A Research About Effect Laws Of Hydrogen And Inert Gas Addition On Stabilization Of Methane/Air Premixed Flames

On the basis of the measurements of Bunsen flames, the stability characteristics ofmethane premixed flames in air had been presented to study the effects of burnerparameters and gas equivalent ratio, and fair agreements with those previous literaturedata were obtained. The study focuses on testing CH4/Air laminar premixed flamestability combustion characteristic which are mixed hydrogen and inert gas N2and CO2.This paper shows the following conclusions:In scope of equivalent ratio of the research, the blow-out limit of CH4/Airpremixed laminar flame are increased with the increase of the ratio of equivalent, butblow-out limit are decreased with the increase of size of the burner. The flash-back limitpresent "parabola" shape with the increase of equivalence ratio, the maximum valueappears equals unity (=1). When mixtures became richer or leaner, their flashbacklimit would be smaller, at the same time the flash-back limit decreases with theincreasing of burner size as well. The data of this article has also been existed with thoseprevious literature data and proved the rationality of this study.On the basis of CH4/Air premixed flame limit, the research of mixed H2is furtherdiscussed in CH4/Air premixed flame in order to get the law that influence premixedflame limit. It shows that CH4/Air premixed flame blow-out limit and flash-back limitincreased in a certain range when mixing the H2, and the limits increase greater with theincreasing blending ratio. Experiment is studied by selecting specific equivalent ratio topresent growth rate of CH4/Air premixed flame limit when the critical velocity gradientis chosen as characterization, it concluded that linear coefficients were proposed tocharacterize the effects of hydrogen blending ratio on flame limits of blow-out andflash-back. And the smaller burner is the larger coefficients, while equivalent ratiopresents a weak effect. The results indicate that in CH4/Air/H2premixed gases flamelimits increase more obvious in small size diameter. It is shown that the hydrogenenriched flame stability is enhanced because of the strong diffusion of hydrogen.The CH4/Air premixed flame blow-out limit and flash-back limit were decreasedwhen N2and CO2are mixed, and its decreases constantly with increase of theproportion of addition. The CH4/Air premixed flame blow-out and flash-back limitdecreases constantly with increase the proportion of CO2addition rate. Because CO2haslower temperature and smaller thermal conductivity, it lead CH4/Air mixed laminar flame propagation speed to decreased more fast, so CH4/Air premixed flame blow-outlimit and flash-back limit which CO2mixed is much larger than N2. Naturally, the valueof flame limit that mixed CO2is smaller.Finally, the paper explained the reason that flame limit are effected by CO2aregreater than N2from its original characteristics, as well as discussed the reasons whichinfluence CH4/Air laminar flame limit, at last the laminar flame speed influence factorsare emphasized.