Low Leakage Designs for Rotor Teeth and Honeycomb Lands in Labyrinth Seals

2008 ◽  
Author(s):  
Hasham H. Chougule ◽  
Douglas Ramerth ◽  
Dhinagaran Ramachandran
Keyword(s):  
Numerical Modeling ◽  
Flow Field ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Wall Friction ◽  
Radial Clearance ◽  
Labyrinth Seals ◽  
Low Leakage ◽  
Total Leakage ◽  
Flow Turbulence

Design improvements on labyrinth seal teeth and a honeycomb land are examined by three-dimensional CFD numerical modeling of the flow field. The only objective is reduction of the total leakage through the new seal. CFD assumptions and analysis was validated by comparison with leakage data from labyrinth seal experiments conducted by Stocker [1]. The baseline chosen for comparison of sealing effectiveness is a conventional low clearance straight-through labyrinth seal with four teeth and a honeycomb land of symmetrical hexagonal cells. The proposed new seal has a staggered honeycomb land and straight teeth with an inclined notch. CFD predicts ∼17% reduction in seal leakage at a radial clearance of 0.005 inch (0.122mm) due to higher wall friction and flow turbulence.

Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal

2000 ◽  
Vol 124 (1) ◽  
pp. 140-146 ◽  
Author(s):  
V. Schramm ◽  
K. Willenborg ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Labyrinth Seal ◽  
Honeycomb Structure ◽  
Experimental Investigations ◽  
Labyrinth Seals ◽  
Numerical Predictions ◽  
Flow Through ◽  
Aero Engines

This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a seal configuration with a honeycomb facing mounted on the stator wall were investigated. The seal geometry is representative of typical three-step labyrinth seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-ε turbulence model. The computational grid includes the basic seal geometry as well as the three-dimensional honeycomb structures.

CFD Leakage Predictions of Unworn and Worn Labyrinth Seals With and Without Tooth Axial Offset

2017 ◽  
Author(s):  
Hasham H. Chougule ◽  
Alexander Mirzamoghadam
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Modeling ◽  
Steady State ◽  
Flow Field ◽  
Labyrinth Seals ◽  
Small Clearance ◽  
Total Leakage ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Deflection

The objective of this study is to develop a Computational Fluid Dynamics (CFD) based methodology for analyzing and predicting leakage of worn or rub-intended labyrinth seals during operation. The simulations include intended tooth axial offset and numerical modeling of the flow field. The purpose is to predict total leakage through the seal when an axial tooth offset is provided after the intended/unintended rub. Results indicate that as expected, the leakage for the in-line worn land case (i.e. tooth under rub) is higher compared to unworn. Furthermore, the intended rotor/teeth forward axial offset/shift with respect to the rubbed land reduces the seal leakage. The overall leakage of a rubbed seal with axial tooth offset is observed to be considerably reduced, and it can become even less than a small clearance seal designed not to rub. The reduced leakage during steady state is due to a targeted smaller running gap because of tooth offset under the intended/worn land groove shape, higher blockages, higher turbulence and flow deflection as compared to worn seal model without axial tooth offset.

Numerical Investigations for Leakage and Windage Heating in Straight-Through Labyrinth Seals

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Kali Charan Nayak ◽  
Pradip Dutta
Keyword(s):  
Cell Size ◽  
Turbulence Model ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Radial Clearance ◽  
Labyrinth Seals ◽  
Turbine Engine ◽  
Honeycomb Cell

The ability to quantify leakage flow and windage heating for labyrinth seals with honeycomb lands is critical in understanding gas turbine engine system performance and predicting its component life. Variety of labyrinth seal configurations (number of teeth, stepped or straight, honeycomb cell size) are in use in gas turbines, and for each configuration, there are many geometric factors that can impact a seal's leakage and windage characteristics. This paper describes the development of a numerical methodology aimed at studying the effect of honeycomb lands on leakage and windage heating. Specifically, a three-dimensional computational fluid dynamics (CFD) model is developed utilizing commercial finite volume-based software incorporating the renormalization group (RNG) k-ε turbulence model with modified Schmidt number. The modified turbulence model is benchmarked and fine-tuned based on several experiments. Using this model, a broad parametric study is conducted by varying honeycomb cell size, pressure ratio (PR), and radial clearance for a four-tooth straight-through labyrinth seal. The results show good agreement with available experimental data. They further indicate that larger honeycomb cells predict higher seal leakage and windage heating at tighter clearances compared to smaller honeycomb cells and smooth lands. However, at open seal clearances larger honeycomb cells have lower leakage compared to smaller honeycomb cells.

Flow Simulation in a Labyrinth Seal

2014 ◽  
Vol 630 ◽  
pp. 234-239 ◽  
Author(s):  
G.A. Bondarenko ◽  
V.N. Baga ◽  
I.A. Bashlak
Keyword(s):  
Centrifugal Compressor ◽  
Physical Modeling ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Labyrinth Seal ◽  
Swirl Flow ◽  
Radial Clearance ◽  
Geometrical Parameters ◽  
Three Dimensional Model ◽  
Labyrinth Seals

The paper studies the labyrinth seals of centrifugal compressor profit-proved stages using modern methods of numerical and physical modeling of the centrifugal compressor stages. A series of studies of the effect of operational and geometrical parameters on the maze, namely the quantities of the packed differential pressure, speed, fluid, geometric parameters of the seal, the magnitude of the eccentricity and radial clearance swirl flow at the inlet of a seal, etc. The technique of physical modeling seal has been specified. Research was conducted in two phases: numerical simulation using complex software Flow Vision and receiving data on a universal test bench to study the labyrinth seals.. A three-dimensional model of the labyrinth seal has been created, its verification by "known data has been held.. Integral characteristics in the form of distribution of flow velocities and pressures, flow visualization were obtained. Results of studies made ​​it possible to refine the workflow and introduce amendments to the known calculation formula for a more accurate calculation of leakage through the seal, subject to a number of additional factors that were not previously taken into account

Labyrinth Seal With Variable Height Teeth Tips for Efficient Leakage Control

2019 ◽  
Author(s):  
Hasham Chougule ◽  
Abhay Naik ◽  
Mohd. Qizar
Keyword(s):  
Experimental Data ◽  
Numerical Modeling ◽  
Flow Field ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Baseline Model ◽  
Engine Operation ◽  
Proposed Modification ◽  
Radial Gap

Abstract A modification of a conventional straight tooth labyrinth seal with variable tooth height is proposed. The baseline and modified labyrinth seal teeth with solid land are examined by three-dimensional CFD numerical modeling of the flow field and evaluated for predicting the leakage through the seal during the engine operation. Stocker’s [1] static labyrinth seal experimental data is used to validate the CFD methodology used in this paper. The baseline and the proposed modified design [2] — “Labyrinth seal with variable tooth heights” are numerically studied with solid lands and evaluated to measure the reduction in leakages. The objective of this study is to provide an improved sealing effectiveness by restricting the leakage flow and controlling the seal leakage during the operation of the engine. In this study, a conventional straight-through four-tooth labyrinth seal with solid land is used as the baseline model. It is first evaluated at different unworn constant radial gaps — between the teeth tips and solid land. In the proposed modification, the height of the intermediate teeth of the baseline four-tooth are varied. The teeth heights are designed in such a way that intermediate longer teeth form a very small or tighter radial gap at start of operation. The shorter ones are designed based on the expected wear groove/rub depth considered by the seal designer. Results indicate that the proposed modification — Variable height teeth tips, reduce the seal leakage by over 50% compared to the baseline. The advantage of this modified design over a baseline seal is that at unworn or worn conditions, the teeth tips always forms a considerable tighter radial gap when compared with baseline seal. The achieved sealing is such that during engine operation of the seal, even if the seal gets worn, the overall leakage is significantly reduced.

Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal

2000 ◽  
Author(s):  
V. Schramm ◽  
K. Willenborg ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Labyrinth Seal ◽  
Honeycomb Structure ◽  
Experimental Investigations ◽  
Labyrinth Seals ◽  
Numerical Predictions ◽  
Flow Through ◽  
Aero Engines

This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a seal configuration with a honeycomb facing mounted on the stator wall were investigated. The seal geometry is representative of typical three-step labyrinth seals of modern aero engines. The flow field was predicted using a commercial finite-volume code with the standard-k-ε-turbulence model. The computational grid includes the basic seal geometry as well as the three-dimensional honeycomb structures.

CFD Simulation of Single Step and Double Notched Tooth for Labyrinth Seals

2014 ◽  
Author(s):  
Hasham H. Chougule ◽  
Alexander Mirzamoghadam ◽  
Douglas Ramerth
Keyword(s):  
Cfd Simulation ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Single Step ◽  
Comparison Study ◽  
Labyrinth Seals ◽  
Baseline Model ◽  
Total Leakage ◽  
Sharp Knife ◽  
Cfd Analyses

A variant “Stepped Double Notched Tooth” for conventional sharp teeth of a labyrinth seal has been proposed and investigated by three-dimensional CFD numerical modeling of the flow field. The purpose is to reduce total leakage through the seal. The tooth is numerically tested with both solid and honeycomb lands. CFD assumptions and analysis were validated by comparison with leakage data from stationary labyrinth seal experiments conducted by Stocker [1]. The baseline model considered for comparison study consists of the conventional straight-through four sharp knife shaped teeth in combination with solid and honeycomb land. The variant tooth is also straight having a sharp tip but has a stepped inclined notch opposing the flow at both sides of the tip. CFD analyses revealed that this double notched tooth reduces seal leakage by ∼10.7% when used with solid land and ∼12.5% when used with honeycomb land compared to a conventional baseline tooth.

Effect of Rub-Grooves on Leakage and Windage Heating in Straight-Through Labyrinth Seals

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Kali Charan Nayak ◽  
Pradip Dutta
Keyword(s):  
Cell Size ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Radial Clearance ◽  
Labyrinth Seals ◽  
Turbine Engine ◽  
Geometric Factors ◽  
Computational Fluid Dynamics Cfd ◽  
Honeycomb Cell

Prediction of leakage flow and windage heating for labyrinth seals with honeycomb lands is critical in understanding gas turbine engine system performance and predicting its component life. There are several labyrinth seal configurations in use in gas turbines, and for each configuration, there are many geometric factors that can impact a seal's leakage and windage characteristics. One of the factors which has not been thoroughly investigated in previously published work is the presence of rub-grooves in the honeycomb land and its impact on seal performance. This paper describes the development of a numerical methodology aimed at studying this effect. Specifically, a three-dimensional (3D) computational fluid dynamics (CFD) model is developed utilizing commercial finite volume-based software incorporating the renormalization group (RNG) k-ε turbulence model. Using this model, a broad parametric study is conducted by varying honeycomb cell size and radial clearance for a four-tooth straight-through labyrinth seal with and without rub-grooves. The results show good agreement with available experimental data. They further indicate that presence of rub-grooves increases seal leakage and decreases windage heating. The absolute levels depend on the clearance and honeycomb cell size.

CFD Leakage Predictions of Labyrinth Seals Having Straight and Inclined Notched Teeth With Staggered Honeycomb Land

2018 ◽  
Author(s):  
Hasham H. Chougule ◽  
A. V. Mirzamoghadam
Keyword(s):  
Flow Resistance ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Operating Conditions ◽  
Labyrinth Seals ◽  
Cfd Simulations ◽  
Maximum Improvement ◽  
Total Leakage ◽  
Flow Through ◽  
Honeycomb Cell

Labyrinth seal designs for reduced leakage have been analyzed by three-dimensional CFD simulations. The objective is to learn the effect of seal geometry modifications on total leakage through the seal and arrive at an advanced seal setting for improved seal effectiveness through reduction in leakage. Numerical modeling of the flow field were conducted at various operating conditions. The baseline seal model for this study is a conventional straight-through rotating four-tooth labyrinth seal and static honeycomb land having symmetrical hexagonal cells. The tooth design configurations include stepped single & double notched straight and inclined teeth. Another objective is to learn the effect of staggered honeycomb land with respect to rotor/teeth rotation. The effect of teeth inclination & teeth rotation compared to stationary is also discussed. CFD results indicate improved seal effectiveness with staggered honeycomb cell land. The maximum improvement of ∼9% was observed with stepped and notched inclined teeth configuration when combined with staggered honeycomb land. The leakage reduction leading to improvement in seal effectiveness as compared to baseline configuration is largely due to higher flow resistance, higher turbulence and higher blockages by introducing vortex in leakage flow through step and cavities.

Progressive Clearance Labyrinth Seal for Turbo-Machinery Applications

2011 ◽  
Author(s):  
Binayak Roy ◽  
Hrishikesh V. Deo ◽  
Xiaoqing Zheng
Keyword(s):  
Theoretical Models ◽  
Labyrinth Seal ◽  
Tip Clearance ◽  
Labyrinth Seals ◽  
Lower Efficiency ◽  
Thermal Transients ◽  
Low Leakage ◽  
Packing Ring ◽  
Lift Off ◽  
Large Rotor

Turbomachinery sealing is a challenging problem due to the varying clearances caused by thermal transients, vibrations, bearing lift-off etc. Leakage reduction has significant benefits in improving engine efficiency and reducing emissions. Conventional labyrinth seals have to be assembled with large clearances to avoid rubbing during large rotor transients. This results in large leakage and lower efficiency. In this paper, we propose a novel Progressive Clearance Labyrinth Seal that is capable of providing passive fluidic feedback forces that balance at a small tip-clearance. A modified packing ring is supported on flexures and employs progressively tighter teeth from the upstream to the downstream direction. When the tip-clearance reduces below the equilibrium clearance, fluidic feedback forces cause the packing ring to open. Conversely, when the tip-clearance increases above the equilibrium clearance, the fluidic feedback forces cause the packing ring to close. Due to this self-correcting behavior, the seal provides high differential pressure capability, low leakage and non-contact operation even in the presence of large rotor transients. Theoretical models for the feedback phenomenon have been developed and validated by experimental results.

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