Control of Instability on Premixed Lean Combustion using Pyragas method

预混稀薄燃烧因其火焰温度低于化学计量燃烧而被认为是低NOx排放和高效率的燃烧过程。然而，由于在火焰中引入了过量的O2，预混稀薄燃烧往往是不陈旧的。这项研究的目的是为了提高燃烧室的效率，将混沌控制理论应用于燃烧动力学不稳定的火焰气方法。燃烧状态的传感或氧气过剩比的测量无论对于工业应用还是学术研究都不是一件容易的事情。我们研究了三种光学方法来定位代表高温燃烧的蓝色火焰。第一种方法是利用高速CCD摄像机和高分辨率A/D转换器进行光谱分析。由于火焰的形状和蓝色部分的位置易于再现以便于可视化，因此不适合工业应用，但有助于了解火焰动力学。第二种方法也是利用光电二极管阵列系统进行光谱分析，它需要光纤来引导火焰的某个部分的光线。虽然这种方法需要更短的处理时间(约10ms)，与第一种CCD相机方法(约100ms)相比，但它并不被认为是可用于工业应用的。因此，我们将单色滤光片和高灵敏度的光电二极管组合在一起进行高速处理。本研究中测试的火焰传感系统与大提速合成射流激励器和燃气控制方法相结合，对稳定不稳定的升力火焰是有效的。

Premixed lean combustion is known for low NOx emission and high-efficiency combustion process, because flame temperature is lower than stoichiometric combustion. However, premixed lean combustion tends to be unstale due to introduction of excessive amount of O2 into flame. Aim of this research was improving efficiency of combustors applying a Chaos control theory, known as Pyragas method, for unstable combustion dynamics.Sensing of combustion state or measuring of O2 excess ratio is not easy task for industrial application nor academic research. We investigated three optical methods for locating blue flame, which represents high temperature combustion. First method is spectroscopy using high speed CCD camera and high resoltion A/D converter. It is not suit for industrial application but beneficial to understand the flame dynamics, because shape of the flame and location of blue part is easily reproduced for visualization. The second method is also spectroscopy using photo-diode array system, with which optical fiber is necessary to guide ray of a certain part of flame. Though this method requires shorter process time (about 10ms) compared to the first CCD Camera method(about 100ms), it is not conceived to be practical for industrial application. Therefore, monochroic optical filter and high sensitivity photo-diode were assembled for high speed processing.Loud speeker synthetic jet actuator and Pyragas control method was shown to be effective to stabilize unstable lift flame, coupled with flame sensing system tested in this research.