Transcript Parameter Identification of an End Sealed SFD Part II

ASME
Turbo Expo 2011
Power for
Sea and
Air June
6-10, 2011, Vancouver, BC
GT2011-45274
Grooved
OilLand,
Seals:
Force
Coefficients
A Novel Bulk-Flow Model for Improved
Predictions of Force Coefficients in
Grooved Oil Seals Operating Eccentrically
Luis San Andrés
Adolfo Delgado
Mast-Childs Professor
Texas A&M University
Mechanical Engineer
GE Global Research Center
ASME GT2011-45274
accepted for journal publication
Presentation available at http://rotorlab.tamu.edu
1
Supported by TAMU Turbomachinery Research Consortium
GT2011-45274
Grooved Oil Seals: Force Coefficients
Oil supply (PS+P)
Oil Seals
commonly used to prevent
leakage of process fluid in
centrifugal compressors.
Anti-rotation pin
Seal loading
spring
Inner seal
Outer seal
- Locked oil seal rings can induce
instability in compressors.
- A common remedy: seals are
grooved to reduce cross-coupled
stiffness and lower lock-up forces
Process
Gas (PS)
Pa
Outer seal
land
Inner seal
land
Shaft
Oil seal in a compressor [1]
Kirk, R., 1986, “Oil Seal Dynamic Considerations for Analysis of
Centrifugal Compressors,” Proc. 15th Turbomachinery Symposium,
Houston, TX, pp. 25-34.
2
GT2011-45274
Grooved Oil Seals: Force Coefficients
Predictive Models
Semanate and San Andrés, (1993)
- Bulk flow equation model
- Grooves should reduce force coefficients
by a factor of four, i.e.
KXY (1 land)= 4 KXY(2 lands)
CXX (1 land)= 4 CXX(2 lands)
-Fluid inertia effects not predicted (assumed negligible)
Baheti and Kirk, (1995)
- Reynolds and energy equation (FEM)
- Grooves should effectively isolate seal lands
- Cross-coupled stiffness and damping coefficients are
reduced by ~60 % for grooved configurations
3
Grooved Oil Seals: Force Coefficients
GT2011-45274
Damping, Cross-coupled Stiffness & Inertia
2L
CXX  8
  D L3
4 c3
; K XY
1
  D L3
  CXX ; M XX  8
2
20 c
; K XY
1
  D L3
  CXX ; M XX 
2
20 c
c
Journal
Constant pressure
CXX 
  D L3
4c
3
2-land seal: (deep groove divides lands)
L
30c
5c
Coeffs are ¼ of original seal
c
CXX  2
Short length seal
  D L3
4c
3
; K XY
1
  D L3
  CXX ; M XX  2
2
20 c
4
Smooth&
oil
seals:
test
results
GT2011-45274 grooved
Grooved Oil
Seals:
Force
Coefficients
Parallel oil seal configuration [1]
Childs et al., (2006, 2007)
Parallel seal configuration (balance thrust force due
to pressure drop across the seals)
Includes ‘deep’ inlet (central) groove to feed seals
Parameter identification: FSEAL=
1/2 FTest conf.
Predictions do not consider groove or fluid inertia effects
(Zirkelback and San Andrés 1996)
Results
Oil supply
17 mm
25 mm
Seal length
Force coefficients are well predicted (C,K) except added
mass coefficients
Large added mass coefficients (~15 kg)
136c
76c
Added mass predictions using Classical model (Reinhardt & Lund – c
Journal
[1] Graviss, M., 2005, “The Influence of a Central
1975) (single land- i.e. not including inlet groove) (2.84 kg)
5 of an
Groove on Static and Dynamic Characteristics
Annular Liquid Seal with Laminar Flow,” M.S. Thesis,
Texas A&M Univ., College Station, TX.
GT2011-45274
Grooved Oil Seals: Force Coefficients
Old Predictions
≠
Experiments
Inlet (central) groove not
considered (null dynamic
pressure). Ignores fluid inertia
Inner land groove should reduce
crossed-coupled stiffness and direct
damping coefficients by a factor of four
Large added mass
coefficients
≠
Groove does not effectively
separate seal lands
At most:
KXY (1 land)= 2 KXY(2 lands)
CXX (1 land)= 2 CXX(2 lands)
Kxy (1 land)= 4 Kxy(2 lands)
Cxx (1 land)= 4 Cxx(2 lands)
Null (neglected) added
mass coefficients
≠
Large added mass
coefficients, increasing with
increasing groove depth
Need for better predictive models
6
GT2011-45274
Oil Seals:
Force Coefficients
Fluid
flowGrooved
predictive
model
• Bulk flow for incompressible liquid
• Qualitative observations of laminar flow field
• Boundary Conditions
• Characteristic groove depth
oil supply, Ps
Streamlines in axially symmetric
grooved annular cavity.
feed plenum groove
mid-land groove
Ps- Pd >0
Pd :discharge pressure
Pd
z
Delgado, A., and San Andrés, L., 2010, “A Model for Improved
Prediction of Force Coefficients in Grooved Squeeze Film Dampers
and Oil Seal Rings,” ASME J. Tribol., 132
Pd
y
7
GT2011-45274
Grooved
Oil Seals:
Force Coefficients
Linear
fluid
inertia
model
No fluid inertia advection
Oil supply
1
zI
I
2
zII
II
3
III
zIII
4
IV
zIV
n
N
n+1
zN
In each flow region:
Reynolds equation
  3  P
 h
x
x
   3  P
 h

 z
  z 
with temporal fluid inertia




12

h

6

R

 
 h

t
x

   h 2 
2
 h 
2 
t
  I , II ,...8N
Off-centered
operation
GT2011-45274
GroovedSolution
Oil Seals: Force
Coefficients
Finite
Element
x= qR
h
R
w
e

Y
e
Film thickness
X
h = h0 + eiwt  eX cos ( q ) + eY sin ( q )
9
GT2011-45274 conditions
Boundary
Grooved Oil Seals: Force Coefficients
Laminar flow
Ps= supply pressure
Pa= ambient pressure
Oil supply
Ps
Pa
1
2
I
zI
Null axial flow rate
(axial symmetry)
zII
4
3
IV
III
II
zIII
First-order pressures
and axial flow rates
must be equal
zIV
n
N
n+1
Pa
zN
No generation of
dynamic pressure
10
GT2011-45274
Finite
Element
forOil
solution
of Reynolds
Grooved
Seals: Force
Coefficients Eqn.
Flow
domain
 h3
   h  h  h2  2 h

P  


12

2



t
12  t 2


Nodal
pressures
z
e
q Flow rate
x=R
n pe
P   i P
e
0
i 1
e
0i
n pe
k
j 1
e
ij
e
0j
P
 q  f i
e
i
R
e
h

i . x dx dz

2 e
e
3
e
 h 
e
kij   
 i , x  j , x   i , z  j , z  dx dz


12  
e 
f ie 
e
Assemble
system of
equations,
impose
boundary
conditions
and solve
11
GT2011-45274 Grooved
Perturbation
analysis
of flow
Oil Seals:
Forceequations
Coefficients
Consider small amplitude journal (rotor) motions about a static equilibrium position
(SEP)
An applied external static load (Wo)
determines the rotor equilibrium position (eX,
Static load
W
eY)o with steady pressure field Po and film
Y
o
eXo
thickness ho
X
X
eo
eY

Y
Let the journal whirl with frequency w and
small amplitude motions (eX, eY) about
the equilibrium position. Hence
e X  e Xo  e X e iwt ,
Journal
center
clearance
circle
eY  eYo  eY e
iwt
12
Small amplitude journal motions about an equilibrium position
,
GT2011-45274
Seal
dynamic
reaction
forces
Grooved
Oil Seals:
Force Coefficients
Y
Lateral displacements (X,Y)
X
Z
 FX 
 K XX
F K
 Y
 YX
K XY   X  C XX
  

KYY  B  Y   CYX
C XY  
X 
  M XX
 

CYY  B 
Y 
  M YX
M XY  
X 

 
M YY  B 
Y 

Stiffness
Damping
Inertia
coefficients
coefficients
coefficients
Force coefficients are independent of excitation frequency for
incompressible fluid. Force coefficients depend on rotor speed
& static load
Measure of stability: Whirl frequency ratio
WFR = Kxy/(Cxx
13
GT2011-45274
Test
Grooved
Oil Seal
& FE
mesh
Grooved
Oil Seals:
Force
Coefficients
Childs, D. W., Graviss, M., and Rodriguez, L. E., 2007,
“The Influence of Groove Size on the Static & Rotordynamic
Characteristics of Short, Laminar-Flow Annular Seals,”
ASME J. Tribol, 129(2), 398-406.
Inlet
Outlet plane
h0
4
1
e
3
2
e
Grooves
z
q
2
0
Inlet plane
z
x=R
q
x=R
q
Clearance = 86 m
Oil supply
17 mm
25 mm
2 mm
Seal length
Discharge plenum
136c
76c
Journal diameter: 117 mm
Journal
c
(0-15) c
Buffer seal
14
Parallel oil seals Configuration [Childs et al]
Laminar flow
GT2011-45274 Grooved
Oil Seals: Force Coefficients
Boundary
conditions
Outlet plane
Constant static pressure at exit plane
P=Pexit
Null dynamic pressure at exit plane
Zeroth Order Pressure Field
Groove
First Order Pressure Field
Flow continuity is
automatically satisfied
at boundaries
If oil cavitation
(Pcav=0), the firs
order dynamic
pressure field
vanishes
Groove
Constant static pressure at inlet plane z
P=Psupply
Null axial flow rate (axial symmetry)
x
Inlet plane
P(q,z)=P(q+2,z)
Zeroth and first order pressure
and flow fields are periodic in
circumferential direction
15
GT2011-45274effective
Grooved Oildepth
Seals: Force Coefficients
Groove
CFD simulations show streamline separating flow regions IS a physical boundary
delimiting the domain for squeeze film flow due to journal radial motions.
Ps= supply pressure
Pa= ambient pressure
Ps
Pa
Test seal
Laminar flow
10c
15c
16
Inner land groove close up (CFD -Pressure driven flow)
GT2011-45274
Test
Grooved
Oil Seal
Grooved
Oil Seals: Force Coefficients
Childs, D. W., Graviss, M., and Rodriguez, L. E., 2007,
“The Influence of Groove Size on the Static & Rotordynamic
Characteristics of Short, Laminar-Flow Annular Seals,”
ASME J. Tribol, 129(2), 398-406.
Inlet
z
x=R
q
x=R
q
Effective depths
in model
Central groove = 9c
Inner land groove = 6c
Diameter
117 mm
Land length
24.89 mm
Radial land clearance, c
85.9 mm
Central groove length
17 mm
Central groove depth
136c
Inner land groove length
2 mm
Inner land groove depth
0c and 15c
Static journal eccentricity (e/c)
0-0.7
Shaft speed
4,000-10,000 rpm
Supply pressure
70 bar
Oil density
850 kg/m3
Oil viscosity (smooth seal)
0.016 Pa.s (54 0C)
Oil viscosity (grooved seal)
0.019 Pa.s (49 0C)
17
GT2011-45274
Test
oil seal
operating
conditions
Grooved
Oil Seals:
Force Coefficients
Childs, D. W., Graviss, M., and Rodriguez, L. E., 2007, “The Influence of Groove Size on the Static & Rotordynamic
Characteristics of Short, Laminar-Flow Annular Seals,” ASME J. Tribol, 129(2), 398-406.
Shaft speed: 10,000 rpm
1.0
Test data
smooth seal
Smooth
smooth seal
seal
smooth seal
Grooved seal
0.8
Static eccentricity ratio: 0, 0.3, 0.5, 0.7
Grooved seal
Load
Grooved seal
Grooved seal
0.5
Supply pressure: 70 bar
e y
ey
ey
0.3
-1.0
0.0
-0.8
-0.5
-0.3
0.0
0.3
-0.3
-0.5
-0.8
-1.0
ex
eex
x
x
Journal
locus
0.5
0.8
1.0
Journal center locus
shows oil seal
operates with oil
cavitation at the
largest test
eccentricities (large
static load)
18
rpm, 70 bar
GT2011-45274
Grooved Oil Seals: 10,000
Force Coefficients
Oil
Seal Leakage
0.45
Smooth Seal
0.40
Leakage [kg/s]
0.35
Grooved Seal
0.30
0.25
0.20
0.15
0.10
0.00
0
Figure 14
4000
0.1
0.2
0.3
0.4
0.5
3500
Static journal eccentricity ratio (e/c)
3000
2500
2000
1500
Force [N]
0.05
0.6
Predicted
leakage
correlates very
well with tests
for both
smooth land
and grooved
seal
Smooth seal- Predictions
Smooth seal- Experiments
Grooved seal- Predictions
Grooved seal- Experiments
(c = 7c)
(cg= 15c)
19
GT2011-45274
Grooved Oil Seals: Force
Coefficients
10,000
rpm, 70 bar
Oil
Seal Forces
Smooth seal- Theory
8000
Smooth seal- Theory
7000
Force [N]
6000
5000
4000
KXX
Smooth
sealSmooth
seal-Theory
Experiments
Smooth
seal- sealPredictions
Smooth
Theory
Smooth seal- Experiments
Smooth seal-sealExperiments
Smooth
Experiments
Grooved
seal-Theory
Smooth sealExperiments
Grooved
seal- Predictions
Grooved
seal-Theory
Grooved seal-Theory
Grooved
seal- Experiments
Grooved
seal- Experiments
Grooved
seal-Theory
Grooved
sealExperiments
Grooved
sealExperiments
Grooved seal- Experiments
3000
Smooth
Seal
Grooved
Seal
4000
Smooth seal- Predictions
3500
1000
Smooth seal- Experiments
3000
0
0
0.2
0.4
0.6
0.8
Grooved seal- Predictions
(c = 7c)
2500
60.6 0.80.8
Static journal eccentricity ratio (e/c)
.5ratio (e/c) 11
y
Grooved seal- Experiments (c = 15c)
2000
atio (e/c)
city
ratio
(e/c)
tricity ratio (e/c)
1500
1000
At high eccentricity,
test data shows larger seal reaction force for
smooth & grooved seals
500
0
20
0
1
2000
0.5
1
Force [N]
ccentricity ratio (e/c)
Figure 7

g
GT2011-45274
GroovedStiffness
Oil Seals: Force
Coefficients
10,000
rpm, 70 bar
Oil
Seal Direct
Smooth seal- Theory
250
Smooth seal- Theory
Smooth
sealTheory
Experiments
Smooth
sealTheory
Smooth
seal- sealPredictions
Smooth
Theory
Experiments
Smooth seal- Theory
Smooth sealExperiments
Smooth
sealExperiments
Grooved
seal-Theory
Smooth
sealTheory
Smooth
sealExperiments
Smooth
sealExperiments
Smooth
sealPredictions
Smooth
Theory
Grooved
seal-sealPredictions
Grooved
seal-Theory
Smooth
sealExperiments
Grooved
seal-Theory
Smooth
sealExperiments
Smooth
sealExperiments
Grooved
sealExperiments
sealExperiments
Grooved
seal-Theory
Grooved
seal-Theory
Smooth sealExperiments
sealExperiments
Grooved
seal- Predictions
Grooved
seal-Theory
Grooved
sealExperiments
Grooved
seal-Theory
Grooved
sealExperiments
Grooved
seal- Experiments
Grooved
seal- Experiments
Grooved
seal-Theory
Grooved
sealExperiments
sealExperiments
KXXGrooved
Grooved seal- Experiments
5
Stiffness
Stiffness
[MN/m]
[MN/m]
250
200
200
150
150
100
100
50
50
0
1
Smooth
Seal
XX
KKXX
ricity ratio (e/c)
1
0
-50
ricity ratio (e/c)
0
6 0.80.8 -50
1
io (e/c) 1 0
(e/c)
6ratio
0.8
y 0.8
ratio(e/c)
(e/c)
1
io (e/c) 1
(e/c)
250
yratio
ratio(e/c)
(e/c)
Stiffness
Stiffness
[MN/m]
[MN/m]
250
200
1
200
150
100
50
50
0
0.80.8
11
0
0
0
Figure
8
o (e/c)
e/c)
0.8
0.8
atio
ratio(e/c)
(e/c)
Grooved
Seal
0.6
Smooth seal- Predictions
Smooth seal- Experiments
Smooth seal- Predictions
Grooved seal- Predictions
(c = 7c)
Smooth seal- Experiments
Smooth
Groovedsealseal-Predictions
Predictions
Grooved seal- Experiments
(cg= 15c)
Smooth
Seal
Grooved seal- Experiments
150
100
ity ratio (e/c)
0.6
Smooth
Groovedsealseal-Experiments
Experiments
Grooved seal- Predictions
ity ratio (e/c)
1
4000
0.5
0.4
0.3
0.2
0.1
ratio (e/c)
Static journal eccentricity
3500
0.1
0.2
0.3
0.4
0.5
Static journal eccentricity ratio (e/c)
3000
Smooth seal- Theory
Smooth seal- Theory
Smooth
sealTheory
Experiments
Smooth
sealTheory
Smooth seal- Theory 2500
Experiments
Smooth seal- Theory
Smooth
sealExperiments
Smooth
sealTheory
Grooved
seal-Theory
Smooth
sealExperiments
Smooth
sealExperiments
Smooth
sealTheory 2000
Grooved
seal-Theory
Smoothseal-Theory
sealExperiments
Grooved
Smooth
sealExperiments
sealExperiments
Grooved
seal-Theory
Grooved
seal-Theory
Smooth sealExperiments
sealExperiments
Grooved
seal-Theory
Grooved
sealExperiments
1500
Grooved
seal-Theory
Grooved
sealExperiments
Grooved
seal- Experiments
Grooved seal-Theory
Grooved
sealExperiments
Grooved
sealExperiments
Grooved
sealExperiments
1000
KYY
K
YY
KYY
500
0
0.5
0.4
0.3
0.2
0.1
Static journal eccentricity ratio (e/c)0
0.1
0.2
0.3
0.4
0.5
Force [N]
5
Model predicts well
direct stiffness for
smooth & grooved
seals
Grooved
Seal
0.6
0.6
1
21
Stiffness
[MN/m]
Stiffness
[MN/m]
150
GT2011-45274
GroovedStiffness
Oil Seals: Force
Coefficients
10,000
rpm, 70 bar
Oil
Seal Cross
100
150
KXY
50
100
XY
KKXY
0
50
Smooth seal- Theory
Smooth seal- Theory
-50
0
-100
-50
-150
-100
-200
-150
0
-200
0
1
1
ity ratio (e/c)
100
50
Stiffness
[MN/m]
Stiffness
[MN/m]
11 50
0
o (e/c)
e/c)
0.8(e/c)
0.8
atio
ratio (e/c)
11
0
o (e/c) -50
e/c)
atio
ratio(e/c)
(e/c)
-50
-100
4000
3500
Static journal eccentricity ratio (e/c)
3000
KYX
2500
K
YX
KYX
2000
Smooth seal- Theory
Smooth seal- Theory 1500
Smooth
sealExperiments
Smooth
seal-Theory
Theory
Smooth seal- Theory
Experiments
Smooth seal- Theory
1000
Smooth
sealExperiments
Smooth
sealTheory
Grooved
seal-Theory
Smooth
sealExperiments
Smooth sealseal- Theory
Experiments
Smooth
Grooved
seal-Theory
Smoothseal-Theory
seal- Experiments
Grooved
Smooth
sealExperiments
Grooved
seal-Theory
sealExperiments
Grooved
seal-Theory
500
Smooth sealExperiments
Grooved
sealExperiments
seal-Theory
Grooved
sealExperiments
Grooved
seal-Theory
Grooved seal-Theory
seal- Experiments
Grooved
Experiments
Grooved
0.1
0.2 seal- 0.3
0.4
0.5
Grooved
sealExperiments
0
Grooved seal- Experiments
Static
journal
ratio (e/c)
Grooved
seal-eccentricity
Experiments
Smooth seal- Predictions
0.6
Smooth seal- Experiments
Grooved
Seal
Grooved seal- Predictions
(c = 7c)
Grooved seal- Experiments
(cg= 15c)
Smooth
Seal
Smooth
Groovedsealseal-Experiments
Experiments
Grooved seal- Predictions
0
0
Figure 9
1
Model predicts well
decrease in crossstiffness when adding
inner groove
0.6
Smooth seal- Experiments
Smooth
Groovedsealseal-Predictions
Predictions
-150
-200
ity ratio (e/c)
Grooved
Seal
Smooth seal- Predictions
-100
-150
-200
Smooth
sealTheory
Smooth
sealExperiments
Theory
Smooth
seal- sealPredictions
Smooth
Theory
Smooth
sealExperiments
SmoothsealsealTheory
Smooth sealExperiments
Smooth
Experiments
Grooved
seal-Theory
Smooth
sealTheory
Smooth
sealExperiments
Smooth
sealExperiments
Smooth
sealPredictions
Smooth
Theory
Grooved
seal-sealPredictions
Grooved
seal-Theory
Smooth
sealExperiments
Grooved
seal-Theory
Smooth
sealExperiments
Smooth
sealExperiments
Grooved
sealExperiments
Grooved
sealExperiments
Grooved
seal-Theory
seal-Theory
Smooth
sealExperiments
Grooved
sealExperiments
Grooved
sealPredictions
Grooved
seal-Theory
Grooved seal-Theory
seal- Experiments
Grooved
Grooved
sealExperiments
Grooved
seal- Experiments
Grooved
seal- Experiments
Grooved
0.1
0.2seal-Theory
0.3
0.4
0.5
Grooved
sealExperiments
Grooved
sealExperiments
Grooved
seal-eccentricity
Experimentsratio (e/c)
Static
journal
0.1
0.2
0.3
0.4
0.5
Force [N]
ity ratio (e/c)
100
0.80.8
Smooth
Seal
Grooved seal- Experiments
0.1
0.2
0.3
0.4
0.5
Static journal eccentricity ratio (e/c)
0.6
0
0.6
1
22
GT2011-45274
Grooved Oil Seals: Force Coefficients
Oil
Seal Cross-Stiffnesses
70 bar
e = 0.0, 0.3
60
60
Eccentricity=0
Stiffness
Stiffness[MN/m]
[MN/m]
Stiffness
[MN/m]
50
50
Smooth
Seal
40
40
30
30
Grooved
Seal
20
20
KXY
10
10
00
00
2000
2000
4000
4000
6000
6000
8000
8000
10000
10000
12000
12000
Rotor
(RPM)
Rotor speed
speed (RPM)
60
60
Eccentricity=0.3
40
40
Force [N]
[MN/m]
Stiffness
Stiffness[MN/m]
Stiffness
[MN/m]
50
50
30
30
20
20
KXY
10
10
00
00
2000
2000
4000
4000
6000
6000
8000
8000
Rotor
(RPM)
Rotor speed
speed (RPM)
Figure 10
4000
3500
3000
2500
2000
1500
100012000
10000
10000
12000
500
Smooth
Seal
Grooved
Seal
rotor speed increases
Model effectively
predicts reduction
in cross-coupled
stiffness due to midland groove.
Smooth seal- Predictions
Smooth seal- Experiments
Grooved seal- Predictions
(c = 7c)
Grooved seal- Experiments (cg= 15c)
23
GT2011-45274
GroovedDamping
Oil Seals: Force
Coefficients
10,000
rpm, 70 bar
Oil
Seal Direct
Damping [kN.s/m]
300
CXX
200
100
0
4000
0.2
0.4
0.6
3500
Static journal eccentricity ratio (e/c)
3000
2500
2000
CYY
1500
1000
500
0
0.2
0.4
0.6
Static journal eccentricity ratio (e/c
0)
Force [N]
0
300
Damping [kN.s/m]
Smooth
Seal
200
100
0
0
Figure 11
Grooved
Seal
Model predicts
accurately reduction
in direct damping due
to inner land groove.
Smooth seal- Predictions
Smooth seal- Experiments
Grooved seal- Predictions
(c = 7c)
Grooved seal- Experiments
(cg= 15c)
Smooth
Seal
Grooved
Seal
1
24
GT2011-45274
GroovedDamping
Oil Seals: Force
Coefficients
10,000
rpm, 70 bar
Oil
Seal Cross
Damping
[kN.s/m]
Damping
[kN.s/m]
50
.5
0
50
CXY Smooth seal- Theory
-50
0
Smooth seal- Theory
Smooth
sealTheory
Smooth
sealExperiments
Smooth
seal- sealPredictions
Smooth
Theory
Smooth
sealExperiments
CXYSmooth
Smooth
sealTheory
Smooth
sealExperiments
sealExperiments
-100
Grooved
seal-Theory
-50
XY
Smooth
sealExperiments
Smooth
sealTheory
Grooved
seal- Predictions
Grooved
seal-Theory
Smooth
sealTheory
Grooved
seal-Theory
Smooth
sealExperiments
Grooved
seal-Predictions
Experiments
Smooth
sealSmooth
Grooved
seal-Theory
Experiments
Grooved
seal-Theory
SmoothsealsealExperiments
Grooved
sealExperiments
Smooth sealExperiments
Smooth
sealExperiments
Grooved
sealExperiments
-150
-100
Grooved
seal-Theory
Smooth sealExperiments
Grooved
sealExperiments
Grooved
seal- Predictions
Grooved
seal-Theory0.4
0
0.2seal-Theory
0.6
Grooved
Grooved
seal- Experiments
Grooved
seal- Experiments
Grooved
seal-Theory
Grooved
sealExperiments
StaticGrooved
journal
eccentricity
ratio (e/c)
sealExperiments
-150
Grooved seal- Experiments
C
0
1
ricity ratio (e/c)
1
6ricity
0.8(e/c)
ratio
0.8
1 50
0
tio (e/c) 1
(e/c)
tyratio
ratio(e/c)
(e/c)
6 0.80.8
1-50
0
tio (e/c) 1
(e/c)
tyratio
ratio(e/c)
(e/c)
5
Grooved
Seal
4000
0.2
0.4
0.6
3500
Static journal eccentricity ratio (e/c)
3000
Smooth
2500
Seal
Grooved
CCYX
YXSmooth seal- Theory 2000
Smooth seal- Theory
Seal
Smooth
sealTheory
Smooth
sealExperiments
Smooth seal- Theory
Smooth sealseal- Theory
Experiments
1500
Smooth
CYXSmooth
sealExperiments
Grooved
seal-Theory
Smooth
sealExperiments
Smooth sealTheory
Grooved
seal-Theory
Smooth
sealTheory
Grooved
seal-Theory
Smooth
sealExperiments
1000
Smooth sealGrooved
seal-Theory
Experiments
Grooved
seal-Theory
Smooth sealExperiments
Grooved
sealExperiments
Smooth
sealExperiments
Grooved
sealExperiments
Grooved
seal-Theory
Smooth sealExperiments
Grooved
sealExperiments
Grooved seal-Theory 500
0.2
0.6
Grooved
seal-Theory 0.4
Grooved
seal- Experiments
Grooved seal-Theory
Grooved
sealExperiments
Static
journal
eccentricity
ratio
Grooved
sealExperiments
0 (e/c)
Grooved seal- Experiments
0.2
0.4
0.6
0
1
Static journal eccentricity ratio (e/c)
Force [N]
Damping
[kN.s/m]
Damping
[kN.s/m]
50
.5
Smooth
Seal
Small cross-damping,
test data shows
larger magnitude than
predictions
Smooth seal- Predictions
Smooth seal- Experiments
Grooved seal- Predictions
(c = 7c)
Grooved seal- Experiments
(cg= 15c)
Smooth seal- Predictions
Smooth seal- Experiments
-100
-50
Grooved seal- Predictions
Smooth sealGrooved
seal-Predictions
Experiments
-150
-100
Smooth seal- Experiments
0
-150
1
icity ratio (e/c)
0
Figure 12
Grooved seal- Predictions
Grooved seal- Experiments
25
GT2011-45274
GroovedMass
Oil Seals: Force Coefficients
10,000 rpm, 70 bar
Oil
Seal Added
Figure 13
Test data shows large added
mass coefficients.
Predictions correlate well
with experimental results.
40
Added Mass [kg]
35
MXX
Grooved
Seal
30
25
Smooth
Seal
20
15
10
Added mass coefficients
are larger for grooved seal
Classical theory (*)
predicts ~ 1/10 of test
value
5
4000
3500
0
0.1
0.2
0.3
0.4
0.5
0.6
3000
Static journal eccentricity
ratio (e/c)
2500
2000
1500
1000
[1] Reinhardt, F., and Lund, J. W., 1975, “The Influence of Fluid
Inertia on the Dynamic
Properties of Journal Bearings,” ASME J. Lubr. Technol., 97(1),500
pp. 154-167.
Force [N]
0
Smooth seal- Predictions
Smooth seal- Experiments
Grooved seal- Predictions
Grooved seal- Experiments
(c = 7c)
(cg= 15c)
26
GT2011-45274
Grooved Oil Seals: Force Coefficients
Conclusions:
• Good correlation for direct force coefficients for the lower journal
eccentricities (e/c=0,0.3) and moderate to good correlation for
e/c=0.5.
• Cross-coupled stiffnesses also predicted accurately for the
smaller eccentricities. FE model accurately predicts the reduction
of the direct stiffness, direct damping, and cross-coupled
stiffness coefficients when adding a circumferential groove to the
seal land.
• Added mass coefficients for both seals (smooth and grooved) are
also predicted accurately (within 20 %). Both analysis and test
results show a grooved seal has larger direct added mass
coefficient than a smooth seal.
27
GT2011-45274
Grooved Oil Seals: Force Coefficients
Conclusions:
• Discrepancies between test results and predictions for
large journal eccentricities (e/c)~0.70. Discrepancies due
to (unknown) changes in seal clearance and oil viscosity
induced by thermal effects.
• Current model is a significant improvement over
prevailing predictive tools to analyze grooved oil seals.
• Deep grooves do not fully uncouple parallel film lands!!
• Model applied successfully to grooved SFDs (+ additional
experimental verifications)
28
GT2011-45274
Grooved Oil Seals: Force Coefficients
Acknowledgments
Thanks to TAMU Turbomachinery Research Consortium
Questions (?)
Learn more at http://rotorlab.tamu.edu
© 2011 Luis San Andres
29
GT2011-45274
Grooved
Oil for
Seals:
Force
Coefficients
Prediction:
pressure
fields
oil seal
without
inner groove
Journal whirl motion with r=5 m, w=200 Hz)
(a) Classical:
central groove dyn. pressure = 0
(b) Current – central groove interacts with
film lands
30
GT2011-45274
Grooved
Oil for
Seals:
Force
Coefficients
Prediction:
pressure
fields
oil seal
with
inner groove
Journal whirl motions with r=5 m, w=200 Hz)
(a) Classical:
central groove dyn. pressure = 0
inner land dyn. pressure = 0
(b) Current – central groove and inner
groove interacts with film lands
31