微混喷嘴结构对氢混燃料/空气掺混均匀性的影响分析

Analysis of the Influence of Micromixing Nozzle Structure on the Uniformity of Hydrogen Fuel/Air Mixing

采用数值仿真方法开展了燃气轮机燃烧室微混喷嘴中富氢燃料/空气掺混均匀性问题研究。首先分析了三种不同微混喷嘴结构的燃料浓度分布和掺混均匀性指数变化规律,发现采用燃料轴向进气、空气径向进气的燃料/空气掺混方式,能够在合理的总压损失范围内,获得更好的掺混均匀性。然后分析了三种喷嘴的流场特性,不同径向位置处的轴向速度分布表明,燃料和空气的射流速度会对喷嘴内燃料/空气掺混水平造成影响,燃料径向喷入和从喷嘴中心区域轴向喷入在轴向高速射流作用下被吹向下游,不能均匀的沿径向扩散并分布到喷嘴流道内部,使燃料/空气掺混均匀性提高受限。最后分析了富氢燃料中氢含量变化对掺混均匀性的影响,研究结果表明,氢含量变化会带来燃料射流速度的改变,当燃料射流速度超出合理范围后,会导致掺混均匀性下降。研究结果为微混喷嘴燃料/空气喷注策略设计提供参考。

Numerical simulation method was applied to study the uniformity of hydrogen-rich fuel/air blending in the micromixing nozzle of the combustion chamber of the gas turbine.Firstly,the fuel concentration distribution and mixing uniformity index of the three different structures of the micromixing nozzle were analyzed,and it was found that the fuel/air mixing method of the fuel axial intake and the air radial intake obtained better mixing uniformity within a reasonable total pressure loss range.Then the flow field characteristics of the three nozzles were analyzed,and the axial velocity distribution at different radial positions showed that the jet velocity of fuel and air would affect the level of fuel/air mixing in the nozzle,and the way of radial injection of fuel and axial injection from the central area of the nozzle were quickly blown downstream under the action of axial high-speed jet,and could not be evenly diffused along the radial direction or distributed to the inside of the nozzle flow channel,so that the uniformity of fuel/air mixing was limited.Finally,the effect of the change of hydrogen content in hydrogen-rich fuel on the uniformity of blending was analyzed,and the results show that the change of hydrogen content will bring about a change in the fuel jet velocity,and when the fuel jet velocity exceeds a reasonable range,it will lead to a decrease in the uniformity of blending.The results of the study provide a reference for the design of the micromixing nozzle fuel/air injection strategy.