Deflagration combustion models

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. 

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]

GASFLOW models geometrically complex containments, buildings, and ventilation systems with multiple compartments and internal structures. It calculates gas and aerosol behavior of low-speed buoyancy driven flows, diffusion-dominated flows, and turbulent flows dunng deflagrations. It models condensation in the bulk fluid regions heat transfer to wall and internal stmetures by convection, radiation, and condensation chemical kinetics of combustion of hydrogen or hydrocarbon.s fluid turbulence and the transport, deposition, and entrainment of discrete particles. 

To overcome this problem, they proposed a working-fluid heat-addition model. This model implies that the gas dynamics are not computed on the basis of real values for heat of combustion and specific heat ratio of the combustion products, but on the basis of effective values. Effective values for the heat addition and product specific heat ratios were determined for six different stoichiometric fuel-air mixtures. Using this numerical model, Luckritz (1977) and Strehlow et al. (1979) systematically registered the properties of blast generated by spherical, constant-velocity deflagrations over a large range of flame speeds. 

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.)... 

Rogg, B., A. Linan, and F. A. Williams. 1986. Deflagration regimes of laminar flames modeled after the ozone decomposition flame. Combustion Flame 65 79-101. 

The problem of determining the propagation velocity of a deflagration wave was first studied by Mallard and le Chatelier [1], who considered heat loss to be of predominant importance and rates of chemical reactions to be secondary. The essential result that the burning velocity is proportional to the square root of the reaction rate and to the square root of the ratio of the thermal conductivity to the specific heat at constant pressure was first demonstrated by Mikhel son [2], whose work has been discussed in more recent literature [3], [4]. Independent investigations by Mallard s student Taffanel [5] and by Daniell [6] based on simplified models of the combustion wave reached the same conclusion. Subsequently, improved basic equations became available for use in theoretical analyses. 

Let us now consider combustion mechanisms that, strictly speaking, are not represented by the model illustrated in Figure 7.1. Specifically, at the interface in Figure 7.1, let us introduce the dispersed phase mentioned in Section 7.1. The consequent occurrence of two-phase flow adds substantial complication to the deflagration mechanism. 

The theoretical model and numerical method outlined in the above sections were implemented to study steady-state combustion of nitramine monopropellants [33.34], laser-induced ignition of RDX [39,40], and steady-state combustion of nitramine/GAP pseudo-propellants [37-39]. The analyses were carried out over a broad range of operating conditions. Various important burning and ignition characteristics were investigated systematically, with emphasis placed on the detailed flame structure and the effect of the subsurface two-phase layer on propellant deflagration. 

The Sandia code CONTAIN is a lumped parameter code with mechanistical models for simulating the physical and chemical conditions in the nuclear containment to predict hydrogen and steam concentration distribution as well as the consumption of H2 by respective combustion. Assuming a core meltdown accident and no vessel breach, i.e., no corrosion/concrete interaction, the code has predicted a thermally stratified containment atmosphere with relatively low temperatures in the central and lower regions which would permit steam condensation. Concerning H2 deflagration, CONTAIN predicts respective bums, if sprays are used for steam removal [56],... 

Chippett S (1984) Modeling of vented deflagrations. Combust Flame 55 127-140 Bjerketvedt D, Bakke JR, van Wingerden K (1992) Gas explosion handbook, GexCon... 

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