Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Pressure Activated Leaf Seal Technology Readiness Testing
GT2014-27046
Presented by Peter Crudgington - Director Cross Manufacturing Co. (1938) Ltd
in conjunction with CMG TECH
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Acknowledgements
Co-authors: Aaron Bowsher, Engineering Manager, Cross Mnfg Clayton Grondahl, Director, CMG TECH James Dudley, Aircraft Engine Design Consultant Tracey Kirk, Test & Development Engineer, Cross Mnfg Andrew Pawlak, Senior Technician, Cross Mnfg The authors would like to thank the directors of Cross Manufacturing for the funding of this work and allowing publication. They would also like to thank the dedicated team of engineers and manufacturing staff at Cross who work together to produce products of outstanding quality
2
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Content
• Pressure Activated Leaf Seal – PALS
• Smooth Rotor Testing
– Static
– Dynamic
• Acoustic Noise Investigation
• Simulated Shrouded Turbine Blade Testing
• Summary
• Future Work
3
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Introduction PALS Design
4
Center of rotation.+
Stator - cut away to show leaf seal assembly.Backing ring - keyed in stator
Leaf Seal elements: - slotted ‘shim’ stock- multiple frusto-conical layers - wear resistant alloy
Support member - assembled withseal members and backing ring
Rotor / shaft - seal surface
Highpressure
side.
Larger diameter
& Segmented design
Concept Welded Design
Bolted Design
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Introduction Pressure Activated Leaf Seal (PALS) Concept
5
Large startup & shut down clearance: Rub avoidance.
Minimum operating clearance: Performance gain.
Non-contacting operation: Long seal life. CLICK IMAGE
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Smooth Rotor Testing Overview
6
Conditions:
• Speed – Typically 300ft/s (up to 345ft/s)
• Pressure Drop – Up to 120psi
• Seal Diameter pre Wear-in – 5.105” deflected (5.185” un-deflected)
AIR FLOW
• Rotor Diameter – 5.080” to 5.133”
• Fluid – Compressed air
• Rotor material – Aubert & Duval 819B (Ni-Cr-Mo Alloy) uncoated
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Smooth Rotor Testing Static Leakage with Various Disk Sizes
7
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.016
0.018
5.070 5.080 5.090 5.100 5.110 5.120 5.130
Effe
ctiv
e Cl
eara
nce
(inch
es),
[mm
]
Disk Diameter (inches), [mm]
30 psi [207 kPa]
40 psi [276 kPa]
50 psi [345 kPa]
60 psi [414 kPa]
70 psi [483 kPa]
80 psi [552kPa]
5.105" PALS ID,leaves deflected
Leaf vibration
[130.0] [130.3] [128.8] [129.0] [129.5] [129.8]
[0.051]
[0.102]
[0.152]
[0.203]
[0.254]
[0.305]
[0.356]
[0.406]
[0.457]
[129.3]
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Smooth Rotor Testing Dynamic Offset Test
8
• 13500rpm • 50psi • 5.105” Seal Bore Size • 5.115” Disk Size • 0.010” Radial Offset to create a 0.005” rub. • Effective Clearance 0.007” prior to rub • Effective Clearance 0.0077” after rub
•After test, bore of seal re-edm’d to 5.114”
CLICK IMAGE
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Smooth Rotor Testing - Wear-in Results Rotor Ø5.133”, Seal (deflected) Ø 5.114”
9
0.000
0.002
0.004
0.006
0.008
0.010
0.012
20 30 40 50 60 70 80 90 100
Effe
ctiv
e Cl
eara
nce
(inch
es),
[mm
]
Pressure Drop (psi), [kPa]
Wear-inRepeat 1Repeat 2Repeat 3Repeat 4Repeat 5
Start of wear-in
End of wear-in,start of
repeat 1
Rotor speed 13,500rpm, 302 ft/sPotential error of up to -15% of repeat
point value on effective clearance
Repeat cycle 1 difference
attributed to leaf tip burrs[0.051]
[0.102]
[0.152]
[0.203]
[0.254]
[0.305]
[138] [207] [276] [552] [621] [690][345] [414] [483]
• Orange line - ‘Wear-in’, the first time the seal is run
• Blue line repeat 1– post wear in burr stabilisations
• Consistent effective clearance throughout repeat 3 to 5
• Leaf tips wear to the rotor to establish good synchronicity
• Burrs form on both top and bottom leaves in both positive and negative axial direction
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Smooth Rotor Testing Repeatability – Static Rotor Ø5.133”
10
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0 10 20 30 40 50 60 70 80 90
Effe
ctiv
e Cl
eara
nce
(inch
es),
[mm
]
Pressure drop (psi), [kPa]
Repeat 1 Repeat 2 Repeat 3 Repeat 4 Repeat 5
[138] [207] [276] [552] [621][69] [345] [414] [483]
[0.127]
[0.254]
[0.381]
[0.762]
[0.889]
[1.016]
[0.508]
[0.635]
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.016
0 20 40 60 80 100 120 140
Effe
ctiv
e Cl
eara
nce
(inch
es),
[mm
]
Pressure Drop (psi), [kPa]
Repeat 6 Repeat 7 Repeat 8 Repeat 9 Repeat 10
[0.051]
[0.102]
[0.152]
[0.203]
[0.254]
[0.305]
[0.355]
[138] [276] [552] [690] [966][414] [828]
[0.406]
• Higher pressure static leakage sweeps up to 120 psid post wear-in
• Repeatable closure with pressure
• No hysteresis
• Low pressure static leakage sweeps up to 80 psid post wear-in
• Repeatable closure with pressure
• No hysteresis
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Smooth Rotor Testing Interleaf Leakage – Static Rotor Ø5.133”
11
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0 10 20 30 40 50 60 70 80 90Ef
fect
ive
Clea
ranc
e (in
ches
), [m
m]
Pressure Drop (psi), [kPa]
Normal Leaves taped-up Interleaf Leakage
[138] [207] [276] [552] [621][69] [345] [414] [483]
[0.127]
[0.254]
[0.381]
[0.762]
[0.508]
[0.635]
• Removed front shroud to expose leaves
• Tested statically as standard
• Upstream face of top leaves taped to block air flow between leaves
• Tested statically with taped leaves
• Difference in effective clearance accounted to interleaf leakage
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Smooth Rotor Testing Analytical Comparison- Static Rotor Ø5.133”
12
0.000
0.010
0.020
0.030
0.040
0.050
0 20 40 60 80 100 120 140
Effe
ctiv
e Cl
eara
nce
(inch
es),
[mm
]
Pressure Drop (psi), [kPa]
Pre-Dynamic Test
Post-Dynamic Test
Interleaf leakage adjusted
FEA top leaf
Acousticnoise
[138] [276] [552] [690] [966][414] [828]
[0.254]
[0.762]
[0.508]
[1.270]
[1.016]
CLICK IMAGE
• Post wear-in closure
• Ø5.133” rotor
• Ø5.202” un-deflected PALS bore
• Analytical results follow closely to the measured results adjusted for interleaf leakage
• Acoustic noise was present at low pressures during the post dynamic testing
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Frequency (Hz)
0.05 [1.27] 0.04 [1.02] 0.03 [0.76] 0.02 [0.51] 0.01 [0.25]
P-P,
mils
[μm
]
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Acoustic Noise Investigation Experimental Set-up
13
Air in Kulite port
Down-streampressure tap
Air outUp-stream
pressure tap
Borescope port
Up-stream airthermocouple
Stator, max leaf deflection contact
plane
Rotating leaf assembly
• Leaf vibration resulted in an audible noise at low differential pressures
• Noise stopped at pressures above 30psid
• 2D bespoke rig designed and build to investigate potential causes along with existing static and dynamic set-ups
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Acoustic Noise Investigation Hypothesized Cause and Discreditation
14
Hypothesis Result
Upstream pressure fluctuations Disproved – Unaffected by controlled bypass leakage A cavity in the air supply system resonates at the
frequency of the leaves
After wear-in burrs at the tip of the middle leaf silence the noise by supporting top leaves Disproved – Comparison testing from post wear-
in and re-machined chisel like bore. No noise or vibration Vortex shedding from leaf tips excites leaves at their
natural frequency
Wear-in changes leaf natural frequency Disproved – Shim testing proved interleaf gap controlled noise and vibration
Flow approach relative to leaf angle a factor in vortex shedding
Disproved –Leaf angle ineffective on noise and vibration
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Acoustic Noise Investigation Hypothesized Cause and Discreditation
15
Hypothesis Result
HCF cracking Disproved – No evidence of HCF from visual inspections using a microscope and dye penetrant
Cushion of air between the support and the leaves Disproved – No need for testing due to noise elimination before venting test
Insufficient damping Disproved – Manual excitation unsuccessful
Interleaf gaps allow relative motion without damping Proved – Shim testing proved interleaf gap greater then .001” (0.025mm) would instigate noise and vibration
Blunt leaf ends redirect flow up leaves Proved – Re-cut leaves with chisel end ensuring at full pressure only the top leaves were in contact with the rotor. No noise or vibration
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Acoustic Noise Investigation Established Cause – Interleaf Separation
16
5.133in PALS bore dia. [130.4mm] No burrs, 5psi, [34.5kPa]
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Frequency (Hz)
0.05 [1.27]
0.04 [1.02]
0.03 [0.76]
0.02 [0.51]
0.01 [0.25]
P-P,
mils
[μm
]
5.133in PALS bore dia.[130.4mm] No burrs, 10psi, [69kPa]
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Frequency (Hz)
0.05 [1.27]
0.04 [1.02]
0.03 [0.76]
0.02 [0.51]
0.01 [0.25]
P-P,
mils
[μm
]
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Simulated Shrouded Turbine Blade Test Overview – Dynamic
17 [0
.08]
View
B
View B
View A
0.0125in[0.32mm]
[0.64]
[4.6
5]
0.025in[0.64mm]
0.00
3in
[0.0
8mm
]
0.18
3in
[4.6
5mm
]
Conditions: • Speed – 20,000rpm • Slot frequency – 4000Hz • Rotor Diameter – Ø5.120” • Cold build clearance – 0.018” • Fully deflected leaf interference – 0.003”
ROTOR AIR FLOW ΔP = 65psi (448kPa)
SEAL AIR FLOW ΔP = 55psi (379kPa)
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU 18
Simulated Shrouded Turbine Blade Test 15 Hour Steady State Results - Dynamic
0.000
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0:00:00 3:00:00 6:00:00 9:00:00 12:00:00 15:00:00
Tota
l Effe
ctiv
e Cl
eara
nce
(inch
es),
[mm
]
Time (h:mm:ss)
1 2 3 4
[0.025]
[0.051]
[0.076]
[0.152]
[0.178]
[0.203]
[0.102]
[0.127]
• Rotating down the step
• 15 hrs broken down into 4 stages with inspection
• Total effective clearance reported
• Initial period of wear-in before stabilisation
.045in [1.14]
.0003in [7.6μm]
15hr
.0001in [2.5μm]
.048in [1.22]
1hr
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU 19
Simulated Shrouded Turbine Blade Test Reverse Rotation Results - Dynamic
0
3000
6000
9000
12000
15000
18000
21000
24000
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0:00:00 0:10:00 0:20:00 0:30:00 0:40:00
Roto
r Spe
ed (r
pm)
Tota
l Effe
ctiv
e Cl
eara
nce
(inch
es),
[mm
]
Time (h:mm:ss)
Total Effective Clearance Rotor Speed (rpm)
[0.025]
[0.051]
[0.076]
[0.152]
[0.178]
[0.203]
[0.102]
[0.127]
• Rotating up the step
• Rotor speeds from 5,000rpm to 20,000rpm
• Slot frequency from 1000Hz to 4000Hz
• Improved effective clearance with speed
• Comparable results to the 15hr steady state test
• Stable running
CLICK IMAGE
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Simulated Shrouded Turbine Blade Test Pre and Post Test Comparison - Static
20
0.000
0.004
0.008
0.012
0.016
0.020
0.024
0 10 20 30 40 50 60 70 80
Effe
ctiv
e Cl
eara
nce
(inch
es),
[mm
]
Pressure Drop (psi), [kPa]
Pre-Testing Post Testing
[0.102]
[0.203]
[0.406]
[0.508]
[0.610]
[0.305]
[138] [207] [276] [552][69] [345] [414] [483]
• Noise and vibration present on the pre testing test at pressure drops under 20psi both increasing and decreasing the pressure
• No noise post dynamic tests
• Improvement on total effective clearance
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Summary
21
• The PALS design is technology ready
• Smooth rotor testing – No loss of integrity
– Velocity of 300ft/s
– Pressure drop of 120psi
– Radial offsets and 360° rub
• Wear in process
– Relax manufacturing tolerances
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Summary
22
• Acoustic noise accounted to interleaf separation
• Simulated shrouded turbine blade testing - Suitability for turbine blade tip applications
– 15 hours consistent performance
– Seal pressure drop of 55psi
– Rotor pressure drop of 65psi
– Rotor pressure 10psi higher than seal pressure
– Radial step of .003”
– Step frequency of 4000Hz
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU
Future Work
23
• Influences of manufacturing tolerances and preload
• Additional reverse rotation testing on simulated shrouded turbine blade with varying degrees of radial offset, eccentricity and rotor pressure to investigate the effects on stability, wear, excitation and high cycle fatigue
• An analytical approach to predicting wear rate based on operating conditions
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU 24
• sCO2 turbomachinery small size requires leakage control in limited space.
- PALS effective clearance is < 0.004in (0.1mm) and has small cross-section.
• sCO2 turbomachinery operating speed is typically very high. - PALS performance is independent of speed.
• sCO2 turbomachinery operating pressure is high and can require high DP seals.
- PALS design for high pressure is unrestricted.
• sCO2 turbomachinery rotor stability can be affected by ‘flashing’ within seals. - PALS single pressure drop mitigates this concern.
• sCO2 turbomachinery power loss within seals and from windage.
- PALS non-contacting leaves and low leakage should diminish power loss.
• sCO2 turbomachinery manufacturing cost. - PALS ‘Wear-in’ capability can reduce tolerance requirements and cost.
Assessment of application in sCO2 turbomachinery
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU 25
PALS Compared to Other Seals
Startup Rub
Vulnerability
Operating Rub
Tolerance
‘Wear-in’ Seal
Compliance
Low Leakage
Long Seal Life
High Seal ΔP
Capability
Reverse Rotation Hazard
Axial Length
Rotor Dynamic Issues
Cost
Labyrinth Seals
Brush Seals
Pressure Actuated
Leaf Seals Limited ~ 0.004in
W/o rub.
Improved to 8+ years.
AbradibleLabyrinth
Seals
Symbol key: Unfavorable comparison
Favorable comparison
Somewhat favorable comparison
400psid capability.
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU 26
• Pressure Actuated Leaf Seal technology readiness test
results and favorable evaluation of attributes vs other seals
show benefit potential for their application in sCO2
turbomachinery.
• Consideration of their use in sCO2 turbomachinery is
recommended.
Recommendation
Cross Manufacturing Company (1938) Limited Brush Seals and Aerospace Products, South Site, Hopton Road, Devizes, Wiltshire, SN10 2EU 27
Head Quarters - Bath Automotive Division Devizes North Site
Brush Seal & Aerospace Division Devizes South Site
Thank You for Listening
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