Detonation gas

Flessner, M. F. and Bjorklund, R. A. 1981. Control of Gas Detonations m Pipes. CEP Loss Prevention Manual, 14, 113-126. American Institute of Chemical Engineers, New York, NY. 

Bull, D. C., J. E. Elsworth, M. A. McCleod, and D. Hughes. 1981. Initiation of unconflned gas detonations in hydrocarbon-air mixtures by a sympathetic mechanism. Progress in Astronautics and Aeroruiutics. 75 61-72. AIAA Inc., New York. 

N)5Q. N(N02).CH3, mw 377.17, N 26.00%, OB to C02 —14.85%, colorless cryst, mp 132° (evolves gas), detonates upon heating. Sol in chlf. Prepn by nitration of a mixt of 3,5-dinitro-N-methylaniline 3,5-dinitro-N,N-dimethylani-line. It is unstable and decomposes readily above... 

Related to both DDT and initiation by shock is the initiation of solid expls by gas detonations. Weiss et al (Ref 61) found that PETN at 0.7g/cc could be initiated by a gas detonation of 21 atm initial pressure, which produced an initial (presumably in the PETN) pressure of 2kbar. Under these conditions initiation delay in the PETN was less than one microsecond... 

Except for 02 (a product in oxygen-rich expls), equilibria (1) thru (6) account for all, major detonation products of condensed CHNO expls. In gas detonations (ie, at low detonation pressures) such species as OH, H etc may also exist. In experimental measurements of detonation products (to be discussed later) HCN frequently appears as a minor product... 

Zel dovich Ya.B., Theory of combustion and gas detonation, Moscow Akad. Nauk SSSR, 1944. 

A.A. Vasiliev and V.V. Grigoriev, Critical conditions for gas detonations in sharply expanding channels, Fizika Gorenyia i Vzryva, 16,117-125,1980. 

Unfortunately, the extensive work on gas detonations has had little impact on the development of the theory for condensed phas es. The reason is the lack of a reliable equation of state for these. While fundamental significance must be achieved eventually, an empirical fit to actual performance would be helpful at present. A sophisticated general equation for the isentrope, which is a C-J isentrope, is called for. Above 150-200 kbar, the polytropic (gamma-law) equation of state is valid (Skidmore Hart, in Ref 19, p 47). 

Nauk (UkrainRSR) 1966(7), 871-74 CA 65, 19919 (1966) "Criterion of Uni-dimensional Instability of Gas Detonations (The criterion was derived by using Zel dovich-Von Neumann model, which represents a detonation wave in an ideal gas as a stationary complex consisting of a shock wave and the front of an instantaneously occurring reaction with a characteristic induction time that follows the shock wave at a definite distance. The results showed that the criterion assumes the form dependent... 

A phenomenon in gas detonation which is qualitatively similar to the decay zone observed above is described by White (Ref 67b). 

This equation shows that ID will increase as p0D increases, eg I0 will be much larger for HE than for gas detonations because Peas ie... 

Initiation (of Condensed Explosives) by Gas Detonations does not involve the same phenomena as Initiation by Primers or Boosters. The pressures generated in gas detonations are too low to produce sufficiently intense shocks in condensed explosives for shock phenomena to play a major role in the initiation of the latter. Even the energetic C2H2 + 02 detonation produces a detonation pressure of only ca 43 atm for an initial gas pressure of 1 atm. The max shock... 

Thus gas detonations initiate condensed explosives (if at all) by some direct heat transfer process. In oxy-acetylene detonations, the equilibrium temperature (CJ temp) is quite high 4500°K... 

Gas detonation at reduced initial pressures were studied by Vasil ev et al (Ref 8). They point out the errors in glibly comparing ideal lossless onedimensional computations with measurements made in 3-dimensicnal systems. We quote In an ideal lossless detonation wave, the Chapman-Jouguet plane is identified with the plane of complete chemical and thermodynamic equilibrium. As a rule, in a real detonation wave the Chapman-Jouguet state is assumed to be the gas state behind the front, where the measurable parameters are constant, within the experimental errors. It is assumed that, in the one-dimensional model of the detonation wave in the absence of loss, the conditions in the transient rarefaction wave accompanying the Chapman-Jouguet plane vary very slowly if the... 

Close to the theory of gas detonation is the theory of transonic and supersonic flow in a tube and in nozzles developed by G. N. Abramovich and L. A. Vulis,27 and also the problem of supersonic motion of a body (a blunt or sharp bullet) in an explosive mixture. 

Theoretical analysis of gas detonation leads to the conclusion that a shock wave propagates at the detonation front, compressing and heating the gas mixture. The chemical reaction runs in the already compressed gas, and it is only after completion of the reaction that the state of the explosion products calculated in the classical theory is attained (pressure pc, velocity wc, temperature Tc). In particular, in the wave front the velocity w1 and the pressure p1 of the compressed gas are approximately twice as large as in the reaction products w1 2wc, p1 2pc. The amount of the compressed gas at the pressure px and the thickness of this layer are proportional to the chemical reaction time, r. 

Under the simplest assumptions, that the chemical reaction rate depends on the compression temperature Tx (corresponding to a time rx), while the reaction itself runs uniformly over the entire cross-section of the tube, it may be concluded that propagation of detonation is possible only in the case when the ratio rx/d is less than some quantity. Starting from these assumptions, an investigation was performed at the Combustion Laboratory of the AS USSR Institute of Chemical Physics on gas detonation in a tube whose diameter was equal to 305 mm, i.e., 10-15 times greater than in ordinary laboratory conditions. It could be expected that detonation of mixtures with greater... 

Gas detonations were used to initiate low d pressings of RDX and other expls (Ref 19a). The initial gas pressure required to initiate RDX at 0.9g/cc, within 1 microsec, was 26 atm. At lower gas pressures the induction times increased, and at still lower pressures no detons were obtained. It was concluded that unconfined external gas detons will not initiate deton in a pile of RDX... 

It was mentioned above that the only approximation in the above eqns for ideal gas detonation is the neglect of p0 in comparison to pj. Unfortunately, this is not always completely justified because p0 can be of the order of O.lpj. It is simple enough to derive equations in which p0 is included. Since the writer has never seen a correct set of such equations in the literature, the equations he derived (unpublished results)... 

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