Methane flame properties

The properties of natural gas are dominated by those of methane, notably a low maximum flame speed of 0.33 m/s. This strongly influences burner design, which must ensure that the mixture velocity is sufficiently low to prevent blow-off. Light-back , on the contrary, is very unlikely with such a low flame speed. 

Driscoll et al. [5] studied NO emission properties of turbulent partially pre-mrxed hydrogen-air and methane-air flames. The emission results for hydrogen-air flames showed that the emission index decreased monotonically with increasing levels of partial premixing because of the reduction in residence time caused by increasing jet velocity. The results for the methane-air flames were more complicated. 

Stagnation flames are also being used to modify the surface properties of various materials. For example, premixed methane-air flames can beneficially alter the properties of polymer films [41,358,381,382,388]. Flames can also modify surface properties of ferrous and nonferrous metals, for example, improving surface hardness [360] by creating... 

Results of a comprehensive study of the absolute spectral radiance of the infrared emissions from methane—air expins have been reported (Ref 44). The spectral growth of these expanding flames was recorded with a time resolution of one msec in the spectral range 1.7— 5.0 microns. Time resolved spectra were obtained as a function of stoichiometry, nitrogen dilution and Halon dilution. Similar data are also available for coal dust-air explns. Additional applications of rapid scan IR spectroscopy are discussed in Ref 50. In this work, flare spectra (Mk45, LUU-2B and LUU-2B/B) in the 1.7-4.7 and 9—14 micron regions were studied. The Mk-45 and LUU-2B/B showed similar spectral character with Na and C02 emissions superimposed on a gray body continuum, while LUU-2B flares demonstrated variable emittance properties... 

Flames formed from air combined with the lighter hydrocarbons, such as methane, propane, butane, or natural gas, behave in a very similar fashion with similar temperatures, similar chemical properties, etc. 

A turbulent jet diffusion flame was investigated. The apparatus and experimental procedure are described in detail in the article by Rambach et al. (11). The fuel jet had the following properties diameter of 1.6 mm, Reynolds number of 4400, and a fuel composition of 37% methane and 63% hydrogen. 

Hassan, M.I., K.T. Aung, and G.M. Faeth. 1998. Measured and predicted properties of laminar premixed methane/air flames at various pressures. Combustion Flame 115 539. 

Much of the recent research in combustion in porous media has focused on developing a porous burner as a radiant heater [7-13]. This is an attractive application because the porous solid is an efficient radiator while still permitting the use of a clean fuel such as methane. One design that has shown promise is a burner consisting of two sections of porous medium with different characteristics [2, 9, 10]. This design is based on the idea that the effective flame speed within the matrix is determined by the porous medium properties such as solid conductivity, porosity, and pore diameter. The interface between the two sections of porous media acts as a flame holder preventing flashback. 

In this paper we first summarize the ability of the NH kinetic mechanism of Dasch and Blint ( ) to describe the major properties of ammonia-oxygen-diluent flames. This mechanism is constructed solely from literature rate constants and is specifically valid only for flames leaner than 0=1.2 Having validated the ammonia mechanism, we then investigate the yield of NO from methane-air flames which have been doped with NH3 and NO. The NH3 doped... 

Table 4.12 shows a comparison of safety-relevant thermo-physical and combustion properties of hydrogen with those of methane, propane and gasoline [26]. The flammability limits are affected by temperature, as shown in Figures 4.9 and 4.10, so that a preheated mixture has considerably wider limits for coherent flames [27]. An increase in pressures up to lOkPa has only a small effect. Water vapor has a strongly inhibiting influence on the oxyhydrogen reaction. 

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