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

Rhode, D. L.; Younger, J. S.; Wernig, Marcus D.

doi:10.1115/96-gt-137

Cited by 5 publications

(4 citation statements)

References 7 publications

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“…Using the same test rig, Rhode, et al (1997a) experimented with labyrinth seals featuring a new annular groove. In that study, a new design increased the leakage resistance by 26% over a standard design.…”

Section: Previous Workmentioning

confidence: 99%

“…Using the Kline-McClintock method of uncertainty analysis (Kline and McClintock, 1953;Fox and McDonald, 1992), the experimental uncertainty of measuring the Reynolds number and the leakage resistance coefficient was estimated. With the same facilities and procedures as presently used, Rhode, et al (1997b) calculated the uncertainty in the leakage resistance coefficient as 3.4 percent.…”

Section: Uncertainty Analysismentioning

confidence: 99%

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Visualization and Measurements of Rub-Groove Leakage Effects on Straight-Through Labyrinth Seals

Rhode

Allen

1998

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration

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For the first time flow visualization images and leakage measurements were obtained and analyzed for an enhanced understanding of the effect of rub-grooves on straight-through labyrinth seal leakage. It was found that leakage resistance decreases sharply with increasing rub-groove axial width. Further, for smalltooth clearances with medium-or large-width rub-grooves, the groove gives an approximate 50 percent drop in leakage resistance. At the medium clearance, the presence of medium-or large-width rubgrooves increases and decreases the resistance at low Re and high Re, respectively. At the large clearance, the presence of grooves increases the resistance by some 200 percent and 40 percent for low Re and high Re, respectively. However, large clearance applications generally give very high Re where the 40 percent increase occurs.In addition, a vena contracta effect from the throughflow jet penetration into the rub-grooves was found on the flow pattern and on the leakage resistance. When penetration occurs, the trajectory angle of the jet entering the subsequent labyrinth cavity is sometimes dramatically altered, giving less kinetic energy carry-over to the subsequent tooth clearance. NOMENCLATUREc Clearance between tooth tip and opposing surface (excluding any groove depth) [cm] p Fluid density [kg/m ] K Leakage resistance coefficient P Pressure [kPa] Re Reynolds number based on clearance Vc Bulk fluid velocity at the clearance [m/s] It Dynamic fluid viscosity [N-s/m ]

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Section: Previous Workmentioning

confidence: 99%

Section: Uncertainty Analysismentioning

confidence: 99%

Visualization and Measurements of Rub-Groove Leakage Effects on Straight-Through Labyrinth Seals

Rhode

Allen

1998

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration

Self Cite

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“…Through their PIV measurements they reported on the significance for leakage reduction of the fin axial location and angle and the step height. Flow visualization was also used by Rhode et al [16], [17] to measure the leakage resistance with respect to step shape and height. Pfau et al [18], [19], carried out a detailed study of the dominant kinematic flow feature in the cavity region, the toroidal vortex residing in the cavity and derived design recommendations to make use of the interaction flow.…”

Section: Introductionmentioning

confidence: 99%

Controlling Mixing at the Interaction Zone Through Systematic Variation of the Inlet Rotor Cavity Volume and Length Scale

Barmpalias

Sasaki

Hirano

et al. 2012

JGPP

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Mixing losses due to cavity related flows in axial steam turbines contribute considerably to overall aerodynamic losses. The coherent study presented in this paper examines the influence of rotor inlet cavity geometry on stage efficiency. The experimental work is supported by computational analysis. Inlet cavity geometry has been varied by reducing the axial and radial cavity lengths along with the volume. Six different configurations have been examined, focusing mainly on the flow interactions occurring at the zone between the cavity and main flow and their impact on stage efficiency. An upper stator-casing platform prolonged by 17% and 34%, and a radial wall length shortened by 13% and 25% offered a cavity volume reduction of 14% and 28%, respectively, compared to the initial cavity volume. The axial cavity wall length reduction impacts drastically on the vortex formation inside the cavity. A 17% length reduction leads initially to the bifurcation and re-connection of the vortex during inflow, whereas the 34% length reduction completely eliminates the presence of any vortex. On the other hand, the radial cavity wall length reduction affects the vortex positioning. Generally, the cases with radial wall length reduction show higher efficiency relative to the axial cavity length reduction. For the 14% cavity volume reduction cases this difference rises to 1%, and for the 28% cavity volume reduction the difference is even higher, attaining a 1.7% efficiency increase. NOMENCLATURE a cavity axial wall length b cavity radial wall length c normalized cavity axial length C pt pressure coefficient

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“…In the course of designing a hydraulic turbine, engineers seek to estimate and minimize these losses while respecting all the geometric constraints mentioned above. There are three main types of seals which are widely used and studied in the literature: straight seals, labyrinth seals and stepped seals (or cascade seals) with some variants [2,3]. Figures 1 to 3 display sketches of these three seal geometry types.…”

Section: Introductionmentioning

confidence: 99%

Validation of a CFD model for hydraulic seals

Roy¹,

Guibault

2009

International Journal of Fluid Machinery and Systems

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Optimization of seal geometries can reduce significantly the energetic losses in a hydraulic seal [1], especially for high head runner turbine. In the optimization process, a reliable prediction of the losses is needed and CFD is often used. This paper presents numerical experiments to determine an adequate CFD model for straight, labyrinth and stepped hydraulic seals used in Francis runners. The computation is performed with a finite volume commercial CFD code with a RANS low Reynolds turbulence model. As numerical computations in small radial clearances of hydraulic seals are not often encountered in the literature, the numerical results are validated with experimental data on straight seals and labyrinth seals. As the validation is satisfactory enough, geometrical optimization of hydraulic seals using CFD will be studied in future works.

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

Cited by 5 publications

References 7 publications

Visualization and Measurements of Rub-Groove Leakage Effects on Straight-Through Labyrinth Seals

Visualization and Measurements of Rub-Groove Leakage Effects on Straight-Through Labyrinth Seals

Controlling Mixing at the Interaction Zone Through Systematic Variation of the Inlet Rotor Cavity Volume and Length Scale

Validation of a CFD model for hydraulic seals

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