Experimental Investigation on the Rubbing Process of Labyrinth Seals Against Honeycomb Liners

2020 ◽  
Author(s):  
Oliver Munz ◽  
Lisa Hühn ◽  
Corina Schwitzke ◽  
Hans-Jörg Bauer ◽  
Tim Fischer ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Service Life ◽  
Wear Mechanism ◽  
Relative Velocity ◽  
Labyrinth Seal ◽  
Honeycomb Structure ◽  
Labyrinth Seals ◽  
Mechanical Loads ◽  
Low Leakage ◽  
Mass Flows

Abstract Sealing systems contribute significantly to the efficiency of turbomachinery. Small gap widths, which are important for low leakage mass flows in labyrinth seals, combined with thermal and mechanical expansion of the rotor can lead to contact with the stator. During these so-called rubbing processes, it is necessary to make an accurate prediction with respect to the performance and service life of the seal. For this purpose, the influence of relative velocity in the contact (up to 165ms−1) and incursion rate (up to 0.5 mms−1) on the resulting thermal and mechanical loads as well as wear mechanisms are studied for the rubbing process between an inclined labyrinth seal fin and a honeycomb segment. Furthermore, different axial configurations of the seal fin with respect to the honeycomb structure are considered. The system reacts very sensitively to a change of the seal fin position relative to the honeycomb structure. The incursion per revolution reflects a change of the wear mechanism from abrasive to plastic for a certain value. The results of this study contribute to the optimization of labyrinth seals and the development of new types of liner materials as well as geometries.

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.

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.

Hybrid Brush Pocket Damper Seals for Turbomachinery

2000 ◽  
Vol 122 (2) ◽  
pp. 330-336 ◽  
Author(s):  
Hector E. Laos ◽  
John M. Vance ◽  
Steven E. Buchanan
Keyword(s):  
Active Vibration Control ◽  
Design Feature ◽  
Aircraft Engine ◽  
Computer Code ◽  
Labyrinth Seal ◽  
Dual Function ◽  
Rotating Shaft ◽  
Labyrinth Seals ◽  
Low Leakage ◽  
Brush Seal

Pocket damper seals perform a dual function: both sealing the pressurized gas around a rotating shaft and providing large amounts of vibration damping. The annular cavity between the labyrinth seal teeth is subdivided into separate annular cavities around the circumference of the rotor by partitioning walls. Also, the upstream and downstream teeth have different radial clearances to the rotor. These seals have been shown to provide a remarkable amount of direct damping to attenuate vibration in turbomachinery, but they generally leak more than conventional labyrinth seals if both seals have the same minimum clearance. Conversely, brush seals allow less than half the leakage of labyrinth seals, but published test results show no significant amount of damping. They are considered to be a primary choice for the seals in new aircraft engine designs because of their low leakage. This paper will describe a recently invented hybrid brush/pocket damper seal that combines high damping with low leakage. Previous brush seal results were studied and calculations were made to select a brush seal to combine with the pocket damper design. The result is a hybrid seal with high damping and low leakage. A special design feature can also allow active vibration control as a bonus benefit. A computer code written for the original pocket damper seal was modified to include the brush element at the exit blade. Results from the computer code indicate that the hybrid seal can have less leakage than a six bladed (or 6 knives) labyrinth seal along with orders of magnitude more damping. Experimental evaluations of the damping and leakage performance of the hybrid seal are being conducted by the authors. The experimental work reported here tested the damping capability of the new hybrid brush seal by exciting the seal journal through an impedance head. A conventional six-bladed labyrinth seal of the same working dimensions was also tested. The brush hybrid pocket damper seal is found to leak less than the labyrinth seal while producing two to three times more damping than the original pocket damper seal (orders of magnitude more than the conventional labyrinth). [S0742-4795(00)01102-9]

Hybrid Brush Pocket Damper Seals for Turbomachinery

1999 ◽  
Author(s):  
Hector E. Laos ◽  
John M. Vance ◽  
Steven E. Buchanan
Keyword(s):  
Active Vibration Control ◽  
Design Feature ◽  
Aircraft Engine ◽  
Computer Code ◽  
Labyrinth Seal ◽  
Dual Function ◽  
Rotating Shaft ◽  
Labyrinth Seals ◽  
Low Leakage ◽  
Brush Seal

Pocket damper seals perform a dual function: both sealing the pressurized gas around a rotating shaft and providing large amounts of vibration damping. The annular cavity between the labyrinth seal teeth is subdivided into separate annular cavities around the circumference of the rotor by partitioning walls. Also, the upstream and downstream teeth have different radial clearances to the rotor. These seals have been shown to provide a remarkable amount of direct damping to attenuate vibration in turbomachinery, but they generally leak more than conventional labyrinth seals if both seals have the same minimum clearance. Conversely, brush seals allow less than half the leakage of labyrinth seals, but published test results show no significant amount of damping. They are considered to be a primary choice for the seals in new aircraft engine designs because of their low leakage. This paper will describe a recently invented hybrid brush/pocket damper seal that combines high damping with low leakage. Previous brush seal results were studied and calculations were made to select a brush seal to combine with the pocket damper design. The result is a hybrid seal with high damping and low leakage. A special design feature can also allow active vibration control as a bonus benefit. A computer code written for the original pocket damper seal was modified to include the brush element at the exit blade. Results from the computer code indicate that the hybrid seal can have less leakage than a six bladed (or 6 knives) labyrinth seal along with orders of magnitude more damping. Experimental evaluations of the damping and leakage performance of the hybrid seal are being conducted by the authors. The experimental work reported here tested the damping capability of the new hybrid brush seal by exciting the seal journal through an impedance head. A conventional six-bladed labyrinth seal of the same working dimensions was also tested. The brush hybrid pocket damper seal is found to leak less than the labyrinth seal while producing two to three times more damping than the original pocket damper seal, (orders of magnitude more than the conventional labyrinth).

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 ◽  
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.

Impact of Rotational Speed on the Discharge Characteristic of Stepped Labyrinth Seals

2007 ◽  
Author(s):  
Roger Paolillo ◽  
Sean Moore ◽  
David Cloud ◽  
J. Axel Glahn
Keyword(s):  
Labyrinth Seal ◽  
Leakage Rate ◽  
Labyrinth Seals ◽  
Discharge Characteristic ◽  
Design Concepts ◽  
Cooling Flow ◽  
Seal Design ◽  
Low Leakage ◽  
Performance Requirements ◽  
Through Flow

Current and future gas turbine engines are subject to increasing performance requirements and improved fuel efficiencies. The resultant engine cycles increase core flow temperatures requiring additional cooling flow while requiring a reduction in parasitic leakage by more than 25% to meet the performance goals. The achievement of the reduced leakage requires that seal design concepts be tested and improvements validated in engine like conditions before they are introduced into the actual engine. A previous paper [1] described a set of rotating seal designs that have been tested in various combinations of rotating and static design features for low leakage potential. This paper is a continuation of the previous effort and focuses in particular on the effect of rotational speeds on the discharge characteristic of various stepped labyrinth seal designs. Leakage reductions will be characterized in terms of CD/DD,0 (i.e. ratio of leakage rate with rotation over leakage rate without rotation) as a function of circumferential to axial through flow velocity, U/Cax. For large velocity ratios of U/Cax > 5, leakage reductions of more than 20% were observed. Experimental data are compared with literature [2].

scholarly journals The Wear of Seal Fins during High-Speed Rub between Labyrinth Seal Fins and Honeycomb Stators at Different Incursion Rates

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 979
Author(s):  
Bin Lu ◽  
Xiaojian Ma ◽  
Caiguang Wu ◽  
Haijun Xuan ◽  
Weirong Hong
Keyword(s):  
Wear Mechanism ◽  
High Speed ◽  
Great Influence ◽  
Labyrinth Seal ◽  
Labyrinth Seals ◽  
Thermomechanical Stress ◽  
Delamination Wear ◽  
Metal Wear ◽  
Aero Engine ◽  
Worn Surface

Labyrinth seals as a noncontact sealing technology are widely used in aero-engine. To improve the efficiency of the aero-engine, the clearance between the rotor and stator must be as small as possible. However, the change of the clearance between the rotor and stator because of thermal expansion, vibration, mechanical loading may lead to undesirable high-speed rub, which will lead to the cracking of the seal fins. This paper focuses on the wear of the seal fin after the rub and presents the rubbing tests between seal fins and the metal honeycomb under rubbing speed of 380 m/s and incursion rates between 20 and 180 μm/s, with an incursion depth of 1500 μm and a temperature of 350 °C. The rubbing force and temperature were recorded, and the seal fins were checked by SEM and EDS. The results show that the wear mechanism of seal fins changed from oxidation wear and adhesive wear to delamination wear and then to metal wear with the increasing incursion rate. The axial cracks appeared on the worn surface of the seal fins due to the cracking of tribo-layers under periodic thermomechanical stress. The wear mechanism of the seal fin also has a great influence on the rubbing force and temperature.

Lateral Forces From Single Gland Rotor Labyrinth Seals in Turbines

2004 ◽  
Vol 126 (3) ◽  
pp. 626-634 ◽  
Author(s):  
Bum Ho Song ◽  
Seung Jin Song
Keyword(s):  
Axial Direction ◽  
Labyrinth Seal ◽  
Turbine Stage ◽  
Labyrinth Seals ◽  
Flow Response ◽  
Lateral Forces ◽  
Downstream Flow ◽  
Shrouded Rotor ◽  
Upstream Flow ◽  
Sealing Gap

Even though interest in labyrinth seal flows has increased recently, an analytical model capable of predicting turbine flow response to labyrinth seals is still lacking. Therefore, this paper presents a new model to predict flow response in an axial turbine stage with a shrouded rotor. A concentric model is first developed, and this model is used to develop an eccentric model. Basic conservation laws are used in each model, and a nonaxisymmetric sealing gap is prescribed for the eccentric model. Thus, the two models can predict the evolution of a uniform upstream flow into a nonuniform downstream flow. In turbines with concentric shrouded rotors, the seal flow is retarded in the axial direction and tangentially underturned. In turbines with eccentric shrouded rotors, flow azimuthally migrates away from and pressure reaches its peak near the maximum sealing gap region. Finally, the rotordynamic implications of such flow nonuniformities are discussed and compared against eccentric unshrouded turbine predictions.

Impact of Frequency Dependence of Gas Labyrinth Seal Rotordynamic Coefficients on Centrifugal Compressor Stability

2010 ◽  
Author(s):  
Giuseppe Vannini ◽  
Manish R. Thorat ◽  
Dara W. Childs ◽  
Mirko Libraschi
Keyword(s):  
Molecular Weight ◽  
Numerical Model ◽  
Control Volume ◽  
Labyrinth Seal ◽  
Labyrinth Seals ◽  
Frequency Dependent ◽  
Rotordynamic Coefficients ◽  
Frequency Independent ◽  
Rotor Surface ◽  
Independent Model

A numerical model developed by Thorat & Childs [1] has indicated that the conventional frequency independent model for labyrinth seals is invalid for rotor surface velocities reaching a significant fraction of Mach 1. A theoretical one-control-volume (1CV) model based on a leakage equation that yields a reasonably good comparison with experimental results is considered in the present analysis. The numerical model yields frequency-dependent rotordynamic coefficients for the seal. Three real centrifugal compressors are analyzed to compare stability predictions with and without frequency-dependent labyrinth seal model. Three different compressor services are selected to have a comprehensive scenario in terms of pressure and molecular weight (MW). The molecular weight is very important for Mach number calculation and consequently for the frequency dependent nature of the coefficients. A hydrogen recycle application with MW around 8, a natural gas application with MW around 18, and finally a propane application with molecular weight around 44 are selected for this comparison. Useful indications on the applicability range of frequency dependent coefficients are given.

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