Flame Quenching

The mechanical flame barriers, which are used for explosion isolation of flammable gas and solvent vapor explosions, are veiy susceptible to the action of dirt and, with one exception, are thus not suitable for dust-canying pipelines. The exception involves the rotaiy valve (see Fig. 26-45), which is based on the flame-quenching effect through narrow gaps and is mainly used at product charging and discharging points. 

BSI Straight pipe for flame quench Propane, ethylene, hydrogen 15 Atmospheric Yes, if specified... 

Porous Media Any solid material through which gas can flow, and that affords some measure of heat extractive capability and flame quenching by cooling. 

Tulip-flame formation begins simultaneously with the rapid decrease in the flame area that accompanies the flame quench at the sidewalls of fhe combustion vessel... 

Flame Quenching by Turbulence Criteria of Flame Quenching.110... 

Flame Propagahon in a Rotahng Cylindrical Vessel Mechanism of Flame Quenching.128... 

However, a number of theories on flame quenching were also developed. Some of these were based on arbitrary assumptions concerning the conditions for quenching [7,11]. Another group of theories were based on the energy conservation equation for the flame, including heat loss [19-21]. 

In the later years, studies on flame quenching were inspired by different applications and were undertaken sporadically [22-24]. 

Definitions of flame parameters in channels. D, distance between channel walls effective in flame quenching (quenching distance). D, flame width dead space R, radius of curvature of the flame. 

To understand the mechanism of flame quenching in narrow channels in detail, one should first examine the data of flames in mixtures of constant composition, but in charmels of different sizes (Figure 6.1.2). The measured propagation velocities in stoichiometric propane/ air mixture are shown in Figure 6.1.2a. For channel widths slightly larger than the quenching distance, the... 

A view of a flame quenched in a channel of 9 mm. Picture recorded by a camera with open shutter ( = 0.57). 

Numerical simulation results of specific mixture consumption rates during flame quenching a channel with D = 4 mm. Time between the frames is At = 0.004 s = 0.729). 

Spalding, D.B., A theory of flammability limits and flame quenching, Proc. Roy. Soc., A240 83,1957. 

Ferguson, G.R. and Keck, J.G., On laminar flame quenching and its application to spark ignition engines, Combust. Flame, 28 197,1977. 

Jarosinski, J., Flame quenching by a cold wall, Combust. Flame, 50 167,1983. 

The concept of turbulent flame stretch was introduced by Karlovitz long ago in [15]. The turbulent Karlovitz number (Ka) can be defined as the ratio of a turbulent strain rate (s) to a characteristic reaction rate (to), which has been commonly used as a key nondimensional parameter to describe the flame propagation rates and flame quenching by turbulence. For turbulence s >/ />, where the dissipation rate e and u, L and v... 

Figure 6.2.5 reveals fhe criferia of flame quenching in fhe Ka- plof obfained from three different turbulent... 

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