Study On The Premixed Combustion And Pollutant Generation Characteristics Of Natural Gas

At present,combustion chemical reaction mechanism is mostly used in premixed combustion under ideal conditions,but for the staged combustion chamber,there will be two states of premixed and diffusion combustion at the same time.Whether the mechanism model can effectively describe these two states of combustion in gas turbine under complex conditions,and whether it can ilustrate the generatioin mechanism and predict the generation rate of typical pollutants in gas turbine are still not completely determined.Based on this purpose,the experimental research wil be carried out in this paper.The flame characteristics and influencing factors of premixed combustion of natural gas are analyzed by theoretical analysis and experimental measurement.The flame stability and laminar burning velocity of natural gas premixed combustion were measured in a constant volume chamber with initial temperatures of 303K,372K,443K,initial pressures of 0.1MPa,0.2MPa,oxygen contents of 19%,20%,21%,CO₂ contents of 0%,20%,40%and water contents of 0%,20%,40%.The results show that the initial temperature and water content have little effect on the Markstain length;the effects of initial pressure,oxygen content and carbon dioxide content on the Markstein length are related to the equivalent ratio.With the increase of initial temperature,the laminar burning velocity increases and it reaches maximum when the equivalent ratio is 1.1;with the increase of initial pressure,the laminar burning velocity decreases;with the increase of oxygen content,the laminar burning velocity increases;with the increase of carbon dioxide,the laminar buring velocity decreases;the water content has an non-liner effect on the laminar burning velocity,when the water content increases from 0%to 20%,the laminar burning velocity decreases slightly,and when the water content increases from 20%to 40%,the laminar burning velocity decreases significantly.The generation characteristics of main pollutants as well as the influencing factors of premixed combustion of natural gas are also analyzed by theoretical analysis and experimental measurement.In JSR,the production rate of main intermediate components?CH₄,C₂H₆,C₂H₄,C₂H₂,H₂?and main pollutants?NOx,CO,CO₂?were measured under the conditions of equivalence ratios of 0.2,0.5,1,2,oxygen contents of 2%,4%,8%,carbon dioxide contents of 0%,10%,20%and water contents of 0%,10%,20%.The results show that:with the increase of equivalence ratio,the initial and low-temperature oxidation temperatures of CH₄ are gradually increase,and the acute reaction zone tends to move to the high-temperature zone;with the increase of oxygen content,the initial oxidation temperature of CH₄ and acute reaction zone of low-temperature oxidation gradually move to the low-temperature zone;while the carbon dioxide and water contents have little effect on the initial temperature and acute reaction zone of CH₄.The increased equivalent ratio,oxygen content and water content will increase the production of C₂H₆,C₂H₄,and H2;the increase of carbon dioxide content will reduce the amount of C₂H₆,C₂H₄,and H₂.The C₂H₂ was detected only when the equivalence ratio is 2and with the oxygen content of 8%by a gas chromatograph;C₂H₂can not be detected with the carbon dioxide and water content of 0%.CO is the main oxygenated product with rich oxygen and under low-temperature oxidation condition;with the increase of oxygen content,the production of CO and CO₂ also increases;with the increase of carbon dioxide content,the production of CO increases;the effect of water content on CO is non-linear,and the effect of water content on CO₂ is small.