Surface combustion

The alloy powder (used in hydrogen-storage systems) may ocasionally be pyrophoric after hydriding-dehydriding operations, igniting when placed on a combustible surface (e.g. weighing paper). 

Combustible surfaces Combustible components Interior protection and all exterior surfaces... 

Niioka, T., Mitani, T and Ishii, S Observation of the Combustion Surface by Extinction Tests of Spinning Solid Propellant Rocket Motors, Proceedings of the 11th International Symposium on Space Technology and Science, Tokyo, 1975, pp. 77-82. 

Diffusion Flame. When a slow stream of fuel g s flows from a tube into the atmosphere, air diffuses across the boundary of the stream and Brms an envelope of expl mixture around a core of gas. The core decreases in height until it disappears at some distance above the tube. It thus assumes the shape of a cone. On ignition, a flame front spreads thru the mixture and stabilizes itself around the cooe of fuel gas. The hydrocarbons in common fuel gases crack to form free C H. The shell of carbon-bearing gas so formed gives such flames their luminosity Turbulent Jet Flame. When a gas stream issues from an orifice above a certain critical velocity, it breaks up into a turbulent jet that entrains the surrounding air. The flame of such a jet consists of random patches of combustion and no cohesive combustion surface exists... 

The reaction of the two systems to an ignition stimulus is markedly dissimilar the cohesive material presents a combustible surface wherein the rate of regression is controlled by thermal diffusivity into the propellant the non-cohesive system offers flame paths of convection into the explosive bulk, which if ignited produce gases to fracture the ma-... 

Table 11.1 Catalytic Combustion Surface Reaction Mechanism [361]...

Temp and relative intensities of the combustion products detected as a function of height along an RDX flame are shown in Fig 8 (Ref 67d). Intense radiation from the OH radical is observed immediately next to the combustion surface of the RDX sample. The intensity of the radiation attains its max value at a distance of 0.1mm and varies slowly with further increase in height along the flame. Luminescence of the radicals C2, CN, and CH appears at a distance of 0.1—0.2mm from the combustion surface and increases markedly as the zone of max temp in the flame is approached... 

There now exists a public demand for a high-quality fire-resistive paint or treatment process which combines the essential qualifications of good grade paint with the ability to prevent ignition of combustible surfaces it protects. 

No doubt, an extensive investigation of the combustion wave structure under different conditions would permit to verify many conceptions of the current flame spread theories, and also to determine the applicability limits of the latter. Even now, since more experimental investigations of the rate of flame spread over polymer material surfaces as a function of various factors are bdng carried out, it is becoming increasingly clear that the mechanism of heat transfer from the flame to the combustible surface can change radically as the size of the combustion zone increases. 

Caution. Dehydrided alloy powders have been found, in a few cases, to burst into flames when placed on a combustible surface (for example on a piece of weighing paper). As a consequence, when exposed to the air, both the hy-drided and dehydrided alloy powders should be handled as potentially pyrophoric materials. 

Contact of liquid oxygen with a combustible material may not immediately cause a fire, because of the combination of low temperature and lack of an ignition source. It is important to keep ignition sources away from a spill of liquid oxygen vmtil it dissipates, and to recognize that equipment moved across a combustible surface (e.g., asphalt) or even foot traffic can cause ignihon. 

Obstructions. Sprinklers should be located within the cleanroom where obstructions would prevent wetting of a combustible surface. Wherever obstructions would occur, additional sprinklers are necessary. This will occur under hoods, in pass-throughs and even plenums of wet stations. In most cases, these sprinklers should be supplied by a valve connection to... 

Equation (5.28) also incorporates the mass fraction of the combustible surface species, which is carbon wc here, and an effectiveness feictor rj, which is defined as the area of the reacting surface divided by the external (equivalent-sphere) surfece area of the particle [7] the latter is the basis for the reaction rate terms. The effectiveness factor and the carbon mass fraction determine the accessible surface of the particle, allowing the empirical adoption of a pore diffusion restriction as indicated in Equation (5.17). In the frequent case of the reaction order being unity, expression (5.28) can be simplified to... 

Thus, natural flow turbulence serves as an efficient flame accelerator it speeds up the transport processes and increases the combusting surface area. It was reported in [8] that five to ten time increase in flame velocity and propagation is practicable in a nonobstructed volume. The artificial turbulence caused by differences in the shape... 

Confirmation of the fact that TCN zones of supercritical size may serve as sources of shock-free generation of combustion instability or explosion, requires thorough parametric analysis. First of all, processes in a region between the combustion wave front and the combustion surface in ducts and tubes are to be considered. Besides, it is reasonable to investigate TCN zones near confining surfaces. 

Study of the powder agglomeration at the combustion surface level, by means of high-speed cameras. 

The plants impact the environment mainly through emissions from biofuel combustion, surface runoff from timber storage, noise fi om production and transport, and waste management. 

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