Combustion Oscillation by Premixed Flame in a Tube and its Suppression

在锅炉炉膛和燃气轮机燃烧室中，燃烧有时会变得振荡，并产生恼人的声音。从节能和环保的角度考虑，很难找到抑制振动的方法。燃烧相当复杂，因为有两种以上的流体发生反应，而且火焰本身很容易不稳定。作为研究的基础，将燃烧振荡与电加热器的激励特性进行了比较。其中一个重要的特点就是加热器的作用取决于加热器在管内的位置。类似于薄而均匀的电加热器，预混火焰安全地设置在安装在管子中的金属纤维垫的表面上。测试了氢气、甲烷和丙烷，并测量了燃料和空气的流量条件，以产生声音。在两端开口的管子中，如果电加热器位于管子的下游半部分，则它会抑制振荡的基模，但火焰可以激发振荡。为了从管子长度的影响中分离出来，对乙醇在小容器中的扩散火焰进行了测试，改变了管子中的位置。这种现象与燃气火焰和电加热器的发声特性不同。这些现象是首次出现的，并对其特性进行了解释和抑制方法的测试。从这些实验来看，对于燃烧振荡，还需要从不同于电加热器的相似性的新的角度进行进一步的研究。

In a boiler furnace, and a gas turbine combustor, the combustion sometimes becomes oscillating, and generates annoying sound. Considering saving energy and making exhaust gas environmentally friendly, it is difficult to find an oscillation suppression method.The oscillation of an air-column in a tube excited by an electric heater was studied before. Combustion is considerably complicated because more than two kinds of fluids react, and a flame itself is apt to be unstable. As a research basis, the combustion oscillations are compared with the excitement characteristics by the electric heater. One of the important features is the heater effect dependent on the heater location in a tube. As an analogy with a thin uniform electric heater, a premixed flame is set up safely on the surface of the metal fiber matt mounted in a tube. Hydrogen, methane, and propane were tested, and the flow rate conditions of fuel and air were measured for the generation of sound. In a tube of both ends open, an electric heater suppresses the fundamental mode of oscillations if it its located in the downstream half part of the tube, but a flame can excite the oscillation. The reason was not yet clarified.In order to separate from the tube length influence, a diffusion flame of ethanol in a small container was tested, changing the position in the tube. The characteristics of the emitted sound are different from those by the gas burned flame and the electric heater.These phenomena are first experienced, and the characteristics are note yet explained as well as the testing of suppression methods.From these experiments, as for combustion oscillation, the further study is needed from the new standpoint different from the similarity with the electric heater,