The effect of purge-mainstream density ratio on turbine cavity flows.

净化-主流密度比对涡轮机腔流的影响。

• 批准号: 2594399
• 金额: --
• 依托单位: University of Bath
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2594399
• 关键词: effect; purge; mainstream; density; ratio

A major challenge facing gas turbine designers is preventing hot (1300-1800K) main-annulus flows entering the wheel-space between the turbine disc (rotor) and its adjacent casing (stator). Designers tend to use complex rim seal designs and divert relatively dense sealant flows (800K) to avoid this occurring in the gas turbine. Insufficient sealing can cause hot gas ingress deep into the wheel-space and can lead to premature failure and limited life of the components, excessive sealing can cause reductions in efficiency of the engine which would lead to it becoming uncompetitive in a world of increasing fuel prices and emphasis on CO2 emissions. Preliminary studies of hot gas ingress conducted at Bath employed CO2 as a tracer gas at isothermal conditions (300K). Early results revealed a significant reduction in rim-seal effectiveness when the density ratio between the hot main flow and cold sealing flow was not properly modelled, demonstrating the potential for significant impact within industry.This PhD research will primarily be conducted in the Large Annulus Rig (LAR) at the University of Bath and seek to investigate the effect of the density ratio between the purge flow and main annulus flow on ingress into the rotor-stator cavity of a geometrically scaled industrial turbine stage. This will be achieved through a number of individual considerations. Firstly, the LAR requires a new collection system, allowing for a fundamental study of density-ratio with insensitivity to exit swirl. The instrumentation available in the LAR will also be reconfigured to include high frequency pressure transducers. At this point, investigations into the density ratio will begin by varying the CO2 composition of the purge flow. To ensure this is consistent with simulations, bespoke CFD will be conducted in OpenFOAM to directly match the experiments. This concomitant approach will aim to unravel the complex ingress mechanisms and significant effect of density ratio. The CFD will then be further supplemented (and validated) by using Volumetric Velocimetry (VV) measurements to identify flow structures. The first aspect that will be investigated is the presence of vanes and blades on the density ratio effect. This will be achieved by conducting experiments and simulations with a simple, un-bladed ring on both the rotor and stator, then introducing turning vanes onto the stator, and blades onto the rotor. This will be modelled concurrently in CFD by having no vanes or blades, then either vanes or blades and finally both vanes and blades. The second stage will look into the effects of end-wall contouring on the density ratio. Finally, using the knowledge obtained, scaling models and equations will be developed which could be used by industry during the preliminary design phase when it would be uneconomical and impractical to use CFD due to the rapid development of designs.

燃气轮机设计人员面临的一个主要挑战是防止热（1300-1800K）主环空流进入涡轮盘（转子）与其相邻的机匣（定子）之间的轮空间。设计人员倾向于使用复杂的边缘密封设计，并转移相对密集的密封胶流量（800K），以避免在燃气轮机中发生这种情况。密封不足会导致热气体进入轮距深处，导致部件过早失效和寿命缩短，过度密封会导致发动机效率降低，在燃油价格不断上涨和二氧化碳排放日益受到重视的当今世界，这将使发动机失去竞争力。在巴斯进行的热气体进入的初步研究采用CO2作为示踪气体在等温条件下（300K）。早期的研究结果显示，当热主流和冷密封流之间的密度比没有正确建模时，轮辋密封的有效性会显著降低，这表明在工业中可能会产生重大影响。这项博士研究将主要在巴斯大学的大环空钻机（LAR）进行，并试图研究吹扫流和主环空流之间的密度比对几何尺寸工业涡轮级进入转子-定子腔的影响。这将通过若干个别考虑来实现。首先，LAR需要一个新的收集系统，允许对出口涡流不敏感的密度比进行基础研究。LAR中可用的仪器也将重新配置，包括高频压力传感器。此时，对密度比的研究将从改变吹扫流的二氧化碳组成开始。为了确保这与模拟结果一致，将在OpenFOAM中进行定制的CFD，以直接匹配实验结果。该方法旨在揭示密度比的复杂进入机制和显著影响。然后，通过使用体积测速（VV）测量来识别流动结构，进一步补充（并验证）CFD。要研究的第一个方面是存在叶片和叶片对密度比的影响。这将通过在转子和定子上安装一个简单的无叶片环进行实验和模拟，然后在定子上引入旋转叶片，在转子上引入叶片来实现。这将在CFD中同时建模，通过没有叶片或叶片，然后是叶片或叶片，最后是叶片和叶片。第二阶段将研究端壁轮廓对密度比的影响。最后，利用所获得的知识，将开发可用于工业的比例模型和方程，在初步设计阶段，由于设计的快速发展，使用CFD将是不经济和不切实际的。