Investigation Of Flame Structure And Burning Intensity Of Partially Premixed Methane Enrichment Of Syngas Using Oh-PLIF And CHEMKIN Simulation

As energy crisis and environmental problem are being more and more serious,syngas,which can be produced through the process of coal and biomass gasification,has drawn a lot of interests.The composition of syngas is quite different with different gasification technology and feed material.And some gas turbines used in IGCC power plants are the transformation from gas turbines which are designed for nature gas originally,the engine efficiency can be significantly reduced when using syngas in it directly.Co-firing with nature gas can improve the stability of syngas combustion process obviously,increase the heat value of fuel,and improve the adaptability of gas turbine.Thus,understanding the combustion characteristics of methane enrichment of syngas is essential for improving the efficiency of IGCC power plants.In this article,experimental and numerical studies on partially premixed syngas flame were conducted.OH-PLIF technology was used to measure flame structure and radical distribution,combined with Davis software,the heights of inner flame front and OH signal intensity was captured.Meanwhile,the effect of methane addition on thermal and chemical properties was also conducted by using CHEMKIN-Pro software.Experimental results are summarized as follows:?1?The height of the inner flame front increases greatly with the increase of X_CH4,and the stability of the flame improves.As X_CH4 increases,OH radical concentration decreases gradually in the outer flame cone region along the upstream of the flame front while the concentration of OH radical increases progressively at the downstream.?2?With the increase of the ratio of CO/H₂,the flame width decreases,and OH concentration decreases gradually in the outer flame front but increases in the tip of inner flame front.?3?With the increase of the inner equivalence ratio,inner flame front fades away,the structure of the flame changes from double flame structure to typical diffusion flame structure.?4?The height of inner flame front changes with?_overall,X_CH4 and the ratio of CO/H₂,but the flame height is less sensitive to the variation of?_overall and the ratio of CO/H₂,methane concentration plays a dominant role in combustion characteristic of syngas.Simulation results also keep consistent with experimental results,the main results are concluded as follows:?1?With the increase of X_CH4,the rate of production of H/OH radicals decrease,and there is competition relationship between R46 and R38.?2?With the increase of the ratio of CO/H₂,R46 is promoted,and the temperature profile moves backwards and the maximum value of temperature decreases.The combustion process is weakened with CO/H₂ increases.?3?The maximum value of temperature appeared at diffusional combustion area whenever in fuel-lean or fuel-rich condition,and the reaction rate of H/OH radicals is weakened with the increase of?_overall.?4?The flame temperature and the OH radicals are less sensitive to the variation of?_overallverall compared with the impact of methane concentration and the ratio of CO/H₂.