scholarly journals Performance of Worn Labyrinth Seals

1994 ◽  
Author(s):  
H. Zimmerman ◽  
A. Kammerer ◽  
K. H. Wolff
Keyword(s):  
Reynolds Number ◽  
Labyrinth Seal ◽  
Numerical Results ◽  
Labyrinth Seals ◽  
Discharge Coefficients ◽  
Surface Imperfections ◽  
Sealing Device

The major sealing device between rotating and static aeroengine parts is still of labyrinth type. Nowadays the fins and the stator may be coated and the running conditions very often cause heavy rubs which leads to severe surface imperfections. This paper investigates the influence of rounded fins and worn coatings on the discharge coefficients of straight through labyrinth seals. The relevant effects of Reynolds number are investigated. Some measured fin and coating surfaces from engine parts are presented. Experimental and numerical results show a strong effect of wear on labyrinth seal performance.

Influence of Rub-Grooves on Labyrinth Seal Leakage

2003 ◽  
Vol 125 (2) ◽  
pp. 387-393 ◽  
Author(s):  
J. Denecke ◽  
V. Schramm ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Gas Turbines ◽  
Water Channel ◽  
Large Data ◽  
Labyrinth Seal ◽  
Labyrinth Seals ◽  
Data Set ◽  
Engine Efficiency ◽  
Discharge Coefficients ◽  
Flow Mechanisms ◽  
Insight Into

An experimental investigation on the influence of stator rub-grooves on labyrinth seal leakage is presented in the present paper. In current labyrinth seal designs, abradable lands allow the rotor labyrinth teeth to rub grooves into the stator. These rub-grooves have a large influence on the seal leakage characteristic and impair the overall engine efficiency. To improve the understanding of rub-groove effects, discharge coefficients were determined using a plain nonrotating labyrinth seal model of scale 4:1 considering a wide variation of rub-groove geometries at different seal clearances. Three labyrinth seal types were covered in this investigation that are generally used in gas turbines, namely 1) straight-through labyrinth seals, 2) stepped labyrinth seals with forward facing steps, and 3) stepped labyrinth seals with backward facing steps. To attain a deeper insight into the flow mechanisms, water-channel visualizations were performed. The large data set generated in this study, provides the basis to analyze and quantify the influence of rub-grooves on the seal leakage for the three aforementioned labyrinth seal types. Current results were in agreement with previous studies on worn labyrinth seals for several seal geometries.

Modelling the Labyrinth Seal Discharge Coefficient Using Data Mining Methods

2010 ◽  
Author(s):  
Tim Pychynski ◽  
Klaus Dullenkopf ◽  
Hans-Jo¨rg Bauer ◽  
Ralf Mikut
Keyword(s):  
Data Mining ◽  
Data Base ◽  
Design Space ◽  
Labyrinth Seal ◽  
Analytical Models ◽  
Model Quality ◽  
Labyrinth Seals ◽  
Data Set ◽  
System Sensitivity ◽  
Discharge Coefficients

This paper presents a data-based method to predict the discharge coefficients of labyrinth seals. At first, leakage flow rate data for straight-through and stepped labyrinth seals from various sources was collected and fused in one consistent data base. In total, over 15000 data points have been collected so far covering a 25-dimensional design space. Secondly, this leakage data set was analysed using open-source Data Mining software, which provides several algorithms such as Multiple Linear Regression (MLR) and Artificial Neural Networks (ANN). The suitability of MLR and ANN for modelling labyrinth discharge coefficients and analysing system sensitivity was tested and evaluated. The developed leakage models showed promising prediction qualities within the design space covered by data. Further improvements of model quality may be achieved by continuing data analysis using advanced methods of Data Mining and enlarging the existing data base. The major advantages of the presented method over numerical or analytical models are possible automation of the modelling process, low calculation efforts and high model qualities.

Influence of Rub-Grooves on Labyrinth Seal Leakage

2002 ◽  
Author(s):  
J. Denecke ◽  
V. Schramm ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Gas Turbines ◽  
Water Channel ◽  
Large Data ◽  
Labyrinth Seal ◽  
Labyrinth Seals ◽  
Data Set ◽  
Engine Efficiency ◽  
Discharge Coefficients ◽  
Flow Mechanisms ◽  
Insight Into

An experimental investigation on the influence of stator rub-grooves on labyrinth seal leakage is presented in the present paper. In current labyrinth seal designs, abradable lands allow the rotor labyrinth teeth to rub grooves into the stator. These rub-grooves have a large influence on the seal leakage characteristic and impair the overall engine efficiency. To improve the understanding of rub-groove effects, discharge coefficients were determined using a plain non-rotating labyrinth seal model of scale 4:1 considering a wide variation of rub-groove geometries at different seal clearances. Three labyrinth seal types were covered in this investigation that are generally used in gas turbines, namely (1) straight-through labyrinth seals, (2) stepped labyrinth seals with forward facing steps and (3) stepped labyrinth seals with backward facing steps. To attain a deeper insight into the flow mechanisms, water-channel visualizations were performed. The large data set generated in this study, provides the basis to analyze and quantify the influence of rub-grooves on the seal leakage for the three labyrinth seal types listed above. Current results were in agreement with previous studies on worn labyrinth seals for several seal geometries.

Leakage Flow of Labyrinth Seals in Hydraulic Components

Volume 3 ◽  
2004 ◽  
Author(s):  
Minter Cheng
Keyword(s):  
Reynolds Number ◽  
High Speed ◽  
Labyrinth Seal ◽  
Industrial Applications ◽  
Width Ratio ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Cavity Depth ◽  
Analysis Technique ◽  
Cavity Width

Leakage flow plays an important role on the performance evaluation of hydraulic components. Leakage flow induces adverse influences on many practical industrial applications. For the sake of reducing friction and/or abrasion, most of the high-speed hydraulic components install some kind of non-contact seals to minimize leakage flow, the labyrinth seal is the most popular one. This research is to investigate the leakage flow of labyrinth seals in hydraulic components by using numerical analysis technique. The parameters investigated in this study are cavity number, cavity width, cavity depth, cavity gap, and Reynolds number. The traditional rectangular cavity is considered in this research. It shows that cavity width is about 20∼30 times of clearance, cavity depth is about 3∼5 times of clearance, cavity gap is greater than 50 times of clearance, cavity depth to width ratio is about 0.15∼0.25, and cavity gap to width ratio is greater than 2.5 have better sealing capability.

Effect of Tooth Height, Tooth Width and Shaft Diameter on Carry-Over Coefficient of Labyrinth Seals

2009 ◽  
Author(s):  
Saikishan Suryanarayanan ◽  
Gerald L. Morrison
Keyword(s):  
Reynolds Number ◽  
Kinetic Energy ◽  
Labyrinth Seal ◽  
Major Effect ◽  
Labyrinth Seals ◽  
Shaft Diameter ◽  
Tooth Width ◽  
Pitch Ratio ◽  
Carry Over ◽  
Coefficient Of Discharge

The accuracy of rotodynamic analysis of any turbomachinery is dependent upon the accuracy of seal leakage prediction. An expression for the leakage through a labyrinth seal can be developed by combining the coefficient of discharge under each tooth and a carryover coefficient to account for the dissipation of kinetic energy of the jet emerging from under each tooth in the subsequent cavity through turbulence viscosity interaction. While most popularly used leakage models consider the carry-over coefficient only as a function of clearance and pitch, it was established in our earlier work that Reynolds number and clearance/pitch ratio have a major effect on the carry-over coefficient. This work extends the carry-over coefficient model presented by Saikishan Suryanarayanan and G.L. Morrison [1] for incompressible, straight through, rectangular cavity, tooth on stator labyrinth seals by studying and incorporating the effect of tooth width, pitch, tooth height and shaft diameter in addition to Reynolds number and clearance on the carry-over coefficient. It is shown that the tooth width/pitch ratio has a significant effect upon the carry-over coefficient.

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.

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.

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.

Theoretical leakage equations towards liquid-phase flow in the straight-through labyrinth seal

2021 ◽  
pp. 1-44
Author(s):  
Lingsheng Han ◽  
Yongqing Wang ◽  
Kuo Liu ◽  
Ziyou Ban ◽  
Bo Qin ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Numerical Approach ◽  
Labyrinth Seal ◽  
Resistance Coefficient ◽  
Cryogenic Cooling ◽  
Geometrical Parameters ◽  
Phase Flow ◽  
Labyrinth Seals ◽  
Leakage Flow Rate ◽  
Empirical Coefficients

Abstract Labyrinth seals are widely applied in turbomachinery for gas and liquid sealing. A series of labyrinth seal leakage equations so far have been proposed for compressible gas, but few equations for incompressible liquid. Based on the flow conserving governing equations, this paper originally presents semi-empirical analytic equations of the leakage flow rate and tooth-clearance pressure for liquid-phase flow in the straight-through labyrinth seal. The equations indicate that the leakage and pressure are closely related to the inlet pressure, outlet pressure, seal geometrical parameters and four empirical coefficients, whilst no relation to the temperature and compressibility effects compared to the common gas equations. The empirical coefficients include the velocity compensation coefficient, friction coefficient, jet contraction coefficient and resistance coefficient. Particularly, the velocity compensation coefficient is determined through an optimization by the genetic algorithm, while others are referred from previous research. Ultimately, taking the sealing of deeply subcooled liquid nitrogen within the spindle of the cryogenic cooling machine tool as a case, the accuracy of proposed equations is evaluated under various pressure ratios and geometry conditions using the numerical approach, whose numerical model has been validated by the experimental data in the literature. The results show that errors between calculation and simulation are generally within the limit of ±5%, except for the pressure values at the first two teeth. This work provides a theoretical basis for further studies on the liquid leakage equations in other labyrinth seal types.

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