost instantly as a shock or detonating wave propagates through the entire mass from the initiation point at supersonic speeds that can approach 8,000 or 9,000 m/s in the case of nitroglycerine. Reaction occurs at the wave front. 

The classic detonation theory has proved that the stable/steady detonation waves of explosives propagate with CJ rate and there are sonic flows in the boundaries of detonation reactions. If the detonation waves propagate faster than CJ rate, there are subsonic flows in the boundaries of reactions. The classic detonation theory predicted that there were sustaining stable/steady detonation waves and possible special unsustaining detonation waves. The spread rates of ultrasonic waves in the boundaries of reactions are eigenvalue detonation rates. 

Tlie principle of the continuous determination of detonation velocity is based on the continuous oscilloscopic recording of an electric resistance change of special types of probes through which constant current flows, caused the detonation wave propagation through the test explosive charge. 

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