Mixed Helical Labyrinth Groove Seal Optimization Using Computational Fluid Dynamics

2017 ◽  
Author(s):  
Wisher Paudel ◽  
Cori Watson ◽  
Houston G. Wood
Keyword(s):  
Kinetic Energy ◽  
Regression Models ◽  
Labyrinth Seal ◽  
Response Surfaces ◽  
Design Parameters ◽  
Labyrinth Seals ◽  
Ansys Cfx ◽  
Helical Groove ◽  
Groove Seal ◽  
Annular Seals

Non-contacting annular seals are used in rotating machinery to reduce the flow of fluid across a pressure differential. Helical and labyrinth groove seals are two types of non-contacting annular seals frequently used between the impeller stages in a pump. Labyrinth seals have circumferential grooves cut into the surface of the rotor, the stator, or both. They function to reduce leakage by dissipating kinetic energy as fluid expands in the grooves and then is forced to contract in the jet stream region. Helical groove seals have continuously cut grooves in either or both of the rotor and stator surfaces. Like labyrinth seals, they reduce leakage through dissipation of kinetic energy, but have the added mechanism of functioning as a pump to push the fluid back towards the high pressure region as it tries to escape. Previous work has shown that both labyrinth and helical groove seals with grooves on both the rotor and the stator have lower leakage than seals with grooves on just one surface. The goal of this work is to analyze seals with helical grooves on one surface and labyrinth grooves on the other. Designs for both helical stator, labyrinth rotor and labyrinth stator, helical rotor will be simulated and the performance of each configuration will be compared. The primary variables considered for the designs of the seals include the width, depth, and the number of grooves for labyrinth seal and the width, depth, and the angle of the grooves for helical. The designs to simulate will be chosen using a Kennard-stone algorithm to optimally space them within the design space. Then, for both configurations, multi-factor quadratic regression models will be generated. Backward regression will be used to reduce the models to only statistically significant design parameters. From there, the response surfaces will be created to demonstrate the effects of each design parameter on the performance of the seal. Finally, optimal designs will be produced based on the regression models. These designs will be simulated to show the predictive power of the regression models. The simulations for this work will be run in ANSYS CFX for each seal type and configuration will be used to compare solutions for the two different types of designs to previous studies. The findings from this study is expected to show substantial decrease in leakage for a mixed helical-labyrinth seal in comparison to the seal with either helical or labyrinth grooves on both surfaces and thus will provide useful results needed to minimize amount of leakage and therefore improve the efficiency of the machine.

The Impact of Adding a Labyrinth Surface to an Optimal Helical Seal Design

2018 ◽  
Author(s):  
Wisher Paudel ◽  
Cori Watson ◽  
Houston G. Wood
Keyword(s):  
High Pressure ◽  
Kinetic Energy ◽  
Labyrinth Seal ◽  
Groove Width ◽  
Design Parameters ◽  
Labyrinth Seals ◽  
Pressure Application ◽  
Helical Groove ◽  
Helical Grooves ◽  
Annular Seals

Non-contacting annular seals are used in rotating machinery to reduce the flow of working fluid across a pressure differential. Helical and labyrinth grooved seals are two types of non-contacting annular seals frequently used between the impeller stages in a pump and at the balance drum. Labyrinth seals have circumferential grooves cut into the surface of the rotor, the stator, or both. They function to reduce leakage by dissipating kinetic energy as fluid expands in the grooves and then is forced to contract in the jet stream region. Helical groove seals have continuously cut grooves on either or both the rotor and stator surfaces. Like labyrinth seals, they reduce leakage through dissipation of kinetic energy, but have the added mechanism of functioning as a pump to push the fluid back towards the high-pressure region. Previous work has shown that mixed helical-labyrinth seals with labyrinth grooves on stator and helical grooves on rotor or labyrinth grooves on rotor and helical grooves on stator have an approximately 45% lower leakage than an optimized helical groove seal with grooves just on the stator in a high pressure application. The primary objective of this study is to determine whether the same performance gains can also be achieved in a low pressure application. Simulations were run in ANSYS CFX for seal designs with a helical stator and labyrinth rotor. Several labyrinth design parameters including the number of grooves and the groove width and depth are varied while the helical variables such as the groove width and depth as well as helix angle are kept constant. The data obtained are analyzed using backward regression methods and various response plots to determine the relationship between the design parameters and mass flow and power loss. The optimized helical design was simulated and the axial pressure profiles of the designs were compared to analyze the mechanism of the mixed helical-labyrinth seal. Then, the same labyrinth seal designs were simulated for a labyrinth rotor and a smooth stator to determine whether the optimal number of grooves, groove width and groove depth change due to the helical stator. The findings of this study show the effectiveness of mixed helical labyrinth grooved seals for both low and high pressure cases, and thus their efficiency and reliability for numerous industrial applications.

Second Stage Optimization of Helical Groove Seals Using Computational Fluid Dynamics to Evaluate the Dependency of Optimized Design on Preswirl

2018 ◽  
Author(s):  
Cori Watson ◽  
Houston Wood
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Power Loss ◽  
Pressure Differential ◽  
Design Parameters ◽  
Working Fluid ◽  
Second Stage ◽  
Trade Offs ◽  
Helical Groove ◽  
Groove Seal

Helical groove seals are non-contacting annular seals used in pumping machinery to increase the efficiency and, in the case of the balance drum, to manage the axial force on the thrust bearing. Prior work has shown that optimization of helical groove seals can reduce the leakage by two thirds given a desired pressure differential or, conversely, can significantly increase the pressure differential across the helical groove seal given a flow rate. This study evaluates the dependency of the optimal helical groove seal design on the inlet preswirl, which is the ratio of the inlet circumferential velocity to the rotor surface speed. To accomplish this goal, second stage optimization from the previously optimized helical groove seal with grooves on the stator and water as the working fluid were conducted at a series of preswirls ranging from −1 to 1. Optimization is performed using ANSYS CFX, a commercial computational fluid dynamics software and mesh independence is confirmed for the baseline case. For each preswirl case, design of experiments for the design parameters of groove width, groove depth, groove spacing, and number of grooves was performed using a Kennard-Stone Algorithm. The optimized solution is interpolated from the simulations run by using multi-factor quadratic regression from the 30 simulations in each optimization and the interpolated solution is simulated for comparison. In addition to evaluating the optimized solution’s dependency on preswirl, the viability of using swirl breaks or swirl promoting inlet passages to improve the overall efficiency of the seal is discussed. Finally, the power loss performance is evaluated for each of the seal designs simulated so that potential trade-offs can be evaluated. Overall, the results show that increasing preswirl can increase the efficiency of the helical groove seal both by improving power loss and by improving leakage.

Labyrinth Seal Leakage Tests: Tooth Profile, Tooth Thickness, and Eccentricity Effects

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Ahmed J. M. Gamal ◽  
John M. Vance
Keyword(s):  
Labyrinth Seal ◽  
Design Parameters ◽  
Working Fluid ◽  
Test Results ◽  
Blade Profile ◽  
Labyrinth Seals ◽  
Seal Design ◽  
Blade Thickness ◽  
Center Position ◽  
Blade Tip

The effects of two seal design parameters, namely blade (tooth) thickness and blade profile, on labyrinth seal leakage, as well as the effect of operating a seal in an off-center position, were examined through a series of nonrotating tests. Two reconfigurable seal designs were used, which enabled testing of two-, four-, and six-bladed see-through labyrinth seals with different geometries using the same sets of seal blades. Leakage and cavity pressure measurements were made on each of 23 seal configurations with a in.(101.6mm) diameter journal. Tests were carried out with air as the working fluid at supply pressures of up to 100psia (6.89bar). Experimental results showed that doubling the thickness of the labyrinth blades significantly influenced leakage, reducing the flow rate through the seals by up to 20%. Tests to determine the effect of blade-tip profile produced more equivocal results, with the results of experiments using each of the two test seal designs contradicting each other. Tests on one set of hardware indicated that beveling blades on the downstream side was most effective in limiting leakage, whereas tests on newer hardware with tighter clearances indicated that seals with flat-tipped blades were superior. The test results illustrated that both blade profile and blade thickness could be manipulated so as to reduce seal leakage. However, an examination of the effects of both factors together indicated that the influence of one of these parameters can, to some extent, negate the influence of the other (especially in cases with tighter clearances). finally, for all configurations tested, results showed that leakage through a seal increases with increased eccentricity and that this phenomenon was considerably more pronounced at lower supply pressures.

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.

scholarly journals Shape Optimization of Labyrinth Seals to Improve Sealing Performance

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 92
Author(s):  
Yizhen Zhao ◽  
Chunhua Wang
Keyword(s):  
Support Vector Machine ◽  
Shape Optimization ◽  
Optimization Algorithm ◽  
Labyrinth Seal ◽  
Least Square ◽  
Design Parameters ◽  
Support Vector ◽  
Labyrinth Seals ◽  
Gas Leakage ◽  
Expansion Angle

To reduce gas leakage, shape optimization of a straight labyrinth seal was carried out. The six design parameters included seal clearance, fin width, fin height, fin pitch, fin backward, and forward expansion angle. The CFD (Computational Fluid Dynamics) model was solved to generate the training and testing samples for the surrogate model, which was established by the least square support vector machine. A kind of chaotic optimization algorithm was used to determine the optimal design parameters of the labyrinth seal. As seal clearance, fin width, fin height, fin pitch, fin backward and forward expansion angles are 0.2 mm, 0.1 mm, 7 mm, 9 mm, 0°, and 15°, the discharge coefficient can reach its minimum value in the design space. The chaotic optimization algorithm coupled with least square support vector machine is a promising scheme for labyrinth seal optimization.

Optimization of the Straight-Through Labyrinth Seal With a Smooth Land

2018 ◽  
Author(s):  
Włodzimierz Wróblewski ◽  
Daniel Frączek ◽  
Artur Szymański ◽  
Krzysztof Bochon ◽  
Sławomir Dykas ◽  
...  
Keyword(s):  
Discharge Coefficient ◽  
Experimental Testing ◽  
High Capacity ◽  
Labyrinth Seal ◽  
Response Surfaces ◽  
Measuring System ◽  
Cfd Model ◽  
Test Rig ◽  
Ansys Cfx ◽  
Wide Range

The primary goal of this study was to develop and experimentally validate the methodology of labyrinth seals optimization concerning leakage. The problem was investigated using the ANSYS CFX commercial software. This paper presents the methodology and results of the optimization of a straight-through labyrinth seal with two inclined fins against smooth-land. The optimization was performed using commercial tools implemented in the ANSYS Workbench environment, such as Goal-Driven Optimization (GDO). The response surfaces were created based on Latin hypercube samples found from CFD calculations. The CFD solver — Ansys CFX, using a steady-state scheme with the k-omega Shear Stress Transport turbulence model, was applied. The CFD model was previously validated concerning spatial discretisation and turbulence modelling. A screening algorithm was used to find the best candidates on the response surfaces. The objective function adopted in the labyrinth seal optimization was the minimization of the discharge coefficient value. A wide range of parameters of the fins position and shape, such as the angles, heights and widths, were taken into account, with physically justified degrees of freedom. The leakage reductions being the effect of the optimization were considerable. The cuts in the discharge coefficient significantly exceed the uncertainties of the CFD model and the test rig accuracy. The factors that have the strongest impact on the leakage reduction in are the inclination, thickness of the fin tips, and the distance between fins. The optimization results were supported with the results of an in-house experiment performed on a stationary, linear test rig. The specimens tested experimentally were on the same scale (1:1) as the optimised ones. The test rig was fed by a high-capacity vacuum air blower, which made it possible to reach critical pressure ratios, with high-precision hot wire anemometry (HWA) mass flow evaluation. The measuring system also enabled assessment of the pressure distribution along the labyrinth structure. The experimental testing results were compared to the CFD calculations and the optimization effects, highlighting some specific tendencies in the labyrinth seal flow behaviour. Good agreement was obtained between the optimization results and the experimental data, which proves that the presented methodology is sufficient for the labyrinth seal optimization. The same methods will also be applied to more sophisticated sealing structures.

Labyrinth Seal Analysis

1972 ◽  
Vol 94 (1) ◽  
pp. 5-11
Author(s):  
H. A. Koenig ◽  
W. W. Bowley
Keyword(s):  
Gas Turbine ◽  
Theoretical Consideration ◽  
Computer Code ◽  
Labyrinth Seal ◽  
Design Parameters ◽  
Flow Conditions ◽  
Labyrinth Seals ◽  
Seal Design ◽  
Theoretical Considerations ◽  
Actual Test

A computer code is developed herein which is shown to be a useful tool in the design of labyrinth seals for gas turbine and other engineering applications. The algorithm is based upon theoretical considerations and is general enough to provide seal design parameters for a variety of input and flow conditions. Two examples are solved. The first, a theoretical consideration, demonstrates the ability of the program to effectively treat various geometrical and dynamic conditions. The second, an actual test, demonstrates the accuracy with which the analysis will predict the actual seal leakage behavior.

Clearance Effects on Corresponding Annular and Labyrinth Seal Flow Leakage Characteristics

1993 ◽  
Vol 115 (4) ◽  
pp. 699-704 ◽  
Author(s):  
D. L. Rhode ◽  
R. I. Hibbs
Keyword(s):  
Computer Code ◽  
Labyrinth Seal ◽  
Momentum Conservation ◽  
Navier Stokes ◽  
Unexpected Finding ◽  
Labyrinth Seals ◽  
Swirl Velocity ◽  
Small Clearance ◽  
Annular Seal ◽  
Annular Seals

A previous Navier-Stokes finite difference computer code is extended in order to compute seal leakage directly from given upstream and downstream reservoir pressures. The numerical results are in excellent agreement with previous measurements, the discrepancy being less than eight percent. Annular seals are found to leak approximately twenty percent more than corresponding labyrinths over the entire range of realistic clearance. A rather unexpected finding is that a dramatic increase of swirl velocity occurs near the discharge of small-clearance annular seals, which does not arise in corresponding labyrinth seals. The results, which are used to explain this finding, show that a large density drop occurs near the small-clearance annular seal exit, which provides the swirl velocity increase in accordance with angular momentum conservation.

Labyrinth Seal Leakage Tests: Tooth Profile, Tooth Thickness, and Eccentricity Effects

2007 ◽  
Author(s):  
Ahmed M. Gamal ◽  
John M. Vance
Keyword(s):  
Labyrinth Seal ◽  
Design Parameters ◽  
Working Fluid ◽  
Test Results ◽  
Blade Profile ◽  
Labyrinth Seals ◽  
Seal Design ◽  
Blade Thickness ◽  
Center Position ◽  
Blade Tip

The effects of two seal design parameters, namely blade (tooth) thickness and blade profile, on labyrinth seal leakage, as well as the effect of operating a seal in an off-center position, were examined through a series of non-rotating tests. Two reconfigurable seal designs were used, which enabled testing of two- four-, and six-bladed see-through labyrinth seals with different geometries using the same sets of seal blades. Leakage and cavity pressure measurements were made on each of twenty-three seal configurations with a four inch (101.6 mm) diameter journal. Tests were carried out with air as the working fluid at supply pressures of up to 100 psi-a (6.89 bar-a). Experimental results showed that doubling the thickness of the labyrinth blades significantly influenced leakage, reducing the flow-rate through the seals by up to 20%. Tests to determine the effect of blade-tip profile produced more equivocal results, with the results of experiments using each of the two test seal designs contradicting each other. Tests on one set of hardware indicated that beveling blades on the downstream side was most effective in limiting leakage whereas tests on newer hardware with tighter clearances indicated that seals with flat-tipped blades were superior. The test results illustrated that both blade profile and blade thickness could be manipulated so as to reduce seal leakage. However, an examination of the effects of both factors together indicated that the influence of one of these parameters can, to some extent, negate the influence of the other (especially in cases with tighter clearances). Lastly, for all configurations tested, results showed that leakage through a seal increases with increased eccentricity and that this phenomenon was considerably more pronounced at lower supply pressures.

Quantifying the Linearity of the Fluid Dynamics for Noncontacting Annular Seals

2016 ◽  
Author(s):  
Cori Watson ◽  
Wisher Paudel ◽  
Houston G. Wood ◽  
Brian K. Weaver
Keyword(s):  
Differential Equation ◽  
Fluid Dynamics ◽  
Surface Texture ◽  
Inertial Force ◽  
Working Fluid ◽  
Labyrinth Seals ◽  
Relative Significance ◽  
Helical Groove ◽  
Reynold’S Number ◽  
Annular Seals

Non-contacting annular seals are used in turbomachinery to reduce the leakage of working fluid. The leakage is caused by a pressure differential across the seal and is reduced through textures cut into the surface of the seal. Three common types of non-contacting annular seals are labyrinth seals, hole-pattern seals, and helical groove seals. Labyrinth seals have circumferentially cut grooves as their surface texture. Helical groove seals have continuously cut grooves following a helical path along the surface. Hole-pattern seals have holes patterned across the surface. Each surface texture causes different flow patterns and sealing mechanisms. These non-contacting annular seals can have textures cut across the surface of the rotor, the surface of the stator, or both. The goal of this study is to determine the degree to which the flow of seals with textures on both surfaces can be viewed as the superposition of the flow for a seal with the rotor surface textured and a smooth stator combined with the flow for a seal with the stator surface textured and a smooth rotor. To accomplish this goal, simulations were run in ANSYS CFX for each seal type and configuration for a variety of rotor speeds and pressure ratios to compare superimposed solutions to standard 3D solutions. The ability to superimpose solutions to a differential equation — and therefore a fluid dynamics system — is determined by the linearity of the differential equation. By comparing the superimposed solution with the standard solution, this study will quantify the degree of non-linearity in the system. The degree of divergence away from linearity will be compared against the rotor speed and pressure ratio, which are proportional to the Reynold’s number. The Navier-Stokes equation contains a non-linear inertial force term. The relative significance of the inertia forces is predicted by the Reynold’s number so a strong correlation is expected between the Reynold’s number and the agreement between the flow found by superposition and the flow found by the actual seal model. The other application of this research is to the computational modeling of annular seals. Annular seals can be computationally demanding and time consuming to model. This is especially true for seals with texture on both surfaces where millions of finite volumes may be needed in the simulation in order to find a convergent solution. For rotor speeds with strong agreement between the actual flow and the superimposed flow, superposition can be applied to perform faster simulations of seals with texture on both surfaces.

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