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.

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.

A CFD Study on the Dynamic Coefficients of Labyrinth Seals

2012 ◽  
Author(s):  
Donghui Zhang ◽  
Chester Lee ◽  
Michael Cave
Keyword(s):  
High Speed ◽  
Fluid Dynamic ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Dynamic Coefficients ◽  
Rotating Impeller ◽  
Coupling Stiffness ◽  
Direct Stiffness ◽  
Compressor Efficiency

Labyrinth seals are widely used in gas compressors to reduce internal leakage and increase the compressor efficiency. Due to the eccentricity between the rotating impeller and the stationary part as *well as the shaft whirling motion, forces are generated when the leakage flow passing through the cavities and the seals. For a lot of applications with high speed and pressure, these forces can drive the system unstable. Thus, predicting the forces accurately become a very important for compressor rotordynamic designs. A lot of research and studies has been done to the seals itself, including bulk flow method, computational fluid dynamic (CFD) and test measurement. The seal and leakage flow interaction forces can be predicted relatively accurate. But very few research treat the seal and cavities as one component interacting with the leakage flow and produce the forces. This paper presents results of CFD investigations on the dynamic coefficients of one typical impeller eye seal and front cavity. The CFD results show that large forces are generated in the front cavity due to circumferential uniform pressure distribution, which caused by the downstream labyrinth seal. The forces generated in the front cavity are more than in the front seal. It was found that the inertia, damping, and stiffness are proportional to average pressure. The cross-coupling stiffness increases with speed with power of 2 while the direct stiffness increases with speed with power of about 1.7.

High-Speed Dry Tribological Behaviors of CrNiMo Steel in Nitrogen and Oxygen Atmospheres

2011 ◽  
Vol 704-705 ◽  
pp. 877-885
Author(s):  
San Ming Du ◽  
Yong Zhen Zhang ◽  
Bao Shangguan
Keyword(s):  
Abrasive Wear ◽  
Tribological Properties ◽  
Wear Mechanism ◽  
Wear Mechanisms ◽  
High Speed ◽  
Normal Load ◽  
Dry Sliding ◽  
Tribological Behaviors ◽  
Electron Dispersion ◽  
Worn Surface

Abstract: In this article, the high-speed dry sliding tribological behaviors of CrNiMo steel against brass in nitrogen and oxygen atmospheres are investigated using a pin-on-disc tribometer. The worn surface is characterized by scanning electron microscopy and electron dispersion spectrums analysis. The wear mechanisms of CrNiMo steel are also analyzed. The results indicate that the tribological properties of CrNiMo steel are coincidental with the law of dry sliding of metal, where the friction coefficients decreases with an increase in sliding speed and with normal load. However, the atmosphere has obvious effects on the tribological properties of CrNiMo steel. In the sliding process, friction heat plays an important role on the tribological properties of materials in high-speed dry friction. The high-speed wear mechanism of CrNiMo steel varies at different atmospheres. In a nitrogen atmosphere, the wear mechanism of CrNiMo steel is mainly characterized by adhesion at a lower speed and load. When the speed and load are increased, melting trace is found in the worn surface accompanied by an abrasive wear. In an oxygen atmosphere, the mechanism is characterized by adhesion at a lower speed and load; with an increase in speed and load, it gradually transformed into oxidation wear and abrasive wear. The difference of the wear mechanisms in the different atmospheres and test parameters is primarily due to the transfer films formed on the contact surfaces of the sliding pairs. In our experimental conditions, the surface film is mainly the metal film in nitrogen, whereas, it is the oxide film in oxygen.

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.

A New Method to Realize Unsteady Calculation of Flow in Labyrinth Seals

2011 ◽  
Vol 199-200 ◽  
pp. 68-71
Author(s):  
Zhen Ping Liu ◽  
Shu Lian Liu ◽  
Shui Ying Zheng
Keyword(s):  
High Speed ◽  
High Performance ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Nonlinear Behaviour ◽  
Labyrinth Seals ◽  
Mesh Density ◽  
Excitation Force

As non-contact seal, labyrinth seal is widely used in rotor system of high speed. However, with the development of turbo-machinery toward high performance and huge capacity, gas excitation vibration within the labyrinth seal becomes the main reason threatening safe operating of machinery sets. Recently three dimensional computational fluid dynamic was applied to analyse inside flow in labyrinth seal. These researches, while greatly improve rotordynamic prediction of labyrinth seals, are mostly focused in steady calculation. In fact, rotor inside the seal is whirling in a nonlinear behaviour, which makes the flow unstable. In an effort to analyse the non-linear behaviour of flow in labyrinth seal, this paper utilizes an improved dynamic mesh technology to realize unsteady calculation. The Reynolds Averaged Navier Stokes equations is solved by a commercial CFD program, FLUENT. Steady calculations are firstly done to determine mesh density and turbulence model, then an unsteady analysis is used to study gas excitation force. The influence of initial condition to the unsteady analysis is discussed. This method allows modeling of rotor orbit around the eccentric position and gives prediction of nolinear gas excitation force.

scholarly journals An investigation into the role of specimen geometry when undertaking tribological testing on seal fin components

2021 ◽  
pp. 095440622110250
Author(s):  
Boxiu Zhang ◽  
Matthew Marshall ◽  
Roger Lewis
Keyword(s):  
Wear Mechanism ◽  
High Speed ◽  
Heat Removal ◽  
Labyrinth Seal ◽  
Specimen Geometry ◽  
Speed Test ◽  
Sealing Performance ◽  
Post Test ◽  
Surface Examination

Labyrinth seal systems are used in aeroengines to seal the clearance, the understanding of the wear mechanism of labyrinth seal system is necessary to achieve better sealing performance. In this work a series of tests are conducted on a high-speed test rig capable of fin tip speeds of 100 m/s. With force and temperature measurements recorded in each case, the influence of specimen geometry is investigated. Surface examination and debris analysis is also performed using microscopy post-test. The wear mechanism was found to be influenced by fin geometry. A discrete fin was observed to trigger a more efficient material removal mechanism at both incursion conditions. Where the fin segment and ring-shaped fin leading to increased temperatures and material smearing. The heat dissipate role of fin was also observed during test where longer contact time of fin and abradable gives better heat removal performance.

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.

Flexible Seal Strip Design for Advanced Labyrinth Seals in Turbines

2013 ◽  
Author(s):  
N. Herrmann ◽  
K. Dullenkopf ◽  
H.-J. Bauer
Keyword(s):  
High Speed ◽  
Discharge Coefficient ◽  
Life Time ◽  
Labyrinth Seal ◽  
Labyrinth Seals ◽  
Seal Design ◽  
Discharge Rates ◽  
Balanced Designs ◽  
Cooling Effects ◽  
The Impact

The paper discusses the potential benefit of flexible seal strips in labyrinth seals for turbines. By reducing the radial stiffness compared to a standard straight and stiff knife, seal clearance could be reduced without significantly reducing the seal durability and long-term performance. As contact between the seal strips and the rotor can occur especially during transient operating phases, a more flexible design of the seal strips can prevent damage and wear, keeping the discharge rates constantly low. However, the pressure difference across the fin will cause a deflection of the seal strip due to the increased flexibility and thus creating an additional possible risk for an unwanted contact. Pressure balanced designs and supports on the low pressure side are used on the investigated seal designs to eliminate that risk. To give evidence of possible performance gain a standard labyrinth seal configuration is compared to two configurations with segmented and curved seal strips. In a first step, the discharge coefficient and the leakage rates for the nominal seal design are calculated using two-dimensional CFD. In order to investigate the impact of a worn seal tip on the leakage flow, the geometry change due to a rubbing event is simulated with FEA tools. Therefore, a specific high-speed wear model is implemented and calibrated by experimental data, enabling the correct cooling effects and plastic deformation. The discharge coefficient and the leakage mass flow rates of the worn geometry are then again modeled with CFD for the various seal configurations and compared to the unworn state. The study shows that a wise combination of the advantages of flexible curved seal strips can be used to reduce the leakage rates significantly, improving the life time of seal elements at the same time.

Comparison Between a CFD Code and a Three-Control-Volume Model for Labyrinth Seal Flutter Predictions

2011 ◽  
Author(s):  
R. Phibel ◽  
L. di Mare
Keyword(s):  
Flow Model ◽  
Control Volume ◽  
Large Diameter ◽  
Labyrinth Seal ◽  
Control Flow ◽  
Cfd Analysis ◽  
Aeroelastic Stability ◽  
Labyrinth Seals ◽  
Aero Engine ◽  
Secondary Air

Labyrinth seals are extensively used in turbomachinery to control flow leakage in secondary air systems. While a large number a studies have been performed to investigate the leakage and rotordynamics characteristics of these seals, the studies on their aeroelastic stability remain scarce. Little is known about this phenomenon and the design methods are limited to a stability criterion which does not take into account many of the parameters which are known to influence labyrinth seal aeroelastic stability. As a consequence the criterion can be unreliable or overly pessimistic. The alternative to this criterion is the use of CFD methods which, although reliable, are computationally expensive. This paper presents a three-control-volume (3CV) bulk-flow model specifically developed for flutter calculations in labyrinth seals. The model is applied to a turbine labyrinth seal of a large diameter aero-engine and the results are compared to those of a CFD analysis. Conclusions are drawn on the potential of this 3CV model for design purposes.

Aeroelastic Instability in Labyrinth Seals

1968 ◽  
Vol 90 (4) ◽  
pp. 369-374 ◽  
Author(s):  
F. Ehrich
Keyword(s):  
High Speed ◽  
Stability Boundary ◽  
Low Pressure ◽  
Labyrinth Seal ◽  
Stability Parameter ◽  
Pressure Perturbation ◽  
Labyrinth Seals ◽  
Stick Slip ◽  
Pivot Point ◽  
The Stability

Labyrinth seals and associated structural elements have been noted to sustain fatigue failure in high powered, high speed rotating machinery under circumstances that preclude blaming standing wave resonances or “stick-slip” excitation from rotor/stator rubs. Alford [2] has hypothesized that such failures may be caused by self-excited aeroelastic vibration of the seal. A model is defined in which a pressure perturbation in the seal internal volume between the high and low pressure teeth can cause an elastic rotation of the seal rotor or stator element about a virtual pivot point located on the high or low pressure side of the seal. This rotation, in turn, causes a nonuniform opening and closing of the high and low pressure clearances which can give rise to the hypothesized pressure perturbation. A stability parameter is then derived in terms of the high pressure and low pressure tooth clearances, the supply pressure to the seal, the seal width and height, and two parameters indicative of the elastic properties of the seal—its stiffness to radial motion and the location of its virtual pivot point. The stability criterion is applied to a pair of actual labyrinth seal rotors which differ from each other only slightly and are known, from actual practice, to straddle the stability boundary. That is, the larger diameter unit is known to be unstable and the smaller diameter unit known to be stable. On the basis of an instability incident simulated on component test, the stiffness used in evaluating the stability parameter is modified to be representative of the least stiff vibratory mode, and the stability parameter is shown to give reasonable indication of the stability problem in labyrinth seals.

Sign in / Sign up

Export Citation Format

Share Document