Detonation combustion models

M. W. Beckstead and co-workers, "Convective Combustion Modelling AppHed to Deflagation Detonation Transition," in Proceedings of the 12th JANNAF Combustion Meeting, Pub. No. 273, Chemical Propulsion Information Agency (CPIA), Johns Hopkins University, Laurel, Md., 1975. 

Although the status of many 3D codes makes it possible to carry out detailed scenario calculations, further work is needed. This is particularly so for 1) development and verification of the porosity/distributed resistance model for explosion propagation in high density obstacle fields 2) improvement of the turbulent combustion model, and 3) development of a model for deflagration to detonation transition. More data are needed to enable verification of the model in high density geometries. This is particularly needed for onshore process plant geometries. 

Model of Transition from Combustion to Detonation in Porous Explosives... 

Fig 15 Model of transition from combustion to detonation in porous explosives (Ref 68)... 

A. Analytical Models of Propellant Combustion and Detonation 57) N.S. Cohen C.F. Price, Combustion of Nitramine Propellants , JSpacecraft -Rockets 12 (10), 608-12 (1975) CA 84,... 

The techniques just described have been extensively used in modeling reactive flow problems at NRL. Efficient solution of the coupled ordinary differential equations associated with these problems has enabled us to perform a wide variety of calculations on H2 °2 anC Ha/Oo mixtures which have greatly extended our understanding of tne combustion and detonation behavior of these systems. In addition numerous atmospheric problems have been studied. Details on these investigations are provided in references (7) and (9). 

S. Z. Burstein, S. S. Hammer, and V. D. Agosta, Spray Combustion Model with Droplet Breakup Analytical and Experimental Results, in Detonation and Two-Phase Flow, vol. 6 of Progress in Astronautics and Rocketry, S. S. Penner and F. A. Williams, eds.. New York Academic Press, 1962, 243-267. 

Because we work on such a small scale, we can be somewhat venturesome in making measurements. We want to describe briefly some measurements of species that have not been reported in explosives by any other method, namely carbon clusters. The problem of soot formation is certainly a long standing one in any hydrocarbon combustion study as well as in modeling detonations. For example, neglecting the heat release from soot formation in... 

The Chapman-Jongnet (CJ) theory is a one-dimensional model that treats the detonation shock wave as a discontinnity with infinite reaction rate. The conservation equations for mass, momentum, and energy across the one-dimensional wave gives a unique solution for the detonation velocity (CJ velocity) and the state of combustion products immediately behind the detonation wave. Based on the CJ theory it is possible to calculate detonation velocity, detonation pressure, etc. if the gas mixtnre composition is known. The CJ theory does not require any information about the chemical reaction rate (i.e., chemical kinetics). 

The flux-corrected-transport technique was also used by Phillips (1980), who successfully simulated the process of propagation of a detonation wave by a very simple mechanism. The reactive mixture was modeled to release its complete heat of combustion instantaneously after some prescribed temperature was attained by compression. A spherical detonation wave, simulated in this way, showed a correct propagation velocity and Taylor wave shape. 

Assume that blast modeling on the basis of deflagrative combustion is a sufficiently safe and conservative approach. (The basis for this assumption is that an unconiined vapor cloud detonation is extremely unlikely only a single event has been observed.)... 

The consequence of the second approach is that, if detonation of unconfined parts of a vapor cloud can be ruled out, the cloud s explosive potential is not primarily determined by the fuel-air mixture in itself, but instead by the nature of the fuel-release environment. The multienergy model is based on the concept that explosive combustion can develop only in an intensely turbulent mixture or in obstructed and/or partially confined areas of the cloud. Hence, a vapor cloud explosion is modeled as a number of subexplosions corresponding to the number of areas within the cloud which bum under intensely turbulent conditions. 

Kuhl, A. L., R. E. Ferguson, K. Y. Chien, J. P. Collins, and A. K. Oppenheim. 1995. Gasdynamic model of turbulent combustion in an explosion. Combustion, Detonation, Shock Waves. Zel davich Memorial Proceedings. Eds. A. G. Merzhanov and... 

Detonation from Burning, Transition of. See under Detonation (and Explosion) Development (Transition) from Burning (Combustion) or Deflagration and the following paper by A. Macek, "Transition from Slow Burning to Detonation. A Model for Shock Formation in a Deflagrating Solid , NOLNavOrd Rept 6105(1958) [See also Andreev Belyaev(1960), 141-44]... 

The velocity of advance of the front is super sonic in a detonation and subsonic in a deflagration. In view of the importance of a shock process in initiating detonation, it has seemed difficult to explain how the transition to it could occur from the smooth combustion wave in laminar burning. Actually the one-dimensional steady-state combustion or deflagration wave, while convenient for discussion, is not easily achieved in practice. The familiar model in which the flame-front advances at uniform subsonic velocity (v) into the unburnt mixture, has Po> Po> an[Pg.249]

In a stationary detonation wave, the shock front is followed by a zone of chemical reaction which can be considered as an ordinary stationary-state combustion wave propagating through the denser and hotter gases behind the shock front (Fig. XIV.7). Such a combustion wave is characterized by a pressure decrease and a temperature increase across the flame front. Because of this and because, in the stationary state, the flame front must follow the shock front at a fixed distance, the model of the moving surface is not quite adequate to describe a stationary detonation/ A further difference between the two is that, whereas in the mechanical shock the surface velocity Vb was an independent parameter at the disposal of the experimenter, in the detonation the chemical composition of the reacting gases is the collective parameter which replaces vt and is the means by which the experimenter can control the detonation velocity. 

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