Effects of Novel Combustor Geometries on the NGV for Future Flexible Operations of Gas Turbines with Flexible Fuels

多年来，燃气轮机发电的使用显著增加，全球市场预计从2013年到2020年将增长45%。随着来自不同来源的可再生能源在经济和技术上变得更加可行，能源市场也变得更加多样化。因此，燃气轮机很可能成为提供基本负荷的主要动力，从而推动了对运行负荷以及氢和生物燃料等燃料灵活性的需求。未来灵活操作和燃料的一个主要挑战是燃烧室的设计及其对涡轮机的影响。燃烧室通常是单独设计和测试的，除了通过目标的总体流动特性外，很少参考下游涡轮。然后，NGV的设计依赖于入口剖面的简单模型，如各向同性湍流强度、湍流强度剖面或在空间和时间上静态的涡流剖面。潜在的假设是NGV周围的流场基本上是稳定的。然而，大多数现代工业燃气轮机使用稀薄预混，涡流稳定燃烧，降低火焰温度，从而减少氮氧化物的形成。涡流对于混合和稳定火焰以及防止闪回或回火是必要的。在旋流器下游形成一个再循环区，形成一个总压较低的旋流核心，持续到旋流器下游很远的地方，甚至对流到NGV下游。这个中心低压核心不仅仅是漩涡中心体的“尾迹”，而是由膨胀过渡管道中所谓的漩涡破裂产生的。因此，燃烧室下游的流动本质上是不稳定的，并以大规模的相干结构为特征。这些结构已被证明对NGV的空气动力学和传热有显著影响。本文研究了不同的燃烧室涡流几何形状对这些流动结构的定常和非定常影响，从而研究了气膜冷却NGV的空气动力学和传热。随着时间的变化，整个叶片上HTC的全表面地图在这里呈现，清楚地解决了这些结构。在这项研究中包括了一个大型旁路旋流器，因为它是当今使用的传统旋流器的代表。这项研究表明，这种几何形状导致了最大的结构，从而导致了最高的HTC波动。这些影响可以通过燃烧室的设计来减少，因此表明通过燃烧室和NGV的集成设计可以实现更大的优化。这项研究将是同类研究中首次使用各种高速实验技术来研究燃烧室流动的非定常效应，这些实验技术包括高速红外热像仪、薄膜计和高速表面贴装压力传感器。同时进行高保真大涡模拟，全面解析非定常流场。该项目属于EPSRC能源与工程研究领域。

The use of gas turbines for power generation has increased significantly over the years, with the global market predicted to grow by 45% from 2013 to 2020. The energy market is also growing more diverse as renewables from different sources become more viable financially and technologically. Gas turbines are therefore likely to become the mainstay for providing the base load, thus driving the need for increased flexibility in terms of operational load as well as flexibility of fuels such as hydrogen and biofuels.One main challenge towards this future of flexible operations and fuels is the combustor design and its effects on the turbine. Combustion chambers are typically designed and tested in isolation, with little reference to the downstream turbine except through targeted bulk flow properties. The design of the NGV then relies on simple models for the inlet profile such as isotropic turbulence intensity, a turbulence intensity profile, or a swirl profile that is static in space and time. The underlying assumption is that the flow field around the NGV is essentially steady.However, most modern industrial gas turbines use lean premixed, swirl stabilised combustion which lowers the flame temperature, thus reducing the formation of NOx. The swirl is necessary to mix and stabilise the flame and prevent flashback or backfiring. A recirculation zone is created downstream of the swirler which results in a lower total pressure swirl core that persists far downstream of the swirler and even convects downstream of the NGV.This central low pressure core is not simply the `wake' of the swirler centre body, but rather is created by so-called vortex breakdown of the swirl in the expanding transition duct. As a result, the flow downstream of a combustor is inherently unsteady and is characterised by large scale coherent structures. These structures have been shown to significantly affect the aerodynamics and heat transfer on an NGV.This study investigates the steady and unsteady effects of different combustor swirl geometries on these flow structures and consequently, the aerodynamics and heat transfer on a film-cooled NGV. Time-varying, full surface maps of HTC across the vane are presented here which clearly resolve these structures. A single large bypass swirler has been included in this study as it is representative of conventional swirlers in use today. It is shown in this study that this geometry results in the largest structures and consequently the highest fluctuations in HTC. These effects can be reduced through combustor design, hence showing that greater optimisation could be achieved through the integrated design of the combustor and NGV.This study will be the first of its kind in investigating the unsteady effects of combustor flows using various high-speed experimental techniques such has high-speed infrared thermography, thin-film gauges, and high-speed surface mount pressure transducers. High-fidelity Large Eddy Simulations will also be carried out to full resolve the unsteady flow field.This project falls within the EPSRC Energy and Engineering research area.