Velocity burning

Fig. 27. Approximate boundary of the low-velocity burn-out regime for water flowing in round tubes. The low-velocity regime lies to the left of any given curve [from Macbeth (M2)].

The wave travels at some definite velocity (burning vel) against the unbumed mixture. Velocity depends on ihe composition of the mixture being zero at the limits and at a max at some intermediate composition (eg 9.5% for firedamp). There are three types of flame ... 

Flame thickness Burning velocity Burning velocity Quenching distance Quenching distance Homogeneous turbulent reactor... 

Effects of Variables on Laminar Burning Velocity. Burning velocity has not yet been made an absolute measurement, as various techniques give different results. However, any one method, carefully used, shows up trends, and it is the trends that are discussed. 

These equations permit converging detonation calculations using the programmed velocity burn down to R/Ro of at least 0.5. They must be used with care because they are approximate, and other equations of state could give different convergence effects. 

Of our special interest is the thickness measurement of powder coatings. While the sound velocity of the electrostatic applied powder/air mixture is estimated to be two times the velocity in air it is also an estimation that thickness powder / air layer is reduced by a factor of 5 by smelting (burning in process, hardening). 

Oxidation. Carbon monoxide can be oxidized without a catalyst or at a controlled rate with a catalyst (eq. 4) (26). Carbon monoxide oxidation proceeds explosively if the gases are mixed stoichiometticaHy and then ignited. Surface burning will continue at temperatures above 1173 K, but the reaction is slow below 923 K without a catalyst. HopcaUte, a mixture of manganese and copper oxides, catalyzes carbon monoxide oxidation at room temperature it was used in gas masks during World War I to destroy low levels of carbon monoxide. Catalysts prepared from platinum and palladium are particularly effective for carbon monoxide oxidation at 323 K and at space velocities of 50 to 10, 000 h . Such catalysts are used in catalytic converters on automobiles (27) (see Exhaust CONTHOL, automotive). 

S has been approximated for flames stabili2ed by a steady uniform flow of unbumed gas from porous metal diaphragms or other flow straighteners. However, in practice, S is usually determined less directly from the speed and area of transient flames in tubes, closed vessels, soap bubbles blown with the mixture, and, most commonly, from the shape of steady Bunsen burner flames. The observed speed of a transient flame usually differs markedly from S. For example, it can be calculated that a flame spreads from a central ignition point in an unconfined explosive mixture such as a soap bubble at a speed of (p /in which the density ratio across the flame is typically 5—10. Usually, the expansion of the burning gas imparts a considerable velocity to the unbumed mixture, and the observed speed will be the sum of this velocity and S. ... 

In the reaction 2one, an increase in the intensity of the turbulence is related to the turbulent flame speed. It has been proposed that flame-generated turbulence results from shear forces within the burning gas (1,28). The existence of flame-generated turbulence is not, however, universally accepted, and in unconfined flames direct measurements of velocity indicate that there is no flame-generated turbulence (1,2). 

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