Improvement of Ultra-High Lift Low-Pressure Turbine Blade Aerodynamic Performance Based on Evolutional Optimization Technique

本文对固体度变化的低压涡轮线性叶栅周围的流场进行了实验和数值研究。他们的目的是澄清的影响，进入尾迹在叶栅的气动损失，是伴随着分离的翼型吸力面，特别是在低雷诺数条件和/或低固体条件。正时皮带上的圆柱形杆作为尾流发生器来模拟影响叶栅的尾流。气动探头测量得到叶栅下游的总压损失分布。热线探头测量也进行了翼型吸力表面。此外，为了加深对来流尾迹与含分离泡边界层相互作用的理解，还进行了基于les的数值模拟。本文还提出了一种新的基于ranss的边界层旁路跃迁预测方法。基程序基于Schmidt和Patankar（1988）给出的边界层分析代码，采用Myong-Kasagi k -e湍流模型实现。本文提出的间歇性输运方程是对Cho和Chung模型（1992）在扩散项和经验模型常数方面的修正。当基于动量厚度的雷诺数超过由Abu-Ghannam和Shaw（1980）的经验相关给出的准则时，在计算中调用过渡流的间歇性行为。将本文提出的方法应用于自由流湍流和压力梯度影响下的边界层转捩预测。通过计算结果与ERCOFTAC T3A等实验数据的比较，证明了该方法作为FST（自由流湍流强度）诱导边界层转捩的预测工具的潜力。本文最后对超高压低压涡轮翼型进气道自由流湍流与带分离泡边界层的相互作用进行了LES研究和实测。测试翼型的横截面是典型的高负荷低压涡轮民用航空发动机。叶栅的坚固性可以通过增加至少25%的翼型俯距来降低，同时保持在叶片到叶片通道中的喉道。根据弦长和平均出口速度，检测的雷诺数为57,000。自由流湍流度约为0.85%（无网格条件）和2.1%（有网格条件）。利用热线探针对边界层进行了测量，得到了自由流湍流作用下边界层的时间平均和时间分辨特性。一个新开发的探头定位工具，这是安装在下游的梯级与最小的堵塞，使精确的探头定位沿线正常的翼型表面。基于高分辨率LES（大涡模拟）进行了数值分析，以加深对超高升力和高升力低压涡轮翼型周围流场的理解。重点讨论了分离泡剪切层的固有不稳定性与自由流湍流的关系。采用标准Smagorinsky模型进行亚网格尺度建模。所使用的流求解器是一个内部代码，最初是由一位作者开发的基于FVM（有限体积法）的完全隐式和时间精确的reynolds -平均Navier-Stokes代码。本文采用冯卡门-鲍湍流能谱法，利用SNGR （Stochastic Noise Generation and Radiation）方法产生均匀各向同性湍流，对进气道湍流进行模拟。少

This study dealt with experimental and numerical studies on the flow field around a low-pressure linear turbine cascade whose solidity was changeable. The purpose of them was to clarify the effect of incoming wakes upon the aerodynamic loss of the cascade that wasaccompanied with separation on the airfoil suction surface, in particular for low Reynolds number conditions and/or low solidity conditions. Cylindrical bars on the timing belts worked as wake generator to emulate wakes that impacted the cascade. Pneumatic probe measurement was made to obtain total pressure loss distributions downstream of the cascade. Hot-wire probe measurement was also conducted over the airfoil suction surface. Besides, LES-based numerical simulation was executed to deepen the understanding of the interaction of the incoming wakes with the boundary layer containing separation bubble.This study also developed a new RANS-based method for predicting bypass transition of the boundary layer using intermittency t … More ransport equation. The base program was based on the boundary-layer analysis code given by Schmidt and Patankar (1988), implemented with Myong-Kasagi k -e turbulence model. The intermittency transport equation proposed in this study was the modification of Cho and Chung model (1992) with respect to the diffusion term and empirical model constants. The intermittent behavior of the transitional flow was invoked in the computation when the momentum-thickness based Reynolds number exceeded a criterion given by the empirical correlation of Abu-Ghannam and Shaw (1980). The method proposed in this study was applied to the prediction of boundary layer transition under the influence of free stream turbulence and pressure gradient. Through the comparison of the calculated results with the corresponding experimental data, for example ERCOFTAC T3A, the proposed method was proved to have a potential as a predictive tool of FST (free stream turbulence intensity)-induced boundary layer transition.This study lastly carried out LES investigation, along with measurements, on the interaction between inlet free stream turbulence and boundary layers with separation bubble over ultra-high lift low-pressure turbine airfoils. The cross section of the test airfoils is typical for highly-loaded LP turbines for civil aeroengines. The solidity of the cascade can be reduced by increasing the airfoil pitch by at least 25%, while maintaining the throat in the blade-to-blade passage. Reynolds number examined is 57,000, based on chord length and averaged exit velocity. Free-stream turbulence is about 0.85% (no grid condition) and 2.1% (with grid condition). Hot-wire probe measurements of the boundary layer are carried out to obtain time-averaged and time-resolved characteristics of the boundary layers under the influence of the freestream turbulence. A newly developed probe positioning tool, which is installed downstream of the cascade with minimal blockage, enables precise probe positioning along lines normal to the airfoil surface. Numerical analysis based on high-resolution LES (Large-Eddy Simulation) is executed to enhance the understanding of the flow field around the Ultra-High Lift and High Lift LP turbine airfoils. Emphasis is placed on the relationship of inherent instability of the shear layer of the separation bubble and the free-stream turbulence. Standard Smagorinsky model is employed for subgrid scale modeling. The flow solver used is an in-house code that was originally developed by one of the authors as FVM (Finite Volume Method)-based fully implicit and time-accurate Reynolds-Averaged Navier-Stokes code. Homogeneous isotropic turbulence created with SNGR (Stochastic Noise Generation and Radiation) method using von Karman-Pao turbulent energy spectrum is applied in the present study for the emulation of inlet turbulence. Less