燃料分级对贫预混多喷嘴燃烧器火焰动态响应特性影响的实验研究

Experimental study on effects of fuel staging on flame dynamic response of a lean premixed multi-nozzle burner

关键词:  燃气轮机  多喷嘴  燃料分级  当量比  火焰动态响应  火焰传递函数

Key words:  Gas turbine  Multi-nozzle  Fuel staging  Equivalent ratio  Flame dynamic response  Flame transfer function

摘要:

贫预混多喷嘴燃料分级技术可以有效降低局部热负荷，从而降低NO_x排放并拓宽工况范围，是现代重型燃气轮机低排放燃烧室的主要燃烧方式。本文开展了燃料分级及当量比变化对贫预混多喷嘴燃烧火焰动态响应的影响研究。利用扬声器产生火焰的受迫振荡，利用压力脉动传感器与光电倍增管完成了多喷嘴火焰响应特性的试验分析。试验表明，燃烧室内压力波动与热释放率波动随扰动频率同步变化。当量比低于0.53时，多喷嘴火焰传递函数呈现单峰的特征。当量比大于0.64时，多喷嘴火焰传递函数呈现双峰特征，且火焰响应增强。延迟时间τ随着当量比的增大而减小。燃料分级将使得火焰动态响应特征频率发生偏移。增加喷嘴数量使得火焰传递函数幅值上升，火焰响应增强，峰值频率增大，延迟时间偏短。对于采用多喷嘴燃料分级技术的燃烧室，负荷上升将导致火焰趋于不稳定。

Abstract:

Lean premixed multi-nozzle fuel staging technology can effectively reduce local heat load， thus reducing NO_x emissions， and broadening the range of working conditions. It has been the main combustion method of modern heavy gas turbine combustor with low emission. In this research， the effects of fuel staging and equivalent ratio on the flame dynamic response of a lean premixed multi-nozzle burner were studied. Forced oscillations of the flame are created using a loudspeaker. Pressure sensors and a photomultiplier tube were used to analyze the flame response characteristics of the multiple-nozzle burner. The results show that pressure fluctuation and heat release rate fluctuation in combustor change synchronously with disturbance frequency. When the equivalent ratio is lower than 0.53， the multi-nozzle flame transfer function （FTF） presents the characteristic of single-peak. When the equivalent ratio is greater than 0.64， the multi-nozzle FTF presents the characteristic of double-peak and the flame response intensity is enhanced. The delay time τ decreases with the increase of equivalent ratio. The characteristic frequency of flame dynamic response will be offset under fuel staging. Increasing the number of nozzles will increase the amplitude of FTF， enhance the flame response， increase the peak frequency， and reduce the delay time. For combustor using multi-nozzle fuel staging technology， the flame tends to be unstable due to the increase of load.