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.

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 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.

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.

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.

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.

scholarly journals The World’s First Test Facility That Enables the Experimental Visualization of Cavitation on a Rotating Inducer in Both Cryogenic and Ordinary Fluids

2021 ◽  
Author(s):  
Yu Ito
Keyword(s):  
Flow Visualization ◽  
Liquid Nitrogen ◽  
Cavitation Number ◽  
Tip Vortex ◽  
Test Facility ◽  
Working Fluid ◽  
Cryogenic Pump ◽  
Thermodynamic Effect ◽  
Pump Head ◽  
Visualization Experiments

Abstract It is well known that cavitation breakdown, which is a phenomenon in which the pump head suddenly drops with a decrease in the inlet cavitation number, occurs in turbopumps. Especially in cryogenic pumps, cavitation breakdown occurs at a lower inlet cavitation number than that of ordinary fluids such as water. This phenomenon is referred to as a thermodynamic effect, as Stepanoff reported. The thermodynamic properties of the working fluid affect the sizes of cavitation elements, and the sizes affect cavitation breakdown; therefore, experimental flow visualization is an effective approach to realize a more efficient and more reliable cryogenic pump. In 2010, the author and colleagues developed the worldߣs first test facility to enable the visualization of cavitation on a rotating inducer in both cryogenic and ordinary fluids. At that time, only two reports on the flow visualization of a rotating cryogenic impeller had been published: one on flow visualization in liquid hydrogen by NASA in 1967 and the other in liquid nitrogen by JAXA in 2010. The present facility employs a triple-thread helical inducer with a diameter of 65.3 mm and a rotation rate of up to 8000 rpm with both liquid nitrogen and water available as working fluids. Unsteady visualization experiments for cavitation on an inducer in liquid nitrogen and water have revealed the characteristics of tip vortex cavitation, backflow vortex cavitation, and cavitation element size based on comparisons between cryogenic fluids that exhibit a stronger thermodynamic effect and ordinary fluids such as water.

Performance of Core Exit Thermocouple for PWR Accident Management Action in Vessel Top Break LOCA Simulation Experiment at OECD/NEA ROSA Project

2008 ◽  
Author(s):  
Mitsuhiro Suzuki ◽  
Takeshi Takeda ◽  
Hideo Nakamura
Keyword(s):  
Time Delay ◽  
Large Scale ◽  
Simulation Experiment ◽  
Three Dimensional ◽  
Test Facility ◽  
Large Temperature ◽  
Energy Agency ◽  
Pressurized Water ◽  
The Core ◽  
Accident Management

Presented are experiment results of the Large Scale Test Facility (LSTF) conducted at the Japan Atomic Energy Agency (JAEA) with a focus on core exit thermocouple (CET) performance to detect core overheat during a vessel top break loss-of-coolant accident (LOCA) simulation experiment. The CET temperatures are used to start accident management (AM) action to quickly depressurize steam generator (SG) secondary sides in case of core temperature excursion. Test 6-1 is the first test of the OECD/NEA ROSA Project started in 2005, simulating withdraw of a control rod drive mechanism penetration nozzle at the vessel top head. The break size is equivalent to 1.9% cold leg break. The AM action was initiated when CET temperature rose up to 623K. There was no reflux water fallback onto the CETs during the core heat-up period. The core overheat, however, was detected with a time delay of about 230s. In addition, a large temperature discrepancy was observed between the CETs and the hottest core region. This paper clarifies the reasons of time delay and temperature discrepancy between the CETs and heated core during boil-off including three-dimensional steam flows in the core and core exit. The paper discusses applicability of the LSTF CET performance to pressurized water reactor (PWR) conditions and a possibility of alternative indicators for earlier AM action than in Test 6-1 is studied by using symptom-based plant parameters such as a reactor vessel water level detection.

An automated procedure to properly handle digital images in large scale Tissue Microarray experiments

2005 ◽  
Vol 79 (3) ◽  
pp. 197-208 ◽  
Author(s):  
Rossana Dell’Anna ◽  
Francesca Demichelis ◽  
Mattia Barbareschi ◽  
Andrea Sboner
Keyword(s):  
Tissue Microarray ◽  
Large Scale ◽  
Digital Images ◽  
Microarray Experiments
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