Investigation of Brush Seal Flow Characteristics Using Bulk Porous Medium Approach

2003 ◽  
Author(s):  
Yahya Dogu
Keyword(s):  
Porous Medium ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Force Balance ◽  
Complex Flow ◽  
Blow Down ◽  
Permeability Coefficients ◽  
Backing Plate ◽  
Brush Seal

The flow behavior through a brush seal has been investigated by developing a flow analysis procedure with a porous medium approach. In order to increase the brush seal performance and use at more severe operating conditions, the complex flow in the bristle pack has become the major concern affecting seal features such as blow-down, hang-up, hysteresis and bristle flutter. In this study, an axi-symmetric CFD model is employed to calibrate anisotropic permeability coefficients for the bristle pack based on available experimental data; leakage, axial pressure on the rotor surface and radial pressure on the backing plate. A simplified form of the force balance equation is introduced for the flow in the porous bristle pack. Different sets of permeability coefficients are defined for fence height region below the seal backing plate and the upper region of the seal to correlate the different physical structures and behavior of these regions during operation. The upper region is subject to more stiffening due to backing plate support while fence height region is free to spread and bend in the axial direction. It is found that flow resistance for upper region should be 20% higher than fence height region in order to match the experimental pressure within the bristle pack. Analysis results prove that the brush seal is well represented as a porous medium with this approach. Based on the model developed, characteristic flow and pressure fields in the entire bristle pack have been explored.

Investigation of Brush Seal Flow Characteristics Using Bulk Porous Medium Approach

2005 ◽  
Vol 127 (1) ◽  
pp. 136-144 ◽  
Author(s):  
Yahya Dogu
Keyword(s):  
Porous Medium ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Force Balance ◽  
Complex Flow ◽  
Blow Down ◽  
Permeability Coefficients ◽  
Backing Plate ◽  
Brush Seal

The flow behavior through a brush seal has been investigated by developing a flow analysis procedure with a porous medium approach. In order to increase the brush seal performance and use at more severe operating conditions, the complex flow in the bristle pack has become the major concern affecting seal features such as blow-down, hang-up, hysteresis, and bristle flutter. In this study, an axisymmetric CFD model is employed to calibrate anisotropic permeability coefficients for the bristle pack based on available experimental data: leakage, axial pressure on the rotor surface, and radial pressure on the backing plate. A simplified form of the force balance equation is introduced for the flow in the porous bristle pack. Different sets of permeability coefficients are defined for the fence height region below the seal backing plate and the upper region of the seal to correlate the different physical structures and behavior of these regions during operation. The upper region is subject to more stiffening due to backing plate support while the fence height region is free to spread and bend in the axial direction. It is found that flow resistance for the upper region should be 20% higher than the fence height region in order to match the experimental pressure within the bristle pack. Analysis results prove that the brush seal is well represented as a porous medium with this approach. Based on the model developed, characteristic flow and pressure fields in the entire bristle pack have been explored.

Modeling and Computation of Flow in a Passage With 360-Degree Turning and Multiple Airfoils

1993 ◽  
Vol 115 (1) ◽  
pp. 103-108 ◽  
Author(s):  
W. Shyy ◽  
T. C. Vu
Keyword(s):  
Porous Medium ◽  
Global Analysis ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Hydraulic Turbine ◽  
Complex Flow ◽  
The Individual ◽  
Spiral Casing

The spiral casing of a hydraulic turbine is a complex flow device which contains a passage of 360-degree turning and multiple elements of airfoils (the so-called distributor). A three-dimensional flow analysis has been made to predict the flow behavior inside the casing and distributor. The physical model employs a two-level approach, comprising of (1) a global model that adequately accounts for the geometry of the spiral casing but smears out the details of the distributor, and represents the multiple airfoils by a porous medium treatment, and (2) a local model that performs detailed analysis of flow in the distributor region. The global analysis supplies the inlet flow condition for the individual cascade of distributor airfoils, while the distributor analysis yields the information needed for modeling the characteristics of the porous medium. Comparisons of pressure and velocity profiles between measurement and prediction have been made to assess the validity of the present approach. Flow characteristics in the spiral casing are also discussed.

Effects of Geometry on Brush Seal Pressure and Flow Fields—Part II: Backing Plate Configurations

2005 ◽  
Vol 128 (2) ◽  
pp. 379-389 ◽  
Author(s):  
Yahya Dogu ◽  
Mahmut F. Aksit
Keyword(s):  
Constant Pressure ◽  
Decisive Role ◽  
Flow Fields ◽  
Control Flow ◽  
Blow Down ◽  
Backing Plate ◽  
Seal Design ◽  
Pressure Fields ◽  
Brush Seal ◽  
Flow Features

Brush seal dynamic behavior is strongly related to pressure and flow fields. Developments in brush seal design have led to geometric modifications to control flow field and consequent brush seal issues including blow-down, hang-up, and pressure stiffening. Some of the geometric enhancements have been found to have common use as backing plate modifications. Over the two decades of brush seal evolution, many backing plate configurations have been suggested in numerous patent disclosures. Even so, literature on the effects of geometric modifications on pressure and flow fields remains limited. This study numerically investigates brush seal pressure and flow fields for such common conceptual backing plate configurations as single and multiple grooves, with and without by-pass passages. The CFD analysis presented employs a bulk porous medium approach for the bristle pack. The effectiveness of various backing plate configurations outlining important flow features is discussed. Results indicate that backing plate configurations have a decisive role in shaping seal pressure fields. In general, it has been found that all cases having bypass configuration leak more. Moreover, the major portion of the seal leakage through fence height is fed from the backing plate cavity. The single backing plate groove forms a constant pressure behind the bristle pack. In contrast, multiple grooves form multiple constant pressure regions.

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.

Computational Fluid Dynamics Investigation of Brush Seal Leakage Performance Depending on Geometric Dimensions and Operating Conditions

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Yahya Dogu ◽  
Ahmet S. Bahar ◽  
Mustafa C. Sertçakan ◽  
Altuğ Pişkin ◽  
Ercan Arıcan ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Ratio ◽  
Plate Thickness ◽  
Operating Conditions ◽  
Design Parameters ◽  
Backing Plate ◽  
Brush Seal ◽  
Front Plate ◽  
Brush Seals

Brush seals require custom design and tailoring due to their behavior driven by flow dynamic, which has many interacting design parameters, as well as their location in challenging regions of turbomachinery. Therefore, brush seal technology has not reached a conventional level across the board standard. However, brush seal geometry generally has a somewhat consistent form. Since this consistent form does exist, knowledge of the leakage performance of brush seals depending on specific geometric dimensions and operating conditions is critical and predictable information in the design phase. However, even though there are common facts for some geometric dimensions available to designers, open literature has inadequate quantified information about the effect of brush seal geometric dimensions on leakage. This paper presents a detailed computational fluid dynamics (CFD) investigation quantifying the leakage values for some geometric variables of common brush seal forms functioning in some operating conditions. Analyzed parameters are grouped as follows: axial dimensions, radial dimensions, and operating conditions. The axial dimensions and their ranges are front plate thickness (z1 = 0.040–0.150 in.), distance between front plate and bristle pack (z2 = 0.010–0.050 in.), bristle pack thickness (z3 = 0.020–0.100 in.), and backing plate thickness (z4 = 0.040–0.150 in.). The radial dimensions are backing plate fence height (r1 = 0.020–0.100 in.), front plate fence height (r2 = 0.060–0.400 in.), and bristle free height (r3 = 0.300–0.500 in.). The operating conditions are chosen as clearance (r0 = 0.000–0.020 in.), pressure ratio (Rp = 1.5–3.5), and rotor speed (n = 0–40 krpm). CFD analysis was carried out by employing compressible turbulent flow in 2D axisymmetric coordinate system. The bristle pack was treated as a porous medium for which flow resistance coefficients were calibrated by using literature based test data. Selected dimensional and operational parameters for a common brush seal form were investigated, and their effects on leakage performance were quantified. CFD results show that, in terms of leakage, the dominant geometric dimensions were found to be the bristle pack thickness and the backing plate fence height. It is also clear that physical clearance dominates leakage performance, when compared to the effects of other geometric dimensions. The effects of other parameters on brush seal leakage were also analyzed in a comparative manner.

Numerical Simulation of Inner Flow in a Double Blades Pump Based on OpenFOAM and its PIV Verification

2012 ◽  
Author(s):  
Yun Ren ◽  
Houlin Liu ◽  
Kai Wang ◽  
Minggao Tan ◽  
Denghao Wu ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Flow Behavior ◽  
Energy Performance ◽  
Operating Conditions ◽  
Centrifugal Pumps ◽  
Complex Flow ◽  
Unstable Flow ◽  
Software Packages ◽  
Flow Phenomena ◽  
Particle Imaging

The presence of unstable flow phenomena may significantly alter the flow pattern and characteristics of centrifugal pumps; that is, the unstable flows may seriously deteriorate the pumps performance. In this paper, considering the high cost of running license fees and not available with all the computing resources, a high quality Open Source CFD simulation platform like OpenFOAM instead of commercial software packages is adopted. Furthermore, the required capability such as GGI is added and boundary conditions are specialized to better simulate complex flow behavior through rotor-stator components in a double blades pump, whose specific speed is 115.6. In order to disclose the characteristics completely, six research schemes are developed and are now presented in this paper. The ratios (Q/Qd) of the flow rate are 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, respectively. The task mainly focuses on the comparison of energy performance under different operating conditions between numerical calculations and experiments, the analysis of the inner flow in the impeller and the comparison of the velocity field in the impeller mid-height between simulation data and the Particle Imaging Velocimetry (PIV) experimental data. The results show that good agreements are found both in terms of the energy performance with experimental results and computed velocities with the PIV data, but improvements can be made.

CAE Based Brush Seal Characterization for Stiffness and Stress Levels

2015 ◽  
Author(s):  
E. Tolga Duran ◽  
Mahmut F. Aksit ◽  
Murat Ozmusul
Keyword(s):  
Operating Conditions ◽  
Design Parameters ◽  
Backing Plate ◽  
Seal Design ◽  
Brush Seal ◽  
Stress Levels ◽  
Brush Seals ◽  
Main Effects ◽  
State Pressure

Brush seals are complex structures having variety of design parameters, all of which affect the seal behavior under turbine operating conditions. The complicated nature of the seal pack and frictional interactions of rotor, backing plate and bristles result in nonlinear response of the brush seal to variances of design parameters. This study presents CAE based characterization of brush seals, which aims to investigate the main effects of several brush seal design parameters on brush seal stiffness and stress levels. Characterization work of this study includes free-state rotor rub (unpressurized seal), steady state (pressure load without rotor interference) and pressurized-rotor interference conditions.

Numerical investigation of high-temperature effects in the UTIAS–RPI hypersonic impulse tunnel

1991 ◽  
Vol 69 (7) ◽  
pp. 897-918 ◽  
Author(s):  
C. P. T. Groth ◽  
J. J. Gottlieb ◽  
P. A. Sullivan
Keyword(s):  
High Temperature ◽  
Test Section ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Vibrational Modes ◽  
Blow Down ◽  
Riemann Solvers ◽  
University Of Toronto ◽  
High Mach ◽  
The University

The hypersonic impulse tunnel of the University of Toronto Institute for Aerospace Studies (UTIAS) and Ryerson Polytechnical Institute (RPI) is a short-duration blow-down experimental wind tunnel capable of producing high-Mach-number flows (Ma ≈ 8). A generalized quasi-one-dimensional nonstationary flow analysis and associated total-variation-diminishing (TVD) finite-difference solution schemes, including aproximate Riemann solvers, are presented for predicting the high-temperature flows in such facilities. The analysis is used to investigate the operation of the UTIAS–RPI facility and produce performance data that are not always easily determined or available from experimental measurements. The thermodynamic state of the nozzle-exit flow and high-temperature or real-gas effects are assessed for this facility under various operating conditions. Numerical results, coupled with additional comparisons with available experimental data, demonstrate the range of test-section flows that may be achieved. They also illustrate that for typical operating conditions, the air (working gas used in UTIAS–RPI facility) freezes in the nozzle very close to the throat and results in test-section flows with considerable energy bound in the vibrational modes of the nitrogen (N2) and oxygen (O2) molecules. In particular, the test-section temperatures associated with the vibrational modes of N2 are only marginally less than barrel-end stagnation temperatures, whereas the vibrational temperatures of O2, although lower than stagnation temperatures, are still much higher than the predicted translational–rotational temperatures.

Flow Pattern Evolution and Energy Decomposition of Flows at Different Operating Conditions in a Hydrodynamic Torque Converter

2016 ◽  
Author(s):  
Wei Wei ◽  
Mingxing Huang ◽  
Yu Li ◽  
Qingdong Yan
Keyword(s):  
Vortex Structure ◽  
Velocity Vector ◽  
Power Transmission ◽  
Flow Behavior ◽  
Internal Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Energy Decomposition ◽  
Complex Flow

Power loss and flow blockage in turbomachinery such as hydrodynamic torque converter are usually caused by jet flow, second flow and flow separation. In this paper, the velocity vector and the pressure distribution of the internal flow field in hydrodynamic torque converter were reduced by the method of the Proper Orthogonal Decomposition (POD) to find the main flow structures and the energy decomposition in the passages of pump, turbine and stator. In order to find their evolutionary processes and energy decompositions, oil flow visualizations were conducted at different speed ratios from 0 to 0.8, including stall condition and design operating condition. The results showed that the first few modes containing the majority of energy could provide enough accuracy to predict flow behavior and flow structure in flow passages. Especially when the energy percentage of the first mode was majority, its vortex structures could be recognized easily. But the flow patterns of other modes were different from each other and they made the flow more turbulent and complex, which increases the energy loss in the process of power transmission. Besides that, the change of pressure gradient had a direct influence to velocity vector. The results also indicated that the observed fluid pattern of vortex structure became extensive while the influence of secondary flow decreased in the flow passage of pump with the increase of speed ratio. But the situation is just reversed in turbine, that is, the vortex disappeared gradually and the irregular turbulent flow appeared as the increase of speed ratio. In stator, the vortex structure emerged gradually when the speed ratio increased. So the method of snapshots is a very useful way to analyze the complex flow flied in depth and to predict the trend of development.

Brush Seal Free State Stiffness Analyses, Tests and Inspection on Dynamic Effects

2015 ◽  
Author(s):  
E. Tolga Duran ◽  
Mahmut F. Aksit ◽  
Murat Ozmusul
Keyword(s):  
Load Capacity ◽  
Dynamic Stiffness ◽  
Operating Conditions ◽  
Test Results ◽  
Wear Rates ◽  
Backing Plate ◽  
Brush Seal ◽  
Study Test ◽  
Brush Seals ◽  
Interference Measurements

While the efficiency of a brush seal is measured by its leakage rate, the overall performance of the seal is mostly affected by wear rate and durability. Seal stiffness and hysteresis behavior play important roles in determining the leakage performance and rotor stability due to the fact that they directly affect wear rates and pressure load capacity of the seal. The complicated nature of the bristle, rotor and backing plate interactions at typical operating conditions makes it difficult to determine the stiffness and durability of brush seals. In this study, test and computer aided engineering (CAE) methodologies have been developed to simulate brush seal stiffness and stress levels at unpressurized conditions. Unpressurized stiffness tests have been conducted by using two different test rigs, one of which uses a simple metallic pad and the other one uses a full-sized rotor for seal interference measurements. Test results for the two different rigs have been compared and the drawbacks of the simple stiffness test rig have been detailed in this study. CAE analyses at unpressurized conditions have been conducted by using 3D finite element (FE) models, and analyses have been correlated with the stiffness tests. The influence of rotor rotation has also been analyzed at unpressurized seal conditions. Transient simulation results also demonstrated good agreement with the dynamic stiffness tests of the brush seals.

Sign in / Sign up

Export Citation Format

Share Document