Combustion Oscillation by Premixed Flame in a Tube and its Suppression

在锅炉炉膛和燃气涡轮机燃烧器中，燃烧有时变得振荡，并产生恼人的声音。考虑到节能和环保的需要，目前还没有一种有效的抑制振荡的方法，以往研究的是电加热器激励下管内气柱的振荡。燃烧是相当复杂的，因为两种以上的流体反应，火焰本身容易不稳定。作为研究的基础，燃烧振荡与电加热器的激励特性进行了比较。其中一个重要的特征是加热器效应取决于加热器在管中的位置。与薄的均匀电加热器类似，预混火焰安全地建立在安装在管中的金属纤维垫的表面上。测试了氢气、甲烷和丙烷，并测量了用于产生声音的燃料和空气的流量条件。在两端开口的管中，如果电加热器位于管的下游半部分，则电加热器抑制振荡的基本模式，但是火焰可以激发振荡。原因尚不清楚，为了不受管长的影响，在小容器中进行了乙醇扩散火焰试验，改变了在管中的位置。燃烧振荡与燃气火焰和电加热器的燃烧振荡不同，这些现象是首次体验到的，并对其特征进行了解释和抑制方法的试验，从这些试验中可以看出，对于燃烧振荡，需要从与电加热器不同的新的观点进行进一步的研究，

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,