ASME TURBO EXPO 2014
June 16 – 20, 2014 - Düsseldorf, Germany
EXPERIMENTAL AND THEORETICAL
ROTORDYNAMIC COEFFICIENTS OF
SMOOTH AND ROUND-HOLE PATTERN
WATER FED ANNULAR SEALS
P. Jolly*, A. Hassini, M. Arghir, O. Bonneau, S. Guingo
Institut P’ • UPR CNRS 3346
SP2MI • Téléport 2
Boulevard Marie et Pierre Curie • BP 30179
F86962 FUTUROSCOPE CHASSENEUIL Cedex
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Outline
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The test rig BALAFRE
Experimental procedure and identification method
The tested seals
Static results: flowrates
Dynamic coefficients: identified vs predicted
Summary
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• The test rig BALAFRE: Presentation
– BALAFRE : Banc d’essais A LAmes Fluide à haut REynolds = Test rig with thin
fluid film thickness and high Reynolds Numbers (Re  100 000 for seals)
– Objective : identify dynamic coefficients of fluid film components (annular
seal, bearing, …), according to the Reynolds principle of similarity
– Originality 1 : dynamic excitations are transmitted to the shaft (rather than
to the housing contrary to many existing facilities)
– Originality 2 : complex displacements of the rotor (translation, precession,
…) in centered and/or off-centered position. Displacements are obtained
via 8 piezoelectric exciters (shakers) positioned in two radial plans
– Originality 3 : the tested component is overhung mounted
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• The test rig BALAFRE : cross section view
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• The test rig BALAFRE: overall characteristics
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Fluid: water
Temperature range: 5 -> 50 °C
High pressure hydraulic system: up to15 MPa
Low pressure hydraulic system: up to 4.5 MPa
Shaft speed: 50 -> 6000 rpm
Diameter of the tested components: 100 -> 350 mm
Radial clearance: up to 1mm
Force balance capacity: 20kN per axis
Dynamic displacements of the shaft: ±100µm
Shaking frequency range of: 20 -> 200 Hz
Measurements:
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6 eddy current displacements sensors
3 triaxial force sensors
3 triaxial accelerometers
Pressure: 11 + 3 insitu sensors
Temperature: up to 5 Pt100 sensors
Torque: up to 250 N.m
Flowrate: up to 120m3/h
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• The test rig BALAFRE: example of tested components
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Hydrostatic journal bearing
Labyrinth seal
Impellers: open and closed (front shrouded)
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• Experimental procedure and identification
method
Zero eccentricity
-1
 (tr.min )
Centered Rotor
Palim 17 bar
-1
 (tr.min )
6000
Amplitude (%)
0
55
50
0
50
2000
4000
6000
Phase Shift (%)
XAVANT YAVANT XARRIERE YARRIERE XAVANT YAVANT XARRIERE YARRIERE
50
0
9
1
2
3
4
Palim (barg )
17
5
6
7
8
0
55
0
0
0
0
0
0
20
30
40
50
F (Hz)
60
24
9
10
11
12
70
80
90
110
0
0
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• Experimental procedure and identification
method
Calculation of fluid forces & Displacements
(at the center of the rotor, for each DOF i=1,2)
&
FFT
Kxx
‐Kyx
Kxy
Kyy
Cxx
‐Cyx
Cxy
Cyy
Mxx
‐Myx
Mxy
Myy
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• The tested seals
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1 smooth annular seal (noted SS)
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2 textured seals with Round Hole Pattern:
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1 with shallow holes (noted TSSH): p/Dh=0,0187
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1 with deep holes (noted TSDH) ): p/Dh=0,475
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L/D=0,625 and CR/R=4,75.10-3
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Texture Density:
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No pre-swirl
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Inlet pressure = 9bar
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Centered Rotor
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≅ 38%
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• Numerical Predictions
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Simplified thin flow model dominated by inertia effects: Bulk-Flow equations
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Wall shear stress calculation
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Smooth annular seal: Colebrook formula
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Textured seals: particular wall friction laws for stator and rotor
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• Textured seals
Particular wall friction laws for stator and rotor: 4 parameters (
, , ,
ln
ln
ln
ln
.
.
,
, ,
)
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Rotor Friction Coefficient
Stator Friction Coefficient
Texture depth p (mm)
Texture depth p (mm)
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• Static results : mass flow rates of seals
Dimensionless Mass Flow Rate 3.00
2.50
2.00
1.50
Smooth Seal ‐ Num
Smooth Seal ‐ Exp
Shallow Texture ‐ Num
Shallow Texture ‐ Exp
Deep Texture ‐ num
Deep Texture ‐ Exp
1.00
0.50
0.00
0
2000
 (rpm) 4000
Dimensionless Mass Flow rate
6000
∗
2
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• Dynamic coefficients - Seals : predicted vs identified
P = 5bar
1.00
Kyy ‐ exp
Kxy ‐ exp
‐Kyx ‐ exp
0.60
Kxx=Kyy ‐ num
Kxy=‐Kyx ‐ num
0.40
Kxy
Dimensionless Stiffness 0.80
0.20
0.00
‐0.20
Kxx
‐0.40
0
2000
 (rpm)
1.00
0.80
Dimensionless Stiffness Kxx ‐ exp
4000
Smooth Seal
0.60
Kxx ‐ exp
Kyy ‐ exp
Kxy ‐ exp
‐Kyx ‐ exp
Kxx=Kyy ‐ num
Kxy=‐Kyx ‐ num
0.80
Dimensionless Stiffness 1.00
Kxy
0.40
0.20
0.00
‐0.20
Kxx
‐0.40
6000
0.60
Kxx ‐ exp
Kyy ‐ exp
Kxy ‐ exp ‐Kyx ‐ exp
Kxx=Kyy ‐ num
Kxy=‐Kyx ‐ num
Kxy
0.40
0.20
0.00
‐0.20
Kxx
‐0.40
0
2000
 (rpm)
4000
6000
Textured Seal
with Shallow Holes
0
2000
 (rpm)
4000
6000
Textured Seal
with Deep Holes
Dimensionless Stiffness = KCR/(PLD)
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• Dynamic coefficients - Seals : predicted vs identified
P = 5bar
3.50
3.50
Cxy ‐ exp ‐ AS
‐Cyx ‐ exp ‐ AS
Cxx=Cyy ‐ num ‐ AS
2.50
Cxy=‐Cyx ‐ num ‐ AS
Cxx
1.00
Cyy ‐ exp
Cxy ‐ exp
‐Cyx ‐ exp
Cxx=Cyy ‐ num
Cxy=‐Cyx ‐ num
3.00
2.00
1.50
3.50
Cxx ‐exp
0.50
0.00
Cxy
2.50
3.00
Dimensionless Damping
Cyy ‐exp ‐ AS
Dimensionless Damping
Dimensionless Damping
3.00
Cxx ‐ exp ‐ AS
2.00
Cxx
1.50
1.00
0.50
0.00
Cxy
‐0.50
‐0.50
0
2000
 (rpm)
Smooth Seal
4000
6000
0
2000
 (rpm)
4000
2.50
2.00
Cxx ‐ exp
Cyy ‐ exp
Cxy ‐ exp
‐Cyx ‐ exp
Cxx=Cyy ‐ num
Cxy=‐Cyx ‐ num
Cxx
1.50
1.00
0.50
0.00
Cxy
‐0.50
6000
Textured Seal
with Shallow Holes
0
2000
 (rpm)
4000
6000
Textured Seal
with Deep Holes
Dimensionless Damping = CCR/(PLD)
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• Dynamic coefficients - Seals : predicted vs identified
Dimensionless Added Mass
3.00
Mxx ‐ SS ‐ exp
Myy ‐ SS ‐ exp
Mxx=Myy ‐ SS ‐ num
Mxx ‐ TSSH ‐ exp
Myy ‐ TSSH ‐ exp
Mxx=Myy ‐ TSSH ‐ num
Mxx ‐ TSDH ‐ exp
Myy ‐ TSDH ‐ exp
Mxx=Myy ‐ TSDH ‐ num
2.50
2.00
1.50
1.00
0.50
0.00
0
2000
 (rpm)
4000
6000
Dimensionless Added Mass = M2CR/(PLD)
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Conclusion
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Comparisons between experimental and numerical predictions of the stiffness
and damping coefficients are good
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Main differences brought by a textured stator compared to a smooth one are:
• The mass-flow rate decreases
• The absolute values of the direct and cross coupled stiffness decreases
• The direct damping increases and the cross coupled damping decreases
• The added mass coefficient decreases
• The predictions of dynamic coefficients for textured seals still need
improvements
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The test rig proved its ability to adapt to all kind of thin fluid film components as
encountered in liquid Rocket Engine Turbopump
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The authors would like to thank CNES and SAFRAN for their financial
support and their agreement for presenting this work
Thank you for your Attention
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