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Active Control and Noise Reduction of Turbulent Diffusion Flames with Coherent Structure by Acoustic Excitation

相干结构湍流扩散火焰的声激励主动控制与降噪

基本信息

批准号：
08650255
负责人：
OHIWA Norio
金额：
$ 1.47万
依托单位：
Nagoya Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

In this investigation two types of diffusion flames, which are established behind a rear facing semi-circular cylinder in a 2-D combustion tunnel and are characterized by the coherent structure inherent in shear flows, are acoustically excited under the same geometrical and flow conditions. Two kinds of excitation techniques are used ; one is the flat speaker method, in which the sound pressure fluctuation applied by the speaker stimulates directly the Kelvin-Helmholtz instability in the shear layr and promotes the formation of a series of coherent structure, and the other is the fuel supply velocity fluctuation method, in which fluctuation having a prescribed amplitude of fuel flow rate is applied to the fuelflow supply line upstream of the nozzle. In order to elucidate effects of the acoustic excitation on the combustion characteristics, mean concentration profiles and temperature fluctuations are measured. Also an attempt is made to construct algorithm using the PIV-technique, that … More enables optical and planar measurements of the velocity vector profiles with a recirculation zone behind a bluffbody. The results obtained are summarized as follows.(1) addition of the bias-velocity using a rotating mirror method makes discrimination of the velocity vector direction possible. Based on various kinds of observations and considerations, the PIV-algorithm is constructed, which consists of the pattern discrimination, the vector calculation, the error vector elimination and the vector interpolation. It is shown that the proposed PIV-algorithm makes possible picture processing of the reactive turbulent flow field with reverse flows.(2) Although two types of excitation techniques equally enhance the periodicity of the coherent structure, the fuel supply velocity fluctuation method is found to be more effective than the flat speaker method.(3) With increasing the excitation intensity, the scale of organized eddies becomes uniform, the flame region is concentrated into the central zone behind the semicircular nozzle, and the flame length becomes short, indicating the promotion of reaction and combustion intensity. As a result, in the central flame region NOx and CO_2 increase, and CO and HC decrease, whereas in the organized eddy-flame region the very reverse holds, due to the severe cooling effect by the intense engulfing motion of the organized eddies. Less

在这项研究中，在相同的几何和流动条件下，对两种类型的扩散火焰进行了声学激发，这两种扩散火焰建立在二维燃烧风洞中的后向半圆柱后面，其特征在于剪切流固有的拟序结构。采用了两种激振技术;一种是平板扬声器法，扬声器施加的声压波动直接激发剪切层中的Kelvin-Helmholtz不稳定性，促进一系列相干结构的形成;另一种是燃油供应速度波动法，其中具有预定幅度的燃料流率的波动被施加到喷嘴上游的燃料流供应管线。为了阐明声激励对燃烧特性的影响，测量了平均浓度分布和温度波动。还尝试使用PIV技术构建算法， ...更多信息利用钝体后面的回流区，能够对速度矢量分布进行光学和平面测量。所得结果总结如下。(1)使用旋转镜方法的偏置-速度的相加使得速度矢量方向的辨别成为可能。基于各种观察和考虑，构造了PIV算法，该算法包括模式识别、矢量计算、误差矢量消除和矢量插值。结果表明，所提出的PIV算法使图像处理的反应湍流流场与反向流。(2)虽然两种类型的激励技术同样提高了相干结构的周期性，燃料供应速度波动的方法被发现是更有效的比平板扬声器的方法。(3)随着激励强度的增加，有组织的涡流尺度变得均匀，火焰区域集中在半圆形喷嘴后的中心区域，火焰长度变短，表明反应和燃烧强度得到促进。结果表明，在中心火焰区，NOx和CO_2含量增加，CO和HC含量减少，而在有序涡火焰区，由于有序涡强烈的吞噬运动，产生了强烈的冷却作用，结果正好相反。少