涡轮转子后盘腔封严气流与主流非定常干涉流动及损失机理研究

In order to match the requirement of increasing turbine performance, integration of a variety of factors affecting turbine performance gradually becomes mainstream in the turbine precise design process. Influence of the purge flow on turbine main flow and turbine performance has become one of issues in advanced aviation gas turbine, but massive investigations on the rim seal flow are focused on the upstream wheel-space purge flow, the effect of the downstream wheel-space purge flow is generally lack of concern. In this project, unsteady interaction mechanism between downstream wheel-space purge flow and main flow in turbine stage and flow loss mechanism would be conducted. The unsteady interaction mechanism between the downstream wheel-space purge flow and main flow would be deeply explored. The impact mechanism of the geometrical and aerodynamic parameters on the flow field and the performance would be obtained. The relation between the downstream wheel-space purge flow / main flow parameters and the turbine performance parameteres, the flow loss induced by the unsteady interaction between the downstream wheel-space purge flow and main flow would be quantified. The unsteady flow characteristic and flow loss mechanism of the interaction between the purge flow and the main flow would also be explored thoroughly in the real engine environment, with the upstream and downstream wheel-space purge flow existed simultaneously. The investigation result can provide technical support for the precise turbine aerodynamic design with unsteady influence of the purge flow integrated, and obtain the approach to further improve turbine design level.

为实现涡轮性能不断提高的目标，充分考虑多种影响涡轮性能因素的精细化设计逐渐成为主流。涡轮转子前/后盘腔轮缘封严气流对主流流动特性及性能的影响成为关注的焦点之一，然而，相关研究基本是针对涡轮转子前盘腔轮缘封严气流所开展，对转子后盘腔轮缘封严气流的影响却缺乏关注。本项申请拟开展涡轮转子后盘腔轮缘封严气流与主流非定常干涉流动和损失机理研究：阐明转子后盘腔轮缘封严气流与主流之间非定常作用的物理机制，诠释转子后盘腔轮缘封严气流和主流非定常干涉效应对涡轮流动结构、气动性能和损失分布的影响规律，建立非定常框架下涡轮转子后盘腔轮缘封严气流/主流相互作用与涡轮气动性能和损失分布的定量关联式，探索真实涡轮工作环境下转子前-后盘腔轮缘封严气流与主流的耦合干涉效应和损失机制。研究成果可为融合涡轮轮缘封严气流非定常影响效应的涡轮精细化设计提供理论支持，并进一步提升涡轮设计水平。

为实现涡轮性能不断提高的目标，充分考虑多种影响涡轮性能因素的精细化设计逐渐成为主流。涡轮转子前/后盘腔轮缘封严气流对主流流动特性及性能的影响成为关注的焦点之一。项目围绕轮缘封严气流与主流的非定常干涉效应及损失控制，以1.5级涡轮为研究对象，对封严气流与主流非定常干涉的物理机制、损失机理、不同参数的影响规律以及损失控制等方面进行了研究。结果表明，0.9%的封严流量使得涡轮级效率降低0.56%。封严腔体出口中间轴向位置的静压梯度可以用于判断燃气入侵和封严出流的位置和强度。封严出流通过堵塞作用减弱导叶轮毂二次流的强度，封严出流与主流的粘性剪切作用形成的剪切诱导涡增加了动叶轮毂二次流的径向位置和强度。轮缘封严气流与主流的干涉产生了四种损失：粘性剪切损失、堵塞效应损失、二次流交互作用损失和第二级导叶的附加损失，基于四种损失具有明显的空间分布特性，结合粘性耗散系数差值云图的分布，提出了轮缘封严气流与主流干涉损失分解量化方法。在设计工况下，粘性剪切损失的比例为67.68%，其它三种损失的权重相当。封严流量增加时，四种损失都增加；预旋比增加时，除了二次流交互作用损失，其它三种损失减小。封严流量、落压比、轴向位置比、倾斜角度和导流段倒圆角角度的增加都使得总损失增加，而预旋比和转速的增加使得总损失减小。封严流量的影响最显著，1%封严流量使得总损失相对于设计点平均增加约104.25%，预旋比其次，100%预旋比使得总损失相对于设计点平均减小约24.46%，其它参数的影响较小。导叶轮毂端壁造型使得叶型载荷呈现出明显的后加载方式，减小了堵塞效应造成的导叶损失，动叶轮毂端壁造型通过减小通道中段的叶表压差，减小了二次流交互作用损失。导流段倒圆角造型与导叶和动叶结合的轮毂端壁造型结合，进一步改善了干涉损失和动叶的非定常波动水平，并减小了对于不同封严流量的敏感性，其总损失相对于基准减小了17.64%。研究成果可为实现涡轮轮缘封严气流与主流流动和损失匹配的精细化设计提供指导。