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.

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.

scholarly journals Exploring biological data: Mappings between ontology- and cluster-based representations

2013 ◽  
Vol 12 (3-4) ◽  
pp. 291-307 ◽  
Author(s):  
Ilir Jusufi ◽  
Andreas Kerren ◽  
Falk Schreiber
Keyword(s):  
Hierarchical Clustering ◽  
Visual Analysis ◽  
Large Data ◽  
Biological Data ◽  
Data Set ◽  
Metabolomics Data ◽  
Domain Experts ◽  
Data Points ◽  
Biological Input ◽  
Insight Into

Ontologies and hierarchical clustering are both important tools in biology and medicine to study high-throughput data such as transcriptomics and metabolomics data. Enrichment of ontology terms in the data is used to identify statistically overrepresented ontology terms, giving insight into relevant biological processes or functional modules. Hierarchical clustering is a standard method to analyze and visualize data to find relatively homogeneous clusters of experimental data points. Both methods support the analysis of the same data set but are usually considered independently. However, often a combined view is desired: visualizing a large data set in the context of an ontology under consideration of a clustering of the data. This article proposes new visualization methods for this task. They allow for interactive selection and navigation to explore the data under consideration as well as visual analysis of mappings between ontology- and cluster-based space-filling representations. In this context, we discuss our approach together with specific properties of the biological input data and identify features that make our approach easily usable for domain experts.

Design approach for maximising contacting filament seal performance retention

2014 ◽  
Vol 229 (5) ◽  
pp. 926-942 ◽  
Author(s):  
Ingo HJ Jahn
Keyword(s):  
Gas Turbines ◽  
Labyrinth Seal ◽  
Generic Properties ◽  
Labyrinth Seals ◽  
Blow Down ◽  
Operating Cycle ◽  
And Performance ◽  
Gas Turbine Cycle ◽  
Operating Cycles ◽  
The Ideal

Good sealing is a key requirement for modern efficient turbomachinery such as steam and gas turbines. A class of seals that promise better performance, compared to conventional labyrinth seals, are contacting filament seals such as brush, leaf, or finger seal. When new, these filament seals offer better performance; however, if poorly designed they wear excessively, resulting in leakages higher than a comparable labyrinth seal. This paper outlines a design methodology for selecting ideal contacting filament seal properties for a given operating cycle or set of operating cycles. Following this approach ensures the seal performs well, the seal retains its performance, and performance is retained if the operating cycle is altered. In the approach, the seals are described by four generic properties (stiffness, blow-down, cross-coupling, and build clearance), which are then used for a performance evaluation based on a number of test cycles. Once the ideal seal properties for a given operating cycle have been identified, a seal to match these can be designed. The approach is evaluated with a generic gas turbine cycle and recommendations for ideal contacting filament seal properties for this cycle are made.

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.

Rotordynamic Characterization of a Staggered Labyrinth Seal: Experimental Test Data and Comparison With Predictions

2018 ◽  
Author(s):  
Filippo Cangioli ◽  
Giuseppe Vannini ◽  
Paolo Pennacchi ◽  
Lorenzo Ciuchicchi ◽  
Leonardo Nettis ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Flow Model ◽  
Labyrinth Seal ◽  
Accurate Estimation ◽  
Stability Assessment ◽  
Labyrinth Seals ◽  
Rotordynamic Coefficients ◽  
Working Principle ◽  
The Stability

As well known, the stability assessment of turbomachines is strongly related to internal sealing components. For instance, labyrinth seals are widely used in compressors, steam and gas turbines and pumps to control the clearance leakage between rotating and stationary parts, owing to their simplicity, reliability and tolerance to large thermal and pressure variations. Labyrinth seals working principle consists in reducing the leakage by imposing tortuous passages to the fluid that are effective on dissipating the kinetic energy of the fluid from high-pressure regions to low-pressure regions. Conversely, labyrinth seals could lead to dynamics issues. Therefore, an accurate estimation of their dynamic behavior is very important. In this paper, the experimental results of a long-staggered labyrinth seal will be presented. The results in terms of rotordynamic coefficients and leakage will be discussed as well as the critical assessment of the experimental measurements. Eventually, the experimental data are compared to numerical results obtained with the new bulk-flow model (BFM) introduced in this paper.

Effect of Air-Curtains on Labyrinth Seal Performance

2016 ◽  
Author(s):  
Aakash C. Rai ◽  
Deoras Prabhudharwadkar ◽  
Sunil Murthy ◽  
Andrew Giametta ◽  
David Johns
Keyword(s):  
Gas Turbines ◽  
Cross Flow ◽  
Labyrinth Seal ◽  
Labyrinth Seals ◽  
Air Curtain ◽  
Baseline Design ◽  
Leakage Flows ◽  
Seal Design ◽  
Parametric Studies ◽  
Secondary Air

Labyrinth seals are used in many key sealing locations in gas turbines to control various leakage flows, e.g., to control the secondary air-flow from the compressor (bypassing the combustor), the turbine inter-stage leakages and blade tip leakages. This study was performed to assess the improvement in the performance of a labyrinth seal by using an air-curtain (cross-flow jet(s)) from the stator. Detailed parametric studies were performed to study the effect of the air-curtain jet pressure, location, and the number of jets on the seal performance with respect to the leakage flow. The analysis was done using 2-dimensional axisymmetric CFD simulations. It was found that in the case of a labyrinth seal with a flat stator (without a honeycomb attached to the stator) the air-curtain design can reduce the seal leakage by about 30% over the baseline seal design without air-curtains. This reduction happened because the air-curtain jet deflected the main seal jet away from the seal clearance. A similar conclusion was also obtained in case of a labyrinth seal with a honeycombed stator. Furthermore, our parametric studies with different air-curtain designs parameters implemented over a honeycombed labyrinth seal showed that the air-curtain jet pressure, location, and the number of jets were crucial factors governing the seal leakage. Amongst the air-curtain designs studied, it was found that implementing three air-curtains in the 1st pocket gave the maximum leakage reduction (by about 50%) over the baseline design.

Experimental Investigation of the Total Temperature Increase and Swirl Development in Rotating Labyrinth Seals

2005 ◽  
Author(s):  
J. Denecke ◽  
K. Dullenkopf ◽  
S. Wittig ◽  
H.-J. Bauer
Keyword(s):  
Gas Turbines ◽  
Temperature Increase ◽  
Labyrinth Seal ◽  
Laser Doppler Velocimeter ◽  
Test Rig ◽  
Labyrinth Seals ◽  
Total Temperature ◽  
Discharge Behavior ◽  
Cooling Air ◽  
Rotor Dynamic

Labyrinth seals are widely used as reliable components in many areas of turbo machines, e.g. the cooling air system in gas turbines. While the discharge behavior is generally well predictable, the uncertainty predicting the exit circumferential velocity (exit-swirl) and the total temperature increase due to internal losses (windage heating) is comparably large. In order to evaluate analytical correlations and for the validation of numerical simulations convergent and divergent stepped labyrinth seals were investigated experimentally. The change in total temperature across the labyrinth seal was measured in a test rig capable to establish different rotational speeds, pressure ratios and various inlet swirls. In an engine, honeycomb abrasive liners on the stator protect the seal fins. To simulate real engine conditions honeycombs were applied in the test setup, too and the influence of these liners on the windage heating was compared to smooth stator configurations. Detailed velocity profiles within the seal chambers were determined using a 2D Laser-Doppler-Velocimeter. Additionally, the ability of axisymmetric numerical k-ε simulations to predict the data was evaluated. The present study provides important data for the design of future turbo machines, because the exact knowledge of the labyrinth seal exit swirl and temperature is expected to further improve the design of downstream components such as the pre-swirl system. Additionally, more accurate boundary conditions for the thermal analysis will be available and the rotor dynamic stability of the seal can be estimated better.

Experimental and Numerical Investigation on Leakage Characteristic of Stepped Labyrinth Seal

2016 ◽  
Author(s):  
Li Zhang ◽  
Hui-ren Zhu ◽  
Cun-liang Liu ◽  
Fei Tong
Keyword(s):  
Gas Turbines ◽  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Scaling Effects ◽  
Labyrinth Seals ◽  
Maximal Deviation ◽  
Tooth Number ◽  
Leakage Coefficient ◽  
Secondary Air ◽  
Aero Engines

Labyrinth seals represent an important flow element in the secondary air system of aero engines. The influence of seal clearance and teeth parameters on the leakage characteristic of a real size stepped labyrinth seal was experimentally and numerically analyzed in a stationary state. Two kinds of labyrinth seals were studied in this investigation that are generally used in gas turbines, namely downward stepped labyrinth and upward stepped labyrinth. The differences of seal flow leakage mechanisms between the two types of the labyrinth were investigated. In order to eliminate the scaling effects on leakage losses in labyrinth seals, the experimental labyrinth seal model took the size of the real one in an aero engine. The experiments covered a range of pressure ratio from 1.1 to 3.5. The experimental and numerical results show that in the range of the studied parameters the main teeth parameters affecting leakage coefficient are seal clearance, tooth tip thickness, tooth number and tooth front inclination. The influence of tooth height, pith and rear inclination angle on leakage coefficient of downward stepped labyrinth seal can almost be neglected in this research. And when the step height is more than twice the width of seal clearance, its effect on seal performance can be ignored. An empirical formula express of leakage coefficient with pressure ratio, seal clearance and teeth parameters of downward stepped labyrinth seal was organized which fits the experimental data with a maximal deviation of 8%. With similar pressure ratios and seal clearances, the downward stepped labyrinth seal displays lower leakage rates and provides the best sealing efficiency.

Development of Cavity Shapes of Labyrinth Seals Through CFD Analysis

2013 ◽  
Author(s):  
Mohana Rao Ramanadham ◽  
Balakrishna Gaja ◽  
Sravan Kumar Kanchanapally
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Axial Flow ◽  
Labyrinth Seal ◽  
Geometric Shape ◽  
Working Fluid ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Primary Flow ◽  
Flow Through

Axial flow compressors of Gas turbines use labyrinth seals to prevent the backflow of the working fluid. However some fluid will leak through the seals due to the clearance provided between the stationery and rotating components and due to the pressure difference across the seals, which affects the efficiency. The geometric shape of the seal plays an important role in influencing the fluid flow through the seals and the leakage rate. The flow through the seals consists of the primary flow and the secondary flow. The secondary flow is the flow through the cavity which is associated with vortex currents and tends to obstruct the primary flow. The geometric shape of the cavity is varied to study its effect on the vortex and resultant leakage flow through the seals. The curvatures of the seal and the distance of the seal tip to the end of the seal are the main parameters considered to arrive at the desired cavity which helps to create the required whirling action and to reduce the velocity of the leakage flow. Gambit software is used for modeling the geometry and Fluent software is used for the analysis. Axi-symmetric pressure based analysis is carried out using the standard κ-ε turbulence. The results of the standard cavity are compared with different variants. The flow velocity and mass flow is studied at different locations of the seal. The results indicate that by optimizing the shape of the seal cavity, the leakage through the labyrinth seal can be reduced.

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