J0501-3-2 Studies on High Lift Low-Pressure Turbine Airfoils of Aero Engines : Influence that Pressure Distributions give to Boundary Layer Unsteady Behavior

2009 ◽  
Vol 2009.7 (0) ◽  
pp. 25-26
Author(s):  
Ken-ichi FUNAZAKI ◽  
Takahiro SHIBA ◽  
Nozomi TANAKA ◽  
Kazuya KIKUCHI
Keyword(s):  
Boundary Layer ◽  
Low Pressure ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Pressure Distributions ◽  
Aero Engines ◽  
Turbine Airfoils ◽  
Unsteady Behavior

1742 Studies on High-Lift LP Turbine Airfoils of Aero Engines : Unsteady Behavior Separated Boundary Layer under the Influence of Incoming Wakes

2007 ◽  
Vol 2007.2 (0) ◽  
pp. 391-392
Author(s):  
Nozomi TANAKA ◽  
Ken-ichi FUNAZAKI ◽  
Kazutoyo YAMADA ◽  
Hideo TANIGUCHI ◽  
Mamoru KIKUCHI ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Lift ◽  
Aero Engines ◽  
Lp Turbine ◽  
Turbine Airfoils ◽  
Unsteady Behavior

Investigation of the Suction Side Boundary Layer Development on Low Pressure Turbine Airfoils With and Without Separation Using a Preston Probe

2014 ◽  
Author(s):  
Stephan Stotz ◽  
Christian T. Wakelam ◽  
Reinhard Niehuis ◽  
Yavuz Guendogdu
Keyword(s):  
Boundary Layer ◽  
Dynamic Pressure ◽  
Suction Side ◽  
Transition Process ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Low Pressure Turbine ◽  
Pressure Distributions ◽  
Turbine Airfoils ◽  
Probe Geometry

Characterizing the transition process of airfoils can be very challenging and requires often extensive measurement methods. Frequently at low Reynolds numbers the suction side separation often occurs close to the trailing edge so that asserting reattachment of the flow to form a closed separation bubble from the profile pressure distributions becomes uncertain. In the current work the suction side transition process is investigated more precisely with a convenient method to determine the dynamic pressure close to the suction surface using a Preston probe (flattened Pitot tube). Therefore four low pressure turbine airfoils, which show different characteristics of the transition process in the static pressure distribution have been investigated at the High-Speed Cascade Wind Tunnel at the Universität der Bundeswehr München at constant Mach number and under a wide range of Reynolds numbers (40 000 to 400 000). It is shown that this method is appropriate to determine transition start and end as well as the separation and reattachment point of a separated flow as long as the probe height is small enough compared to the boundary layer thickness. The measurement results are compared to profile pressure distributions and hot-wire boundary layer profiles. Also the influence of periodic unsteady inflow conditions on the dynamic pressure near the wall is revealed in the time average. Limitations due to the probe geometry are discussed and a method to estimate the influence of the probe geometry on the measured dynamic pressure coefficient is suggested.

scholarly journals Detailed Studies on Separated Boundary Layers Over Low-Pressure Turbine Airfoils Under Several High Lift Conditions: Effect of Freesteam Turbulence

2009 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Kazutoyo Yamada ◽  
Nozomi Tanaka ◽  
Yasuhiro Chiba
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Separation Bubble ◽  
Low Pressure ◽  
Scale Model ◽  
Freestream Turbulence ◽  
Suction Surface ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Turbine Airfoils

This paper deals with experimental investigation on the interaction between inlet freestream turbulence and boundary layers with separation bubble on a low-pressure turbine airfoil under several High Lift conditions. Solidity of the cascade can be reduced by increasing the airfoil pitch by 25%, while maintaining the throat in the blade-to-blade passage. Reynolds number examined is 57000, based on chord length and averaged exit velocity. Freestream turbulence intensity at the inlet is varied from 0.80% (no grid condition) to 2.1% by use of turbulence grid. Hot-wire probe measurements of the boundary layer on the suction surface for Low Pressure (LP) turbines rotor are carried out to obtain time-averaged and time-resolved characteristics of the boundary layers under the influence of the freestream turbulence. Frequency analysis extracts some important features of the unsteady behaviors of the boundary layer, including vortex formation and shedding. Numerical analysis based on high resolution Large Eddy Simulation is also executed to enhance the understanding on the flow field around the highly loaded turbine airfoils. Standard Smagorinsky model is employed as subgrid scale model. Emphasis of the simulation is placed on the relationship of inherent instability of the shear layer of the separation bubble and the freestream turbulence.

Redesign of High-Lift LP-Turbine Airfoils for Low Speed Testing

2010 ◽  
Author(s):  
Michele Marconcini ◽  
Filippo Rubechini ◽  
Roberto Pacciani ◽  
Andrea Arnone ◽  
Francesco Bertini
Keyword(s):  
Separated Flow ◽  
Low Pressure ◽  
High Lift ◽  
Low Speed ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Flow Configurations ◽  
Artificial Neural Network Ann ◽  
Lp Turbine ◽  
Turbine Airfoils

Low pressure turbine airfoils of the present generation usually operate at subsonic conditions, with exit Mach numbers of about 0.6. To reduce the costs of experimental programs it can be convenient to carry out measurements in low speed tunnels in order to determine the cascades performance. Generally speaking, low speed tests are usually carried out on airfoils with modified shape, in order to compensate for the effects of compressibility. A scaling procedure for high-lift, low pressure turbine airfoils to be studied in low speed conditions is presented and discussed. The proposed procedure is based on the matching of a prescribed blade load distribution between the low speed airfoil and the actual one. Such a requirement is fulfilled via an Artificial Neural Network (ANN) methodology and a detailed parameterization of the airfoil. A RANS solver is used to guide the redesign process. The comparison between high and low speed profiles is carried out, over a wide range of Reynolds numbers, by using a novel three-equation, transition-sensitive, turbulence model. Such a model is based on the coupling of an additional transport equation for the so-called laminar kinetic energy (LKE) with the Wilcox k–ω model and it has proven to be effective for transitional, separated-flow configurations of high-lift cascade flows.

Evaluation of RANS Transition Modeling for High Lift LPT Flows at Low Reynolds Number

2013 ◽  
Author(s):  
Kevin Keadle ◽  
Mark McQuilling
Keyword(s):  
Reynolds Number ◽  
Total Pressure ◽  
Current Model ◽  
Pressure Coefficient ◽  
Low Pressure ◽  
Two Dimensional ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Low Reynolds ◽  
Turbine Airfoils

High lift low pressure turbine airfoils have complex flow features that can require advanced modeling capabilities for accurate flow predictions. These features include separated flows and the transition from laminar to turbulent boundary layers. Recent applications of computational fluid dynamics based on the Reynolds-averaged Navier-Stokes formulation have included modeling for attached and separated flow transition mechanisms in the form of empirical correlations and two- or three-equation eddy viscosity models. This study uses the three-equation model of Walters and Cokljat [1] to simulate the flow around the Pack B and L2F low pressure turbine airfoils in a two-dimensional cascade arrangement at a Reynolds number of 25,000. This model includes a third equation for the development of pre-transitional laminar kinetic energy (LKE), and is an updated version of the Walters and Leylek [2] model. The aft-loaded Pack B has a nominal Zweifel loading coefficient of 1.13, and the front-loaded L2F has a nominal loading coefficient of 1.59. Results show the updated LKE model improves predicted accuracy of pressure coefficient and velocity profiles over its previous version as well as two-equation RANS models developed for separated and transitional flows. Transition onset behavior also compares favorably with experiment. However, the current model is not found suitable for wake total pressure loss predictions in two-dimensional simulations at extremely low Reynolds numbers due to the predicted coherency of suction side vortices generated in the separated shear layers which cause a local gain in wake total pressure.

Parametric Optimization of Unsteady Endwall Blowing on a Highly Loaded LPT

2013 ◽  
Author(s):  
Stuart I. Benton ◽  
Chiara Bernardini ◽  
Jeffrey P. Bons ◽  
Rolf Sondergaard
Keyword(s):  
Large Scale ◽  
Boundary Layer Separation ◽  
Low Pressure ◽  
Suction Surface ◽  
Low Pressure Turbine ◽  
Pressure Distributions ◽  
Image Velocimetry ◽  
Stereo Particle Image Velocimetry ◽  
Turbine Airfoils ◽  
Highly Loaded

Efforts to reduce blade count and avoid boundary layer separation have led to low-pressure turbine airfoils with significant increases in loading as well as front-loaded pressure distributions. These features have been independently shown to increase losses within the secondary flow field at the endwall. Compound angle blowing from discrete jets on the blade suction surface near the endwall has been shown to be effective in reducing these increased losses and enabling the efficient use of highly loaded blade designs. In this study, experiments are performed on the front loaded L2F low-pressure turbine airfoil in a linear cascade. The required mass flow is reduced by decreasing hole count from previous configurations and from the introduction of unsteady blowing. The effects of pulsing frequency and duty cycle are investigated using phase-locked stereo particle image velocimetry to demonstrate the large scale movement and hysteresis behavior of the passage vortex interacting with the pulsed jets. Total pressure loss contours at the cascade outlet demonstrate that the efficiency benefit is maintained with the use of unsteady forcing.

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