Modelling the Labyrinth Seal Discharge Coefficient Using Data Mining Methods

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.

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Influence of Rub-Grooves on Labyrinth Seal Leakage

Journal of Turbomachinery ◽

10.1115/1.1539516 ◽

2003 ◽

Vol 125 (2) ◽

pp. 387-393 ◽

Cited By ~ 17

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.

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Influence of Rub-Grooves on Labyrinth Seal Leakage

Volume 3: Turbo Expo 2002, Parts A and B ◽

10.1115/gt2002-30244 ◽

2002 ◽

Cited By ~ 3

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.

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Optimization of Labyrinth Seal Performance Combining Experimental, Numerical and Data Mining Methods

Volume 4: Heat Transfer, Parts A and B ◽

10.1115/gt2012-68077 ◽

2012 ◽

Cited By ~ 5

Author(s):

Erik Braun ◽

Klaus Dullenkopf ◽

Hans-Jörg Bauer

Keyword(s):

Data Mining ◽

Data Base ◽

Flow Direction ◽

Empirical Studies ◽

Geometry Optimization ◽

Labyrinth Seal ◽

Labyrinth Seals ◽

Research Activities ◽

Input Parameters ◽

Mining Methods

Numerous experimental and numerical studies were performed in the past by various authors to reduce the leakage of labyrinth seals and thus increase the performance of turbo machines. Based on the experience of more than 20 years of research activities in this area at the ITS, the authors aim to improve the prediction quality for labyrinth seal performance by combining experimental, numerical and data mining methods. Special emphasis in this work lies on more complex and also worn labyrinth geometries and thus on a more universal optimization tool for labyrinth seals incorporating more realistic engine running conditions as well as wear mechanisms. Better understanding of labyrinth seal behavior based on the new correlations and models will thus lead to optimized geometries and improved designs. The paper contains the results of experiments to determine the discharge coefficients of different straight-through labyrinth seals with three and five fins and two different fin geometries over a large range of pressure ratios as well as results from a stepped labyrinth seal with six fins in convergent and divergent flow direction. The collected data extends an existing data base of labyrinth seal performance already presented in the paper of Pychynski et al. [1]. This data base is used to create models to calculate labyrinth seal performance depending on up to 25 input parameters. The resulting models will be used as a basis for a universal optimization tool for labyrinth seals. In the paper the new and versatile test rig for various kinds of labyrinth and gap seals is presented and an analysis of measurement accuracy will be given. The results of a first set of experiments performed with new (i.e. unworn) geometries are compared to experimental data of similar labyrinth geometries from previous investigations, showing an excellent agreement. The results are then interpreted using Data Mining Methods to identify correlations between different input parameters and the labyrinth seal discharge coefficient. The paper will show that a data based approach can yield similar quality relations as empirical studies but is much less time consuming and more versatile. Several models with different sets of input parameters will be presented and compared as to their applicability in automated geometry optimization using a newly developed optimization tool.

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Performance of Worn Labyrinth Seals

Volume 1: Turbomachinery ◽

10.1115/94-gt-131 ◽

1994 ◽

Cited By ~ 11

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.

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Assessment of Analytical Predictions for Radial Growth of Rotating Labyrinth Seals

International Journal of Turbo and Jet Engines ◽

10.1515/tjj-2016-0041 ◽

2018 ◽

Vol 35 (3) ◽

pp. 265-279 ◽

Cited By ~ 2

Author(s):

Sivakumar Subramanian ◽

A. S. Sekhar ◽

B. V. S. S. S. Prasad

Keyword(s):

Rotational Speed ◽

Radial Growth ◽

Three Dimensional ◽

Labyrinth Seal ◽

Analytical Models ◽

Length Ratio ◽

Labyrinth Seals ◽

High Rotational Speed ◽

Dimensional Finite Element ◽

Three Dimensional Finite Element

Abstract Radial growth predictions of rotating labyrinth seals are conventionally obtained from one-dimensional analytical models. However, these predictions quantitatively differ within themselves by about 5-500 %. Simulations using three-dimensional finite element method (FEM) are carried out in this paper for a typical labyrinth seal, subjected to high rotational speed and temperature, for a range of radius-to-length ratio of the rotor. Taking the predicted values by FEM as reference, four analytical models are assessed and their errors are quantified. These errors are found to be independent of rotational speed and temperature but significantly vary with the radius-to-length ratio of the rotor. Based on this finding, simple analytical models, together with correction factor charts, are suggested.

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Effective Clearance And Differential Gapping Impact on Seal Flutter Modelling and Validation

10.1115/gt2021-58846 ◽

2021 ◽

Author(s):

Roque Corral ◽

Michele Greco ◽

Almudena Vega

Keyword(s):

Labyrinth Seal ◽

Analytical Models ◽

Navier Stokes ◽

Labyrinth Seals ◽

Theoretical Support ◽

Gap Ratio ◽

Flutter Analysis ◽

The Impact ◽

Cv Model ◽

Additional Loss

Abstract This paper presents an update of the model derived by Corral and Vega (2018, “Conceptual Flutter Analysis of Labyrinth Seal Using Analytical Models. Part I - Theoretical Support”, ASME J. of Turbomach., 140 (12), pp. 121006) for labyrinth seal flutter stability, providing a method of accounting for the effect of dissimilar gaps. The original CV model was intended as a conceptual model for understanding the effect of different geometric parameters on the seal stability comprehensively, providing qualitative trends for seal flutter stability. However, the quantitative evaluation of seal flutter, and the comparison of the CV model with detailed unsteady numerical simulations or experimental data, require including additional physics. The kinetic energy generated in the inlet gap is not dissipated entirely in the inter-fin cavity of straight-through labyrinth seals, and part is recovered in the downstream knife. This mechanism needs to be retained in the seal flutter model. It is concluded that when the theoretical gaps are identical, the impact of the recovery factor on the seal stability can be high. The sensitivity of the seal stability to large changes in the outlet to inlet gap ratio is high as well. It is concluded that fin variations due to rubbing or wearing inducing inlet gaps more open than the exit gaps lead to an additional loss of stability concerning the case of identical gaps. The agreement between the updated model and 3D linearized Navier-Stokes simulations is excellent when the model is informed with data coming from steady RANS simulations of the seal.

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Numerical validation of an analytical seal flutter model

Journal of the Global Power and Propulsion Society ◽

10.33737/jgpps/141210 ◽

2021 ◽

Vol 5 ◽

pp. 191-201

Author(s):

Michele Greco ◽

Roque Corral

Keyword(s):

Analytical Model ◽

Fluid Dynamic ◽

Stability Limit ◽

Labyrinth Seal ◽

Analytical Models ◽

Mode Shapes ◽

Labyrinth Seals ◽

Low Frequencies ◽

Wide Range ◽

The Stability

An analytical model to describe the flutter onset of straight-through labyrinth seals has been numerically validated using a frequency domain linearized Navier-Stokes solver. A comprehensive set of simulations has been conducted to assess the stability criterion of the analytical model originally derived by Corral and Vega (2018), “Conceptual Flutter Analysis of Labyrinth Seals Using Analytical Models - Part I: Theoretical Support,” ASME J. Turbomach., 140 (12), pp. 121006. The accuracy of the model has been assessed by using a simplified geometry consisting of a two-fin straight-through labyrinth seal with identical gaps. The effective gaps and the kinetic energy carried over are retained and their effects on stability are evaluated. It turns out that is important to inform the model with the correct values of both parameters to allow a proper comparison with the numerical simulations. Moreover, the non-isentropic perturbations included in the formulations are observed in the simulations at relatively low frequencies whose characteristic time is of the same order as the discharge time of the seal. This effect is responsible for the bending of the stability limit in the <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mn>0</mml:mn><mml:mi>t</mml:mi><mml:mi>h</mml:mi></mml:math></inline-formula> ND stability map obtained both in the model and the simulations. It turns out that the analytical model can predict accurately the stability of the seal in a wide range of pressure ratios, vibration mode-shapes, and frequencies provided that this is informed with the fluid dynamic gaps and the energy carried over to the downstream fin from a steady RANS simulation. The numerical calculations show for the first time that the model can be used to predict accurately not only the trends of the work-per-cycle of the seal but also quantitative results.

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EFFECTIVE CLEARANCE AND DIFFERENTIAL GAPPING IMPACT ON SEAL FLUTTER MODELLING AND VALIDATION

Journal of Turbomachinery ◽

10.1115/1.4053290 ◽

2021 ◽

pp. 1-16

Author(s):

Roque Corral ◽

Michele Greco ◽

Almudena Vega

Keyword(s):

Labyrinth Seal ◽

Analytical Models ◽

Navier Stokes ◽

Labyrinth Seals ◽

Theoretical Support ◽

Gap Ratio ◽

Flutter Analysis ◽

The Impact ◽

Cv Model ◽

Additional Loss

Abstract This paper presents an update of the model derived by Corral and Vega (2018, “Conceptual Flutter Analysis of Labyrinth Seal Using Analytical Models. Part I - Theoretical Support”, ASME J. of Turbomach., 140 (12), pp. 121006) for labyrinth seal flutter stability, providing a method of accounting for the effect of dissimilar gaps. The original CV model was intended as a conceptual model for understanding the effect of different parameters on the seal stability comprehensively, providing qualitative trends for seal flutter stability. However, the quantitative evaluation of seal flutter, and the comparison of the CV model with detailed unsteady numerical simulations or experimental data, require including additional physics. The kinetic energy generated in the inlet gap is not dissipated entirely in the inter-fin cavity of straight-through labyrinth seals, and part is recovered in the downstream knife. This mechanism needs to be retained in the model. It is concluded that when the theoretical gaps are identical, the impact of the recovery factor on the seal stability can be high. The sensitivity of the seal stability to large changes in the outlet to inlet gap ratio is high as well. It is concluded that fin variations due to rubbing or wearing inducing inlet gaps more open than the exit gaps lead to an additional loss of stability concerning the case of identical gaps. The agreement between the updated model and 3D linearized Navier-Stokes simulations is excellent when the model is informed with data coming from steady RANS simulations of the seal.

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