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

2012 ◽  
Vol 134 (5) ◽  
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 ◽  
Present Generation ◽  
Wide Range ◽  
Flow Configurations ◽  
Artificial Neural Network Ann ◽  
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.

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.

Numerical and Experimental Investigation of the Reynolds Number and Reduced Frequency Effects on Low-Pressure Turbine Airfoils

2021 ◽  
Vol 143 (2) ◽  
Author(s):  
M. Bolinches-Gisbert ◽  
David Cadrecha Robles ◽  
Roque Corral ◽  
Fernando Gisbert
Keyword(s):  
Experimental Data ◽  
Numerical Data ◽  
Low Pressure ◽  
Reconstruction Method ◽  
Low Speed ◽  
Low Pressure Turbine ◽  
Reduced Frequency ◽  
Aerodynamic Properties ◽  
Numerical Solver ◽  
Turbine Airfoils

Abstract This article compares experimental and numerical data for a low-speed high-lift low pressure turbine (LPT) cascade under unsteady flow conditions. Three Reynolds numbers representative of LPTs have been tested, namely, 5 × 104, 105, and 2 × 105; at two reduced frequencies, fr = 0.5 and 1, also representative of LPTs. The experimental data were obtained at the low-speed linear cascade wind tunnel at the Polytechnic University of Madrid using hot wire, Laser Doppler Velocimetry (LDV), and pressure tappings. The numerical solver employs a sixth-order compact scheme based on the flux reconstruction method for spatial discretization and a fourth-order Runge–Kutta method to march in time. The longest case ran 550 h on 40 GPUs to reach a statistically periodic state. Pressure coefficients around the profile, boundary layer profiles and exit cross section distributions of velocity, pressure loss defect, shear Reynolds stress, and angle are compared against high-quality experimental data. Cascade loss and exit angle have also been compared against the experimental data. Very good agreement between experimental and numerical data is seen. The results demonstrate the suitability of the present methodology to predict the aerodynamic properties of unsteady flows around LPT linear cascades accurately.

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.

Aerodynamic Performance of a Very High Lift Low Pressure Turbine Blade With Emphasis on Separation Prediction

2004 ◽  
Vol 126 (3) ◽  
pp. 406-413 ◽  
Author(s):  
Re´gis Houtermans ◽  
Thomas Coton ◽  
Tony Arts
Keyword(s):  
Turbine Blade ◽  
Separation Bubble ◽  
Separated Flow ◽  
Low Pressure ◽  
Secondary Flows ◽  
Flow Mode ◽  
High Lift ◽  
Flow Angle ◽  
Low Pressure Turbine ◽  
Very High

The present paper is based on an experimental study of a front-loaded very high lift, low pressure turbine blade designed at the VKI. The experiments have been carried out in a low-speed wind tunnel over a wide operating range of incidence and Reynolds number. The aim of the study is to characterize the flow through the cascade in terms of losses, mean outlet flow angle, and secondary flows. At low inlet freestream turbulence intensity, a laminar separation bubble is present, and a prediction model for a separated flow mode of transition has been developed.

Measurements of Secondary Losses in a High-Lift Front-Loaded Turbine Cascade With the Implementation of Non-Axisymmetric Endwall Contouring

2009 ◽  
Author(s):  
D. C. Knezevici ◽  
S. A. Sjolander ◽  
T. J. Praisner ◽  
E. Allen-Bradley ◽  
E. A. Grover
Keyword(s):  
Secondary Flow ◽  
Low Pressure ◽  
Current Work ◽  
Test Facility ◽  
Test Case ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Baseline Test ◽  
Endwall Contouring ◽  
Turbine Airfoils

This paper is the second in a series from the same authors studying the mitigation of endwall losses using the low-speed linear cascade test facility at Carleton University. The previous paper documented the baseline test case for the study. The current work investigates the secondary flow in a cascade of more highly-loaded low-pressure turbine airfoils with and without the implementation of endwall profiling. This study is novel in two regards. First, the contouring is applied to low-pressure turbine airfoils, whereas studies conducted by other researchers have focused their endwall profiling efforts on the high-pressure turbine. Second, while previous researchers have optimized contouring designs for a given airfoil, the current work demonstrates the potential to open the design space by employing high-lift airfoils in conjunction with endwall contouring. Seven-hole pneumatic probe measurements taken within the blade passage and downstream of the trailing edge track the progression of the secondary flow and losses generated. The contouring divides the vorticity associated with the passage vortex into two weaker vortices, and reduces the secondary kinetic energy. Overall the secondary losses are reduced and the loss reduction is discussed with regards to changes in the flow physics. A detailed breakdown of the mixing losses further demonstrates the benefits of endwall contouring.

Experiments With Three-Dimensional Passive Flow Control Devices on Low-Pressure Turbine Airfoils

2004 ◽  
Vol 128 (2) ◽  
pp. 251-260 ◽  
Author(s):  
Douglas G. Bohl ◽  
Ralph J. Volino
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Trailing Edge ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Turbine Airfoils

The effectiveness of three-dimensional passive devices for flow control on low pressure turbine airfoils was investigated experimentally. A row of small cylinders was placed at the pressure minimum on the suction side of a typical airfoil. Cases with Reynolds numbers ranging from 25,000 to 300,000 (based on suction surface length and exit velocity) were considered under low freestream turbulence conditions. Streamwise pressure profiles and velocity profiles near the trailing edge were documented. Without flow control a separation bubble was present, and at the lower Reynolds numbers the bubble did not close. Cylinders with two different heights and a wide range of spanwise spacings were considered. Reattachment moved upstream as the cylinder height was increased or the spacing was decreased. If the spanwise spacing was sufficiently small, the flow at the trailing edge was essentially uniform across the span. The cylinder size and spacing could be optimized to minimize losses at a given Reynolds number, but cylinders optimized for low Reynolds number conditions caused increased losses at high Reynolds numbers. The effectiveness of two-dimensional bars had been studied previously under the same flow conditions. The cylinders were not as effective for maintaining low losses over a range of Reynolds numbers as the bars.

The Influence of Reynolds Number, Mach Number and Incidence Effects on Loss Production in Low Pressure Turbine Airfoils

2006 ◽  
Author(s):  
Rau´l Va´zquez ◽  
Antonio Antoranz ◽  
David Cadrecha ◽  
Leyre Arman˜anzas
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Low Pressure ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Flow Features ◽  
Mach Numbers ◽  
Turbine Airfoils ◽  
Annular Cascade ◽  
The Impact

This paper presents an experimental study of the flow field in an annular cascade of Low Pressure Turbine airfoils. The influence of Reynolds number, Mach number and incidence on profile and end wall losses have been investigated. The annular cascade consisted of 100 high lift, high aspect ratio, high turning blades that are characteristic of modern LP Turbines. The investigation was carried out for a wide range of Reynolds numbers, extending from 120k to 315k, exit Mach numbers, from 0.5 to 0.9, and incidences from −20 to +14 degrees. Results clearly indicate a significant effect of incidence and Mach number in secondary loss production; however, the Reynolds number shows it much weaker impact. It has also been found that the profile loss production is strongly influenced by both Reynolds and Mach numbers, being the impact of the incidence weaker. Finally, measured data suggest that, in order to properly reproduce the performance of these types of airfoils, annular cascades can be required as far as linear cascades may miss some essential flow features.

Effects of Surface Groove on Separated Flow Transition on a High-Lift Low-Pressure Turbine Profile Under Steady Inflow Conditions

2009 ◽  
Author(s):  
Hualing Luo ◽  
Weiyang Qiao ◽  
Kaifu Xu
Keyword(s):  
Boundary Layer ◽  
Separated Flow ◽  
Low Pressure ◽  
Separation Point ◽  
Flow Transition ◽  
Suction Surface ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Surface Groove ◽  
Inflow Conditions

LES (Large-Eddy Simulation) computations for a high-lift low-pressure turbine profile equipped with the span-wise groove on the suction surface are done to investigate the mechanism of the surface groove for separated flow transition control under steady inflow conditions, employing the dynamic Smagorinsky model. In addition to the baseline case (no groove), three groove positions which depend on the relative position of the groove trailing edge and the separation point on the suction surface are considered at two Reynolds numbers (Re, based on the inlet velocity and axial chord length). The results show that all grooves can reduce the calculated loss for Re = 50000, due to the further upstream transition inception in the separated shear layer. The analyses indicate two kinds of control mechanism such as the thinning of boundary layer behind the groove and the introduction of disturbances within the groove, depending on the groove position and Reynolds number. At Re = 50000, for the groove located upstream of the separation point, the reason for the further upstream transition inception location is the thinning of boundary layer behind the groove, and for the groove located downstream of the separation point, the reason is the introduction of disturbances within the groove. At Re = 100000, disturbances can also be generated within the groove located upstream of the separation point, promoting earlier transition inception.

Sign in / Sign up

Export Citation Format

Share Document