High-repetition-rate laser diagnostics experiments for prediction and control of thermo-acoustic instabilities in low-emission gas turbine engines

本研究的重点是预测和控制低排放，燃料灵活的燃气涡轮机发动机的热声不稳定性的方法。燃气涡轮机用于绝大多数商用飞机，并越来越多地用于地面发电。为了减少航空旅行和能源生产对环境的影响，因此有必要开发未来的发动机，以最大限度地减少污染物排放，并安全地使用各种可持续的替代燃料。不幸的是，产生低排放的火焰非常不稳定。在燃气涡轮机燃烧室中，这通常导致高振幅燃烧和压力振荡的自激，或热声不稳定性，这会降低效率，增加排放，关闭发动机，甚至导致灾难性故障。这些不稳定性的激发是由目前无法预测或鲁棒控制的复杂的流-燃烧-声耦合引起的。 在这项研究中，最先进的高重复率激光诊断将被用来量化驱动这些不稳定性的机制。模型燃气涡轮机燃烧室，来自工业设计，将采用各种配置和操作与传统和替代燃料。将使用新获得的激光和成像系统，以10 kHz的速率（常规诊断速率的1000倍）测量燃烧室内的速度场和火焰形貌。热声不稳定性通常发生在约0.1-1 kHz的频率，因此这些新的测量能力可以解决相关的动态。由此产生的数据将提供能量在何处以及为什么转移到振荡的地图，以及能量转移如何取决于发动机的几何和操作参数。 这将大大提高我们预测和控制振荡的能力。 此外，它还将促进培养非常合格的实验研究人员，他们能够进行解决现代工程挑战所需的复杂实验。

This research focuses on methods to predict and control thermo-acoustic instabilities in low-emission, fuel-flexible gas turbine engines. Gas turbines are used on the vast majority of commercial aircraft and are increasingly being employed for terrestrial power generation. In order to reduce the environmental impact of air travel and energy production, it therefore is necessary to develop future engines that minimize pollutant emissions and safely operate with a variety of sustainable alternative fuels. Unfortunately, flames that produce low emissions are very unstable. In gas turbine combustors, this often leads to the self-excitation of high-amplitude combustion and pressure oscillations, or thermo-acoustic instabilities, which can reduce efficiency, increase emissions, shutdown the engine, and even cause catastrophic failure. Excitation of these instabilities is caused by a complex flow-combustion-acoustic coupling that currently cannot be predicted or robustly controlled. In this research, state-of-the-art high-repetition-rate laser diagnostics will be used to quantify the mechanisms driving these instabilities. Model gas turbine combustors, derived from industrial designs, will be employed in various configurations and operated with both conventional and alternative fuels. Measurements will be made of the velocity field and flame topography inside the combustors at a rate of 10 kHz (1000x the rate of conventional diagnostics) using a newly acquired laser and imaging system. Thermo-acoustic instabilities typically occur at frequencies of approximately 0.1-1 kHz, and these new measurement capabilities therefore can resolve the relevant dynamics. The resultant data will provide maps of where and why energy is transferred to oscillations, and how the energy transfer depends on the geometric and operational parameters of the engine. This will greatly enhance our ability to predict and control oscillations. Furthermore, it will facilitate the training of exceptionally qualified experimental researchers, who are able to conduct the complex experiments needed to solve modern engineering challenges.