gt2009-59072 hybrid brush seal force coefficients r otordynamic f orce c oefficients of a hybrid...

GT2009-59072 Hybrid Brush Seal Force Coefficients

ROTORDYNAMIC FORCE COEFFICIENTS OF A HYBRID BRUSH SEAL:

MEASUREMENTS AND PREDICTIONS

Luis San Andres Jose Baker Mast-Childs Professor Project Engineer Texas A&M University KBR, Inc.

Adolfo DelgadoMechanical Engineer

GE Global Research Center

ASME GT2009-59175

Supported by Siemens Power Generation

accepted for journal publication

ASME Turbo Expo 2009: Power for Land, Sea, and Air


Justification

Improved Brush Seal Technology Offers:Higher engine performance with less parasitic

leakageImproved engine stability and reduced engine

vibrationLower operating and maintenance costs

Trends in High Performance Turbomachinery: - Higher speeds - Extreme operating temperatures and pressures

Issues of Importance - Increase in secondary flows (parasitic leakage)

- Increase in specific fuel consumption and COST - Reduction in power delivery - Potential for rotordynamic instability


Brush seals vs. Labyrinth Seals

•Handle large amplitudes of vibration

•Less axial space

•Reduced secondary flow leakage (90%)

Advantages

Disadvantages

•Pressure differential limitation

•Wear and local thermal distortion

Shoed Brush Seal (SBS)

Advantages

• Incorporates metal shoes

at the free end of the bristle

– Reduces and eliminates wear

“shoes lift off”

• Bi-directional shaft rotations

Disadvantages

• Pads “roll over” under high pressure differential

Hybrid Brush Seal (HBS) Advantages

• All the advantages of 1st generation SBS

• Reduced leakage (~36%) over 1st

generation shoed brush seal

• Pads connected via EDM-webs, no

spot welds between pads and bristles

• Higher axial stiffness, prevents pad

motions at high pressure differentials


LITERATURE REVIEW: Hybrid Brush Seals

• Justak introduces a film riding seal

with hydrodynamic pad action. • Delgado and San Andrès measure leakage and structural characteristics of a shoed-brush seal.• San Andrès et al. measure leakage and power loss in a Hybrid Brush Seal built with interference. HBS has approximately 36% less leakage then a shoed brush seal.• San Andrès & Ashton compare leakage performance of three seals at high temperature

(U.S. Patent 7,182,345)

(Sealing Technology, 2005)

(ASME GT2008-50532 )

(2009 STLE Meeting)

•Chupp et al. (2006): comprehensive review on sealing technology, including brush seals and shoed brush seals.


Structural parametersKshaft= 243 lbf/in (42.5 kN/m)Ms+d= 9.8 lb (4.45 kg)

: 0.01 % (damping ratio)

Installation:6.550” diameter brush seal Max. air Pressure: 60 psig Shaker (20 lb max)

10 20 30 40 50 60 70 80 90 100

cm

Supply pressure inlet

Eddy current sensosrs

Pressure Vessel

Flexible coupling

Quill shaft

Rotor StingerElectromagneticShaker

DC Motor

Supporting springs

Rollerbearing assembly

Eddy current sensor

Spring

Ball bearing

Shaft

Disk

High pressure air

Flow

Flow Flexible coupling to motor

Hybrid brush sealDetail of brush seal test rig

Experimental Facility

Disc

Ps Pe

Seal

Flow


Test Hybrid Brush Seal (HBS)

High Pressure Side Low Pressure Side

Bristle Bed

Pad or shoe

Back Plate

Spring Lever Mechanism

* Close-up courtesy of Advanced Technologies Group, Inc.

Physical Properties SI unit English Unit Rotor diameter, Dj 167.1 mm 6.580 in

Brush seal (pads) inner diameter, Dsi 166.4 mm 6.550 in Brush seal (retainer) outer diameter, Do 183.1 mm 7.210 in

Brush seal width, Bw 8.53 mm 0.336 in Radial Interference between rotor and seal, Ri 0.381 mm 0.015 in

Number of pads 20 Width of pads 7.23 mm 0.331 in

Bristle lay angle, α 45 deg. - Bristle modulus of elasticity, E 22.48x105 bar 32.6x106psi Bristle density (circumference) 850 bristle/cm 2200 bristle/ in

Courtesy of Advanced Technologies Group®

Disc

Ps Pe

Seal

Flow


Identification of Rotordynamic Force Coefficients

iy

ixx

yyyx

xyxx

yyyx

xyxx

yyyx

xyxx

F

FF

y

x

CC

CC

y

x

KK

KK

y

x

MM

MM

0

Eddy current sensors

Y

X

Ω

Electromagnetic Shaker

Load Cell

Stinger

Disk

HBS

Kxx, Cxx

Kxy, Cxy

Kyx, Cyx

Kyy, Cyy

X

Y

For rotor centered operation:


xxyxx FyZxZ

0 yZxZ yyyx

yxiCMKZ ,2 ,

Identification of HBS rotordynamic force Coefficients

Identification at excitation frequency (ω) ≠ rotor speed (Ω)

System Impedances

Impedance Function

yyxx ZZ and yxxy ZZ


Effect of rotor speed on rotor-HBS natural frequency

-0.1

-0.075

-0.05

-0.025

0

0.025

0.05

0.075

0.1

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

Axial Location, [m]

Sh

aft

Ra

diu

s,

[m]

-0.1

-0.075

-0.05

-0.025

0

0.025

0.05

0.075

0.1

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

Axial Location, [m]

Sh

aft

Ra

diu

s, [

m]

Hybrid Brush Seal location

Axial Location, [m]

Roller bearing support

Disk

Shaft

Location of external force

Location of displacement measurements

Sh

aft

Ra

diu

s, [m

]

Gyroscopic effects negligible

for test rotor speeds

(600 and 1,200 rpm [20 Hz])

RotorSpeed [RPM]

1st Backward Nat. Frequency, [Hz]

1st Forward Nat. Frequency, [Hz]

2nd Forward Nat. Frequency, [Hz]

3rd Forward Nat. Frequency, [Hz]

0 30.5 30.5 146 1351

600 29.7 31.4 154 1351

1200 28.8 32.2 163 1351

Axial Location, z [m]

Sha

ft R

adiu

s [m

]


40 40 120 200 280 360 4400

250

500

750

1000

Frequency [Hz]

X -

Dis

plac

emen

t [um

]

40 40 120 200 280 360 4400

250

500

750

1000

Frequency [Hz]

Y -

Dis

plac

emen

t [um

]

32 Hz Due to excitation

Synchronous with speed (1X)

32 Hz

Due to excitation

22 N

22 N

Synchronous with speed (1X)

Cross coupling effects under rotation

For load along X direction,

rotor (X) motions

>>> cross (Y) motions

1X motions always small compared to

excitation

Load=22 N600 rpm

Frequency [Hz]

X-d

ispl

acem

ent

[m

]Y

-dis

plac

emen

t [m

]

Frequency [Hz]

X

Y


0 20 40 60 80 1001 106

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re(Z

xx1)

[N/m

]

0 20 40 60 80 1001 106

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re(Z

xx1)

[N/m

]

0 20 40 60 80 1001 106

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re(Z

xx1)

[N/m

]

0 20 40 60 80 1001 106

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re(Z

xx1)

[N/m

]

0 20 40 60 80 1001 10

6

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re

(Z

xx1

) [N

/m]

0 20 40 60 80 1001 10

6

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re

(Z

xx1

) [N

/m]

0 20 40 60 80 1001 106

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re(Z

xx1) [N

/m

]

0 20 40 60 80 1001 10

6

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re(

Zxx1

) [N

/m]

0 20 40 60 80 1001 10

6

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re(

Zxx1

) [N

/m]

0 20 40 60 80 1001 10

6

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re(

Zxx1

) [N

/m]

Test Data 600 rpm, Pr = 1.7 1200 rpm, Pr = 1.7 600 rpm, Pr = 2.4 1200 rpm, Pr = 2.4

0 20 40 60 80 1001 10

6

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re

(Z

xx1

) [N

/m]

0 20 40 60 80 1001 10

6

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re

(Z

xx1

) [N

/m

]

0 20 40 60 80 1001 10

6

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re

(Z

xx1

) [N

/m]

0 20 40 60 80 1001 10

6

5 105

0

5 105

Test DataModel

Frequency [Hz]

Re

(Z

xx1

) [N

/m]

Model

Kxx - 2Mxx

Dynamic Stiffness vs. FrequencyLoad = 22 N, frequency 25-80Hz )( 22 yx

xFZ x

xx

Model reproduces

the measured real part of

impedance.Little effect of

pressurization

2xx xxK M

Model

TESTs

Frequency [Hz]

Re

(Zxx

) [k

N/m

]


0 20 40 60 804 104

2 104

0

2 104

4 104

Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)

Frequency [Hz]

Re(

Zxy

) [N

/m]

0 20 40 60 804 104

2 104

0

2 104

4 104


Frequency [Hz]

Re(

Zxy

) [N

/m]

0 20 40 60 804 10

4

2 104

0

2 104

4 104

Zxy=-Zyx (Test Data)Zxy=-Zyx (Model)Zxy=Zyx (Test Data)Zxy=Zyx (Model)

Frequency [Hz]

Re(F

/X) [N

/m

]

0 20 40 60 804 10

4

2 104

0

2 104

4 104


Frequency [Hz]

Re(F

/X

) [N

/m

]

0 20 40 60 804 104

2 104

0

2 104

4 104


Frequency [Hz]

Re

(F

/X

) [N

/m

]

0 20 40 60 804 10

4

2 104

0

2 104

4 104


Frequency [Hz]

Re(F

/X) [N

/m

]

Model

Test Data

Pr = 1.7, Zxy =- Zyx

1200 rpm

600 rpm

0 20 40 60 804 104

2 104

0

2 104

4 104


Frequency [Hz]

Re

(Zxy

) [N

/m]

0 20 40 60 804 104

2 104

0

2 104

4 104


Frequency [Hz]

Re(

Zxy

) [N

/m]

0 20 40 60 804 10

4

2 104

0

2 104

4 104


Frequency [Hz]

Re(F

/X) [N

/m]

0 20 40 60 804 10

4

2 104

0

2 104

4 104


Frequency [Hz]

Re(F

/X

) [N

/m

]

0 20 40 60 804 104

2 104

0

2 104

4 104


Frequency [Hz]

Re

(F

/X

) [N

/m

]

0 20 40 60 804 10

4

2 104

0

2 104

4 104


Frequency [Hz]

Re(F

/X) [N

/m]

Model

Test Data

1200 rpm

600 rpm

Pr = 2.4, Zxy =- Zyx

Cross-coupled Stiffness vs. FrequencyLoad = 22 N, frequency 20-80Hz

•Identified cross-coupled mass is nearly 0 kg.•Identified cross-coupled stiffness (Kxx = -Kyx) is estimated as a constant independent of excitation frequency. •Kxy doubles as rotor speed increases from 600 and 1,200 rpm for both pressure conditions

x

yZZZ xxyxxy

Pressure ratio Pr=1.7 Pr=2.4

Rotor Speed [rpm], Ω600 1200 600 1200

Stiffness [kN/m], Kxy 8.8 15 2.7 6.6

Mass [kg.], Mxy 0 0 0 0


Equivalent Viscous Damping (Cxx~Ceq) vs. Frequency

Damping decreases with frequency, with

little effect of supply

pressure. Minimum value at test system

natural frequency (~32

Hz)

Pr=1.7

600 rpm

Pr=2.4

1200 rpm

Supply Pressure/Exhaust Pressure


Force coefficiensts: system & sealLoad = 22 N, frequency 25-80Hz

No rotationTests with rotor spinning

Pressure ratio Pr = 1.0 Pr=1.7 Pr=2.4

Rotor Speed [rpm], Ω 0 600 1200 600 1200

Stiffness [kN/m], Kxx120

108 98 130 124

Mass [kg.], Mxx2.11 2.62 2.54 2.43 2.39

R2 (correlation factor)Dynamic stiffness (Kxx – Mxxω

2)0.97 0.98 0.98 0.98 0.98

HBS stiffness[kN/m], Ks 93 103 89 135 128

HBS Dry Friction coefficient, μ

0.660.39 0.36 0.37 0.38

HBS Loss Factor coefficient, 0.42 0.29 0.26 0.33 0.34


HBS predicted stiffness vs. frequencyFrequency 25-100 Hz

Predicted HBS stiffness (Ksxx)

drops slightly in range from 20-

100 Hz.Tests show nearly

constant Ksxx

Pressure (Pr = Ps/Pd) has negligible effect on seal direct

stiffness, Ksxx

60

70

80

90

100

110

120

130

140

0 20 40 60 80 100 120

Frequency [Hz]

Stif

fnes

s C

oeffi

cien

ts [k

N/m

]

60

70

80

90

100

110

120

130

140

0 20 40 60 80 100 120

600 rpm

1,200 rpm

60

70

80

90

100

110

120

130

140

0 20 40 60 80 100 120

Ksxx = Ksyy, Pr = 1.0Ksxx = Ksyy, Pr = 1.7Ksxx = Ksyy, Pr = 2.4Ksxx = Ksyy, Pr = 1.0

Ksxx = Ksyy, Pr = 1.7Ksxx = Ksyy, Pr = 2.4

HBS Equivalent Stiffness, Ks HBS Equivalent Stiffness, Ks

HBS Measured Stiffness, Ks

60

70

80

90

100

110

120

130

140

0 20 40 60 80 100 120

Ksxx = Ksyy, Pr = 1.0






HBS Equivalent Stiffness, Ks HBS Equivalent Stiffness, Ks

HBS Measured Stiffness, Ks

Code: XLTPGASBEAR®

Frequency [Hz]

Stif

fnes

s C

oeff

icie

nts

[kN

/m]

ASME GT2004-53614


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120

Frequency [Hz]

Dam

ping

Coe

ffici

ents

[kN

-s/m

]

1200 rpm

Increasing loss factor (

HBS viscous damping coeff. vs. frequencyFrequency 25-100 Hz

HBS direct damping (Csxx) decreases with excitation frequency. Loss factor coefficient () represents physically seal structural (hysteresis) damping

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120

Cxx = Cyy, = 0.25Cxx = Cyy, = 0.55Equivalent Viscous Damping, CeqCxx = Cyy, = 0.25Cxx = Cyy, = 0.55Equivalent Viscous Damping, Ceq

1200 rpm


Pr = 2.4

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120


1200 rpm


Pr = 1.7

1,200 rpm

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 1200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120

1200 rpm

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120

1200 rpm

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120

Frequency [Hz]

Dam

ping

Coe

ffici

ents

[kN

-s/m

]

1200 rpm


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120


1200 rpm


Pr = 1.7

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120


1200 rpm


Pr = 2.4

600 rpm

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 1200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 1200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120

Increasing loss factor () Increasing loss factor ()


Conclusions•Prior to shaft rotation, seal pads lift-off due to hydrostatic effect from pressurization. Break-away torque is 90% less when seal is pressurized. Rotor speed has negligible effect on HBS drag torque (power loss) and leakage.

•A structural loss factor (γ) and a dry friction coefficient() effectively characterize the energy dissipation mechanism of the HBS.

•HBS direct stiffness (Ksxx = Ksyy) decreases minimally with rotor increasing rotor speed for Pr = 1.7 and 2.4.

• HBS cross-coupled stiffness (Ksxy = -Ksyx) is one order of magnitude smaller than direct stiffnesses.

•HBS direct viscous damping coefficients decrease with increasing excitation frequency.


Thanks to

• Siemens Power Generation,

• Advanced Technologies Group (Mr. John Justak) www.advancedtg.com

Acknowledgments

Questions ?

Learn more at http://phn.tamu.edu/TRIBGroup


HIGH TEMPERATURE SEAL FACILITY

1 Hot air inlet 5 Optical displacement sensor2 Pressurized cylinder & shaft 6 Centering mechanism

3 Radial support bearings 7 Coupling and quill shaft4 Disc and test seal location 8 Electric drive motor

8

3

2

3

4

6

1

7

Flow in (supply pressure)

Flow out (ambient pressure) Pe =101 kPa

0 10 20

cm

Voltage Power OutputHeater 240 V 12 kW 300°CMotor 90 V 850 W 3,000 rpm

MaximumProperties Magnitude

Specific gas constant, R 287 J/kg-K

Supply pressure, Ps 101-760 kPa

Inlet temperature, T 298-573 K

Exhaust pressure, Pe 101 kPa

Ambient temperature 298 K

2009 STLE Annual Meeting, May 2009


0

5

10

15

20

25

30

35

40

1.0 1.5 2.0 2.5 3.0 3.5 4.0

Pressure Ratio [Ps/Pe]

Flo

w F

ac

tor

[kg

-K0

.5/(

MP

a-m

-s)]

Max. air temperature (300ºC) & rotor speed (3 krpm)

Compare Leakage from Three Seals

0

5

10

15

20

25

30

35

40

1.0 1.5 2.0 2.5 3.0 3.5 4.00

5

10

15

20

25

30

35

40

1.0 1.5 2.0 2.5 3.0 3.5 4.0

Labyrinth Seal

Brush Seal

Hybrid Brush Seal

•Air temperature and rotor speed affect little the flow

factor. Show comparisons at max conditions

• HBS has lower flow factor than both the labyrinth seal

(38%) and the brush seal (61%)

• The brush seal and HBS begin with same clearance.

HBS is more effective in reducing leakage

Flow factor

DP

Tm

s

2009 STLE Annual Meeting, May 2009


Backup slides


HP LP

ROTOR

Pad profile

Backplate

Cantilever beam

4.445 mm

0.254 mm

7.750 mm

Front plate

Bristle pack

Back plate 16.674 mm

Hybrid brush seal profile section

HBS Pad Lift Off upon Pressurization

Ps

Pd

ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505


0.0

5.0

10.0

15.0

20.0

25.0

30.0

1.0 1.5 2.0 2.5 3.0 3.5Pressure Ratio, Pr

Mas

s F

low

Rat

e [g

/s]

0.0

5.0

10.0

15.0

20.0

25.0

30.0

1.0 1.5 2.0 2.5 3.0 3.50.0

5.0

10.0

15.0

20.0

25.0

30.0

1.0 1.5 2.0 2.5 3.0 3.5

HBS Leakage (No Shaft Rotation)

Measured HBS leakage is ~ 36% less than that for

a 1st generation

SBS over the test supply

pressure range

SBS

HBS

Supply Pressure = 5 to 30 psig

Pressure ratio, Pr

Lea

kag

e [g

/s]



0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

1.0 1.5 2.0 2.5 3.0 3.5Pressure Ratio, Pr

Effe

ctiv

e C

lear

ance

[mm

]

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

1.0 1.5 2.0 2.5 3.0 3.50.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

1.0 1.5 2.0 2.5 3.0 3.5

Calculated Effective Clearance

Effective clearance

(CE) as if one tooth laby seal

.

( 273.15)E

u

m Tc

P D

SBS

HBS


Pressure ratio, Pr

Cle

aran

ce [m

m]



Seal leakage is proportional to pressure ratio

(discharge/exit). Little

dependency on rotor speed.

0.0

5.0

10.0

15.0

20.0

25.0

30.0

1.0 1.5 2.0 2.5 3.0 3.5

Pressure Ratio, Pr

Mas

s F

low

Rat

e [g

/s]

Static Condition

600 RPM

1300 RPM

HBS Leakage vs. Pressure Drop

Pressure ratio, Pr

Leak

age

[g/s

]




0.0

2.0

4.0

6.0

8.0

10.0

1 1.5 2 2.5 3

Pressure Ratio, Pr

Sea

l Dra

g T

orq

ue

[N

-m]

Break-away Torque

HBS Break-Away Torque vs. Pressure Ratio

As pressure increases from Pr =

1.0 to 1.7, the break-away torque

(i.e. no rotation)

drops by ~ 75%

Pads lift-off prior to shaft rotation due to the generation of a hydrostatic gas film as the pressure difference across the seal increases

Pressure ratio, Pr

HB

S D

rag

To

rqu

e [

N-m

]



With external pressurization (Pr =

1.0 to 1.7), HBS Power

losses decrease by ~ 90% over test

rotor speed range Pads lift-off due to the generation of hydrodynamic gas-film eliminating

contact forces at the rotor/pads interface

HBS Power Loss vs. Speed & Feed Pressure

0

100

200

300

400

500

600

0 500 1000 1500Rotational Speed [RPM]

HB

S P

ow

er

Lo

ss [

W]

Pr = 1.7 Pr = 2.4

Pr = 1.0 (No external pressurization)

0

100

200

300

400

500

600

0 500 1000 1500

0

100

200

300

400

500

600

0 500 1000 1500

Pr = 1.0 (No external pressurization)

Pr = 1.7

Pr = 2.4 ΔP +

Rotor Speed [RPM]

HB

S P

ower

Los

s [W

]



Fext x

L

Ks

ss

z

Ls Lf

Fext

Lf =244 mm Lf =221 mm L= 248 mm

Dynamic Load Tests (no shaft rotation)

exteqeqeq FxCxKxM

Equivalent Test System

Meq

Keq

Ceq

Fext

x Lf =244 mm Lf =221 mm L= 248 mm

ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655


Harmonic force & displacements

Impedance Function

Work External

Viscous Dissipation

tixex tiexteFF

eqeqeq CiMKx

FZ )( 2

extFW x dt

xFxKE eqeqdis 42

2xCE eqdis

Parameter Identification (no shaft rotation)

DRY FRICTION &

STRUCTURAL DAMPING



HBS Structural CoefficientsLoad = 63 N, frequency: 20-100 Hz (no shaft rotation)

Hybrid Brush Seal

Pressure ratio* Pr = 1.0 Pr = 1.7 Pr = 2.4 Pr = 3.0 Stiffness [kN/m] 93 (±5) 130 (±6) 141 (±7) 141 (±7) Dry Friction coefficient, μ 0.66 0.51 0.64 0.69 Loss Factor coefficient, γ 0.42 0.40 0.27 0.22

*:atmospheric discharge pressure

• HBS stiffness increases slightly as supply pressure increases (~35% for pressure ratios: 1 to 3).

•Dry friction coefficient increases ~5 % due to increase in contact forces between seal components•Loss factor (structural damping) decreases due to stiffening effect of increasing pressure differential across seal



Frequency [Hz]

Re(

F/X

) [N

/m]

Frequency [Hz]

Re(

F/X

) [N

/m]

Frequency [Hz]

Re(

F/X

) [N

/m]

Frequency [Hz]

Re

(F/X

) [k

N/m

]

0 20 40 60 80 100 120

-400

-300

-200

-100

0

100

200

300

400

Keq – Meqω2

Pr=1.7Pr=1.7

Frequency [Hz]

Re(

F/X

) [N

/m]

Pr=1.7Pr=1.7

Frequency [Hz]

Re(

F/X

) [N

/m]

Pr=3.0Pr=3.0

Frequency [Hz]

Re(

F/X

) [N

/m]

Pr=3.0Pr=3.0

Frequency [Hz]

Re(

F/X

) [N

/m]

Pr=2.4Pr=2.4

Frequency [Hz]

Re(F/X

) [N/m]

Pr=2.4Pr=2.4

Frequency [Hz]

Re(F

/X) [

N/m]

Model Test Data Pr = 1.7

Pr = 2.4

Pr = 3.0

Pr = 1.7

Pr = 2.4

Pr = 3.0

HBS Dynamic Stiffness vs. Frequency (no shaft rotation)

ModelTESTs

Load = 63 N, frequency: 20-100Hz

Model reproduces real part of

the impedance

under the given supply

pressure conditions.

Frequency [Hz]

Re

(F/x

) [k

N/m

]

2eqeq MK



Load = 63 N, frequency 20-110Hz

0 20 40 60 80 100 120 100

1000

10000

Frequency, [Hz]

Log

(Ceq

), [N

-s/m

]

0 20 40 60 80 1000

2000

4000

6000

8000

Pr = 1.7

0 20 40 60 80 1000

2000

4000

6000

8000

Pr = 2.4

0 20 40 60 80 1000

2000

4000

6000

8000

Pr = 3.0

Test Data Test Data

ΔP +

Equivalent damping increases

slightly with pressure

differential. Results typical of a system with dry-friction & material damping

energy dissipation

HBS Equivalent Viscous Damping vs. Frequency (no shaft rotation)

x

FKC eqeq

eq

4

Frequency [Hz]

Log

(Ceq

) [N

-s/m

]

gt2009-59072 hybrid brush seal force coefficients r otordynamic f orce c oefficients of a hybrid...

Documents

shoed brush seal

diameter brush seal

motor hybrid brush seal

shoed brush seals

hybrid brush seals justak

film riding seal

leakage performance

air pressure