Flow field measurements of leading-edge separation vortex formed on a delta wing with vortex flaps

With the desire for increased power output for a gas turbine engine comes the continual push to achieve higher turbine inlet temperatures. Higher temperatures result in large thermal and mechanical stresses particularly along the nozzle guide vane. One critical region along a vane is the leading edge-endwall juncture. Based on the assumption that the approaching flow to this juncture is similar to a two-dimensional boundary layer, previous studies have shown that a horseshoe vortex forms. This vortex forms because of a radial total pressure gradient from the approaching boundary layer. This paper documents the computational design and experimental validation of a fillet placed at the leading edge-endwall juncture of a guide vane to eliminate the horseshoe vortex. The fillet design effectively accelerated the incoming boundary layer thereby mitigating the effect of the total pressure gradient. To verify the CFD studies used to design the leading edge fillet, flow field measurements were performed in a large-scale, linear, vane cascade. The flow field measurements were performed with a laser Doppler velocimeter in four planes orientated orthogonal to the vane. Good agreement between the CFD predictions and the experimental measurements verified the effectiveness of the leading edge fillet at eliminating the horseshoe vortex. The flowfield results showed that the turbulent kinetic energy levels were significantly reduced in the endwall region because of the absence of the unsteady horseshoe vortex.

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A Note on the Vorticity Distribution on the Surface of Slender Delta Wings with Leading Edge Separation

Journal of the Royal Aeronautical Society ◽

10.1017/s0001924000093520 ◽

1961 ◽

Vol 65 (603) ◽

pp. 195-198 ◽

Cited By ~ 5

Author(s):

B. J. Elle ◽

J. P. Jones

Keyword(s):

Experimental Evidence ◽

Delta Wing ◽

Leading Edge ◽

Water Tunnel ◽

Delta Wings ◽

Vorticity Distribution ◽

Edge Separation

A description is given of the distribution of vorticity in the surface of thin wings with large leading edge sweep. Although the delta wing is chosen as the basic plan form the deductions are general and applicable to other types of wing. The conclusions are illustrated with experimental evidence from a water tunnel.

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Midspan Flow-Field Measurements for Two Transonic Linear Turbine Cascades at Off-Design Conditions

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery ◽

10.1115/2001-gt-0493 ◽

2001 ◽

Cited By ~ 3

Author(s):

D. B. M. Jouini ◽

S. A. Sjolander ◽

S. H. Moustapha

Keyword(s):

Flow Field ◽

Turbine Blade ◽

Density Ratio ◽

Leading Edge ◽

Field Measurements ◽

Reynolds Numbers ◽

Experimental Results ◽

Tabular Form ◽

Data Set ◽

Turbine Cascades

The paper presents detailed mid-span experimental results from two transonic linear turbine cascades. The blades for the two cascades were designed for the same service and differ mainly in their leading-edge geometries. One of the goals of the study was investigate the influence of the leading-edge metal angle on the sensitivity of the blade to positive off-design incidence. Measurements were made for incidence values of −10.0°, 0.0°, +4.5°, +10.0°, and +14.5° relative to design incidence. The exit Mach numbers varied roughly from 0.5 to 1.2 and the Reynolds numbers from about 4×105 to 106. The measurements include the midspan losses, blade loadings and base pressures. In addition, the axial-velocity-density ratio (AVDR) was extracted for each operating point The AVDR was found to vary from about 0.98 at −10.0° of incidence to about 1.27 at +14.5°. Thus, the data set also provides some evidence of the influence AVDR on axial turbine blade performance. Detailed experimental results for turbine blade performance at off-design incidence are very scarce in the open literature, particularly for transonic conditions. Among other things, the present results are intended to expand the database available in the open literature. To this end, the key aerodynamic results are presented in tabular form, along with the detailed geometry of the cascades. The results could be used in the development of new or improved correlations for use in the early stages of design. They could also be used to evaluate the ability of current CFD codes to capture reliably the variation in losses and other aerodynamic quantities with variations in blade incidence.

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Measurements of Hub Flow Interaction on Film Cooled Nozzle Guide Vane in Transonic Annular Cascade

Journal of Turbomachinery ◽

10.1115/1.4029242 ◽

2015 ◽

Vol 137 (8) ◽

Cited By ~ 2

Author(s):

Lamyaa A. El-Gabry ◽

Ranjan Saha ◽

Jens Fridh ◽

Torsten Fransson

Keyword(s):

Flow Field ◽

Secondary Flow ◽

Film Cooling ◽

Guide Vane ◽

Leading Edge ◽

Field Measurements ◽

Co2 Concentration ◽

Horseshoe Vortex ◽

Mainstream Flow ◽

Nozzle Guide

An experimental study has been performed in a transonic annular sector cascade of nozzle guide vanes (NGVs) to investigate the aerodynamic performance and the interaction between hub film cooling and mainstream flow. The focus of the study is on the endwalls, specifically the interaction between the hub film cooling and the mainstream. Carbon dioxide (CO2) has been supplied to the coolant holes to serve as tracer gas. Measurements of CO2 concentration downstream of the vane trailing edge (TE) can be used to visualize the mixing of the coolant flow with the mainstream. Flow field measurements are performed in the downstream plane with a five-hole probe to characterize the aerodynamics in the vane. Results are presented for the fully cooled and partially cooled vane (only hub cooling) configurations. Data presented at the downstream plane include concentration contour, axial vorticity, velocity vectors, and yaw and pitch angles. From these investigations, secondary flow structures such as the horseshoe vortex, passage vortex, can be identified and show the cooling flow significantly impacts the secondary flow and downstream flow field. The results suggest that there is a region on the pressure side (PS) of the vane TE where the coolant concentrations are very low suggesting that the cooling air introduced at the platform upstream of the leading edge (LE) does not reach the PS endwall, potentially creating a local hotspot.

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Computational study of incipient leading-edge separation on a supersonic delta wing

Journal of Aircraft ◽

10.2514/3.46145 ◽

1992 ◽

Vol 29 (2) ◽

pp. 203-209 ◽

Cited By ~ 1

Author(s):

S. Naomi McMillin ◽

James L. Pittman ◽

James L. Thomas

Keyword(s):

Delta Wing ◽

Computational Study ◽

Leading Edge ◽

Edge Separation

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Measurements of Hub Flow Interaction on Film Cooled Nozzle Guide Vane in Transonic Annular Cascade

Volume 8: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2012-68088 ◽

2012 ◽

Cited By ~ 1

Author(s):

Lamyaa A. El-Gabry ◽

Ranjan Saha ◽

Jens Fridh ◽

Torsten Fransson

Keyword(s):

Flow Field ◽

Secondary Flow ◽

Film Cooling ◽

Guide Vane ◽

Leading Edge ◽

Field Measurements ◽

Co2 Concentration ◽

Pressure Side ◽

Trailing Edge ◽

Nozzle Guide

An experimental study has been performed in a transonic annular sector cascade of nozzle guide vanes to investigate the aerodynamic performance and the interaction between hub film cooling and mainstream flow. The focus of the study is on the endwalls, specifically the interaction between the hub film cooling and the mainstream. Carbon dioxide (CO2) has been supplied to the coolant holes to serve as tracer gas. Measurements of CO2 concentration downstream of the vane trailing edge can be used to visualize the mixing of the coolant flow with the mainstream. Flow field measurements are performed in the downstream plane with a 5-hole probe to characterize the aerodynamics in the vane. Results are presented for the fully cooled and partially cooled vane (only hub cooling) configurations. Data presented at the downstream plane include concentration contour, axial vorticity, velocity vectors, and yaw and pitch angles. From these investigations, secondary flow structures such as the horseshoe vortex, passage vortex, can be identified and show the cooling flow significantly impacts the secondary flow and downstream flow field. The results suggest that there is a region on the pressure side of the vane trailing edge where the coolant concentrations are very low suggesting that the cooling air introduced at the platform upstream of the leading edge does not reach the pressure side endwall, potentially creating a local hotspot.

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