Full-Field Laser Vibrometry for Combustion Diagnostics

用于发电的工业燃气轮机中的最先进技术使用稀薄预混燃烧以实现高燃烧效率和低排放。高功率密度和稀薄燃烧增加了热声振荡的敏感性。不稳定性的建模和预测通常通过分析火焰传递函数（FTF）来完成，火焰传递函数将火焰的不稳定热释放速率与作为频率的函数的来流速度的扰动相关联。火焰的这种特性对于航空发动机的燃烧也是必要的。由于在能源领域的研究总是与能源相关的研究，对社会产生了很大的影响。在由奥地利科学基金FWF资助的格拉兹工业大学（J. Woisetschläger）以前的项目中，人们发现所谓的激光测振仪--用于表面振动检测的干涉仪--可以直接记录密度和热释放波动。结果还表明，两个激光测振仪可以通过关联密度波动来检测火焰中的流速。热释放和速度都需要FTF记录。受通信工程中调制和解调技术的启发，德累斯顿工业大学的项目（J. Czarske，A. Fischer）利用正弦激光频率调制技术（也是激光测振仪技术所固有的），结合现代高速传感器阵列和用于流体流动研究的时空相关技术，验证了另一种激光光学测量的概念。本项目的假设是激光测振仪技术可以与现代高速摄像传感器相结合，从而提出这样一种基于众多激光测振仪的全场干涉测量方法（每个像素一个振动计）可以记录FTF，并且还提供关于热释放速率和速度以及火焰内的空间-时间相关性的场信息。所有这些都不需要示踪剂颗粒或示踪剂，并且对于燃烧诊断来说都是新颖的。在该项目中，将结合格拉兹工业大学和德累斯顿工业大学的专业知识来验证这一假设，并开发一种用于激光光学高速燃烧诊断的全场激光振动计，从表征火焰所需的热声学开始，包括用于单向和双向观测的适当的空间/时间相关性。该项目包括使用单线激光测振仪（格拉兹工业大学）和高速速度记录（德累斯顿工业大学）进行基准测试。除了两个主要的项目合作伙伴格拉兹工业大学（J.Woisetschläger）和德累斯顿工业大学（J. Czarske，A. Fischer）三家以其在燃烧和计量方面的专业知识而闻名的研究机构将参与验证和测试过程（慕尼黑工业大学、科隆DLR、布伦瑞克PTB）。

State-of-the art technology in industrial gas turbines for power generation uses lean premixed combustion for high combustion efficiency and low emissions. High power densities and lean combustion increase the susceptibility to thermoacoustic oscillations. Modelling and prediction of instabilities is often accomplished by analysing the flame transfer function (FTF), which relates the unsteady heat release rate from the flame to perturbations of incoming velocity as function of frequency. Such characterization of flames is also necessary for turbomachinery in aero-engines. Since research in the field of turbomachinery always is energy related research, a strong impact on society is given. In previous projects of TU Graz (J. Woisetschläger) funded by the Austrian Science Fund FWF it was shown that so-called laser-vibrometers - interferometers used in engineering for surface vibration detection - can directly record density and heat release fluctuations. It also turned out that two laser vibrometers can detect flow velocities in flames by correlating density fluctuations. Heat release and velocity are both needed for FTF recordings. Inspired by modulation and demodulation techniques from communications engineering, projects at TU Dresden (J. Czarske, A. Fischer) funded by the German Research Foundation DFG proofed the concept of another laser-optical measurement using sinusoidal laser frequency modulation technique - also inherent to laser vibrometer technology - in combination with modern highspeed sensor arrays and spatio-temporal correlation techniques for fluid flow investigations. The hypothesis of this project is that laser vibrometer technology can be combined with modern high-speed camera sensors, so that such a proposed full-field interferometry based on numerous laser vibrometers (each pixel one vibrometer) can record FTF, and also provides field information on heat release rate and velocity as well as spatio-temporal correlations within the flame - all without the need for tracer particles or tracers and all novel to combustion diagnostics. In this project the expertise of both TU Graz and TU Dresden will be combined to verify this hypothesis and develop a full-field laser vibrometer for laseroptical high-speed combustion diagnostics, starting from the thermo-acoustics needed to characterize the flame, including appropriate spatial/temporal correlations for single and dual directional observations. This project includes a benchmarking with single line-of-sight laservibrometers (TU Graz) and high-speed velocity recordings (TU Dresden). Additional to the two main project partners TU Graz (J.Woisetschläger) and TU Dresden (J. Czarske, A. Fischer) three research institutes known for their expertise in turbomachinery combustion and metrology will participate in the verification and testing process (TU Munich, DLR Cologne, PTB Braunschweig).