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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >Structures and stabilization of low calorific value gas turbulent partially premixed flames in a conical burner
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Structures and stabilization of low calorific value gas turbulent partially premixed flames in a conical burner

机译：锥形燃烧器中低热值燃气湍流部分预混火焰的结构和稳定性

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Experiments are carried out on partially premixed turbulent flames stabilized in a conical burner. The investigated gaseous fuels are methane, methane diluted with nitrogen, and mixtures of CH4, CO, CO2, H2 and N2, simulating typical products from gasification of biomass, and co-firing of gasification gas with methane. The fuel and air are partially premixed in concentric tubes. Flame stabilization behavior is investigated and significantly different stabilization characteristics are observed in flames with and without the cone. Planar laser induced fluorescence (LIF) imaging of a fuel-tracer species, acetone, and OH radicals is carried out to characterize the flame structures. Large eddy simulations of the conical flames are carried out to gain further understanding of the flame/flow interaction in the cone. The data show that the flames with the cone are more stable than those without the cone. Without the cone (i.e. jet burner) the critical jet velocities for blowoff and liftoff of biomass derived gases are higher than that for methane/ nitrogen mixture with the same heating values, indicating the enhanced flame stabilization by hydrogen in the mixture. With the cone the stability of flames is not sensitive to the compositions of the fuels, owing to the different flame stabilization mechanism in the conical flames than that in the jet flames. From the PLIF images it is shown that in the conical burner, the flame is stabilized by the cone at nearly the same position for different fuels. From large eddy simulations, the flames are shown to be controlled by the recirculation flows inside cone, which depends on the cone angle, but less sensitive to the fuel compositions and flow speed. The flames tend to be hold in the recirculation zones even at very high flow speed. Flame blowoff occurs when significant local extinction in the main body of the flame appears at high turbulence intensities.
机译：对在锥形燃烧器中稳定的部分预混湍流火焰进行了实验。研究的气态燃料为甲烷，氮气稀释的甲烷以及CH4，CO，CO2，H2和N2的混合物，模拟了生物质气化的典型产物，以及气化气与甲烷的共烧。燃料和空气在同心管中部分预混合。研究了火焰稳定行为，并在有和没有圆锥体的火焰中观察到了明显不同的稳定特性。进行了燃料示踪剂，丙酮和OH自由基的平面激光诱导荧光（LIF）成像，以表征火焰结构。进行了锥形火焰的大涡模拟，以进一步了解圆锥中的火焰/流动相互作用。数据显示，带有锥体的火焰比没有锥体的火焰更稳定。没有锥体（即喷射燃烧器）时，生物量衍生气体的吹扫和提起的临界喷射速度要高于具有相同热值的甲烷/氮气混合物的临界喷射速度，这表明混合物中氢气增强了火焰稳定性。对于圆锥体，由于圆锥形火焰中的火焰稳定机理与喷射火焰中的火焰稳定机理不同，火焰的稳定性对燃料的成分不敏感。从PLIF图像可以看出，在圆锥形燃烧器中，火焰通过圆锥体稳定在几乎相同的位置，以用于不同的燃料。从大型涡流模拟来看，火焰受锥体内部的再循环流控制，该再循环流取决于锥体角度，但对燃料成分和流速较不敏感。即使在非常高的流速下，火焰也倾向于保持在再循环区域中。当在高湍流强度下火焰主体中出现明显的局部熄灭时，就会发生火焰吹灭。

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