Detonation gaseous, initiation

Liquid and Solid Acetylene. Both the Hquid and the soHd have the properties of a high explosive when initiated by detonators or by detonation of adjoining gaseous acetylene (85). At temperatures near the freezing point neither form is easily made to explode by heat, impact, or friction, but initiation becomes easier as the temperature of the Hquid is raised. Violent explosions result from exposure to mild thermal sources at temperatures approaching room temperature. 

Solid particle-gaseous oxidizer systems have been studied because of applications to propints and expls (Refs 5 14), and hazards due to dust explns (Refs 1,3, 4, 6, 7, 10 15). Strauss (Ref 9) reported on a heterogeneous detonation in a solid particle and gaseous oxidizer mixt the study concerned A1 powder and pure oxygen in a tube. Detonations initiated, by a weak source were obtained in mixts contg 45-60% fuel by mass. Measured characteristics of the detonations agreed with theoretical calcns within about 10%, and detonation pressures of up to 31 atms were observed. With regard to solid particle-air mixts, detonations have not been reported only conditions for expln have been studied (Ref 2)... 

Egerton, A. and Gates, S.F., On detonation in gaseous mixtures at high initial pressures and temperatures, Proc. R. Soc., Lond. A, 114,152,1927. 

Thus, the elementary cellular structure could be regarded as an intrinsic characteristic of fhe detonation in a mixture at given initial composition, temperature, and pressure. The dimension of X is of fhe order of magnitude of millimeters or less for gaseous mixfures with oxygen, but several centimeters for less sensitive mixtures (even larger, for methane/air af afmospheric pressure). It decreases when the initial pressure increases. Its variation with the initial temperature is more complicated and depends on the value of fhe reduced activation energy of fhe chemical reactions. The value of... 

S.U. Schoffel and F. Ebert, Numerical analyses concerning the spatial dynamics of an initially plane gaseous ZND detonation. AIAA Progr. Astron. Aeron., 114, 3-31,1988. 

Original studies of gaseous detonations have shown no single sequence of events due primarily to what is now known as the complex cellular structure of a detonation wave. The primary result of an ordinary thermal initiation always appears to be a flame that propagates with subsonic speed. When conditions are such that the flame causes adiabatic compression of the still unreacted mixture ahead of it, the flame velocity increases. According to some early observations,... 

Calculate the detonation velocity in a gaseous mixture of 75% ozone (03) and 25% oxygen (02) initially at 298 K and 1 atm pressure. The only products after detonation are oxygen molecules and atoms. Take the AffjfO-,) I40kj/mol and all other thermochemical data from the JANAF tables in the appendixes. 

Refs 1) B. Lewis G. von Elbe,. Combustion, Flame, and Explosion of Gases , Oxford Univ Press, London (1938) la) K.I. Shchelkin, DoklAkadN 23, 636(1939) (On the theory of detonation initiation for gaseous mixtures in pipes) lb) K.I. Shchelkin, ZhEksper i TeoretFiz 10, 823(1940) (The effect of rough-... 

An expl material (solid, liq or gaseous) on proper initiation moves from right to left at deton velocity and passes into the deton zone which is stationary in space. Conditions thruout the deton zone are steady. The tremendous increase in thermal motion of the atoms or molecules as-they pass into the shock zone causes chemical reactions of great rapidity. When the expl products reach the end of the reaction zone they are in chem equilibrium. They can be maintained at these conditions if they are contained by a piston which moves uniformly to the left at the same speed at which the products emerge from the reaction zone. This speed is identical with the local velocity of sound in the gaseous products (See Fig 1 from Ref. l)... 

In order to study sub-detonation reactions and at the same time to take advantage of the available calibration information, the standardized test is modified as shown in Fig 8 reproduced from NOLTR 64-53 (Ref 59). Although this test retains the standardized donor/gap system, its acceptor is unconfined and much shorter. Chemical reaction is desurveillance of the acceptor. Burning is evidenced by the break-out of gaseous products. The curve for time of break-out (time of shock arrival at free surface to time gas is observed) can be extrapolated to give the critical pressures just to initiate the burning... 

On the theory of detonation initiation of gaseous mixts in pipes)... 

V.P. Karpov A.S. Sokolik, "On the Mechanism of Generation of Shock Waves, Their Amplification on Interaction with the Flame, and Transition to Detonation , Ibid, Paper 85, p 149 (Abstracts only) 89h) J.H. Lee et al, "Direct Initiation of Spherical Detonations in Gaseous Explosives , Ibid, Paper 86, p 150 (Abstracts only) 90)... 

G.G. Bach et al, "Direct Initiation of Spherical Detonations in Gaseous Explosions , Ibid, 853-64... 

DETONATION (EXPLOSION AND COMBUSTION), SPHERICAL (Spherical Blast, Spherical Front and Spherical Wave). Spherical detonations (explosion and combustion) are those in which initiation in the center of a charge (preferably spherical in shape) will cause formation of spherical shock and detonation waves. These waves move radially away from the charge into the surrounding medium (gaseous, liquid or solid) in such a manner that particles of their outer boundary (front) are always equidistant from the center of the charge in the manner shown in Fig on p 183 of Vol 2 of Encycl... 

Spherical detonation waves can also be produced by condensed expls (solid ot liquid), especially if the charges are spherical in shape and they are initiated in the center. The above discussion of Baum et al applies to both gaseous and condensed expls. Addnl information on spherical detonation of solid explosives can be obtd from the works of Landau 8c Stanyukovich (Ref 2), Jones Miller (Ref 3), Wecken Sc Muecke (Ref 4a), Lutzky (Ref 26), Rudlin (Ref 26a) and Green James (Ref 27)... 

Where p ° and Pj° are reference values for initial density and initial pressure, respectively usually set = 1.0 pjand p are arbitrary initial density pressure of gaseous mixt D p °and 0 are ideal deton vels... 

EXPLOSIVES ate solid, liquid and gaseous substances possessing the property, when subjected C3 either heat, impact, friction or other initial impulse, of undergoing a very rapid exothermic self propagating transformation or decomposition with the formation of mote stable materials (usually gases), accompanied by the production of a very loud noise (report) and the development of very great pressures and very high temperatures. This action is called explosion or detonation... 

E) G.G. Bach et al, "Initiation Criteria for Diverging Gaseous Detonations", 13thSymp-Combscn, The Combustion Institute, Pittsburgh, Pa (1971), pp 1097-1180... 

---