Development of Pressurized Reducing Combustor for over 1500ﾟC-class Gas turbine

本研究通过实验研究加压条件下空气-甲烷富燃料燃烧特性，开发了一种新型燃气轮机——化学燃气轮机。稳定燃烧的贫燃料极限不依赖于甲烷流速，它是恒定的，而富燃料极限在相当大的范围内扩展。结果表明，空气-甲烷系统的稳定燃烧室在富燃料条件下比在贫燃料条件下更容易实现。测定了不同当量比下产物气体的浓度。实测CO_2浓度略高于计算值。然而，CO的浓度比理论计算的要低。在φ >1.1条件下检测到微量O_2，而计算结果表明O_2不存在。即使在燃料稀薄的燃烧区域也检测到甲烷。这些结果表明，要达到较好的燃烧条件，甲烷和空气的充分混合是必要的。旋转或改进注入器可能有望克服这个问题。从理论和实验得到的NOx排放与当量比之间的关系来看，增压可以控制NOx排放，特别是在富燃料侧。虽然我们都知道在富燃料碳氢化合物燃烧过程中，促动型氮氧化物是NOx总排放的主要来源，但如上所述，随着当量比的增加，所测得的NOx排放量也随之减少。

In this study, the characteristics of the fuel-rich combustions of air-methane under pressurized conditions were experimentally investigated to develop a novel gas turbine, named Chemical Gas Turbine.The fuel-lean limit for the stable combustion does not depend on the methane flow rate and is constant while the fuel-rich limit extends over a wide region of the equivalence ratios.This result suggests that the stable combustor of air-methane system can be easily realized rather under fuel-rich conditions than in fuel-lean ones. Concentrations of product gases under various equivalence ratios were measured. The measured CO_2 concentrations were slightly higher than those calculated. The concentrations of CO,however, were lower than those theoretically calculated. Trace amount of O_2 was detected under a condition of phi>1.1 although the calculation predicted the absence of O_2. Methane was also detected even in a fuel-lean combustion regions. It is suggested by these results that much sufficient mixing of methane and air is necessary to attain preferable combustion conditions. Swirring or improvement of the injector may be promising for overcoming this problem. From the relationships theoretically and experimentally obtained between NOx emissions and the equivalence ratio, it was recognized that pressurization can control the NOx emissions particularly on fuel-rich side. Although it was well-known that prompt NOx mainly contributed to total NOx emissions in fuel-rich hydrocarbon combustion, the measured NOx emissions decreased with the increase in equivalence ratio as mentioned above.