Propane-air mixtures

Table 1. Products from the Reaction of a Propane Air Mixture at Various Pressures, %...

It has been shown by Palmer at the Fire Research Station (FRS) that a crucial variable governing the performance of a flame arrester is the flame speed incident on the arrester. The critical flame speed (minimum speed at which the flame can pass through the arrester) is discussed by Phillips and Pritchard (1986), drawing largely on the FRS work on propane-air mixtures at atmospheric pressure. A simple model based on heat removal from the flame yields the following relation for deflagration flame arresters ... 

Urtiew (1981) performed experiments in an open test chamber 30 cm high x 15 cm wide x 90 cm long. Obstacles of several heights were introduced into the test chamber. Possibly because there was top venting, maximum flame speeds were only on the order of 20 m/s for propane-air mixtures. 

Elsworth et al. (1983) report experiments performed in an open-topped channel 52 m long x 5 m high whose width was variable from 1 to 3 m. Experiments were performed with propane, both premixed as vapor and after a realistic spill of liquid within the channel. In some of the premixed combustion tests, baffles 1-2 m high were inserted into the bottom of the channel. Ignition of the propane-air mixtures revealed typical flame speeds of 4 m/s for the spill tests, and maximum flame speeds of 12.3 m/s in the premixed combustion tests. Pressure transducers recorded strong oscillations, but no quasi-static ovetpressure. 

The jet by which the propane is released. The jet s propane-air mixture is in intensely turbulent motion and will develop an explosive combustion rate and blast effects on ignition. 

When systems involving solvent vapor are considered, use the nomogram for propane/air mixtures because most comvian solvent vapors have maximum explosion pressures of 7.1 to 7.6 bar, and the Kg falls between 40 and 75 bar meter/sec (see Ref. [54]). 

Flow velocity field determined by PIV. Lean limit flames propagating upward in a standard cylindrical tube in methane/air and propane/ air mixtures, (a) Methane/air—laboratory coordinates, (b) propane/air—laboratory coordinates, (c) methane/air—flame coordinates, and (d) propane/air—flame coordinates. 

Streamlines of lean limit flames propagating upward in (a) methane/air and (b) propane/air mixtures (flame coordinates). 

Ishizuka, S., Miyasaka, K., and Law, C.K., Effects of heat loss, preferential diffusion, and flame stretch on flame-front instability and extinction of propane/air mixtures. Combust. Flame, 45,293,1982. 

Vector profile of vortex ring combustion, showing induced velocities along the vortex core. (Lean propane/air mixture, equivalence ratio O = 0.8, Do = 60 mm, P= 0.6 MPa, dotted lines show the flame front taken with the ICCD camera. The right inset shows the relative position of the PIV laser sheet relative to the flame.)... 

Figure 4.2.13 shows the variation of the flame speed with the maximum tangential velocity obtained with vortex ring combustion in the same mixture atmosphere [29]. The cylinder diameter was 100 mm and various lean, stoichiometric, and rich methane/ air and propane/air mixtures were examined. The diameter of the propagating flame was also determined and the ratio of the flame diameter to the core diameter was also plotted against the maximum tangential velocity. 

Finally, we come to the effects of the Lewis number. Figure 4.2.14 shows the intensified images of vortex ring combustion of lean and rich propane/air mixtures. Since the flame is curved and stretched at the head region, the mass and heat is transferred through a stream tube. 

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... 

Measured quenching distance as a function of equivalence ratio for propane/air mixture (top), and pictures of (a) downward and (b) upward propagating flames in channels, close to quenching. Channel widths as in the graph. Frame numbers correspond to the numbers of experimental points. 

Length of the high-temperature zone behind a flame as a function of quenching distance. Downward propagation in lean propane/air mixture. 

Jarosinski, J., Podfilipski, J., and Fodemski, T., Properties of flames propagating in propane-air mixtures near flammability and quenching limits. Combust. Sci. Tech., 174 167, 2002. 

The creation of a steady flame hole was previously carried out by Fiou et al. [36]. In their experiments, a steady-annular premixed edge flame was formed by diluting the inner mixture below the flammability limit, for both methane/air and propane/air mixtures. They found that a stable flame hole was established when the outer mixture composition was near stoichiometry. Their focus, however, was on the premixed flame interaction, rather than on the edge-flame formation, extinction, or propagation. 

Flame images at different time instants for 3% propane/air mixture at 4400rpm. Closed vessel. 

Coriolis acceleration effects in a combustion chamber (dia 90 and width 30mm), vented at the periphery through four orifices, having 7.5 mm in diameter, 4% propane/air mixture, rotation speed (a) lOOOrpm and (b) 2000rpm. 

A backyard barbeque grill contains a 20-lb tank of propane. The propane leaves the tank through a valve and regulator and is fed through a 1/2-in rubber hose to a dual valve assembly. After the valves the propane flows through a dual set of ejectors where it is mixed with air. The propane-air mixture then arrives at the burner assembly, where it is burned. Describe the possible propane release incidents for this equipment. 

Botha, J.P. and Spalding, D.B., The laminar flame speed of propane-air mixtures with heat extraction from the flame, Proc. Royal Soc. London, Ser. A., 1954, 225, 71-96. 

Figure 3. Variation of collision factor with temperature for propane-air mixtures using the Semenov equation...

DeZubay (12) has calculated the change in the collision factor with temperature (propane-air mixtures) by use of the Semenov equation based on the following conditions activation energy of 33 keal. per gram-mole flame velocities at an air-fuel ratio of 14.1 of 38.4, 58.2, and 83.3 cm. per second at inlet temperatures of 537°, 672°. and 852° R., respectively flame temperatures [extrapolated to an air-fuel ratio of 14.1 (50)] of 4022°, 4091°, and 4185° R. at inlet temperatures of 537°, 672°, and 852° R., respectively. This variation of A vs. inlet temperature is shown in Figure 3. 

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