Numerical Model for Condensing Steam Through Labyrinth Seal

2021 ◽  
Author(s):  
Ravindra G. Devi ◽  
Satyanarayanan Seshadri ◽  
Vittorio Michelassi
Keyword(s):  
Labyrinth Seal ◽  
Droplet Growth ◽  
Leakage Flow ◽  
Validation Data ◽  
Data Set ◽  
Ansys Cfx ◽  
Leakage Flow Rate ◽  
Flow Pressure ◽  
Accumulation Trend ◽  
Good Agreement

Abstract This paper presents the flow physics of condensing steam flow across a straight through labyrinth seal from numerical simulations performed using ANSYS CFX. Homogeneous nucleation model and droplet growth model, which are critical in predicting condensation, are validated with good agreement against a well-known experimental data set from convergent-divergent nozzle. Validation data includes static pressure drop, condensation location, condensate mass fraction and Sauter mean radius. CFD study is performed on a five teeth labyrinth geometry to predict leakage flow rate, location of condensate accumulation and condensation rate. Impact of subcooled and condensed steam on leakage flow, pressure and temperature field are also discussed. For condensing steam, the condensate accumulation trend is identified. Some of the key findings and physical insights of interest to the designer are listed including: the effect of cooling on the leakage flow (with and without condensation) and the minimum seal wall temperature to avoid condensation based on subcooling needed for droplet formation (at location condition). Also investigated is whether steam condensation continues or if existing condensate evaporates in the downstream pockets, and the effect of heat release from condensation on number of droplets formed and the Sauter mean radius.

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.

Numerical and Experimental Studies of Labyrinth Seal Aeroelastic Instability

2019 ◽  
Author(s):  
Toshimasa Miura ◽  
Naoto Sakai
Keyword(s):  
Experimental Studies ◽  
Labyrinth Seal ◽  
Low Flow ◽  
Experimental Investigations ◽  
Test Cases ◽  
Aeroelastic Instability ◽  
Ansys Cfx ◽  
Suppression Method ◽  
Aero Engines ◽  
Good Agreement

Abstract A labyrinth seal is commonly used to decrease the flow leakage loss between rotating and static components in aero engines. It is susceptible to aeroelastic instability because of its low stiffness. The aim of this study is to clarify the physical mechanism of labyrinth seal flutter and to establish a method to predict and suppress it effectively. To achieve this, both numerical and experimental investigations are conducted using ANSYS CFX and ANSYS Mechanical. These solvers are coupled to simulate the flutter precisely. Also, to assess the accuracy of the simulation qualitatively and quantitatively, a test rig is built. In the first part of this study, the accuracy of the numerical method is confirmed for several test cases with different seal clearance variations. Both one-way and two-way fluid structure interaction (FSI) analyses are performed. Flutter inception is evaluated in detail for various pressure ratios and rotation speeds. The numerical results show reasonably good agreement with the experimental results. It is also confirmed that the aeroelastic instability is very sensitive to the seal clearance variations. These results show the same tendency as those in previous works [1–5]. In the second part of this study, this paper tries to develop a flutter suppression method without deteriorating the flow leakage performance. This is achieved by changing the seal geometry without changing the seal clearance variation. To detect the important geometric parameters, the contribution of each geometric component to aeroelastic instability is carefully analyzed. On the basis of this, the seal geometry is modified and its performance is also evaluated. The optimized labyrinth seal shows good performance in terms of flow leakage and aeroelastic stability. Through this study, a new method to suppress the flutter with low flow leakage is established.

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.

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.

scholarly journals Data Adaptive Spectral Analysis of Unsteady Leakage Flow in an Axial Turbine

2012 ◽  
Vol 2012 ◽  
pp. 1-7
Author(s):  
Konstantinos G. Barmpalias ◽  
Ndaona Chokani ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari
Keyword(s):  
Spectral Analysis ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Analysis Method ◽  
Axial Turbine ◽  
Spectral Estimates ◽  
Spectral Analysis Method ◽  
Data Adaptive ◽  
Unsteady Processes ◽  
Good Agreement

A data adaptive spectral analysis method is applied to characterize the unsteady loss generation in the leakage flow of an axial turbine. Unlike conventional spectral analysis, this method adapts a model dataset to the actual data. The method is illustrated from the analysis of the unsteady wall pressures in the labyrinth seal of an axial turbine. Spectra from the method are shown to be in good agreement with conventional spectral estimates. Furthermore, the spectra using the method are obtained with data records that are 16 times shorter than for conventional spectral analysis, indicating that the unsteady processes in turbomachines can be studied with substantially shorter measurement schedules than is presently the norm.

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.

scholarly journals A Study on the Leakage Characteristics of a Stepped Labyrinth Seal with a Ribbed Casing

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3719
Author(s):  
Min-Seok Hur ◽  
Seong-Won Moon ◽  
Tong-Seop Kim
Keyword(s):  
Turbine Blades ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Flow Function ◽  
Labyrinth Seals ◽  
Leakage Flow Rate ◽  
New Type ◽  
Computational Fluid Dynamics Cfd ◽  
Leakage Characteristics ◽  
Wide Operating

A new type of stepped seal with a ribbed casing is proposed to efficiently reduce the leakage at the tips of turbine blades. The leakage characteristics of two different types of labyrinth seals (conventional seal vs. ribbed seal) were compared and analyzed through computational fluid dynamics (CFD) in a wide operating range of pressure ratios and clearances. The analysis showed that the ribbed seal has superior leakage performance to the conventional seal at all clearance sizes. With the same clearance size (S/H = 1.0), the flow function of the ribbed seal was approximately 21.5–42.6% less than that of the conventional seal. Also, different trends of variation in the flow function according to the increase of the clearance were found between the conventional and ribbed seals. The leakage flow inside the labyrinth seal was analyzed to explain the cause of this difference in tendency, and it was confirmed that the added ribs cause collision between the leakage flow and the tooth wall, even with the increase of the clearance. Also, the ribbed seal enables operation at a larger clearance with the same leakage performance when comparing the absolute leakage flow rate of the two seals. In addition, a parametric study on the influence of the rib height and rib inclination angle revealed that the flow function generally decreases as both parameters increase.

Dynamic analysis of finger seal using equivalent model based on distributed mass method

2014 ◽  
Vol 228 (16) ◽  
pp. 2992-3005 ◽  
Author(s):  
Guo-Ding Chen ◽  
Fei Lu ◽  
Qiang-Peng Yu ◽  
Hua Su
Keyword(s):  
Dynamic Analysis ◽  
Equivalent Model ◽  
Leakage Flow ◽  
Lumped Mass ◽  
Model Based ◽  
Lumped Mass Method ◽  
Leakage Flow Rate ◽  
Dynamic Performances ◽  
Contact Pressures ◽  
Good Agreement

Dynamic analysis of finger seal can be performed by finite element method or equivalent model based on lumped mass method now available, which is difficult in meeting both the acceptable calculation time and accuracy simultaneously. For this reason, interactions between finger elements are considered and the equivalent dynamic model based on distributed mass method is proposed in this article. Seal dynamic performances are obtained by using this model to calculate the equivalent parameters, air leakage flow, and the contact behavior between finger seal and the rotor. The work to be presented here concerns the mapping of dynamic behavior of the finger seal with a stack of three finger elements, including the dynamic displacement responses of finger elements, the leakage clearances, and the contact pressures between the finger elements and the rotor, as well as the leakage flow rate and the wear rate. The results calculated by the equivalent model presented in this study are evaluated by comparison with the published experimental data and results from the model based on lumped mass method, which shows that the equivalent model based on distributed mass method is far superior to that based on lumped mass method because the calculations are in good agreement with the experimental results.

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