Experimental Study on the Friction Contact Between a Labyrinth Seal Fin and a Honeycomb Stator

2015 ◽  
Vol 138 (6) ◽  
Author(s):  
Tim Pychynski ◽  
Corina Höfler ◽  
Hans-Jörg Bauer
Keyword(s):  
Experimental Study ◽  
Friction Velocity ◽  
Wear Behavior ◽  
Labyrinth Seal ◽  
Contact Forces ◽  
Metal Foil ◽  
Labyrinth Seals ◽  
Friction Temperature ◽  
Rubbing Behavior ◽  
Set Up

This paper presents results from an extensive experimental study on the rubbing behavior of labyrinth seal fins (SFs) and a honeycomb liner. The objective of the present work is to improve the understanding of the rub behavior of labyrinth seals by quantifying the effects and interactions of sliding speed, incursion rate, seal geometry, and SF rub position on the honeycomb liner. In order to reduce the complexity of the friction system studied, this work focuses on the contact between a single SF and a single metal foil. The metal foil is positioned in parallel to the SF to represent contact between the SF and the honeycomb double foil section. A special test rig was set up enabling the radial incursion of a metal foil into a rotating labyrinth SF at a defined incursion rate of up to 0.65 mm/s and friction velocities up to 165 m/s. Contact forces, friction temperatures, and wear were measured during or after the rub event. In total, 88 rub tests including several repetitions of each rub scenario have been conducted to obtain a solid data base. The results show that rub forces are mainly a function of the rub parameters incursion rate and friction velocity. Overall, the results demonstrate a strong interaction between contact forces, friction temperature, and wear behavior of the rub system. The presented tests confirm basic qualitative observations regarding blade rubbing provided in literature.

Experimental Study on the Friction Contact Between a Labyrinth Seal Fin and a Honeycomb Stator

2015 ◽  
Author(s):  
Tim Pychynski ◽  
Corina Höfler ◽  
Hans-Jörg Bauer
Keyword(s):  
Experimental Study ◽  
Friction Velocity ◽  
Wear Behavior ◽  
Labyrinth Seal ◽  
Contact Forces ◽  
Metal Foil ◽  
Labyrinth Seals ◽  
Friction Temperature ◽  
Rubbing Behavior ◽  
Set Up

This paper presents results from an extensive experimental study on the rubbing behavior of labyrinth seal fins and a honeycomb liner. The objective of the present work is to improve the understanding of the rub behavior of labyrinth seals by quantifying the effects and interactions of sliding speed, incursion rate, seal geometry and seal fin rub position on the honeycomb liner. In order to reduce the complexity of the friction system studied, this work focuses on the contact between a single seal fin and a single metal foil. The metal foil is positioned in parallel to the seal fin to represent contact between the seal fin and the honeycomb double foil section. A special test rig was set up enabling the radial incursion of a metal foil into a rotating labyrinth seal fin at a defined incursion rate of up to 0.65 mm/s and friction velocities up to 165 m/s. Contact forces, friction temperatures and wear were measured during or after the rub event. In total, 88 rub tests including several repetitions of each rub scenario have been conducted to obtain a solid data base. The results show that rub forces are mainly a function of the rub parameters incursion rate and friction velocity. Overall, the results demonstrate a strong interaction between contact forces, friction temperature and wear behavior of the rub system. The presented tests confirm basic qualitative observations regarding blade rubbing provided in literature.

scholarly journals Continued Experimental Study on the Friction Contact between a Labyrinth Seal Fin and a Honeycomb Stator: Slanted Position

Aerospace ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 82 ◽  
Author(s):  
Oliver Munz ◽  
Tim Pychynski ◽  
Corina Schwitzke ◽  
Hans-Jörg Bauer
Keyword(s):  
Labyrinth Seal ◽  
Contact Forces ◽  
Strong Interactions ◽  
Metal Foil ◽  
Labyrinth Seals ◽  
Contact Conditions ◽  
Leakage Flows ◽  
Eu Project ◽  
And Control ◽  
Cooling Air

Labyrinth seals are a state-of-the-art sealing technology to prevent and control leakage flows at rotor–stator interfaces in turbomachinery. Higher pressure ratios and the economical use of cooling air require small clearances, which lead to potential rubbing events. The use of honeycomb liners allows for minimal leakage by tolerating rub events to a certain extent. A previous study within an EU project investigated the complex contact conditions of honeycomb liners, with the idealized contact of a seal fin and a single parallel metal foil representing the honeycomb double foil section. In the present work, the results for the slanted foil position are shown and compared to the previous results. The variation of rub velocity, incursion speed, incursion rate, and seal geometry in a test rig allows for the identification of the influence on contact forces, temperatures, and wear. For the slanted position, significantly lower friction temperatures are observed, leading to a higher ratio of abrasive wear. Overall, the rub test results demonstrate strong interactions between the contact forces, friction temperatures, and wear.

Performance evaluation of the inter-stage labyrinth seal for different tooth positions in an axial compressor

2017 ◽  
Vol 232 (6) ◽  
pp. 579-592 ◽  
Author(s):  
Xiaozhi Kong ◽  
Gaowen Liu ◽  
Yuxin Liu ◽  
Zhao Lei ◽  
Longxi Zheng
Keyword(s):  
Axial Compressor ◽  
Labyrinth Seal ◽  
Tip Clearance ◽  
Test Facility ◽  
Leakage Flow ◽  
Rotating Disc ◽  
Labyrinth Seals ◽  
Leakage Flows ◽  
Sealing Performance ◽  
Set Up

Labyrinth seals are normally used to control the leakage flow in the compressor stator well. The upstream and downstream rotor-stator cavities of the labyrinth seal can cause complex reverse leakage flows. Remarkable temperature increases and high swirl velocities are observed in this region. In addition, another characteristic of inter-stage labyrinth seal is that large expansions of rotor and stator may easily lead to severely rubbing between the teeth and shrouds, which can shorten the lifetime of the compressor obviously. Experiments were conducted at a rotating compressor inter-stage seal test facility. Different labyrinth rings were tested to compare the performances of inter-stage labyrinth seals with different tooth positions. Leakage flow rates, windage heating and swirl ratios in the outlet cavity were measured at different rotating speeds and pressure ratios. In order to get the working tip clearance accurately, the set up tip clearance was measured with plug gauges, while the radial displacements of rotating disc and stationary casing were measured separately with two high precision laser distance sensors. Numerical simulations were carried out to present the important flow physics responsible for the effects of different tooth positions. In this article, performances of different cases for single, double and triple teeth were investigated and the experimental data provide a new way for the design of inter-stage seals. This method can reduce the leakage flow and avoid severely rubbing at the same time by changing axial positions of teeth in the stator well. When teeth are placed downstream of the model and the tooth pitch is larger, the inter-stage seal would have better sealing performance. For triple teeth cases, N = 3-Case1 has the lowest discharge coefficients, 15% less than that of N = 3-Baseline.

Wear Prediction of Strip Seals Through Conductance

2004 ◽  
Author(s):  
Farshad Ghasripoor ◽  
Norman A. Turnquist ◽  
Mark Kowalczyk ◽  
Bernard Couture
Keyword(s):  
Thermal Conductivity ◽  
High Speed ◽  
Wear Behavior ◽  
Close Correlation ◽  
Labyrinth Seal ◽  
The Body ◽  
Minor Effect ◽  
Labyrinth Seals ◽  
Steam Leakage ◽  
A Minor

Labyrinth seal assemblies are often used to reduce gas and/or steam leakage in turbines. Caulked-in continuous strip seals are one of the common forms of seals employed on both the rotating and stationary components of turbines. Labyrinth seals perform best when minimum clearances are achieved during the steady state operation of the turbine. However, the design of the turbine and its operation during transient periods of start-up, shut-down and hot re-start often result in interference between the seal components. In the case of the strip seals, this leads primarily to wear of the strip, which in effect adds to leakage. The aim of this paper is to show that strip tip heating and melting during the rub is the main mechanism of wear in the strip. Hence thermal conductivity through the strip and into the body mass in which it is caulked is the primary controlling factor in seal wear. This paper will discuss the use of thermal conductivity and geometry of the strip in predicting wear during high speed rubs against a proprietary material. A close correlation between calculated and experimental strip seal wear data with a number of seal alloys will be demonstrated. Test data will indicate that material properties such as tensile strength and hardness have a minor effect on the wear behavior of continuous seal elements during high-speed rubs.

Experimental Investigation On Wear Behavior of Rectangular Labyrinth Fin Against High Speed Rotor

2021 ◽  
Author(s):  
Xin Yan ◽  
Xinbo Dai
Keyword(s):  
Friction Coefficient ◽  
High Speed ◽  
Wear Behavior ◽  
Early Stage ◽  
Labyrinth Seal ◽  
Contact Forces ◽  
Transient Temperature ◽  
Sliding Velocity ◽  
Material Loss ◽  
Temperature Distributions

Abstract The wear behaviors of a rectangular labyrinth seal fin against high speed rotor were experimentally investigated on the incursion test rig. The material losses, worn geometries, frictional temperature distributions, and contact forces of labyrinth fin in rubbing events were measured at three incursion rates, three final incursion depths and two rotor sliding velocities. The morphologies of the worn labyrinth fin tips were magnified to reveal the wear mechanisms in rubbing events. The transient temperatures and contact forces were detailed to analyze the thermal-mechanical interactions between two contacting parts. The results show that the material loss percentage in the labyrinth fin is higher at the early stage of rubbing process, accounting for 18% mass loss of the worn region, than at final stage. The material loss is decreased with increasing the incursion rate. The incursion rate and final incursion depth have pronounced effects on the mushroom region extensions and curlings. The friction coefficient is fluctuated significantly in the high sliding velocity and low incursion rate conditions, and the averaged value of friction coefficient is about 0.1-0.125 among all experiments. The temperature at labyrinth fin tip is increased with increasing the final incursion depth, incursion rate and sliding velocity. However, the temperature at fin tip is not increased further as it reaches about 1200°C. The heat convection from hot fin to ambient plays an important role in worn geometries and transient temperature distributions at fin tip.

Experimental Study on Rubbing Wear Characteristics of Labyrinth Seal with Trapezoidal Fins

2021 ◽  
pp. 1-42
Author(s):  
Xin Yan ◽  
Xinbo Dai ◽  
Kun He
Keyword(s):  
Mass Loss ◽  
High Speed ◽  
Wear Behavior ◽  
Early Stage ◽  
Labyrinth Seal ◽  
Contact Forces ◽  
Sliding Velocity ◽  
Wear Performance ◽  
Wear Characteristics ◽  
Geometrical Effect

Abstract The wear characteristics of trapezoidal fin against high speed rotor were experimentally investigated at different final incursion depths, incursion rates, and sliding velocities. To characterize the geometrical effect, a small specimen (SS) and a large specimen (LS) were selected to analyze the mass loss, wear geometry, contact forces, and frictional temperature distributions under different conditions. The results show that the contact-separation is most likely to occur between the trapezoidal fin and rotor. In the rubbing process, the plastic deformation is dominating, and the abrasive and adhesive wears have pronounced effects on the wear behavior of rubbing interface. The wear performance of the SS is sensitive to the structure imbalance, which induces the combined mushrooming and bending damage in the trapezoidal fin. However, the symmetrical mushrooming damage is generated in the LS. For both SS and LS, the mass loss is decreased with increasing the incursion rate and sliding velocity, and the mass loss percentage is pronounced at the early stage of rubbing. The averaged friction coefficient is 0.1-0.16 for the LS, while 0.1-0.19 for the SS. The peak frictional temperature is 560-640 °C for the LS, while 360-400 °C for the SS. The contact-separation significantly reduces the effects of final incursion depth, incursion rate, and sliding velocity on the wear geometry, contact forces and temperature rise in the trapezoidal labyrinth fin.

scholarly journals Validation of Flow Coefficients Measurement by Laser Velocimeter in Straight-Through Labyrinth Seal Models With Full Size Test Rig Results

1984 ◽  
Author(s):  
Giulio D’Emilia
Keyword(s):  
Labyrinth Seal ◽  
Laser Doppler Velocimeter ◽  
Test Rig ◽  
Centrifugal Compressors ◽  
Labyrinth Seals ◽  
Full Size ◽  
Carry Over ◽  
Set Up ◽  
Definition Of ◽  
Quantitative Definition

In the computation of overall efficiency in turbomachines the increase of performance in high pressure centrifugal compressors renders of great importance the rôle of leakage in straight-through labyrinth seals. A test rig for labyrinth seals used in process compressors was built in order to carry out a systematic study of the fluidodynamic phenomena characteristic of flow in these devices. Full size seals were tested under different working conditions and the results were utilized for a quantitative definition of the experimental coefficients introduced in previsional methods which were shown the best ones on the basis of previous investigation (1). The coefficients consider the principal fluidodynamic phenomena existent in the seals: fluid flow contraction in the throttlings and kinetic energy carry-over, which have contrasting effects on the leakage of a straight-through labyrinth seal. The results were used to find elements of correct design in these seals. They point out besides the geometric parameters which optimize seal performance, minimizing the leakage on a fixed length of the labyrinth. Larger scale models of the same seals tested on the above mentioned test rig were studied in a smoke tunnel under conditions which satisfied the Reynolds similarity. This experimental set-up permitted the measurement of the velocity distributions within the straight through labyrinth seal models by means of a laser Doppler velocimeter. Particular attention was dedicated to the definition of uncertainty of the experimental coefficients. The information obtained was satisfactory. The results showed promising correlations between real seals and larger models. These relations could be very useful when designing labyrinth seals for centrifugal compressors, as a large part of long, costly tests on real seals could be substituted by faster and more economical measurements on models.

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.

Experimental Investigation on the Rubbing Process of Labyrinth Seals Considering the Material Combination

2020 ◽  
Author(s):  
Lisa Hühn ◽  
Oliver Munz ◽  
Corina Schwitzke ◽  
Hans-Jörg Bauer
Keyword(s):  
Turbine Blades ◽  
Design Guidelines ◽  
Operating Conditions ◽  
Contact Forces ◽  
Experimental Investigations ◽  
Process Data ◽  
Labyrinth Seals ◽  
Material Combination ◽  
Higher Temperature ◽  
And Control

Abstract Labyrinth seals are used to prevent and control the mass flow rate between rotating components. Due to thermally and mechanically induced expansions during operation and transient flight maneuvers, a contact, the so-called rubbing process, between rotor and stator cannot be excluded. A large amount of rubbing process data concerning numerical and experimental investigations is available in public literature as well as at the Institute of Thermal Turbomachinery (ITS). The investigations were carried out for different operating conditions, material combinations, and component geometries. In combination with the experiments presented in this paper, the effects of the different variables on load due to rubbing are compared, and discussed with the focus lying on the material combination. The influence of the material on the loads can be identified as detailed as never before. For example, the contact forces in the current experiments are higher due to a higher temperature resistance of Young’s modulus. The analysis will also be based on the rubbing of turbine blades. Design guidelines are derived for labyrinth seals with improved properties regarding tolerance of rub events. Based on the knowledge obtained, guidelines for designing reliable labyrinth seals for future engines are discussed.

Sign in / Sign up

Export Citation Format

Share Document