Influence of Geometry on Rotordynamic Coefficients of Brush Seal

2017 ◽  
Vol 34 (2) ◽  
Author(s):  
Yuan Wei ◽  
Earl H. Dowell ◽  
Zhaobo Chen ◽  
Yinghou Jiao ◽  
Zhouqiang Zhang
Keyword(s):  
Aerodynamic Force ◽  
Dynamic Pressure ◽  
Reaction Force ◽  
Operating Conditions ◽  
Rotordynamic Coefficients ◽  
Geometric Configurations ◽  
Brush Seal ◽  
Sealing Performance ◽  
Flow Features ◽  
The Relationship

AbstractIt has been observed that the geometry of a brush seal has a significant effect on the sealing performance. However, the relationship between rotordynamic coefficients and geometry factors of the brush seal itself are rarely considered. In this article, the rotordynamic coefficients of a typical single-stage brush seal for different geometries and operating conditions were numerically analyzed using CFD RANS solutions coupled with a non-Darcian porous medium model. The reaction force which plays an essential role in rotordynamic coefficients was obtained by integrating the dynamic pressure distribution. The influence of the bristle pack thickness, fence height, clearance size and other working condition parameters on aerodynamic force, stiffness coefficients, and damping coefficients of brush seal were presented and compared. In addition, the effects of various geometric configurations on pressure and flow features were also discussed.

Evaluation of Flow Behavior for Clearance Brush Seals

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Yahya Dogu ◽  
Mahmut F. Aksit ◽  
Mehmet Demiroglu ◽  
Osman Saim Dinc
Keyword(s):  
Flow Field ◽  
Flow Behavior ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Brush Seal ◽  
Sealing Performance ◽  
Computational Fluid Dynamics Analysis ◽  
Flow Features ◽  
Brush Seals ◽  
Initial Clearance

The industrial applications of brush seals have been increasing due to their superior sealing performance. Advances in the understanding of seal behavior have been pushing the design limits to higher-pressure load, temperature, surface speed, and rotor excursion levels. The highest sealing performance can be achieved when the bristle pack maintains contact with the rotor surface. However, due to many design and operational constraints, most seals operate with some clearance. This operating clearance cannot be avoided due to rotor runouts, transient operating conditions, or excessive bristle wear. In some applications, a minimum initial clearance is required to ensure a certain amount of flow rate for component cooling or purge flow. Typically, brush seal failure occurs in the form of degraded sealing performance due to increasing seal clearance. The seal performance is mainly characterized by the flow field in close vicinity of the bristle pack, through the seal-rotor clearance, and within the bristle pack. This work investigates the flow field for a brush seal operating with some bristle-rotor clearance. A nonlinear form of the momentum transport equation for a porous medium of the bristle pack has been solved by employing the computational fluid dynamics analysis. The results are compared with prior experimental data. The flow field for the clearance seal is observed to have different characteristics compared to that for the contact seal. Outlined as well are the flow features influencing the bristle dynamics.

scholarly journals Dynamic analysis of liquid annular seals with herringbone grooves on the rotor based on the perturbation method

2018 ◽  
Vol 5 (6) ◽  
pp. 180101 ◽  
Author(s):  
Lulu Zhai ◽  
Zhang Zhenjie ◽  
Chi Zhonghuang ◽  
Guo Jia
Keyword(s):  
Dynamic Characteristics ◽  
Operating Conditions ◽  
Geometric Parameters ◽  
Leakage Flow ◽  
Flow Rates ◽  
Rotordynamic Coefficients ◽  
Sealing Performance ◽  
Spiral Angle ◽  
Herringbone Grooves ◽  
Annular Seals

Annular seals have significant effects on the hydraulic and rotordynamic performances of turbomachinery. In this paper, an analysis method for calculating the leakage flow rates and dynamic characteristics of liquid annular seals with herringbone grooves on the rotor is proposed and verified. Leakage flow rates and dynamic characteristics of the model seals under different operating conditions are theoretically analysed and compared with those of plain and spiral-grooved seals of the same size. In addition, the influence of geometric parameters such as spiral angle and the lengths of the constituent parts on the sealing and rotordynamic coefficients of seals with herringbone grooves are also discussed. The results show that seals with herringbone grooves have better sealing performance, while providing better support actions and damping characteristics than the other two seal types under the same operating conditions. The seal geometric parameters including spiral angle, the lengths of the constituent parts and the clearance value have a significant influence on the dynamic characteristics of seals with herringbone grooves.

Fluidic Jet Barriers for Sealing Applications

2011 ◽  
Author(s):  
Simon I. Hogg ◽  
Isabel Gomez Ruiz
Keyword(s):  
New Technology ◽  
Internal Flow ◽  
Labyrinth Seal ◽  
Operating Conditions ◽  
Seal Design ◽  
Brush Seal ◽  
Fluid Jets ◽  
Flow Features ◽  
Upstream Direction ◽  
Physical Barriers

The turbine industry is continually looking for new developments to improve thermodynamic performance and sealing has received significant attention over the years. Fluidic seals employ aerodynamic flow features to create blockage/loss and reduce leakage, rather than relying on physical barriers to flow such as brush seal bristle packs etc. They are also potentially cheaper to implement than contacting seal technologies such as brush seals. The fundamental mechanism by which fluid jets inclined in an upstream direction produce blockage and reduce the flow along leakage channels are examined in the paper. Computational Fluid Dynamics is used to quantify the net gain in leakage performance that can be achieved in simple channel flow for various operating conditions and jet configurations. These results are used to guide further CFD calculations in which the potential for leakage reduction from adapting conventional labyrinth turbomachinery seal designs to include fluidic jets is investigated. Calculations are carried out for operating conditions that are typical of gas and steam turbine applications, in order to demonstrate the potential of new seal designs of this generic type. The device considered in the paper is essentially a conventional labyrinth seal design which is modified to include internal flow channels within the structure supporting the labyrinth fins, to supply the fluidic jets. The new technology is therefore a modification to an existing component with potential for application in existing turbine designs, requiring no/minimal changes outside of the seal design space to implement.

Flow Investigation Around a V-Sector Ball Valve

2001 ◽  
Vol 123 (3) ◽  
pp. 662-671 ◽  
Author(s):  
P. Merati ◽  
M. J. Macelt ◽  
R. B. Erickson
Keyword(s):  
High Speed ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Ball Valve ◽  
Operating Conditions ◽  
Mean Velocity ◽  
Model Flow ◽  
Flow Investigation ◽  
And Behavior ◽  
The Relationship

Experimental and computational methods were used to study the structure and behavior of the shedded vortices around a V-ball valve. Strouhal frequency for shedded vortices around the valve over a range of operating conditions and flow rates using water as the medium were measured. The information gathered in this study would help to predict at what operating conditions pipe ruptures might occur. A dynamic pressure transducer was used to determine the Strouhal frequency. LDV was used to measure the mean velocity and turbulence magnitudes. FLUENT was used to develop a two dimensional fluid dynamics model. Flow was visualized using high-speed video photography. A dominant large three-dimensional vortex downstream of the valve was detected. The centerline of this vortex is a shadow of the valve lip. A fifth degree polynomial describing the relationship between the Strouhal number and Reynolds number is obtained.

Performance Analysis of Hybrid Brush Pocket Damper Seals Using Computational Fluid Dynamics

2016 ◽  
Author(s):  
Alexander O. Pugachev ◽  
Clemens Griebel ◽  
Stacie Tibos ◽  
Bernard Charnley
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Excitation Frequency ◽  
Operating Conditions ◽  
Single Frequency ◽  
Cfd Model ◽  
Rotordynamic Coefficients ◽  
Damping Coefficients ◽  
Brush Seal ◽  
Stiffness And Damping

In this paper, a hybrid brush pocket damper seal is studied theoretically using computational fluid dynamics. In the hybrid sealing arrangement, the brush seal element with cold clearance is placed downstream of a 4-bladed, 8-pocket, fully partitioned pocket damper seal. The new seal geometry is derived based on designs of short brush-labyrinth seals studied in previous works. Transient CFD simulations coupled with the multi-frequency rotor excitation method are performed to determine frequency-dependent stiffness and damping coefficients of pocket damper seals. A moving mesh technique is applied to model the shaft motion on a predefined whirling orbit. The rotordynamic coefficients are calculated from impedances obtained in frequency domain. The pocket damper seal CFD model is validated against available experimental and numerical results found in the literature. Bristle pack in the brush seal CFD model is described as porous medium. The applied brush seal model is validated using the measurements obtained in previous works from two test rigs. Predicted leakage characteristics as well as stiffness and damping coefficients of the hybrid brush pocket damper seal are presented for different operating conditions. In this case, the rotordynamic coefficients are calculated using a single-frequency transient simulation. By adding the brush seal, direct stiffness is predicted to be significantly decreased while effective damping shows a more moderate or no reduction depending on excitation frequency. Effective clearance results indicate more than halved leakage compared to the case without brush seal.

CFD Analysis of Aerodynamic Coefficients in Labyrinth Brush Seal

2015 ◽  
Author(s):  
Yuan Wei ◽  
Zhaobo Chen ◽  
Earl H. Dowell
Keyword(s):  
Aerodynamic Force ◽  
Pressure Ratio ◽  
Tangential Force ◽  
Flow Region ◽  
Radial Force ◽  
Navier Stokes ◽  
Rotordynamic Coefficients ◽  
System A ◽  
Brush Seal ◽  
The Stability

The aerodynamic force between a bristle pack and a rotor should be considered in order to predict the stability of a rotor brush seal system. The high pressure flow region in a brush seal makes the interaction of bristle pack, leakage flow and rotor complicated. It provides a challenge to the study of rotor brush seal system dynamic characteristics. To analyze the rotordynamic coefficients of a rotor brush seal system, a 3D CFD rotor labyrinth brush seal computational model was created using Reynolds-averaged Navier-Stokes (RANS) solutions coupled with a non-Darcian porous medium model. The results show that for the same geometry parameters the radial force rises when the pressure ratio increases, the tangential force rises when the pressure ratio increases, and the radial force is much greater than the tangential force. And the flow leakage will increase when the pressure load increases and the mass flow rate increases with the clearance increase. Direct and cross-coupled stiffness and direct damping and cross-coupled damping under different operating condition are discussed. The direct damping and cross-coupled damping both increase when the clearance increases. The cross-coupled stiffness will increase when the inlet pressure increases.

Numerical Prediction of Impact of Clearance on Rotordynamic Coefficients for Labyrinth Brush Seal

2019 ◽  
Vol 36 (1) ◽  
pp. 31-43 ◽  
Author(s):  
Yuan Wei ◽  
Earl H. Dowell ◽  
Zhaobo Chen
Keyword(s):  
Pressure Ratio ◽  
Tangential Force ◽  
Radial Force ◽  
Operating Conditions ◽  
Stable Factor ◽  
Rotordynamic Coefficients ◽  
Brush Seal ◽  
Direct Stiffness ◽  
The Stability ◽  
Geometry Parameter

Abstract The clearance has an obvious influence on the rotordynamic characteristics of brush seals. In order to better know the influence of brush seal on the stability of the rotor bearing system, the rotordynamic coefficients of labyrinth brush seal under different clearance cases and operating conditions are numerically analyzed using CFD RANS solutions coupling with a non-Darcian porous medium model. The results show that at the same geometry parameter the radial force and tangential force will increase when the pressure ratio rises. And when the clearance increases, the direct stiffness decreases sharply at first and then rises slightly. The variation of cross-coupled stiffness is complex. Moreover, at the same operating condition the value of direct damping coefficients increases when clearance increases, which add a stable factor to the rotor.

Leakage and Rotordynamic Coefficients of Brush Seals With Zero Cold Clearance Used in an Arrangement With Labyrinth Fins

2013 ◽  
Author(s):  
Manuel Gaszner ◽  
Alexander O. Pugachev ◽  
Christos Georgakis ◽  
Paul Cooper
Keyword(s):  
Dynamic Test ◽  
Operating Conditions ◽  
Radial Clearance ◽  
Labyrinth Seals ◽  
Rotordynamic Coefficients ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
Brush Seal ◽  
Brush Seals ◽  
Stiffness And Damping

A brush-labyrinth sealing configuration consisting of two labyrinth fins upstream and one brush seal downstream is studied experimentally and theoretically. Two slightly different brush seal designs with zero cold radial clearance are considered. The sealing configurations are tested on the no-whirl and dynamic test rigs to obtain leakage performance and rotordynamic stiffness and damping coefficients. The no-whirl tests allow identification of the local rotordynamic direct and cross-coupled stiffness coefficients for a wide range of operating conditions, while the dynamic test rig is used to obtain both global stiffness and damping coefficients, but for a narrower operating range limited by the capabilities of a magnetic actuator. Modeling of the brush-labyrinth seals is performed using computational fluid dynamics. The experimental global rotordynamic coefficients consist of an aerodynamic component due to the gas flow and a mechanical component due to the contact between the bristle tips and rotor surface. The CFD-based calculations of rotordynamic coefficients provide however only the aerodynamic component. A simple mechanical model is used to estimate the theoretical value of the mechanical stiffness of the bristle pack during the contact. The results obtained for the sealing configurations with zero cold radial clearance brush seals are compared with available data on three-tooth-on-stator labyrinth seals and a brush seal with positive cold radial clearance. Results show that the sealing arrangement with a line-on-line welded brush seal has the best performance overall with the lowest leakage and cross-coupled stiffness. The predictions are generally in agreement with the measurements for leakage and stiffness coefficients. The seal damping capability is noticeably underpredicted.

A pilot web former designed to study retention-formation relationships

2010 ◽  
Vol 25 (2) ◽  
pp. 185-194
Author(s):  
Anna Svedberg ◽  
Tom Lindström
Keyword(s):  
Pilot Scale ◽  
Operating Conditions ◽  
Montmorillonite Clay ◽  
Speed Ratio ◽  
Good Reproducibility ◽  
Total Solids ◽  
Retention Aids ◽  
Solids Content ◽  
Relationship Of ◽  
The Relationship

Abstract A pilot-scale fourdrinier former has been developed for the purpose of investigating the relationship between retention and paper formation (features, retention aids, dosage points, etc.). The main objective of this publication was to present the R-F (Retention and formation)-machine and demonstrate some of its fields of applications. For a fine paper stock (90% hardwood and 10% softwood) with addition of 25% filler (based on total solids content), the relationship between retention and formation was investigated for a microparticulate retention aid (cationic polyacrylamide together with anionic montmorillonite clay). The retention-formation relationship of the retention aid system was investigated after choosing standardized machine operating conditions (e.g. the jet-to-wire speed ratio). As expected, the formation was impaired when the retention was increased. Since good reproducibility was attained, the R-F (Retention and formation)-machine was found to be a useful tool for studying the relationship between retention and paper formation.

scholarly journals Engine Malfunctioning Conditions Identification through Instantaneous Crankshaft Torque Measurement Analysis

2021 ◽  
Vol 11 (8) ◽  
pp. 3522
Author(s):  
Konstantinos-Marios Tsitsilonis ◽  
Gerasimos Theotokatos
Keyword(s):  
Operating Conditions ◽  
Cylinder Pressure ◽  
Dynamics Model ◽  
Engine Model ◽  
Measurement Analysis ◽  
Start Of Injection ◽  
Rate Of Heat Release ◽  
Relationship Of ◽  
Diagnostic Measurement ◽  
The Relationship

In this study a coupled thermodynamics and crankshaft dynamics model of a large two-stroke diesel engine was utilised, to map the relationship of the engine Instantaneous Crankshaft Torque (ICT) with the following frequently occurring malfunctioning conditions: (a) change in Start of Injection (SOI), (b) change in Rate of Heat Release (RHR), (c) change in scavenge air pressure, and (d) blowby. This was performed using frequency analysis on the engine ICT, which was obtained through a series of parametric runs of the coupled engine model, under the various malfunctioning and healthy operating conditions. This process demonstrated that engine ICT can be successfully utilised to identify the distinct effects of malfunctions (c) or (d), as they occur individually in any cylinder. Furthermore by using the same process, malfunctions (a) and (b) can be identified as they occur individually for any cylinder, however there is no distinct effect on the engine ICT among these malfunctions, since their effect on the in-cylinder pressure is similar. As a result, this study demonstrates the usefulness of the engine ICT as a non-intrusive diagnostic measurement, as well as the benefits of malfunctioning conditions mapping, which allows for quick and less resource intensive identification of engine malfunctions.

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