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首页> 外文会议>ASME turbo expo: turbine technical conference and exposition >AN ACOUSTIC TIME-OF-FLIGHT APPROACH FOR UNSTEADY TEMPERATURE MEASUREMENTS: CHARACTERIZATION OF ENTROPY WAVES IN A MODEL GAS TURBINE COMBUSTOR
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AN ACOUSTIC TIME-OF-FLIGHT APPROACH FOR UNSTEADY TEMPERATURE MEASUREMENTS: CHARACTERIZATION OF ENTROPY WAVES IN A MODEL GAS TURBINE COMBUSTOR

机译：非稳态温度测量的飞行时间声学方法：模型燃气轮机燃烧室中熵波的表征

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Lean premixed combustion promotes the occurrence of ther-moacoustic phenomena in gas turbine combustors. One mechanism that contributes to the flame-acoustic interaction is entropy noise. Fluctuations of the equivalence ratio in the mixing section cause the generation of hot spots in the flame. These so called entropy waves are convectively transported to the first stage of the turbine and generate acoustic waves that travel back to the flame; a thermoacoustic loop is closed. However, due to the lack of experimental tools, a detailed investigation of entropy waves in gas turbine combustion systems has not been possible up to now. This work presents an acoustic time-of-flight based temperature measurement method which allows the detection of temperature fluctuations in the relevant frequency range. A narrow acoustic pulse is generated with an electric spark discharge close to the combustor wall. The acoustic response is measured at the same axial location with an array of microphones circumferen-tially distributed around the combustion chamber. The delay in the pulse arrival times corresponds to the line-integrated inverse speed of sound. For validation of this new method an experimental setup was developed capable of generating well defined entropy waves. As a reference temperature measurement technique a hot-wire anemometer is employed. For the measurement of entropy waves in an atmospheric combustion test rig, fuel is periodically injected into the mixing tube of a premixed combustor. The subsequently generated entropy waves are detected for different forcing frequencies of the fuel injection and for different mean flow velocities in the combustor. The amplitude decay and phase lag of the entropy waves adheres well to a Strouhal number scaling for different mean flow velocities. In addition, simultaneously to the entropy wave measurement, the equivalence ratio fluctuations in the mixing tube are detected using the Tunable Diode Laser Absorption Spectroscopy (TDLAS) technique.
机译：稀薄的预混燃烧促进了燃气轮机燃烧器中热声现象的发生。促成火焰-声相互作用的一种机制是熵噪声。混合部分中当量比的波动会导致火焰中产生热点。这些所谓的熵波通过对流传输到涡轮的第一级，并产生传播回火焰的声波。热声回路关闭。但是，由于缺乏实验工具，迄今为止尚未对燃气轮机燃烧系统中的熵波进行详细研究。这项工作提出了一种基于声学飞行时间的温度测量方法，该方法可以检测相关频率范围内的温度波动。在靠近燃烧室壁的地方通过电火花放电产生狭窄的声脉冲。使用围绕着燃烧室沿周向分布的一系列麦克风在相同的轴向位置处测量声学响应。脉冲到达时间的延迟对应于线积分的声音逆速度。为了验证这种新方法，开发了一种能够产生清晰定义的熵波的实验装置。作为参考温度测量技术，采用了热线风速计。为了在大气燃烧试验台中测量熵波，将燃料定期注入到预混燃烧器的混合管中。对于燃料喷射的不同强制频率和燃烧器中的不同平均流速，检测随后产生的熵波。对于不同的平均流速，熵波的振幅衰减和相位滞后很好地符合Strouhal数标度。此外，与熵波测量同时，使用可调谐二极管激光吸收光谱（TDLAS）技术检测混合管中的当量比波动。

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