Study On Combustion And Spectrum Characteristics Of Methane Diffusion Flame Interacted With Superfine Powder

Superfine powder has much obvious characteristics as a good flame and gas explosion suppression medium, such as wide application, easy to store and transport, good chemical suppression effect. Lots of researches on the inhibition effect of gas combustion and explosion flame for superfine powder had been launched. The mainly method was to characterize and determine the inhibitory effect by observing and analyzing the changes of in the apparent phenomenon and data before and after the powder affected. But there were fewer studies on the inhibition mechanism, and effective means in the mechanism research were lacking.In this paper, we built an experimental device which can be used to research on the mechanism of methane diffusion flame interacted with superfine powder, based on previous studies and integrated the advantages and disadvantages of the experimental device involved in similar researches. After that, imaging device and grating spectrometer were used to observe the combustion status and emission spectrum of flame before and after the powder affected under different conditions. The results of this study showed that:In the diffusion combustion of methane, the oxidizer flow rate changes had little effect both on the combustion state of the flame and the intensity of emission spectrum from the methane combustion flame. Changing the oxygen content of the oxidizing agent could affect the flame color, shape, and the spectrum intensity of carbon particles, CH* and OH* radicals. The OH* radical would create new characteristic radiation at higher oxygen concentration, which made it as the most critical component of the radicals that make chain reaction of methane conducting.Under the influence of four different types of superfine powders, the combustion state of methane flame showed varying degrees of change, in which the flame under higher oxygen content was harder to be suppressed. With the increase of the equivalent concentration of fumed silica, the flame radiation intensity of carbon particles and two radicals had gown to be weaker at first and then stronger. The overall inhibitory effect of fumed silica is not obvious. Increasing the equivalent concentration of commercial ABC powder could significantly suppress the burning flame, both the carbon particles' and two radicals' radiation intensity was greatly inhibited at last, and the inhibitory effect was the best of the four powders. Effects sodium bicarbonate and potassium bicarbonate on the state of flame and radiation spectra were similar, but the overall suppression effect of sodium bicarbonate on flame was more obvious.The micro mechanism of four kinds of superfine powder suppression on flame could be known, combined with the TGA results of the powder samples. The silica only showed physical inhibitory effect, and the inhibition mechanism was cooling the flame and diluting the oxygen. H2 O and P2O5 played a role in cooling the flame and physical isolating the oxygen separately, as main decomposition products of superfine ABC powder; and the major chemical suppression mechanism was the capture and consumption of free form ammonia to OH * radicals. The decomposition of sodium bicarbonate and potassium bicarbonate could generate H2 O and a large amount of CO2, which showed physical oxygen inhibitory effect of cooling the flame and diluting the oxygen. Meanwhile, the gaseous thermal decomposition products could create alkali after interacted with water vapor, which could greatly consume OH* and H* radicals created by methane combustion, making it as the main chemical inhibition mechanism of the two powders.