Flow Visualization and Leakage Measurements of Stepped Labyrinth Seals: Part 2—Sloping Surfaces

1997 ◽  
Vol 119 (4) ◽  
pp. 844-848 ◽  
Author(s):  
D. L. Rhode ◽  
J. S. Younger ◽  
M. D. Wernig
Keyword(s):  
Flow Visualization ◽  
Leading Edge ◽  
Test Facility ◽  
Variable Geometry ◽  
Two Dimensional ◽  
Labyrinth Seals ◽  
Leakage Resistance ◽  
Water Test ◽  
Sloping Surface ◽  
Visualization Techniques

An experimental investigation was conducted to determine the geometry–leakage relationship for advanced, stepped labyrinth seals. A unique, variable-geometry water test facility was constructed and used to acquire leakage resistance measurements for two-dimensional, planar models. Flow visualization techniques were also used to assist in identifying and understanding the turbulence generating flow patterns. It was found that contoured surfaces and restrictor tooth leading-edge shapes of proper dimensions can be incorporated into the cavity geometry to reduce seal leakage. Specifically, the combination of a sloping surface and a curved surface on the rotor within the labyrinth cavity gave significant improvement.

scholarly journals Flow Visualization and Leakage Measurements of Stepped Labyrinth Seals: Part 2 — Sloping Surfaces

1996 ◽  
Author(s):  
David L. Rhode ◽  
James S. Younger ◽  
Marcus D. Wernig
Keyword(s):  
Flow Visualization ◽  
Leading Edge ◽  
Test Facility ◽  
Variable Geometry ◽  
Two Dimensional ◽  
Labyrinth Seals ◽  
Leakage Resistance ◽  
Water Test ◽  
Sloping Surface ◽  
Visualization Techniques

An experimental investigation was conducted to determine the geometry-leakage relationship for advanced, stepped labyrinth seals. A unique, variable-geometry water test facility was constructed and used to acquire leakage resistance measurements for two-dimensional, planar models. Flow visualization techniques were also used to assist in identifying and understanding the turbulence generating flow patterns. It was found that contoured surfaces and restrictor tooth leading-edge shapes of proper dimensions can be incorporated into the cavity geometry to reduce seal leakage. Specifically, the combination of a sloping surface and a curved surface on the rotor within the labyrinth cavity gave significant improvement.

Flow Visualization and Leakage Measurements of Stepped Labyrinth Seals: Part 1—Annular Groove

1997 ◽  
Vol 119 (4) ◽  
pp. 839-843 ◽  
Author(s):  
D. L. Rhode ◽  
J. W. Johnson ◽  
D. H. Broussard
Keyword(s):  
Flow Visualization ◽  
Large Scale ◽  
Digital Images ◽  
Test Facility ◽  
Labyrinth Seals ◽  
Water Leakage ◽  
Tracer Particles ◽  
Leakage Resistance ◽  
Visualization Experiments ◽  
Resistance Improvement

An improved understanding of a new category of stepped labyrinth seals, which feature a new “annular groove,” was obtained. A water leakage and flow visualization test facility of very large scale (relative to a typical seal) was utilized. Flow visualization experiments using a new method and digital facilities for capturing and editing digital images from an 8 mm video were conducted. The presence of an annular groove machined into the stator land increases the leakage resistance by up to 26 percent for the cases considered here. Tracer particles show the degree of throughflow path penetration into the annular groove (i.e., serpentining), which gives the largest and the smallest leakage resistance improvement over that of the corresponding conventional stepped seal.

Flow Visualization and Leakage Measurements of Stepped Labyrinth Seals: Part 1 — Annular Groove

1996 ◽  
Author(s):  
David L. Rhode ◽  
James W. Johnson ◽  
Daniel H. Broussard
Keyword(s):  
Flow Visualization ◽  
Large Scale ◽  
Digital Images ◽  
Test Facility ◽  
Labyrinth Seals ◽  
Water Leakage ◽  
Tracer Particles ◽  
Leakage Resistance ◽  
Visualization Experiments ◽  
Resistance Improvement

An improved understanding of a new category of stepped labyrinth seals, which feature a new “annular groove”, was obtained. A water leakage and flow visualization test facility of very large scale (relative to a typical seal) was utilized. Flow visualization experiments using a new method and digital facilities for capturing and editing digital images from an 8 mm video were conducted. The presence of an annular groove machined into the stator land increases the leakage resistance by up to 26 percent for the cases considered here. Tracer particles show the degree of throughflow path penetration into the annular groove (i.e. serpentining), which gives the largest and the smallest leakage resistance improvement over that of the corresponding conventional stepped seal.

The vortex-shedding process behind two-dimensional bluff bodies

1982 ◽  
Vol 116 ◽  
pp. 77-90 ◽  
Author(s):  
A. E. Perry ◽  
M. S. Chong ◽  
T. T. Lim
Keyword(s):  
Circular Cylinder ◽  
Flow Visualization ◽  
Vortex Shedding ◽  
Bluff Bodies ◽  
Two Dimensional ◽  
Closed Cavity ◽  
Time Exposure ◽  
Starting Flow ◽  
Visualization Techniques ◽  
Insight Into

Using a variety of flow-visualization techniques, the flow behind a circular cylinder has been studied. The results obtained have provided a new insight into the vortex-shedding process. Using time-exposure photography of the motion of aluminium particles, a sequence of instantaneous streamline patterns of the flow behind a cylinder has been obtained. These streamline patterns show that during the starting flow the cavity behind the cylinder is closed. However, once the vortex-shedding process begins, this so-called ‘closed’ cavity becomes open, and instantaneous ‘alleyways’ of fluid are formed which penetrate the cavity. In addition, dye experiments also show how layers of dye and hence vorticity are convected into the cavity behind the cylinder, and how they are eventually squeezed out.

Measurement and Visualization of Leakage Effects of Rounded Teeth Tips and Rub-Grooves on Stepped Labyrinths

2000 ◽  
Vol 123 (3) ◽  
pp. 604-611 ◽  
Author(s):  
D. L. Rhode ◽  
B. F. Allen
Keyword(s):  
Flow Visualization ◽  
Large Scale ◽  
Recirculation Zone ◽  
Step Height ◽  
Test Facility ◽  
Leakage Resistance ◽  
Large Step ◽  
Fluorescein Dye ◽  
Resistance Decrease ◽  
Flow Tracer

The effect of rounded labyrinth teeth tips and worn abradable lands has been found to give substantially increased leakage, which is well known to give reduced machine efficiency. Very little information concerning this exists, and some of the first measurements and visualization movies for stepped labyrinths are provided here to give an enhanced understanding of this phenomenon. A unique, very large-scale seal test facility was used. Glitter, and alternatively fluorescein dye, was employed as the flow tracer material. The flow visualization movies were digitally stored on the hard drive of a computer. Large decreases of leakage resistance due to the presence of worn teeth as well as rub-grooves were found. For the cases considered, the leakage resistance decrease for the large step height configurations were 85 percent, 55 percent, and 70 percent for the small, medium, and large pre-rub clearances, respectively. It was also found that the resistance varied with wear geometry, in order from highest to lowest resistance, as (a) ungrooved-unrounded-teeth, (b) ungrooved-rounded-teeth, (c) grooved-unrounded-teeth and (d) grooved-rounded-teeth. Further, a substantial tooth tip recirculation zone was visually observed only for the grooved-unrounded-teeth cases, and it was shown to be the mechanism by which the unrounded teeth give this configuration a higher resistance than do the rounded teeth.

Numerical Predictions and Measurements of Discharge Coefficients in Labyrinth Seals

1987 ◽  
Author(s):  
S. Wittig ◽  
U. Schelling ◽  
S. Kim ◽  
K. Jacobsen
Keyword(s):  
Discharge Coefficient ◽  
Test Facility ◽  
Geometrical Parameters ◽  
Two Dimensional ◽  
Labyrinth Seals ◽  
Discharge Coefficients ◽  
Numerical Predictions ◽  
Flow Through ◽  
Compressible Turbulent Flow ◽  
Good Agreement

The present paper illustrates the possibilities and limitations in applying advanced numerical codes for the description of the flow through labyrinth seals to evaluate the discharge coefficient. Comparison with data derived from detailed measurements in a newly developed test facility are reported. Pressure ratios and geometrical parameters are varied in wide ranges, reflecting engine conditions. The two-dimensional, elliptic finite difference code is applied to the compressible, turbulent flow in straight and stepped seals utilizing the standard k-ε-model. Good agreement of the predictions with the measurements is achieved for pressure ratios up to 2.5.

Measurement and Visualization of Leakage Effects of Rounded Teeth Tips and Rub-Grooves on Stepped Labyrinths

1999 ◽  
Author(s):  
David L. Rhode ◽  
Brian F. Allen
Keyword(s):  
Flow Visualization ◽  
Large Scale ◽  
Recirculation Zone ◽  
Step Height ◽  
Test Facility ◽  
Leakage Resistance ◽  
Large Step ◽  
Fluorescein Dye ◽  
Resistance Decrease ◽  
Flow Tracer

The effect of rounded labyrinth teeth tips and worn abradable lands has been found to give substantially increased leakage, which is well known to give reduced machine efficiency. Very little information concerning this exists, and some of the first measurements and visualization movies for stepped labyrinths are provided here to give an enhanced understanding of this phenomenon. A unique, very large-scale seal test facility was used. Glitter, and alternatively fluorescein dye, was employed as the flow tracer material. The flow visualization movies were digitally stored on the hard drive of a computer. Large decreases of leakage resistance due to the presence of worn teeth as well as rub-grooves were found. For the cases considered, the leakage resistance decrease for the large step height configurations were 85 percent, 55 percent and 70 percent for the small, medium and large pre-rub clearances, respectively. It was also found that the resistance varied with wear geometry, in order from highest to lowest resistance, as: (a) ungrooved-unrounded-teeth, (b) ungrooved-rounded-teeth, (c) grooved-unrounded-teeth and (d) grooved-rounded-teeth. Further, a substantial tooth tip recirculation zone was visually observed only for the grooved-unrounded-teeth cases, and it was shown to be the mechanism by which the unrounded teeth give this configuration a higher resistance than do the rounded teeth.

A Comparative Study of the Aerodynamics of Several Wind Turbines Using Flow Visualization

1990 ◽  
Vol 112 (4) ◽  
pp. 301-309 ◽  
Author(s):  
D. M. Eggleston ◽  
K. Starcher
Keyword(s):  
Flow Visualization ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Complete Separation ◽  
Laminar Separation ◽  
Reynolds Number Flow ◽  
Oil Flow ◽  
Number Flow ◽  
Visualization Techniques

Flow visualization techniques were used to study the flows over the Enertech 21-5, Carter 25, and Enertech 44-50. Despite centrifugal effects superimposed on the aerodynamics, tufting (gross aerodynamic behavior) and oil flow (average boundary layer behavior), tests reveal the nature and many of the details of the flows involved. Results were compared to expected flow patterns based on angles of attack calculated from the PROPPC code. Chord Reynolds numbers ranged between 75,000 (Enertech 21-5) to 1,340,000 (Enertech 44-50). The typical low Reynolds number flow characteristics of these airfoils, including laminar separation bubbles, turbulent reattachment, and complete separation were observed. Full or partial reattachment due to tower shadow was observed on each machine. Spanwise flow was observed near the leading edge of the Enertech 21-5. Cyclic radial flow from tower dam effect was also noted.

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