Characterization of Brush Seal Permeability

2016 ◽  
Author(s):  
Thomas G. Gresham ◽  
Brian K. Weaver ◽  
Houston G. Wood ◽  
Alexandrina Untaroiu
Keyword(s):  
Porous Media ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Backing Plate ◽  
Physical Mechanisms ◽  
Brush Seal ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through

A basis for the study of flow through a brush seal is established by applying the fundamentals of porous media fluid mechanics. Permeability, the measure of a medium’s ability to transmit flow, is one of the most important factors needed to characterize a brush seal’s ability to reduce leakage. Previous studies have indicated that the performance of a brush seal is highly dependent on operating conditions. By investigating how the permeability is affected by the operating conditions (pressure ratio specifically), further understanding of the performance of this type of seal is developed. Experimental data in the literature was used in tandem with computational fluid dynamics (CFD) simulation results in order to characterize how the permeability of a single-stage brush seal changes as the pressure ratio changes. For each value of pressure ratio, the permeability of the CFD model was adjusted until the leakage calculated from the model matched experimentally measured values. The physical mechanisms behind the observed variations in permeability are discussed. Explanations are proposed based on flutter and deformation of the bristles and how these phenomena can affect the internal tortuosity of the bristle pack. As pressure across the bristles increases, it is expected that they will bend under the backing plate to align with the flow direction in the clearance region, but the increase in pressure will also act to compress the bristle pack in the flow direction, decreasing the spacing between bristles and reducing their ability to move relative to each other, thereby reducing the effective permeability of the bristle pack. By demonstrating the dependence of permeability on operating conditions, it is shown that the common assumption of constant permeability coefficients can often result in an insufficient model. Assumptions regarding the model of a bristle pack as an isotropic porous media are discussed, and the validity and utility of this model are assessed. This paper provides important insight into what a reasonable value of permeability of a typical brush seal is, and how that value may change as a function of operating conditions.

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.

Effect of Shaft Rotation, Hole and Annulus Geometry on the Discharge Behavior Through Rotating Radial Holes

2015 ◽  
Author(s):  
Daniel Riedmüller ◽  
Jan Sousek ◽  
Michael Pfitzner
Keyword(s):  
Discharge Coefficient ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Flow Phenomena ◽  
Flow Through ◽  
Discharge Behavior ◽  
Set Up ◽  
The One

This paper reports on various effects on the flow through rotating radial holes (centrifugal, centripetal) in conjunction with the geometries of hole and surrounding annuli. The aerodynamic behavior of radial rotating holes is different from the one of axial and stationary holes due to the presence of centrifugal and Coriolis forces acting in the main flow direction. Furthermore, the geometry of the inlet and outlet region is often influencing the separation behavior of the flow at the holes. To investigate the flow phenomena and the discharge behavior of these radial holes in detail, an existing test rig containing two independently rotating shafts (co- and counter rotating) was used. Experimental and numerical investigations have been performed for both flow directions through the radial holes (centripetal and centrifugal), for different hole geometries (oblong holes and round holes), inlet types (rounded and sharp), length to diameter ratios (variation of either length or diameter) and gap widths between inner and outer shaft. For each of these geometrical variations flow properties have been varied such as pressure ratio across the holes, incident Mach number and rotational speed of both shafts. To enable large parametric studies and grid independency studies an optimization model with completely automatic grid generation, CFD simulation and post-processing has been set up. As a main result of the current studies it was found, that the shaft to hole diameter is another parameter of interest for the flow behavior through shaft holes. For a centripetal flow through the shaft holes and a decreasing inner gap width, the discharge coefficient was observed to increase initially before it drops significantly. In addition, measurements of centripetal flow though oblong holes revealed higher discharge coefficient in comparison with round holes and equal length to diameter ratio.

CFD Investigation of Brush Seal Leakage Performance Depending on Geometric Dimensions and Operating Conditions

2015 ◽  
Author(s):  
Yahya Doğu ◽  
Mustafa C. Sertçakan ◽  
Ahmet S. Bahar ◽  
Altuğ Pişkin ◽  
Ercan Arıcan ◽  
...  
Keyword(s):  
Pressure Ratio ◽  
Plate Thickness ◽  
Operating Conditions ◽  
Design Parameters ◽  
Operational Parameters ◽  
Backing Plate ◽  
Brush Seal ◽  
Front Plate ◽  
Brush Seals ◽  
Geometric Variables

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 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=0.040–0.150in.), distance between front plate and bristle pack (z2=0.010–0.050in.), bristle pack thickness (z3=0.020–0.100in.), and backing plate thickness (z4=0.040–0.150in.). The radial dimensions are backing plate fence height (r1=0.020–0.100in.), front plate fence height (r2=0.060–0.400in.), and bristle free height (r3=0.300–0.500in.). The operating conditions are chosen as clearance (r0=0.000–0.020in.), pressure ratio (Rp=1.5–3.5), and rotor speed (n=0–40krpm). CFD analysis was carried out by employing compressible turbulent flow in 2-D axi-symmetric 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.

A Fully Coupled Approach for the Integration of 3D-CFD Component Simulation in Overall Engine Performance Analysis

2017 ◽  
Author(s):  
C. Klein ◽  
S. Reitenbach ◽  
D. Schoenweitz ◽  
F. Wolters
Keyword(s):  
Performance Analysis ◽  
Boundary Conditions ◽  
Progress Monitoring ◽  
Cfd Simulation ◽  
System Simulation ◽  
Pressure Ratio ◽  
Performance Model ◽  
Operating Conditions ◽  
Operating Characteristics ◽  
Design Environment

Due to a high degree of complexity and computational effort, overall system simulations of jet engines are typically performed as 0-dimensional thermodynamic performance analysis. Within these simulations and especially in the early cycle design phase, the usage of generic component characteristics is common practice. Of course these characteristics often cannot account for true engine component geometries and operating characteristics which may cause serious deviations between simulated and actual component and overall system performance. This leads to the approach of multi-fidelity simulation, often referred to as zooming, where single components of the thermodynamic cycle model are replaced by higher-order procedures. Hereby the consideration of actual component geometries and performance in an overall system context is enabled and global optimization goals may be considered in the engine design process. The purpose of this study is to present a fully automated approach for the integration of a 3D-CFD component simulation into a thermodynamic overall system simulation. As a use case, a 0D-performance model of the IAE-V2527 engine is combined with a CFD model of the appropriate fan component. The methodology is based on the DLR in-house performance synthesis and preliminary design environment GTlab combined with the DLR in-house CFD solver TRACE. Both, the performance calculation as well as the CFD simulation are part of a fully automated process chain within the GTlab environment. The exchange of boundary conditions between the different fidelity levels is accomplished by operating both simulation procedures on a central data model which is one of the essential parts of GTlab. Furthermore iteration management, progress monitoring as well as error handling are part of the GTlab process control environment. Based on the CFD results comprising fan efficiency, pressure ratio and mass flow, a map scaling methodology as it is commonly used for engine condition monitoring purposes is applied within the performance simulation. Hereby the operating behavior of the CFD fan model can be easily transferred into the overall system simulation which consequently leads to a divergent operating characteristic of the fan module. For this reason, all other engine components will see a shift in their operating conditions even in case of otherwise constant boundary conditions. The described simulation procedure is carried out for characteristic operating conditions of the engine.

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.

scholarly journals The Design and Evaluation of a 14 Stage, 16:1 Pressure Ratio Compressor for an Industrial Gas Turbine

1996 ◽  
Author(s):  
Mohammad R. Saadatmand
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Rotor Blade ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Suction Surface ◽  
Design Intent ◽  
Flow Through ◽  
Industrial Gas Turbine

The aerodynamic design process leading to the production configuration of a 14 stage, 16:1 pressure ratio compressor for the Taurus 70 gas turbine is described. The performance of the compressor is measured and compared to the design intent. Overall compressor performance at the design condition was found to be close to design intent. Flow profiles measured by vane mounted instrumentation are presented and discussed. The flow through the first rotor blade has been modeled at different operating conditions using the Dawes (1987) three-dimensional viscous code and the results are compared to the experimental data. The CFD prediction agreed well with the experimental data across the blade span, including the pile up of the boundary layer on the corner of the hub and the suction surface. The rotor blade was also analyzed with different grid refinement and the results were compared with the test data.

CFD Simulation of Wall-Bounded Laminar Flow Through Screens: Part II — Mixing Characterization

2020 ◽  
Author(s):  
W. Abou Hweij ◽  
F. Azizi
Keyword(s):  
Cfd Simulation ◽  
Flow Behavior ◽  
Particle Method ◽  
Immiscible Fluids ◽  
Laminar Flows ◽  
Operating Conditions ◽  
Static Mixers ◽  
Flow Through ◽  
Dispersive Mixing ◽  
Lagrangian Particle Method

Abstract This paper characterizes the mixing behavior of laminar flows within a circular pipe equipped with plain woven meshes or screens, acting as static mixers. In this quest, their performance was numerically investigated using the Lagrangian particle method in a commercial CFD solver, whereby the effect of changing the screen geometry, number of screens, inter-screen spacing, and operating conditions were considered. Mixing was addressed from a distributive and dispersive perspectives using both qualitative and quantitative descriptions. The distributive mixing indicated that a central injection of a single fluid should be coupled with a short inter-screen spacing to better spread the particles and enhance mixing as opposed to a larger inter-screen spacing. On the contrary, the mixing of two immiscible fluids of similar properties reveal that a large inter-screen spacing is recommended. From a dispersive mixing perspective, extensional efficiency contours revealed that the fluid would undergo all three modes of flow behavior, each of which dominating a certain region depending on the location with respect to the screen. Finally, it was interesting to find that a coarser screen geometry consistently outperformed finer screens in spreading and mixing the particles.

Variable Inlet Guide Vane Effect on Centrifugal Compressor Performance in Wet Gas Flow

2016 ◽  
Author(s):  
Levi André B. Vigdal ◽  
Lars E. Bakken
Keyword(s):  
Centrifugal Compressor ◽  
Guide Vane ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Compressor Stage ◽  
Guide Vanes ◽  
Wet Gas ◽  
Compressor Performance

The introduction of variable inlet guide vanes (VIGVs) upfront of a compressor stage affects performance and permits tuning for off-design conditions. This is of great interest for emerging technology related to subsea compression. Unprocessed gas from the wellhead will contain liquid condensate, which affects the operational condition of the compressor. To investigate the effect of guide vanes on volume flow and pressure ratio in a wet gas compressor, VIGVs are implemented upfront of a centrifugal compressor stage to control the inlet flow direction. The guide vane geometry and test rig setup have previous been presented. This paper documents how changing the VIGV setting affects compressor performance under dry and wet operating conditions. The reduced performance effect and operating range at increased liquid content are of specific interest. Also documented is the change in the VIGV effect relative to the setting angle.

scholarly journals Performance Optimization of Ejector using Computation Fluid Dynamics

2020 ◽  
Vol 8 (5) ◽  
pp. 2905-2910
Keyword(s):  
Fluid Dynamics ◽  
Performance Optimization ◽  
Cfd Simulation ◽  
Experimental Testing ◽  
High Reliability ◽  
Fluid Velocity ◽  
Pressure Ratio ◽  
Operating Cost ◽  
Flow Characteristics ◽  
Operating Conditions

Ejector is a device used for carry low pressure fluids with no mechanical force, high pressure flow. This contains the main nozzle, chamber for suction, chamber for mixing and diffu ser.It is used in vaccum pumps, condensers, steam refrigeration, Because of its simple structure, gas mixing, pneumatic transport (no moving parts) and reliable operation. It is also used in pumps for lifting slurries and waste material containing solids from tanks and sumps. Due to their simplicity and high reliability, however, jet ejectors are widely used in industries with low efficie ncy. The project's goal is to optimize the efficiency of jet ejectors for each operating condition.Consequently, the primary fluid consumption and operating cost is minimized. A commercial computational fluid dynamics tool would be used to analyse the flow characteristics inside the ejector geometry. The results of the CFD simulation could be used to understand the effect of fluid velocity and pressure ratio on the ejector performance. The analysis would also be carried out by varying the primary and secondary nozzle dimensions. Performance of ejectors under various operating conditions is generally obtained through an experimental testing of prototype or scaled ejectors. The availability of performance parameters for such ejectors is limited, and experimental testing can be cost prohibitive.

An Investigation On the Discharge Coefficient of Compound Orifices in Rotating Disks

2021 ◽  
Author(s):  
Jiaxi Yan ◽  
Junkui Mao ◽  
Song Wei ◽  
Zhaolin Sun ◽  
Ranran Tian
Keyword(s):  
Discharge Coefficient ◽  
Positive Impact ◽  
Incidence Angle ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Static Condition ◽  
Operating Conditions ◽  
Confined Space ◽  
Empirical Formulas ◽  
Significant Difference

Abstract In the modern multi-shaft gas turbine engines, orifice is an important throttling element and the discharge coefficient of rotating orifices may vary considerably depending on the operating conditions, the geometry and surrounding environment. The influences of the rotating number and the pressure ratio on the rotating orifices flow characteristics are investigated in the present study. Besides, the effects of confined space, wall inclination angle (a) and the angle between the axis of orifice and the disk wall normal (ß) are also analyzed statistically. It is found that the rotating number has a significant effect on the discharge coefficient. As the rotating number increases from 0 to 0.6, the discharge coefficient reduces by about 47.88%. When rotating number is 0.74 and pressure ratio is 1.10, the discharge coefficient can be improved by 16.88% with a changes from 90° to 180°. The parameter, ß, affects discharge coefficient slightly in rotating condition. However, the maximum discharge coefficient is achieved with ß=0° in the static condition. The results also show that, a confined space weakens the effect of rotation, and changes the air flow direction in the inlet chamber, which also has a positive impact on the discharge coefficient. In the current research, it is found that there is a significant difference between the traditional empirical formulas used in the literature and the fitting result. By modifying the incidence angle and taking account of the influence of the angle of inclination, the maximum error was reduced from 56.79% to 3.16%

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