Investigating the Effects of Surface Topography and Roughness on Turbine Aerodynamic Performance

研究表面形貌和粗糙度对涡轮机空气动力性能的影响

• 批准号: 2299844
• 金额: --
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2299844
• 关键词: Investigating; Effects; Surface; Topography; Roughness

Reducing the SFC of aircraft engines has become an increasingly significant task in order to achieve Advisory Council for Aeronautics Research in Europe's (ACARE) 2050 flightpath plan to reduce aircraft emissions. A part of this challenge is the requirement to improve the overall aerodynamic efficiency of gas turbines by increasing machine stage efficiencies. Within aeroengines, entropy is a useful measure of inefficiency and approximately one third of the entropy generated within an aeroengine turbine is associated with the "aerodynamic friction" between the air flow and the blade surfaces. A major contributor to the rate of entropy production within a boundary layer is the "skin friction" between the air and blade which depends strongly on the roughness (topography) of the blade surface. When the roughness elements protrude through the laminar sublayer, the perturbations resulting from the roughness determines the rise in skin friction. In the rare instance that roughness is accounted for, the capabilities of determining the impact on the skin friction are constrained by insufficient correlations utilising coarse measurements of the centreline averaged roughness height, Ra, as the singular responsible geometric parameter. A surface with the same Ra can have various streamwise roughness distributions where the surface is akin to rolling hills or steep mountains. This determines whether the laminar sublayer perturbs over the topography or is protruded through. An added dimension to the PhD problem is the presence of a pressure gradient in turbine blades and particularly the region of diffusion on the suction surface. The aim of this PhD is to develop understanding of the relationship between surface topography (roughness) and aerodynamic loss. One of the deliverable of this research will be the development of correlations for the effects of surface topography that can be applied to all blade surfaces (i.e engine-run, novel ceramic matrix composites and as-manufactured). An improved understanding of how surface roughness affects skin friction is not only important to current designs but essential for the successful implementation of new materials and manufacturing processes. The PhD will take an experimental and numerical approach. A flat-plate liner working section in the Rhoden wind tunnel (situated in the Low Speed Whittle Lab) will be used to simulate scaled-up engine representative boundary layer, allowing the impact of the surface topography on skin friction to be measured. A numerical tool will be used to determine which surfaces to be 3-D printed and experimentally tested. This will be the main method used to determine correlations which can be applicable to all real turbine blade surfaces. To broaden the scope of the research, high fidelity computational fluid dynamics (in particular, large eddy simulation) will be performed to see if the fluid-structures responsible for the roughness induced aerodynamic loss can be captured.

为了实现欧洲航空研究咨询委员会（ACARE） 2050年减少飞机排放的航线计划，降低飞机发动机的SFC已成为一项日益重要的任务。这一挑战的一部分是要求通过提高机器级效率来提高燃气轮机的整体空气动力学效率。在航空发动机中，熵是一种有效的效率衡量标准，大约三分之一的航空发动机涡轮产生的熵与气流和叶片表面之间的“气动摩擦”有关。边界层内产生熵的一个主要因素是空气和叶片之间的“表面摩擦”，这在很大程度上取决于叶片表面的粗糙度（地形）。当粗糙度元件穿过层流亚层时，由粗糙度引起的扰动决定了表面摩擦的增加。在很少考虑粗糙度的情况下，由于使用粗糙的中线平均粗糙度高度Ra作为唯一负责的几何参数的相关性不足，确定对表面摩擦的影响的能力受到限制。具有相同Ra的表面可能具有不同的流向粗糙度分布，其表面类似于起伏的丘陵或陡峭的山脉。这决定了层流亚层是否在地形上扰动或突出。博士问题的一个附加维度是涡轮叶片中压力梯度的存在，特别是吸力表面上的扩散区域。本博士课程的目的是发展对表面形貌（粗糙度）和空气动力学损失之间关系的理解。这项研究的成果之一将是开发可应用于所有叶片表面（即发动机运行，新型陶瓷基复合材料和制造）的表面形貌影响的相关性。提高对表面粗糙度如何影响表面摩擦的理解不仅对当前设计很重要，而且对新材料和制造工艺的成功实施至关重要。博士将采取实验和数值方法。Rhoden风洞（位于低速惠特尔实验室）中的平板衬垫工作段将用于模拟按比例放大的发动机代表性边界层，从而测量表面形貌对表面摩擦的影响。一个数字工具将用于确定哪些表面要进行3d打印和实验测试。这将是用于确定可适用于所有真实涡轮叶片表面的相关性的主要方法。为了扩大研究范围，将进行高保真计算流体动力学（特别是大涡模拟），以查看是否可以捕获导致粗糙度引起的气动损失的流体结构。