不同速度波动下氢含量变化对氢气-甲烷钝体火焰燃烧不稳定性的影响

Effects of Hydrogen Contents Change on Combustion Instability of Hydrogen-Methane Bluff-Body Flame at Different Velocities

关键词:  钝体火焰  燃烧不稳定性  火焰传递函数  声场  热释放波动  速度波动

Key words:  Bluff-body flame  Combustion instability  Flame transfer functions  Acoustic excitation  Heat release fluctuation  Velocity fluctuation

摘要:

针对燃气轮机贫燃预混条件下容易产生燃烧不稳定问题，探究了不同氢含量对氢气-甲烷混合气钝体火焰燃烧不稳定性的影响，用于获得燃烧不稳定性的控制方法。通过像增强相机（ICCD）、光电倍增管（PMT）、卡塞格林定点采集等装置获得火焰图像，并借助火焰传递函数描述火焰对声场的响应特性。由此得到了不同速度波动A下氢气含量变化（0%，10%，20%，40%）对燃烧不稳定性的影响总规律，并分析了氢含量变化对混合气热释放率的作用机理。实验结果表明：随着速度波动A的增加，燃烧不稳定性增强。当A较小时，火焰传递函数幅值|H|下降较快；当A大于0.3之后，|H|的下降趋势趋于平缓，火焰传递函数发生饱和。当A相同时，分别对90Hz和140Hz作用下的火焰研究后得到了相反的结论。氢气含量的增加导致90Hz作用下的火焰传递函数幅值|H|增加；热释放波动的相位与速度波动的相位相同，并且相位差接近0°，燃烧不稳定性减弱；而140Hz声作用下氢气的加入却使得|H|下降，并且相位差远离0°，热释放波动与速度波动的跟随性变差，燃烧不稳定性增强。

Abstract:

In view of the gas turbine being easy to produce combustion instability problems under the condition of lean burning premixed combustion，the effects of different hydrogen contents on the combustion instability of hydrogen-methane mixture bluff body flame were researched to obtain control method of combustion instability. With the help of the flame transfer function to describe the response characteristics of sound field， several devices were adopted to receive flame picture，such as the image intensifier cameras（ICCD）， photomultiplier tubes（PMT）and cassegrain fixed-point sampling device. Thus the general law of influence under different speed fluctuation of 4 hydrogen contents （0%，10%，20%，40%）on the combustion instability was obtained， and the action mechanism of hydrogen content change on the heat release rate of mixture was analyzed. The experiment results show that the combustion instability strengthens with the increasing of velocity fluctuation A. When A is smaller， amplitude of flame transfer function |H| reduces rapidly.When A is greater than 0.3， the decline of |H| tends to be flat， and the flame transfer function reaches saturation. Under the same velocity fluctuation， the opposite conclusion is obtained after studying the flame under the action of 90Hz and 140Hz. When the hydrogen content increases at 90Hz， flame transfer function amplitude |H| increases.The heat release fluctuation is in phase with the velocity fluctuation phase and the phase difference is close to 0°，and the combustion instability is weakened. At 140Hz， the addition of hydrogen makes |H| decrease while the phase difference is far away from 0°.The following variation of heat release fluction and velocity fluctuation is poor， the combustion instability is enhanced.