Endwall Vortex Effects on Turbulent Dispersion of Film Coolant in a Turbine Vane Cascade

2014 ◽  
Author(s):  
Sayuri D. Yapa ◽  
Christopher J. Elkins ◽  
John K. Eaton
Keyword(s):  
Cross Flow ◽  
Suction Side ◽  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Turbulent Dispersion ◽  
Suction Surface ◽  
Full Field ◽  
Flow Vorticity ◽  
Passage Vortex ◽  
Turbine Vane

Turbine vane cascades produce strong secondary flows due to flow turning. The dominant flow feature is the passage vortex, located in the corner between the endwall and the suction surface of the airfoil. Full-field, 3D velocity and concentration measurements were made using magnetic resonance imaging to study turbulent mixing in a realistic film-cooled nozzle vane cascade. The passage vortex has large effects on the flow features in the vane wake and consequently, on coolant mixing. Cross-flow vorticity on the vane’s suction side rolls up and forms the suction-side leg of the horseshoe vortex, which then interacts with the cross-flow boundary layer and rolls up into the passage vortex. The passage vortex does not measurably increase the turbulent diffusivity, although it does strongly distort streamlines near the endwall.

Flowfield Measurements in the Endwall Region of a Stator Vane

1999 ◽  
Author(s):  
M. B. Kang ◽  
K. A. Thole
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
Secondary Flows ◽  
Laser Doppler Velocimeter ◽  
Transfer Coefficients ◽  
Suction Surface ◽  
Numerical Predictions ◽  
High Heat Transfer ◽  
Passage Vortex ◽  
Stator Vane

A first stage stator vane experiences high heat transfer rates particularly near the end wall where strong secondary flows occur. In order to improve numerical predictions of the complex endwall flow at low speed conditions, benchmark quality experimental data are required. This study documents the flowfield in the endwall region of a stator vane that has been scaled up by a factor of nine while matching an engine exit Reynolds number of Reex = 1.2·106. Laser Doppler velocimeter (LDV) measurements of all three components of the mean and fluctuating velocities are presented for several flow planes normal to the turbine vane. Measurements indicate that downstream of the minimum static pressure location on the suction surface of the vane, an attenuated suction side leg of the horseshoe vortex still exists. At this location, the peak turbulent kinetic energy coincides with the center of the passage vortex location. These flowfield measurements were also related to previously reported convective heat transfer coefficients on the endwall showing that high Stanton numbers occur where the passage vortex brings mainstream fluid towards the vane surface.

Effect of Purge on the Secondary Flow-Field of a Gas Turbine Blade-Row

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
B. D. J Schreiner ◽  
M. Wilson ◽  
Y. S. Li ◽  
C. M. Sangan
Keyword(s):  
Computational Study ◽  
Suction Side ◽  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Pressure Side ◽  
Suction Surface ◽  
Blade Row ◽  
Purge Flow ◽  
Rotational Direction ◽  
Secondary Flow Field

Abstract Turbine disc cooling is required to protect vulnerable components from exposure to the high temperatures found in the mainstream gas path. Purge air, bled from the latter stages of the compressor, is introduced to the turbine wheelspace at low radius before exiting through the rim-seal at the periphery of the discs. The unsteady, complex flowfield that arises from the interaction between the purge and mainstream gases modifies the structure of secondary flows within the blade passage. A computational study was conducted using an unsteady Reynolds-averaged Navir–Stokes (RANS) solver, modeling an engine-representative turbine stage. Preliminary results were validated using experimental data from a test rig. The baseline secondary flowfield was described, in the absence of purge flow, demonstrating the classical rollup of the horseshoe vortex and subsequent convection of the two legs downstream. The unsteady behavior of the model was investigated and addressed, resulting in recommendations for modeling interaction phenomena in turbines. A superposed purge flow, resulting in egress through the upstream rim-seal, was shown to modify the secondary flowfield in the turbine annulus. The most notable effect of egress was the formation of a large plume forming near the pressure minima associated with the blade suction surface. The egress was turned by the mainstream flow, creating a vortical structure consistent in rotational direction to the pressure-side leg of the horseshoe vortex; the pressure-side leg was subsequently strengthened and showed an increased radial migration relative to the unpurged case. The egress plume was also shown to overwhelm the suction-side leg of the horseshoe vortex, reducing its strength.

Formation and Transport of Secondary Flows Caused by Vortex-Blade Interaction in a High Pressure Turbine

2015 ◽  
Author(s):  
Zuo-Jun Wei ◽  
Wei-Yang Qiao ◽  
Ping-Ping Chen ◽  
Jian Liu
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Pressure Gradient ◽  
Suction Side ◽  
Secondary Flows ◽  
Pressure Side ◽  
High Pressure Turbine ◽  
Suction Surface ◽  
Blade Loading ◽  
Passage Vortex

As modern turbines are designed with low aspect ratio and high blade loading, secondary flow interactions become more important. In the present work, numerical simulation is performed in a two-stage high-pressure turbine with divergent meridional passage to investigate the transport and interaction of secondary vortex from the first stage rotor within the second stage’s stator. Scale-Adaptive Simulation model coupled with Shear Stress Transport model (SAS-SST turbulence model) is used to capture the flow structures caused by the interaction in the second stator. Coupled with the passage vortex of the first rotor, the shed vortex rotates opposite in the direction and has comparable strength. As both of these vortices convect downstream to the stator bladerow, each deforms into two legs on the pressure and suction sides in the passage. In the passage due to the cross pressure gradient by blade loading, all the low-momentum fluid contained in these vortices moves towards the suction side. Besides, with the existing static pressure gradient in radial direction and vortex dynamics, the suction-side leg and the pressure-side leg move in different radial directions. The suction side leg of incoming passage vortex moves towards the endwall along the suction surface and interacts with the developing passage vortex of the second stator. The incoming shed vortex moves towards the midspan and rolls up the boundary layer fluid from suction surface. Due to the interactions between the incoming shed vortices from the hub and casing and the boundary layer of second stator, two counter-rotating vortices are formed near the midspan. Additional high loss is found there at the outlet plane, which has a comparable magnitude to the endwall secondary loss. The pressure side leg of the incoming passage vortex remains in a certain span with that of the incoming shed vortex and is not engulfed by the developing passage vortex.

Experimental Investigation of Secondary Flow Structure in a Blade Passage With and Without Leading Edge Fillets

2006 ◽  
Vol 129 (3) ◽  
pp. 253-262 ◽  
Author(s):  
G. I. Mahmood ◽  
S. Acharya
Keyword(s):  
Cross Section ◽  
Pressure Loss ◽  
Leading Edge ◽  
Suction Side ◽  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Blade Passage ◽  
Pressure Loss Coefficient ◽  
Passage Vortex ◽  
Loss Coefficients

Velocity and pressure measurements are presented for a blade passage with and without leading edge contouring in a low speed linear cascade. The contouring is achieved through fillets placed at the junction of the leading edge and the endwall. Two fillet shapes, one with a linear streamwise cross-section (fillet 1) and the other with a parabolic cross-section (fillet 2), are examined. Measurements are taken at a constant Reynolds number of 233,000 based on the blade chord and the inlet velocity. Data presented at different axial planes include the pressure loss coefficient, axial vorticity, velocity vectors, and yaw and pitch angles. In the early stages of the development of the secondary flows, the fillets are seen to reduce the size and strength of the suction-side leg of the horseshoe vortex with associated reductions in the pressure loss coefficients and pitch angles. Further downstream, the total pressure loss coefficients and vorticity show that the fillets lift the passage vortex higher above the endwall and move it closer to the suction side in the passage. Near the trailing edge of the passage, the size and strength of the passage vortex is smaller with the fillets, and the corresponding reductions in pressure loss coefficients extend beyond the mid-span of the blade. While both fillets reduce pressure loss coefficients and vorticity, fillet 1 (linear fillet profile) appears to exhibit greater reductions in pressure loss coefficients and pitch angles.

Flow Visualization in a Linear Turbine Cascade of High Performance Turbine Blades

1995 ◽  
Author(s):  
Hai-Ping Wang ◽  
Steven J. Olson ◽  
Richard J. Goldstein ◽  
Ernst R. G. Eckert
Keyword(s):  
Flow Visualization ◽  
High Performance ◽  
Current Model ◽  
Turbine Blades ◽  
Leading Edge ◽  
Flow Region ◽  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Suction Surface ◽  
Passage Vortex

Multiple smoke wires are used to investigate the secondary flow near the endwall of a plane cascade with blade shapes as used in high performance turbine stages. The wires are positioned parallel to the endwall and ahead of the cascade, within and outside the endwall boundary layer. The traces of the smoke generated by the wires are visualized within a laser light sheet arranged at various cross-sections around the cascade. During the experiment, a periodically fluctuating horseshoe vortex system of varying number of vortices is observed near the leading edge of the cascade. A series of photographs and video tapes was taken in the cascade to trace these vortices. The development and evolution of the horseshoe vortex and the passage vortex are clearly resolved in the photographs. The interaction between the suction side leg of the horseshoe vortex and the passage vortex is also observed in the experiment. A vortex induced by the passage vortex, starting about 1/4 of the curvilinear distance along the blade on the suction surface, is clearly shown in the photographs. This vortex stays close to the suction surface and above the passage vortex in the laminar flow region on the blade. From this flow visualization, a model describing the secondary flows in a cascade is proposed and compared with previous published models. Some naphthalene mass transfer results from a blade near an endwall are cited and compared with the current model. The flows inferred from both techniques agree well with each other.

Experimental Investigation of Flow Structure and Nusselt Number in a Low-Speed Linear Blade Passage With and Without Leading-Edge Fillets

2005 ◽  
Vol 127 (5) ◽  
pp. 499-512 ◽  
Author(s):  
G. I. Mahmood ◽  
R. Gustafson ◽  
S. Acharya
Keyword(s):  
Nusselt Number ◽  
Thermal Loading ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Suction Surface ◽  
Blade Passage ◽  
Low Speed ◽  
Passage Vortex ◽  
End Wall

The potential of contouring the leading edge of a blade to control the development of the secondary flows in the blade passage and to reduce the thermal loading to the end wall is investigated experimentally. Fillets placed at the junctions of the leading edge and the end wall are used for contouring. Four different types of fillet profiles are tested in a low-speed linear cascade a Reynolds numbers of 233,000 based on the inlet velocity. Images of instantaneous smoke flow patterns show a smaller horseshoe vortex along the leading edge with the fillets. In the passage, the fillets cause the passage vortex to be located closer to the suction surface. Upstream of the throat, the normalized axial vorticity values for the passage vortex and the turbulence intensity levels are smaller with the fillets compared to the baseline. For the leading-edge fillet with a concave profile, the end-wall Nusselt number distributions show significant reductions compared to the baseline.

Flow Visualization in a Linear Turbine Cascade of High Performance Turbine Blades

1997 ◽  
Vol 119 (1) ◽  
pp. 1-8 ◽  
Author(s):  
H. P. Wang ◽  
S. J. Olson ◽  
R. J. Goldstein ◽  
E. R. G. Eckert
Keyword(s):  
Flow Visualization ◽  
High Performance ◽  
Current Model ◽  
Turbine Blades ◽  
Leading Edge ◽  
Flow Region ◽  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Suction Surface ◽  
Passage Vortex

Multiple smoke wires are used to investigate the secondary flow near the endwall of a plane cascade with blade shapes used in high-performance turbine stages. The wires are positioned parallel to the endwall and ahead of the cascade, within and outside the endwall boundary layer. The traces of the smoke generated by the wires are visualized with a laser light sheet illuminating various cross sections around the cascade. During the experiment, a periodically fluctuating horseshoe vortex system of varying number of vortices is observed near the leading edge of the cascade. A series of photographs and video tapes was taken in the cascade to trace these vortices. The development and evolution of the horseshoe vortex and the passage vortex are clearly resolved in the photographs. The interation between the suction side leg of the horseshoe vortex and the passage vortex is also observed in the experiment. A vortex induced by the passage vortex, starting about one-fourth of the curvilinear distance along the blade on the suction surface, is also found. This vortex stays close to the suction surface and above the passage vortex in the laminar flow region on the blade. From this flow visualization, a model describing the secondary flows in a cascade is proposed and compared with previous published models. Some naphthalene mass transfer results from a blade near an endwall are cited and compared with the current model. The flows inferred from the two techniques are in good agreement.

Flowfield Measurements in the Endwall Region of a Stator Vane

1999 ◽  
Vol 122 (3) ◽  
pp. 458-466 ◽  
Author(s):  
M. B. Kang ◽  
K. A. Thole
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
Secondary Flows ◽  
Laser Doppler Velocimeter ◽  
Transfer Coefficients ◽  
Suction Surface ◽  
Numerical Predictions ◽  
High Heat Transfer ◽  
Passage Vortex ◽  
Stator Vane

A first-stage stator vane experiences high heat transfer rates, particularly near the endwall, where strong secondary flows occur. In order to improve numerical predictions of the complex endwall flow at low-speed conditions, benchmark quality experimental data are required. This study documents the flowfield in the endwall region of a stator vane that has been scaled up by a factor of nine while matching an engine exit Reynolds number of Reex=1.2×106. Laser Doppler velocimeter (LDV) measurements of all three components of the mean and fluctuating velocities are presented for several flow planes normal to the turbine vane. Measurements indicate that downstream of the minimum static pressure location on the suction surface of the vane, an attenuated suction side leg of the horseshoe vortex still exists. At this location, the peak turbulent kinetic energy coincides with the center of the passage vortex location. These flowfield measurements were also related to previously reported convective heat transfer coefficients on the endwall showing that high Stanton numbers occur where the passage vortex brings mainstream fluid toward the vane surface. [S0889-504X(00)00803-5]

Volumetric Velocimetry Measurements of Purge–Mainstream Interaction in a One-Stage Turbine

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
A. J. Carvalho Figueiredo ◽  
B. D. J. Schreiner ◽  
A. W. Mesny ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Suction Side ◽  
Secondary Flows ◽  
Blade Passage ◽  
One Stage ◽  
Passage Vortex ◽  
Purge Flow ◽  
Secondary Flow Field

Abstract Air-cooled gas turbines employ bleed air from the compressor to cool vulnerable components in the turbine. The cooling flow, commonly known as purge air, is introduced at low radius, before exiting through the rim-seal at the periphery of the turbine discs. The purge flow interacts with the mainstream gas path, creating an unsteady and complex flowfield. Of particular interest to the designer is the effect of purge on the secondary-flow structures within the blade passage, the extent of which directly affects the aerodynamic loss in the stage. This paper presents a combined experimental and computational fluid dynamics (CFD) investigation into the effect of purge flow on the secondary flows in the blade passage of an optically accessible one-stage turbine rig. The experimental campaign was conducted using volumetric velocimetry (VV) measurements to assess the three-dimensional inter-blade velocity field; the complementary CFD campaign was carried out using unsteady Reynolds-averaged Navier–Stokes (URANS) computations. The implementation of VV within a rotating environment is a world first and offers an unparalleled level of experimental detail. The baseline flow-field, in the absence of purge flow, demonstrated a classical secondary flow-field: the rollup of a horseshoe vortex, with subsequent downstream convection of a pressure-side and suction-side leg, the former transitioning in to the passage vortex. The introduction of purge, at 1.7% of the mainstream flowrate, was shown to modify the secondary flow-field by enhancing the passage vortex, in both strength and span-wise migration. The computational predictions were in agreement with the enhancement revealed by the experiments.

Comparison of Steady and Unsteady Secondary Flows in a Turbine Stator Cascade

1989 ◽  
Author(s):  
Gregory J. Hebert ◽  
William G. Tiederman
Keyword(s):  
Secondary Flows ◽  
Rotor Blades ◽  
Velocity Measurements ◽  
Flow Loop ◽  
Suction Surface ◽  
Linear Cascade ◽  
Turbine Stator ◽  
Passage Vortex ◽  
Blade Row ◽  
Secondary Flow Structure

The effect of periodic rotor wakes on the secondary flow structure in a turbine stator cascade was investigated. A mechanism simulated the wakes shed from rotor blades bypassing cylindrical rods across the inlet to a linear cascade installed in a recirculating water flow loop. Velocity measurements showed a passage vortex, similar to that seen in steady flow, during the time associated with undisturbed fluid. However, as the rotor wake passed through the blade row, a large crossflow toward the suction surface was observed in the midspan region. This caused the development of two large areas of circulation between the midspan and endwall regions, significantly distorting and weakening the passage vortices.

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