Influence of Honeycomb Land Geometry on Seal Performance

2016 ◽  
Author(s):  
Daniel Frączek ◽  
Krzysztof Bochon ◽  
Włodzimierz Wróblewski
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Qualitative Assessment ◽  
Labyrinth Seals ◽  
Leakage Flows ◽  
Ansys Cfx ◽  
Cell Shapes ◽  
Geometrical Data ◽  
Three Dimensional Models

The aim of this study was to identify the best structures of the honeycomb (or structures used instead of it) that can be applied to a seal cavity labyrinth in order to improve the sealing performance. The problem was investigated numerically using the ANSYS CFX commercial software. The paper presents geometrical data concerning the proposed solutions to the labyrinth seal land structure. A simple straight-through labyrinth geometry with two leaned fins is analysed. Such a simple structure of the flow conditions was chosen to reduce the influence of other effects on the seal performance. Three-dimensional models of the labyrinth seal were elaborated for each honeycomb or honeycomb-like land structure. The following concepts were analysed: an inclination of the honeycomb cells, a land with different cell shapes (squeezed honeycomb) and honeycomb cells filled with a porous material. The labyrinth seals with different land structures were compared with two reference cases: a seal with a standard honeycomb land (with 1/8-inch cell size) and a seal with a smooth land. Calculations were performed for the pressure ratio values ranging from 1.08 to 1.8 and for varied sizes of the clearance. Main parameters of the leakage flows are discussed. Additionally, the influence of the inlet narrowing on the seal performance is investigated. A qualitative assessment of the seal concepts is made and the most promising solutions are pointed out.

Numerical Investigations for Leakage and Windage Heating in Straight-Through Labyrinth Seals

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Kali Charan Nayak ◽  
Pradip Dutta
Keyword(s):  
Cell Size ◽  
Turbulence Model ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Radial Clearance ◽  
Labyrinth Seals ◽  
Turbine Engine ◽  
Honeycomb Cell

The ability to quantify leakage flow and windage heating for labyrinth seals with honeycomb lands is critical in understanding gas turbine engine system performance and predicting its component life. Variety of labyrinth seal configurations (number of teeth, stepped or straight, honeycomb cell size) are in use in gas turbines, and for each configuration, there are many geometric factors that can impact a seal's leakage and windage characteristics. This paper describes the development of a numerical methodology aimed at studying the effect of honeycomb lands on leakage and windage heating. Specifically, a three-dimensional computational fluid dynamics (CFD) model is developed utilizing commercial finite volume-based software incorporating the renormalization group (RNG) k-ε turbulence model with modified Schmidt number. The modified turbulence model is benchmarked and fine-tuned based on several experiments. Using this model, a broad parametric study is conducted by varying honeycomb cell size, pressure ratio (PR), and radial clearance for a four-tooth straight-through labyrinth seal. The results show good agreement with available experimental data. They further indicate that larger honeycomb cells predict higher seal leakage and windage heating at tighter clearances compared to smaller honeycomb cells and smooth lands. However, at open seal clearances larger honeycomb cells have lower leakage compared to smaller honeycomb cells.

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.

Effects of Inlet Preswirl and Cell Diameter and Depth on Honeycomb Seal Characteristics

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Xin Yan ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Temperature Increase ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Leakage Rate ◽  
Navier Stokes ◽  
Cell Diameter ◽  
Total Temperature ◽  
Honeycomb Seals ◽  
Honeycomb Cell

Three-dimensional Reynolds-averaged Navier–Stokes solutions are employed to investigate the discharge and total temperature increase characteristics of the stepped labyrinth seal with honeycomb land. First, the relations between the windage heating number and the circumferential Mach number at different Reynolds numbers for different honeycomb seals are calculated and compared with the experimental data. The obtained numerical results show that the present three-dimensional periodic model can properly predict the total temperature increase in honeycomb seals. Then, a range of pressure ratios, three inlet preswirl ratios, four sizes of honeycomb cell diameter, and nine sizes of cell depth are selected to investigate the influence of inlet preswirl ratios and honeycomb geometry sizes on the discharge and total temperature increase characteristics of the stepped labyrinth seal. It shows that the leakage rate increases with the increase in cell diameter, and the cell depth has a strong influence on the discharge behavior. However, the influence of the inlet preswirl on the leakage rate is found to be little in the present study. For the total temperature increase characteristic, the inlet preswirl ratio and pressure ratio have more pronounced influence than those of cell depth and diameter. Furthermore, the relations between the leakage rate and cell depth and diameter, as well as the relations between the windage heating power and cell depth and diameter, are not monotonic functions if the pressure ratio is kept constant.

Leakage and Cavity Pressures in an Interlocking Labyrinth Gas Seal: Measurements vs. Predictions

2019 ◽  
Author(s):  
Luis San Andrés ◽  
Tingcheng Wu ◽  
Jose Barajas-Rivera ◽  
Jiaxin Zhang ◽  
Rimpei Kawashita
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Inlet Pressure ◽  
Steam Turbines ◽  
Rotor Speed ◽  
Labyrinth Seals ◽  
Gas Seals

Abstract Gas labyrinth seals (LS) restrict secondary flows (leakage) in turbomachinery and their impact on the efficiency and rotordynamic stability of high-pressure compressors and steam turbines can hardly be overstated. Amongst seal types, the interlocking labyrinth seal (ILS), having teeth on both the rotor and on the stator, is able to reduce leakage up to 30% compared to other LSs with either all teeth on the rotor or all teeth on the stator. This paper introduces a revamped facility to test gas seals for their rotordynamic performance and presents measurements of the leakage and cavity pressures in a five teeth ILS. The seal with overall length/diameter L/D = 0.3 and small tip clearance Cr/D = 0.00133 is supplied with air at T = 298 K and increasing inlet pressure Pin = 0.3 MPa ∼ 1.3 MPa, while the exit pressure/inlet pressure ratio PR = Pout/Pin is set to range from 0.3 to 0.8. The rotor speed varies from null to 10 krpm (79 m/s max. surface speed). During the tests, instrumentation records the seal mass flow (ṁ) and static pressure in each cavity. In parallel, a bulk-flow model (BFM) and a computational fluid dynamics (CFD) analysis predict the flow field and deliver the same performance characteristics, namely leakage and cavity pressures. Both measurements and predictions agree closely (within 5%) and demonstrate the seal mass flow rate is independent of rotor speed. A modified flow factor Φ¯=m.T/PinD1-PR2 characterizes best the seal mass flow with a unique magnitude for all pressure conditions, Pin and PR.

scholarly journals A Three Dimensional Computational Study of Windage Heating Within an Axial Compressor Stator Well

1998 ◽  
Author(s):  
H. K. Ozturk ◽  
P. R. N. Childs ◽  
A. B. Turner ◽  
J. M. Hannis ◽  
J. R. Turner
Keyword(s):  
Flow Rate ◽  
Computational Study ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Labyrinth Seal ◽  
Leakage Flows ◽  
Temperature Boundary ◽  
Blade Row ◽  
Stator Blade ◽  
Tip Leakage Flows

Shrouded stator blades are sometimes used to prevent vibration problems, but more often they are used to eliminate blade over-tip leakage flows. A trench or recess referred to as a stator well must be provided in the rotor drum assembly in order to accommodate the stator shroud. This paper presents a computational study of the flow and windage generation within an axial compressor stator well. Windage heating levels for a three dimensional compressible solution of flow through a geometry comprising upstream and downstream stator well cavities, labyrinth seal and the stator blade row are quantified. The potential for hot fluid ejected from the upstream stator well seal into the mainstream annulus, migrating through the blade row and being re-ingested at the downstream stator well seal for further windage heating has been studied using a layered temperature boundary condition at entry to the stator row. The possible reconfiguration of detailed stator well geometry has been explored to identify options for controlling flow rate and reducing windage levels, other than controlling clearances, yielding a 9% reduction in flow rate and a 9% reduction in windage heating.

Numerical Analysis of Honeycomb Labyrinth Seals: Cell Geometry and Fin Tip Thickness Impact on the Discharge Coefficient

2015 ◽  
Author(s):  
Alessio Desando ◽  
Andrea Rapisarda ◽  
Elena Campagnoli ◽  
Roberto Taurino
Keyword(s):  
Discharge Coefficient ◽  
New Technologies ◽  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Pollutant Emissions ◽  
Cell Diameter ◽  
Labyrinth Seals ◽  
Cell Pattern ◽  
Divergent Flow ◽  
Impact Reduction

The design of the newest aircraft propulsion systems is focused on environmental impact reduction. Extensive research is being carried out with the purpose of improving engine efficiency, enhancing crucial features, in order to decrease both fuel consumption and pollutant emissions. A lot of improvements to fulfill these objectives must be made, focusing on the optimization of the main engine parts through the utilization of new technologies. The leakage flow reduction in the turbo machinery rotor-stator interaction is one of the main topics to which numerous efforts are being devoted. Labyrinth seals, widely employed in the aerospace field thanks to their simple assembly process and maintenance, can be the means to achieve these objectives. This paper mainly focuses on the optimization of the labyrinth seal stator part, characterized, in modern Low Pressure Turbines (LPT), by a honeycomb cell pattern. The first phase of this study deals with the implementation and validation of a Computational Fluid Dynamics (CFD) numerical model, by using the experimental data available in the literature. Discharge coefficients obtained by numerical simulations, performed at different clearances and pressure ratios on both smooth and honeycomb non-rotating labyrinth seals, are presented and compared to the literature data. Then, for both convergent and divergent flow conditions, the effects on the discharge coefficient due to variations in several cell pattern parameters (i.e. cell diameter, depth and wall thickness) and fin tip thickness are shown. For these analyses the values of clearance and pressure ratio are set at a constant value.

Numerical and Experimental Investigation on the Effect of Swirl Brakes on the Labyrinth Seals

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Dan Sun ◽  
Shuang Wang ◽  
Cheng-Wei Fei ◽  
Yan-Ting Ai ◽  
Ke-Ming Wang
Keyword(s):  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Impedance Method ◽  
Swirl Ratio ◽  
Labyrinth Seals ◽  
Rotating Speed ◽  
Simulation And Experiment ◽  
Computational Fluid Dynamics Cfd ◽  
Static Flow

Swirl brake influences the static and rotordynamic characteristics of labyrinth seal which are important in the prediction of turbomachine stability. To study the influence of the swirl brakes on improving seal stability, the effects of swirl brakes on the static and rotordynamic characteristics of labyrinth seals were investigated by the combination of numerical simulation and experiment. First, it was performed to the effects of swirl brake on the static flow characteristics of labyrinth seal with swirl ratio and pressure distribution based on computational fluid dynamics (CFD). And then a comparison between leakage predicted by the CFD model and measurement was presented to verify the accuracy of the simulation. Moreover, an experiment was implemented to analyze the rotordynamic characteristics of labyrinth seal using an improved impedance method based on an unbalanced synchronous excitation method on a rotor test rig. The influences of swirl brake density, length, inlet/outlet pressure ratio, and rotating speed were measured and discussed, respectively. The CFD numerical results show that the swirl brake effectively reduces the seal swirl ratio (∼60–75% less), circumferential pressure difference (∼25–85% less) so that the seal destabilizing forces decrease. With the increasing of the swirl vanes density and length, the seal leakage drops (∼8–20% less). The experimental rotordynamic characteristics results show that it is more obvious to reduce the cross-couple stiffness (∼50–300% less) and increase the direct damping (∼50–60% larger) with the increasing in the number and length of the swirl vanes, and thus the swirl brake improves the seal rotordynamic stability. The efforts of this paper provide a useful insight to clearly understand the effects of swirl brakes on the labyrinth seal static and rotordynamic characteristics, which is beneficial to improve the design of annular seals.

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.

scholarly journals Flow behavior in a contra-rotating transonic axial compressor

2021 ◽  
Vol 15 (3) ◽  
pp. 8440-8449
Author(s):  
Sarallah Abbasi ◽  
Maryam Alizadeh
Keyword(s):  
Flow Behavior ◽  
Pressure Ratio ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Navier Stokes ◽  
Tip Leakage Flow ◽  
Ansys Cfx ◽  
Energy Equations ◽  
Compressor Efficiency

This study investigated a three-dimensional flow analysis on a two-stage contra-rotating axial compressor using the Navier–Stokes, continuity, and energy equations with Ansys CFX commercial software. In order to validate the obtained results, the absolute and relative flow angles curves for each rotor in radial direction were extracted and compared with the other investigation results, indicating good agreement. The compressor efficiency curve also was extracted by varying the compressor pressure ratio and compressor efficiency against mass flow rate. The flow results revealed that further distortion of the flow structure in the second rotor imposed a greater increase in the amount of entropy, especially at near-stall conditions. The increase of entropy in the second rotor is due to the interference of the tip leakage flow with the main flow which consequently caused more drops in the second rotor, suggesting that more efficacy of flow control methods occurred in the second rotor than in the first rotor.

Leakage and Windage Heating in Stepped Labyrinth Seals

2019 ◽  
Author(s):  
Kali Charan Nayak ◽  
Nomesh P. Kandaswamy ◽  
Syed Faheemulla
Keyword(s):  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Vital Role ◽  
Step Height ◽  
Axial Position ◽  
Radial Clearance ◽  
Labyrinth Seals ◽  
Geometric Factors ◽  
Pitch Ratio ◽  
Computational Fluid Dynamics Cfd

Abstract Stepped labyrinth seals are used in multiple locations in the gas turbine with the intent to reduced leakage compared to straight labyrinth seals. However the selection of geometric factors in stepped labyrinth seals is critical to allow lower leakage in its operating envelope. Particularly the step height and axial position during the running condition play a vital role. The influence of these factors on the leakage, swirl development and windage heating in stepped labyrinth seal has not been thoroughly investigated in the previously published work. This paper focuses to study above effects with numerical simulations in a smooth four-fin stepped labyrinth seal. Specifically, a 2D axi-symmetric computational fluid dynamics (CFD) model is developed utilizing commercial finite volume-based software incorporating the standard k-ε turbulence model. Using this model, a broad parametric study is conducted by varying step height, axial position of the knife from the step, radial clearance and pressure ratio for a four-teeth stepped labyrinth seal. It has been observed that the seal leakage reduces with increase in step height to pitch ratio up to 0.35 and with further increase it tails off. The axial position of the tooth has strong influence on the flow structure and swirl development in the seal pocket.

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