An experimental investigation in to the effect of rotor endwall contouring on gas turbine stage efficiency in the presence of egress purge flow

科学界现在普遍认为，全球变暖是人类工业化的直接结果；主要是通过燃烧化石燃料向大气中释放二氧化碳。在美国，大约20%的温室气体排放是由燃烧化石燃料发电造成的，其中工业燃气轮机是主要贡献者。2016年的《巴黎协定》是195个国家之间首个具有法律约束力的协定，旨在限制全球变暖及其对地球的不利影响。这只能通过将产品和工艺对人类生活各个方面的不利环境影响降至最低来实现。这项PHD研究旨在通过使用新的转子端壁轮廓来实现工业燃气轮机级效率提高约1%，其中出口吹气流是转子叶片所在的圆周平台，而出口吹气流是从转子和定子之间形成的轮隙进入主环空中气路的气流。端壁轮廓有可能提高级效率，因为它可以用来抑制在转子叶片通道中发现的寄生二次流结构。过去，为此目的设计端壁轮廓的研究很少考虑它们在出口吹扫流存在时的性能，最近的工作表明，端壁轮廓抑制二次流结构的能力高度依赖于出口吹扫流的水平；本博士论文旨在填补现有文献中的这一重要空白。这将通过测试一系列新型的转子端壁轮廓来实现，这些轮廓已经部分地借助研究赞助商西门子工业涡轮机有限公司的CFD模拟设计。将使用三种主要测量技术：两种非侵入性光学流动可视化技术和一级效率测量技术这两种光学流动可视化技术是体积测速仪(V3V)和二氧化碳平面激光诱导荧光(CO2 PLIF)。V3V提供了流体体积的三分量速度场，在这种情况下是叶片通道。V3V将用于显示转子叶片通道内的二次流动特征，并了解不同端壁轮廓对这些流动特征的影响。二氧化碳PLIF测量将提供涡轮机轮距出口气体路径的可视化。这一点很重要，因为该气体路径会影响叶片通道中二次流特征的形成。级效率测量技术是一个5孔压力探头，用于确定级的上游和下游的流速。这与温度和转子扭矩测量结合使用来计算级效率，这对发动机设计者来说是最重要的。这项研究将确定不同的端壁轮廓与历史上用于燃气轮机设计的基准端壁轮廓相比，在提高级效率方面的有效性。它还将使人们更好地了解端壁轮廓特征的各个方面的根本因果关系，例如波谷和波峰，以及由此导致的二次流结构的变化。这一知识可能会对工业燃气轮机的端壁设计程序产生持久的影响。

It is now widely agreed by the scientific community that global warming is a direct result of human industrialization; and primarily the release of carbon dioxide in to the atmosphere through the burning of fossil fuels. In the United States approximately 20% of greenhouse gas emissions result from the burning of fossil fuels for electrical power generation, of which industrial gas turbines are a major contributor. The 2016 Paris Agreement was the first legally binding agreement between 195 countries which aims to limit global warming and its adverse effects on Earth. This can only be achieved through minimising the adverse environmental impact of products and processes in all aspects of human life. This PhD research aims to achieve an increase in industrial gas turbine stage efficiency in the order of 1% through the use of novel rotor endwall contouring in the presence of egress purge flow; the endwall being the circumferential platform upon which the rotor blades sit, and egress purge flow being flow entering the main annulus gas path from the wheelspace formed between the rotor and stator. Endwall contouring has the potential to benefit stage efficiency as it can be used to suppress parasitic secondary flow structures found in the rotor blade passage. In the past, research in to the design of endwall contours for this purpose has given little consideration to their performance in the presence of egress purge flow, and recent work has shown that the ability for endwall contours to supress secondary flow structures is highly dependent of the levels of egress purge flow; this PhD aims to fill this important gap in the existing literature. This will be achieved by testing a series of novel rotor endwall contours which have been designed, in part, with the aid of CFD simulations by the research sponsor, Siemens Industrial Turbines Ltd. Three primary measurement techniques will be used: two non-invasive optical flow visualisation techniques, and one stage efficiency measurement techniqueThe two optical flow visualisation techniques are Volumetric Velocimetry (V3V) and Carbon Dioxide Planer Laser-Induced florescence (CO2 PLIF). The V3V provides a 3-component velocity field for a volume of fluid; in this case the blade passage. The V3V will be used to visualise the secondary flow features within the rotor blade passage, and gain an understanding of the effect of different endwall contours on these flow features. The CO2 PLIF measurements will provide a visualisation of the egress gas path from the turbine wheelspace. This is important as this gas path effects the formation of secondary flow features in the blade passage. The stage efficiency measurement technique is a 5-hole pressure probe which is used to determine flow velocity upstream and downstream of the stage. This is used in combination with temperature and rotor toque measurements to calculate stage efficiency, which is of primary importance to the engine designer. This research will determine the effectiveness of different endwall contours on increasing stage efficiency when compared to the baseline endwall contour that has been used historically in gas turbine design. It will also allow for a greater understanding of the fundamental cause and effect with regards to individual aspects of endwall contour features, e.g. troughs and peaks, and the resulting changes in the secondary flow structure. This knowledge will potentially have a lasting impact on the design procedure of endwalls in industrial gas turbines.