零预旋涡轮动叶多次激波反射对边界层与尾迹发展的影响与损失抑制方法研究

A Zero Inlet Swirl Turbine Rotor (ZISTR) operates with axial inlet flow and needs no inlet swirl provided by any nozzles upstream of it. Therefore not only the engine length and the design challenge from the rotor dynamics but also the nozzle related aerodynamic losses and the amount of cooling air are obviously reduced. The thin blade profle of a ZSTB results in that the major flow losses are linked to the trailing edge shocks directly or indirectly. On the one hand, there are multiple trailing edge shock reflections between the uncovered suction side and the wake, which make the boundary layer on the uncovered suction side experience several periods of detachment, recovery and re-attachment. On the other hand, the stretching and distortion of the wake are also affected by the multiple trailing edge shock reflections. Hence, this project focuses on the trailing edges shocks of ZISTR blades, using numerial simulation and cascace experiments with hot film, schlieren picture, movable probe and high frequency pressure sensor, to investigage that: the effects of multiple shock incidence on the development of the boundary layer on the uncovered suction side with the variation of turbulence intensicity and Renolds number, the interaction between the wake, the boundary layer and the trailing edge shocks of a relatively long uncovered suction side, the wake disfussion characterisctics interacted with the multiple shock incidences, and the flow control method to lower the trailing shock induced losses for ZISTR. The aerodynamic loading of ZISTR blades is consequently clarifed, which provides theoritical supporting for the blade profile optimization in a fluid-structure coupling design process. This project will help ZISTR applicable to high thrust/power to weight ratio aero engines.

零预旋涡轮动叶在上游无导叶的轴向进气条件下工作，不仅降低发动机长度和重量，而且减少导叶相关的气动损失和冷气用量。零预旋涡轮动叶特有的细长叶型导致其内部流动和损失直接或间接的与尾缘激波相关：尾缘压力面内伸激波在吸力面长无遮盖段与尾迹之间形成多次入射和反射，使边界层经历多个分离、恢复和再附周期，尾迹的拉伸和变形同样受内伸激波反射波多次干扰。本项目围绕零预旋涡轮动叶尾缘激波，利用数值模拟和采用表面热膜、纹影及高频响压力测量等技术的平面叶栅试验，揭示吸力面无遮盖段边界层在不同湍流度下受多次激波反射影响的发展机理，阐明尾迹在激波多次干扰下的耗散特点，建立无遮盖段吸力面边界层、尾迹和尾缘激波之间的内在关联，提出抑制尾缘激波诱导的流动损失控制方法，准确获取零预旋涡轮动叶气动载荷特性，为流固耦合的叶片优化设计提供理论基础。本项目有望促进零预旋涡轮动叶在高推重比/功重比航空发动机中获得应用。

零预旋涡轮动叶在上游无导叶的轴向进气条件下工作，该叶片大安装角、长无遮盖段的特点，使其尾缘激波、边界层、尾迹、叶顶泄漏涡的流动机理及损失特性有别于传统跨声速涡轮，本项目围绕尾缘激波/边界层/尾迹干涉机理，针对尾缘激波、叶顶泄漏涡损失显著的问题，开展了如下工作：（1）通过DES和叶栅试验手段，研究了不同出口马赫数下激波/边界层干扰构型及激波对尾迹涡耗散特性的影响规律，研究表明，在出口马赫数达到1.5时，入射激波使边界层发生分离、再附，因此会产生两道反射激波，分别为分离激波和再附激波；激波/边界层干扰产生的反射激作用于相邻叶排的尾迹涡，使得大尺度的尾迹涡迅速破碎成中等尺度、小尺度的尾迹涡，在频谱分量上出现更多中频和高频分量，尾迹涡耗散率降低约35%。（2）通过RANS和叶栅试验手段，研究了低激波损失内凹型线设计方法的流动控制机理，提出了吸力面无遮盖段内凹型线量化设计方法，将广泛用于进气道中的等强度多激波设计方法迁移应用于涡轮设计中，建立了可实现内凹型线量化设计的激波模型，激波模型以原叶型吸力面尾缘激波的上游马赫数和气流折转角输入参数，输出内凹型线偏折角以量化设计改型叶片。叶栅纹影试验结果表明，基于该模型设计的内凹型线能有效的诱导出等强度的双激波结构，RANS结果表明，激波模型所计算的马赫数、激波角、激波气流折转角的相对误差在1%以下，内凹型线诱导的激波有助于降低吸力面尾缘激波的上游马赫数和激波气流折转角，使激波损失显著降低，边界层和尾迹损失略有增加，但前者远大于后者，因此流动损失减少，涡轮效率提高0.8%。（3）通过RANS手段，研究了叶顶前缘吸力面叶尖小翼流动控制机理，RANS结果表明，叶尖小翼使吸力面叶顶马蹄涡与泄漏涡流相互作用的时间和接触面积增加，泄漏涡强度减弱，损失减少，涡轮效率提高0.85%。基于上述认识，综合吸力面内凹型线量化设计方法及叶顶前缘吸力面叶尖小翼设计方法优化了零预旋涡轮动叶，使尾缘激波及叶顶泄漏涡损失显著降低，设计点涡轮效率提高1.4%。