scholarly journals Optimizing the Geometric Parameters of a Straight-Through Labyrinth Seal to Minimize the Leakage Flow Rate and the Discharge Coefficient

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 705
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Flow Rate ◽  
Axial Length ◽  
Discharge Coefficient ◽  
Labyrinth Seal ◽  
Geometric Parameters ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Leakage Flow Rate ◽  
Tooth Width ◽  
Cavity Width

A straight-through labyrinth seal is one of the most popular non-contacting annular seals through which energy dissipation by turbulence viscosity interaction is achieved with a series of teeth and cavities. The geometric parameters of the straight-through labyrinth seal, such as clearance, tooth width, tooth height, cavity width, and tooth inclination angle, affect its performance. The space for installing a labyrinth seal in turbomachinery is limited, and so it is important to optimize its geometry for a fixed axial length in order to minimize the leakage flow rate and the discharge coefficient. The objective of the current study is to understand the effects of changing the geometric parameters of the seal on the leakage flow rate and the discharge coefficient, and to determine the optimized geometry for a fixed axial length. When the whole axial length is fixed, the most effective way to decrease the discharge coefficient is to reduce the cavity width by increasing the number of cavities. However, if the number of cavities is too high, the beneficial effect of more cavities can be reversed. The results of this study will help turbomachinery manufacturers to design a more efficient labyrinth seal. Numerical simulations of leakage flow for the straight-through labyrinth seal were carried out using Reynolds-Averaged Navier–Stokes (RANS) models, and the results for their discharge coefficients and pressure distributions were compared to previously published experimental data.

scholarly journals Leakage Characteristic Identification of Labyrinth Seals on Reciprocating Piston through Transient Simulations

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Lingzi Wang ◽  
Jianmei Feng ◽  
Mingfeng Wang ◽  
Zenghui Ma ◽  
Xueyuan Peng
Keyword(s):  
Flow Rate ◽  
Pressure Ratio ◽  
Piston Compressor ◽  
Pressure Change ◽  
Labyrinth Seal ◽  
Relative Molecular Mass ◽  
Geometrical Parameters ◽  
Leakage Flow ◽  
Reciprocating Motion ◽  
Leakage Flow Rate

In the reciprocating labyrinth piston compressor, the characteristic of the internal leakage is crucial for the leakage management and performance improvement of the compressor. However, most of the published studies investigated the rotor-stator system, and those who study the reciprocating piston-cylinder system basically focus on the effects of the geometrical parameters. These conclusions could not directly be applied to predict the real-time leakage flow rate through the labyrinth seal because of the fast reciprocating motion of the piston, which will cause continually pressure change in two compression chambers, and then the pressure fluctuation will affect the flow through the labyrinth seal. A transient simulation model employing the multiscale dynamic mesh, which considers the effect of the reciprocating motion of the piston in the cylinder, is established to identify the characteristics of the internal leakage. This model was verified by a specially designed compressor, and the influence of various parameters was analyzed in detail. The sealing performance decreased linearly with the increase in the pressure ratio, and higher pressure inlet leads to higher leakage flow under the same pressure ratio. The labyrinth seal performance positively correlated to the increase of the rotational speed. Leakage characteristics of five working mediums were carried out, and the results indicated that the relative leakage decreased with an increase in the relative molecular mass. From this study, the realistic internal leakage flow rate under different operating parameters in the reciprocating labyrinth piston compressor could be predicated.

Numerical Investigations on the Leakage and Rotordynamic Characteristics of Pocket Damper Seals—Part II: Effects of Partition Wall Type, Partition Wall Number, and Cavity Depth

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Flow Rate ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Cavity Depth ◽  
Partition Wall ◽  
Leakage Flow Rate ◽  
Direct Stiffness ◽  
Cfd Method ◽  
Positive Direct ◽  
Orbit Model

Effects of partition wall type, partition wall number and cavity depth on the leakage and rotordynamic characteristics of the pocket damper seal (PDS) were numerically investigated using a presented 3D transient computational fluid dynamics (CFD) method based on the multifrequency elliptical whirling orbit model. The accuracy and availability of this transient CFD method and the multifrequency elliptical whirling orbit model were demonstrated with the experimental data of the experimental eight-bladed fully partitioned pocket damper seal (FPDS). The leakage flow rates and frequency-dependent rotordynamic coefficients of PDS were computed for two types of partition wall (namely conventional PDS and fully partitioned PDS), four partition wall numbers including the labyrinth seal (no partition wall) and six cavity depths including the plain smooth seal (zero cavity depth) at operational conditions with or without inlet preswirl and 15,000 rpm rotational speed. The numerical results show that the FPDS has the similar leakage performance and more superior stability capacity than the conventional PDS. The FPDS possesses slightly larger leakage flow rate (∼2.6–4.0% larger) compared to the labyrinth seal. Eight is a preferable value for the partition wall number to gain the best leakage performance of the FPDS with the least manufacturing cost. The FPDS possesses significantly larger stiffness and damping than the labyrinth seal. Increasing partition wall number results in a significant increase in the direct stiffness but limited desirable effect on the effective damping. The FPDS possesses the lowest leakage flow rate when the cavity depth is about 2.0 mm. Compared to the plain smooth seal, the FPDS possesses larger positive direct stiffness and significantly less direct damping and effective damping. Increasing cavity depth results in a significant decrease in the stabilizing direct damping and the magnitude of the destabilizing cross-coupling stiffness. H= 3.175 mm is a preferable value of the cavity depth for which the effective damping of the FPDS is largest, especially for the concerned frequencies (80–120 Hz) where most multistage high-pressure centrifugal compressors have stability problem.

Effects of Pressure Ratio and Sealing Clearance on Leakage Flow Characteristics in the Rotating Honeycomb Labyrinth Seal

2007 ◽  
Author(s):  
Jun Li ◽  
Xin Yan ◽  
Guojun Li ◽  
Zhenping Feng
Keyword(s):  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Aerodynamic Efficiency ◽  
Flow Losses ◽  
Leakage Flow Rate ◽  
Swirl Velocity

Honeycomb stepped labyrinth seals in turbomachinery enhance aerodynamic efficiency by reducing leakage flow losses through the clearance between rotating and stationary components. The influence of pressure ratio and sealing clearance on the leakage flow characteristics in the honeycomb stepped labyrinth seal is numerically determined. The geometries investigated represent designs of the honeycomb labyrinth seal typical for modern turbomachinery. The leakage flow fields in the honeycomb and smooth stepped labyrinth seals are obtained by the Reynolds-Averaged Navier-Stokes solution using the commercial software FLUENT. Numerical simulations covered a range of pressure ratio and three sizes of sealing clearance for the honeycomb and smooth stepped labyrinth seals. The numerical discharge coefficients of the non-rotating honeycomb and smooth stepped labyrinth seals are in good agreement with previous experimental data. In addition rotational effects are also taken into account in numerical computations. The numerical results show that the leakage flow rate increases with the increasing pressure ratio at the fixed sealing clearance for the rotating and non-rotating honeycomb labyrinth seal. The influence of the sealing clearance on the leakage flow pattern for the rotating and non-rotating honeycomb labyrinth seal are observed. Moreover, the similar leakage flow rates are obtained at the same flow condition between the rotating and non-rotating honeycomb labyrinth seal due to the honeycomb acts to kill swirl velocity development for the rotating honeycomb labyrinth seal.

Performance Analysis of a Rotating Labyrinth Seal With Radial Growth

2013 ◽  
Author(s):  
Sivakumar Subramanian ◽  
A. S. Sekhar ◽  
B. V. S. S. S. Prasad
Keyword(s):  
Flow Rate ◽  
Radial Growth ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Leakage Flow Rate ◽  
Wide Range ◽  
Structural Deformations ◽  
Angular Velocities ◽  
Computational Methodology ◽  
Initial Clearance

A computational methodology is proposed to predict the running clearance of a six-tooth straight-through rotating labyrinth seal numerically by taking into account both the centrifugal and thermal growths. Four different angular velocities ranging from 0 to 3000 rad/s are chosen to study the influence of rotation on the leakage flow rate. The detailed leakage flow fields and the structural deformations are presented. Further, different pressure ratios in the range of 1.1 to 2.5 have been investigated for a wide range of initial clearances. The methodology is validated against the available data in the literature. It is found out that there is a significant reduction in leakage flow rate by incorporating the radial growth for a particular operating condition. However, for a given initial clearance, the rotation has negligible effect on the reduction in the leakage flow rate, except at pressure ratios lower than 1.7. Further; the rotation has more prominent effect for smaller clearance values.

Effects of Mushroom-Shaped Tooth Wear on the Leakage Performance and Rotordynamic Coefficients of Labyrinth Seals

2018 ◽  
Author(s):  
Yaoxing Chen ◽  
Zhigang Li ◽  
Xin Yan ◽  
Jun Li
Keyword(s):  
Tooth Wear ◽  
Labyrinth Seal ◽  
Linear Increase ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Crossover Frequency ◽  
Labyrinth Seals ◽  
Rotordynamic Coefficients ◽  
Leakage Flow Rate ◽  
Mesh Technique

The leakage performance and rotordynamic coefficients of the labyrinth seal are changed when a mushroom-shaped tooth wear occurs in actual transient operation resulting from rubbing and wear between stator teeth and the rotor. The objective of current study was to numerically investigate and characterize the variation of the leakage performance and rotordynamic coefficients as a result of an increased mushroom-shaped tooth wear at two typical inlet preswirl velocities and enhance the rotor stability of the after-damage labyrinth seal. In this paper, the Unsteady Reynolds-Averaged Navier-Stokes (URANS) solution based on the multi-frequency elliptical orbit rotor whirling mode and dynamic mesh technique was used to calculate the leakage flow rates and rotordynamic coefficients of the labyrinth seal with an unworn clearance and three after-damage clearances at two inlet preswirl velocities. The accuracy and availability of adopted transient computational methods in this work were validated by the published experimental data. Also, the influence of tooth mushroom radius and each cavity in the labyrinth seal on the rotor stability and some approaches to improve the rotor stability were discussed and conducted. The conclusion shows that the leakage flow rate increases with an increase in the clearance, and a linear increase is expected when the after-damage clearance is over 0.4 mm. An increase in the after-damage clearance always leads to a drop in the effective damping or an increase in crossover frequencies. Also, the additional tooth mushroom radius plays an important role in the effective damping or crossover frequency and can not be neglected. The upstream cavity always possesses lower crossover frequency, and a drop of 9.9 Hz in the crossover frequency is found when the seal entrance axially extends 5 mm. In addition, the crossover frequency is decreased from 243.5 Hz to 164.2 Hz when typical anti-swirl brakes are installed in this labyrinth seal with the worn mushroom-shaped teeth.

Effects of Pressure Ratio and Fin Pitch on Leakage Flow Characteristics in High Rotating Labyrinth Seals

2006 ◽  
Author(s):  
Jun Li ◽  
Xin Yan ◽  
Zhenping Feng
Keyword(s):  
Flow Rate ◽  
Geometrical Structure ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Rotational Axis ◽  
Labyrinth Seals ◽  
Sealing Performance ◽  
Leakage Flow Rate

Labyrinth seals represent an important flow element in the sealing equipment of modern turbomachinery industries. The straight-through and stepped labyrinth seal are widely used in modern steam turbine due to their comparable simple structure and low manufactured costs. The influence of pressure ratio and fin pitch on the leakage flow characteristics of the straight-through and stepped labyrinth seals is numerically determined. The pressure ratio is defined as the outlet static pressure divided by the inlet total pressure. The fin pitch varied in the fixed axial distance of the labyrinth seal. The geometries investigated represent designs of the straight-through and stepped labyrinth seal typical for modern steam turbines. The leakage flow fields in the high rotating straight-through and stepped labyrinth seals are obtained by the Reynolds-Averaged Navier-Stokes solution using the commercial software FLUENT with the fixed seal clearance and fins geometrical structure. The effect of the rotational axis is also taken into account in numerical computations. Numerical simulations covered a range of pressure ratio and fin pitch for the straight-through and stepped labyrinth seals. Dimensionless discharge coefficients, describing the sealing performance, are calculated from the simulation results. The numerical results show that pressure ratio and fin pitch both affects the sealing performance with the fixed seal clearance and fin geometrical structure. The leakage flow rate decreases with the decreasing fin pitch for both the straight-through and stepped labyrinth seal at the fixed pressure ratio. Furthermore, the leakage flow rate decreases with the increasing pressure ratio at the fixed fin pitch for two kinds of labyrinth seals in the present study. This research provides technical support for improved design of labyrinth seals in turbomachinery.

Leakage Flow Over Shrouded Turbine Blades

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Flow Rate ◽  
Pressure Difference ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Complex Flow ◽  
Flow Area ◽  
Navier Stokes Equations ◽  
Leakage Flow Rate

In this paper the flows over shrouded turbine blades with single, double, and triple tip seals were simulated by using the two-dimensional Reynolds-averaged Navier-Stokes equations and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the flow in the seal channel is very complicated and the leakage flow rate is dominated by the minimum flow area and the pressure difference. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, it appears there is not a simple function between the leakage flow and the pressure difference.

Numerical Investigations on the Leakage and Rotordynamic Characteristics of Pocket Damper Seals: Part II — Effects of Partition Wall Type, Partition Wall Number and Cavity Depth

2014 ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Flow Rate ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Cavity Depth ◽  
Partition Wall ◽  
Leakage Flow Rate ◽  
Direct Stiffness ◽  
Cfd Method ◽  
Positive Direct ◽  
Orbit Model

Effects of partition wall type, partition wall number and cavity depth on the leakage and rotordynamic characteristics of the pocket damper seal (PDS) were numerically investigated using a presented 3D transient CFD method based on the multi-frequency elliptical whirling orbit model. The accuracy and availability of this transient CFD method and the multi-frequency elliptical whirling orbit model were demonstrated with the experimental data of the experimental eight-bladed fully-partitioned pocket damper seal (FPDS). The leakage flow rates and frequency-dependent rotordynamic coefficients of PDS were computed for two types of partition wall (namely conventional PDS and fully-partitioned PDS), four partition wall numbers including the labyrinth seal (no partition wall) and six cavity depths including the plain smooth seal (zero cavity depth) at operational conditions with or without inlet preswirl and 15000rpm rotational speed. The numerical results show that the FPDS has the similar leakage performance and more superior stability capacity than the conventional PDS. The FPDS possesses slightly larger leakage flow rate (∼2.6–4.0% larger) compared to the labyrinth seal. Eight is a preferable value for the partition wall number to gain the best leakage performance of the FPDS with the least manufacturing cost. The FPDS possesses significantly larger stiffness and damping than the labyrinth seal. Increasing partition wall number results in a significant increase in the direct stiffness but limited desirable effect on the effective damping. The FPDS possesses the lowest leakage flow rate when the cavity depth is about 2.0mm. Compared to the plain smooth seal, the FPDS possesses larger positive direct stiffness and significantly less direct damping and effective damping. Increasing cavity depth results in a significant decrease in the stabilizing direct damping and the magnitude of the destabilizing cross-coupling stiffness. H = 3.175mm is a preferable value of the cavity depth for which the effective damping of the FPDS is largest, especially for the concerned frequencies (80–120Hz) where most multistage high-pressure centrifugal compressors have stability problem.

A Comparative Study of Navier-Stokes Equation and Reynolds Equation in Simulating Spool Valve

2011 ◽  
Author(s):  
S. H. Hong ◽  
S. I. Son ◽  
K. W. Kim
Keyword(s):  
Pressure Distribution ◽  
Stokes Equation ◽  
Flow Rate ◽  
Reynolds Equation ◽  
Navier Stokes ◽  
Radial Clearance ◽  
Leakage Flow ◽  
Navier Stokes Equation ◽  
Leakage Flow Rate ◽  
Spool Valve

In order to maintain the accurate and precise movement of the actuator of the hydraulic systems, it is necessary to guarantee smooth function of the fluid flow control valves. Concerning hydraulic valves, the spool type directional control valve has particular lock problem. The hydraulic lock occurs when uneven pressure distribution surrounding the spool in the clearance between spool and sleeve causes the spool to move sideways out of its centered position. And the contact between spool and sleeve causes to increase friction and eventually, the spool is blocked inside the sleeve. To reduce the possibility of hydraulic lock, peripheral grooves balancing uneven pressure distribution in the radial clearance is commonly applied to spool. Reynolds equation is commonly used to investigate the lubrication characteristics of the spool valve. However, some of assumptions used in Reynolds equation are not valid when cavitation occurs or fluid inertia is significant in spool valve. So, the study on the applicability and precision of Reynolds equation for spool valve analysis is needed. In this study, the differences between the results from Navier-Stokes equation and Reynolds equation are compared when the cavitation is considered. Frictional forces, lateral forces and leakage flow rate with various aspect ratio of groove are calculated. Besides, when the number of groove is increased, the forces and leakage flow rate are compared. Based on the comparison the applicability of Reynolds equation in calculating the spool valve is also discussed.

Sign in / Sign up

Export Citation Format

Share Document