Haruyuki Tanimitsu

Experimental and Numerical Investigations of Wake Passing Effects upon Aerodynamic Performance of a LP Turbine Linear Cascade With Variable Solidity

This paper deals with experimental and numerical studies on the flow field around a low-pressure linear turbine cascade whose solidity is changeable. The purpose of them is to clarify the effect of incoming wakes upon the aerodynamic loss of the cascade that is accompanied 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 work as wake generator to emulate wakes that impact the cascade. Pneumatic probe measurement is made to obtain total pressure loss distributions downstream of the cascade. Hot-wire probe measurement is also conducted over the airfoil suction surface. Besides, LES-based numerical simulation is executed to deepen the understanding of the interaction of the incoming wakes with the boundary layer containing separation bubble.

Studies on Two-Dimensional Contouring of High-Lift Turbine Airfoil Suction Surface as Separation-Control Device: Separation Suppression Under Steady-State Flow Conditions

The study the present authors have been working on is to develop a new method to increase aerodynamic loading of low-pressure turbine airfoils for modern aeroengines to a great extent, which is to achieve drastic reduction of their airfoil counts. For this purpose, this study proposes two-dimensional contouring of the airfoil suction surface as a device to suppress the separation bubble that causes large aerodynamic loss, especially at low Reynolds number condition. The main objective of this paper is to show how and to what extent the surface contouring without any other disturbances affects the suction surface boundary layer accompanying separation bubble. For comparison, rather conventional tripping wire technique is also employed as “local 2D surface contouring” to generate flow disturbances in order to suppress the separation bubble. All measurements are carried out under steady-state flow conditions with low freestream turbulence. It turns out from the detailed experiments and LES analysis that the newly proposed two-dimensional contouring of the airfoil surface can effectively suppress the separation bubble, resulting in significant improvement of cascade aerodynamic performance.Copyright

Effects of Blade Loading Distribution on Aerodynamic Performance of Ultra-High Lift LP Turbine Airfoils Under the Influences of Wake Passing and Freestream Turbulence

This paper deals with studies on the flow field around three types of linear cascades of low pressure turbine (LPT) airfoils with different chordwise loading distributions, while keeping the aerodynamic loading index almost the same. The purpose of the low-speed linear cascade study is to clarify the performance of newly designed two ultra high-lift blade (UHL blade) and compare each of them to that of the conventional LPT blade (Base Model) with low solidity through the measurements of boundary layers accompanied by separation bubble for low Reynolds number conditions. Cylindrical bars on the timing belts work as wake generator to emulate upstream stator wakes that impact the boundary layer on the airfoil suction surface. Freestream turbulence is also enhanced by use of passive turbulence grid. In addition to the pneumatic probe measurements of the midspan loss characteristics of each of the cascades, hot-wire probe measurement is conducted over the blade suction surface to understand to what extent and how the interaction of incoming wakes as well as freestream turbulence affect the boundary layer and separation bubble. Computational Fluid Dynamics (CFD) analyses are also applied to the flow fields around the cascades, mainly using Large-Eddy Simulation (LES) with dynamic Smagorinsky subgrid scale model.Copyright