Deflagration convective

However, it has been observed experimentally that fast reactions can proceed at least transiently at rates that are significantly below those of a detonation in a dense medium, yet are too rapid to be treated as normal deflagrations. Some of the observations are evidently due to the low density of the sample in other cases, such as with ammonium nitrate, the propagation rates are limited by chemical kinetics. Such occurrences can be explained, at least conceptually, within the framework of hydrodynamic theory. However, two other regimes have been described for which well-conceived theories do not exist. These are low-velocity detonation and convective deflagration. 

The former is typified by low reaction pressures and may be initiated by comparatively mild shocks (about one hundredth of that required to initiate a full detonation in the same substance). It is not a well-defined phenomenon, but it occurs most typically in films of liquid and in porous solids transitions to full detonation are common. Convective deflagration in porous solids is a process leading to reaction rates of 1-100 m/sec that are strongly pressure and con-... 

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. 

Deflagration This term refers to an exothermic reaction in a material which propagates from the burning gases to the unreacted material via conduction, convection and radiation. In this process the reaction zone progresses at a rate less than the velocity of sound. 

Ignition of a fuel-oxidizer mixture occurs when an external source of energy initiates interactions among the controlling convective, transport and chemical processes. Whether the process results in deflagration, detonation, or is simply quenched depends on the intensity, duration, and volume affected by an external heat source. Ignition also will depend on the initial ambient properties of the mixture which determine the chemical induction... 

When a premixed gas-oxidant cloud is ignited, the flame can propagate in two different modes through the gas mixture—deflagration and detonation. Deflagrations propagate at subsonic speeds relative to the unburned mixture and the heat and mass are transported by conduction, diffusion, and convection. Gas mixture detonations propagate at speeds faster than the local sound speed of the unburned gas. In a gas mixture detonation, a shock wave is sustained... 

For the bicomposition liquid explosives or severely volatile explosives, there is no obvious deflagration stage in the change process from combustion to detonation. Convection combustion develops into detonation directly. The key feature of this change is that the detonation occurs in the fronts of convection combustion. In volatile liquids, the convection combustion develops rapidly, and forms shock waves in the front of flame fronts. The pressure of liquid surfaces accelerates the heat transfer into the inside of liquids, and leads to the heat explosion in local zone, then to the detonation of other space. If liquid explosives are charged in closed containers, it takes a time period from ignition to detonation of explosives. 

If the volatile fuel and air are well-mixed and react to generate a power density Q (heat of combustion per unit volume per unit time, W/m ), a portion of which accumulates in the reaction volume as a rise in the temperature of the fuel/air mixture and a portion of which is lost to the surroundings at ambient temperature Ta by convection and radiation, the first law energy balance for the fuel/air mixture during deflagration (burning) is... 

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