Brush Seal Element
Brush Element General Description & Quick Guide
FlowSimulator Brush Seal element models the leakage flow across the WSeal. This can be used only in Compressible (e.g. gas systems) analysis.
Figure: Brush Seal Inputs
Brush Seal Element Inputs
Table of the inputs for the Brush Seal Element.
Element Specific Brush Seal Input Variables  

Index  Field  Description 
1  Bristle Length  Length of Bristle 
2  Interference Length  Interference Length if the bristle type is Interference 
3  Cold Clearance  Cold Clearance (=0 for Interference type Bristle) 
4  Bristle Diameter  Diameter of the Bristle 
5  Cant Angle  Angle of Bristles 
6  No.of. Bristles  Number of Bristles per Circumferential length 
7  Fence Height  Fence Height of the Brush Seal 
8  Bristle Inner Dia  Inner Diameter of Bristle from Engine centerline 
9  Bristle Outer Dia  Outer Diameter of Bristle from Engine centerline 
10  Rotor Index (RPMSEL) 
Reference rotor index for usersupplied swirl. Stationary (Database Value = 0.0) Rotor 1 (Database Value = 1.0): Points to general data Shaft 1 Rotor Speed. Rotor 2 (Database Value = 2.0): Points to general data Shaft 2 Rotor Speed Rotor 3 (Database Value = 3.0): Points to general data Shaft 3 Rotor Speed Rotates with Air (database Value = 1.0): Element RPM is based on upstream fluid RPM 
11  Youngs Modulus  Young Modulus 
12  Swirl  Swirl Value for Swirl Carryover 
13  Tip Flow equation 
Flow equation

14  Solving methodology 
Solving methodology

15  Element Inlet Orientation: Tangential Angle (THETA) 
Angle between the element centerline at the entrance of the element and the reference direction. If the element is rotating or directly connected to one or more rotating elements, the reference direction is defined as parallel to the engine centerline and the angle is the projected angle in the tangential direction. Otherwise, the reference direction is arbitrary but assumed to be the same as the reference direction for all other elements attached to the upstream chamber.
THETA for an element downstream of a plenum chamber has no impact on the solution except to set the default value of THETA_EX. (See also THETA_EX) 
16  Element Inlet Orientation: Radial Angle (PHI) 
Angle between the element centerline at the entrance of the element and the THETA direction. (spherical coordinate system)
PHI for an element downstream of a plenum chamber has no impact on the solution except to set the default value of PHI_EX. (See also PHI_EX) 
17  Element Exit Orientation: Tangential Angle (THETA_EX) 
Angle between the orifice exit centerline and the reference direction. THETA_EX is an optional variable to be used if the orientation of the element exit differs from that of the element inlet.
The default value (THETA_EX = 999) will result in the assumption that THETA_EX = THETA.
Other values will be interpreted in the manner presented in the description of THETA. 
18  Element Exit Orientation: Radial Angle (PHI_EX) 
Angle between the orifice exit centerline and the THETA_EX direction.
PHI_EX is an optional variable to be used if the orientation of the element exit differs from that of the element inlet.
The default (PHI_EX = 999) will result in the assumption that PHI_EX = PHI.
Other values will be interpreted in the manner presented in the description of PHI. 
19  Portion of Ustrm Chamb. Dyn. Head Lost (DQ_IN)  Inlet dynamic head loss. Refer General solver theory sections for more details about this input 
Brush Seal Element Theory Manual
Assumptions
Porous Flow Model
 Flow is isothermal
 Losses due to radial flow across the bristles are not accounted
 Flow area is equal to back plate area exposed to the downstream only
 Bristle liftoff is modeled with coupling with the simplified onedimensional deflection model
Tip clearance leak flow model
 Flow is incompressible through the clearance
 Bristles are treated to be equivalent of one tooth of labseal
 A constant CD = 0.6 is assumed by treated the gap as a sharpedged orifice
Brush seal Flow calculations
Nomenclature:  
: Mass flow rate  Specific heat Ratio 
Tt: Total Temperature  R: Gas Constant 
Pt: Total pressure  Ts: Static Temperature 
Ps: Static pressure  ρ: Density 
gc: Gravitational Constant  G: Mass Flux 
D:Diamter  N: Total Number of Bristles 
f:Friction Factor  h_{f}:Axial Clearane 
N_RE:Reynolds Number  θ:Cant Angle 
Δp:Pressure Difference  B_{ρ}:Bristle Density 
j: Number rows in the azimuthal direction  i: Number rows in the axial direction 
l:Length  y:Max Axial Deflection 
F_{h}:Fence Height  C_{c}:Cold Clearance 
BL_{DN}:Blowdown  
Subscripts:  
in: Upstream station  ex: Downstream station 
b:Bristle  Inter: Interference 
b,o:Bristle Outer  b,i:Bristle Inner 
If (C_{c}=0) & (l_{inter}=0)→No Blow Down
If (C_{c}>0) & (l_{inter}=0)→Blow Down exixts
If (C_{c}=0) & (l_{inter}>0)→No Blow Down
If Blow Down exists, then
Calculate “Bristle Leak” through modified Chupp method with h_{f}=0
Calculate “Leak rotor Tip” through Alexiou /Yan/Orifice Formulation.
Calculate “Effective Thickness without Blowdown” for “Brush Leak = Bristle Leak + Leak rotor Tip” with h_{f}=0
Calculate “Effective Thickness inline” for “Bristle Leak” with h_{f}=0
Total Mass flow rate is W=Bristle Leak+Leak Rotor Tip

Calculate “Bristle Leak” through modified Chupp method

Calculate “Leak rotor Tip” through Alexiou /Yan/Orifice Formulation.
Flow through the Bristles (Porous Flow) Modified Chupp method
Clearance calculations – Axial (hf)
If (Clearance >=F_{h}), Clearance = F_{h}
Max Axial Deflection(y)Calculation
Effective Thickness Calculation
Flow Through the Rotor Tip Clearance Alexiou Model
Flow Through the Rotor Tip Clearance Orifice Equation
Flow Through the Rotor Tip Clearance Yans Formulation
Brush Seal Element Outputs
The following listing provides details about Brush Seal Element output variables.
Element Specific Brush Seal Input Variables  

Index  Field  Description  Units 
1  Bristle Length  Length of Bristle (User Input)  in, m 
2  Interference Length  Interference Length if the bristle type is Interference (User Input)  in, m 
3  Cold Clearance  Cold Clearance (=0 for Interference type Bristle) (User Input)  in, m 
4  Cant Angle  Angle of Bristles (User Input)  deg 
5  Bristle Diameter  Diameter of the Bristle (User Input)  in, m 
6  No.of. Bristles (Bristle Density)  Number of Bristles per Circumferential length (User Input)  1/in, 1/m 
7  Fence Height  Fence Height of the Brush Seal (User Input)  in, m 
8  Youngs Modulus  Young Modulus (User Input)  psi, mPa 
8  Bristle Inner Dia  Inner Diameter of Bristle from Engine centerline (User Input)  in, m 
9  Bristle Outer Dia  Outer Diameter of Bristle from Engine centerline (User Input)  in, m 
10  XK  Swirl (User Input)  unitless 
11  RPM  Element RPM is based on upstream fluid RPM. (User Input)  Rad/min 
12  Solving methodology 
Solving methodology 1.Modified Chupp 
(None) 
13  Tip Flow equation 
Flow equation

(None) 
14  BlowDown_New  BlowDown  in, m 
15  Cold Clearance Calculated  Cold Clearance calculated  in, m 
16  Bristle Leak  Bristle leak  Lbm/s, kg/s 
17  Leak Rotor Tip  Leak Rotor tip  Lbm/s, kg/s 
18  Bristle Leak with BlowDown  Bristle Leak with BlowDown  Lbm/s, kg/s 
19  Leak Rotor Tip with BlowDown  Leak Rotor Tip with BlowDown  Lbm/s, kg/s 
20  Brush Leak  Brush Leak  Lbm/s, kg/s 
21  Effective Thickness without Blowdown  Effective Thickness without Blowdown  in, m 
22  Effective thickness inline  Effective thickness inline  in, m 
23  Effective thickness with Blowdown  Effective thickness with Blowdown  in, m 
24  Max_Axial_Def  Max_Axial_Def  in, m 
25  CLR_Axial_Def  CLR_Axial_Def  in, m 
26  Clearance  Clearance  in, m 
27  MDOT  Mass flow rate  Lbm/s, kg/s 
28  EXMN  Exit Mach number  (None) 
29  EXVEL  Exit velocity  ft/s, m/s 
Validation
References
 Dogu, Y, Aksit, M, E., Demiroglu, M., Dinc, S, O., “Evaluation of flow behavior for clearance brush selas”, J. Engg Gas Turbines and Power, 130, 2008.
 Andres, L, S., Baker, J., Delgado., “Measurements of leakage and power loss in a hybrid seal”, J. Engg Gas Turbines and Power, 131, 2009.
 Dogu, Y., “Investigation of brush seal flow characteristics using bulk porous medium approach”, 127, 2005.
 Dogu, Y., Aksit, M., “Brush seal temperature distribution analysis”, J. Engg Gas Turbines and Power, 128, 2006.
 Zhao, H., Stango, R. J., “Role of distributed ibterbristle friction force on brush seal hysterisis”, J. Tribology, 129, 2007, pp199.
 Sayma, A, I., Breard, C., Vahdati, M., Imregun, M., “Aeroelasticity analysis of airriding seals for aero engine applictions, J. Tribology, 124, 2002, PP607
 Dogu, Y., Aksit, M, F., “Effect of geometry on brush seals pressure and flow fields – PartII : Backing plate configurations”, J. Turbomachinery, 128, 2006.
 Dogu, Y., Aksit, M, F., “Effect of geometry on brush seals pressure and flow fields – PartI : Front plate configurations”, J. Turbomachinery, 128, 2006.
 Chen, L, H., Wood, P, E., Jones, T, V., Chew, J, W., “Detailed experimental studies of flow in large scale brush seal model and a comparison with CFD predictions”, Trans ASME, 122, 2000.
 Chew, J, W., Hogg, S, I., Porosity modeling of brush seals”, J. Tribology, 119, 1997.
 Lelli, D., Chew, J, W., Cooper, P., “Combined threedimensional fluid dynamics and mechanical modeling of brush seals”, Trans ASME., 128, 2006.
 Chupp, R, E., Holle, G, F., “Generalized circular brush seal leakage through randomly distributed bristle bed”, J. Turbomachinery, 118, 1996.
 Turner, M, T., Chew, J, W., Long, C, A., “Experimental investigation and mathematical modeling of clearance brush seals”, J. Engg Gas Turbines and Power, 120, 1998.
 Owen, J, M., Zhou, K., Pountney, O., Wilson, O., Lock, G., “Prediction of ingress through turbine rim selas – Part1, externally induced ingress”, J. Turbomachinery, 134, 2012
 Sangan, C, M., Pountney, O, J., Zhou, K., Wilson, M., Owen, J, M., Lock, G., “Experimental measurements of ingestion through turbine rim sealspart1, externally induced ingress”, J. Turbomachinery, 135, 2013.
 Owen, J, M., “Prediction of ingestion through turbine rim seals,part2 externally induced and combined ingress, J. Turbomachinery, 133, 2011.
 Sangan, C, M., Pountney, O, J., Zhou, K., Wilson, M., Owen, J, M., Lock, G., “Experimental measurements of ingestion through turbine rim sealspart12 rotationally induced ingress”, J. Turbomachinery, 135, 2013.
 Owen, J, M., “Prediction of ingestion through turbine rim seals,part1 externally induced and combined ingress, J. Turbomachinery, 133, 2011.
 Owen, J, M., “thermodynamic analysis of buoyancy induced flow in rotating cavities”, J. Turbomachinery, 132, 2010.
 Pascovici, D., Cicone, T., “A simplfiied elsto thermo tribological model for brush seals”, http://www.omtr.pub.ro/t_cicone/stiintific/publicatii/Brush Sinaia HT
 Lattime, S, B., Braun, M, J., Choy, F, K., Hendricks, R, C., Steinetz, R, M., “Rotating brush seal”, Int. J. Rotating machinery, 8(20, 153160, 2002.
 Carlie, J, A., Hendricks, R, C., “Brush seals leakage performance with gaseous working fluids at static and low rotor speed conditions, J. Engg. Gas turbines and power, 115, 1993.
 Hendricks, R, C., Flower, R., Howe, H., “ A brush seal program modeling and developments”, Int. J. of Rotating turbomachinery, 4(2), 9196, 1997.
 Bayley, F, J., Long, C, A., A combined experimental and theoretical study of flow and pressure distributions in a brush seal”, Trans. ASME, 115, 1993.
 Pugache, A, O., Helm, P., “Calibration of porous medium models for brush seals”, Proc. IMechE, 223, Part.A, J. Power and Energy, 2009.
 Li, J., Qiu, Bo., Feng, Z., “Experimental and numerical investigations on the leakage flow characteristics of the labyrinth brush seal”, J. Engg. Gas Turbines and power, 134, 2012.
 Rhode, D., Hibbs, R., “A new efficient model for the computation of flow over shear layer driven cavities:part2: Assesment of labyrinth seal leakage”, AIAA, 25^{th} Joint propulsion conference, 1989.
 Braun, M., Hendricks, R, C., “Effect of brush seal morphology on leakage and pressure drops”, 27^{th} Joint propulsion conference, 1991.
 Kudriavstev, V, V., Braun, M, J., “Model developments for the brush seal numerical simulation”, J. Propulsion and power, 12 (1), 1996.
 Holloway, P. E., Mehta, J., Rosado, L., Cooke, J., Hubley, C., “Rotating brush seal experimental performance evaluation “, AIAA, 44^{th} joint propulsion conference, 2008.
 Mehta, J., Holloway, P, E., ., Rosado, L., Cooke, J., Hubley, C., “Innovative rotating intershaft brush seal for sealing between rotating shaftsPartII Modeling of brush seal leakage flows”, 42^{nd} Joint propulsion conference, 2006.
 Chupp, R, E., Holle, G, F., “Simple effective thickness model for circular brush seals”, 28^{th} joint propulsion conference, 1992.
 Chupp, R, E., Nelson, p., “Evaluation of brush seals for limited life engines”, J. propulsion and power, 9 (1), 1993.
 Dowler, A., Chupp, R, E., Holle, G, F., “Simple effective thickness model for circular brush seals”, AIAA, 28^{th} Joint propulsion conference, 1992.
 Hendricks, R, C., Braun, M, J., Choy, F., Mullen, R, L., “A bulk flow model of brush seal system”, International gas turbines and aero engine congress, 1991.