Measurement of leakage in a novel all metal non-contacting
annular seal at high temperatureAlain AndersonGraduate Research Assistant
Luis San AndrésMast-Childs Professor
TRC project 2010-2011 TRC 32513/15193S/ME
START DATE: September 1, 2010
Trends in High Performance Turbomachinery• Higher speeds & more compact units• Extreme operating temperatures and pressures• More efficient & reliable
JUSTIFICATION
Issues of Importance• Reduce secondary flows
(parasitic leakage)• Reduce specific fuel consumption & COST• Increase power delivery• Eliminate potential for rotordynamic instability
Source: GE Energy
TRC funded a two-year program- Conduct non-proprietary leakage tests with a
HALOTM seal- Conduct leakage tests with a three tooth labyrinth
seal for comparison
OBJECTIVE
Desired outcomes- Enable the application of state of the art sealing
technology- Increase system efficiency
- Reducing leakage- Eliminating wear of components- Extending maintenance intervals
PRIOR WORK 2007-2009 [1]
• To measure leakage in three test seals by varying:• Supply pressure (upstream) from 1 bar to 3.5 bar• Air inlet temperature from 30ºC to 300ºC• Rotor speed from 0 rpm to 3,000 rpm
• To estimate drag torque (power loss) from each seal• Compare three seals and provide recommendations
A power gas turbine OEM wished to benchmark novel seal types against a (traditional) labyrinth seal to realize benefits and to ensure potential gains
TEST SEALS 2007-2009 [1]
Labyrinth Seal Brush Seal
Hybrid Brush Seal
EXPERIMENTAL FACILITY
Heater
Exhaust duct
Air pressurization cylinder
Motor Test seal
Roller bearings
cm
50 25 75 0
Flow in
Flow out
Rotor
Voltage Power OutputHeater 240 V 12 kW 300°CMotor 90 V 850 W 3,000 rpm
Maximum
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
5
4
6
1
7
Flow in (supply pressure)
Flow out (ambient pressure)
0 10 20
cm
Properties 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
EXPERIMENTAL FACILITY
Test seal
Maximum air pressure: 100 psig
EXPERIMENTAL FACILITY
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
Rollerbearing assembly
Eddy current sensor
Spring
Ball bearing
Shaft
Disk
High pressure air
Flow
Flow Flexible coupling to motor
Hybrid brush seal
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
Centering mechanism
Test seal
a) Revamp test rig for operation at higher rotor speeds to reach a tip surface speed of 120 m/s (15 krpm). Thermal and centrifugal growth at high speeds is expected to further decrease leakage
b) Perform clearance and leakage measurements with a three teeth labyrinth seal and the HALOTM seal operating with pressure ratios as high as 8, temperatures to 300ºC, and tip surface speeds to 120 m/s
c) Compare the labyrinth seal measured leakage with XLLaby® predictions at high temperature. The benchmarking is essential to trust, modify or discard current predictive models
Proposal to TRC (2 years)TRC members benefit from existing high temperature seal test rig
a) Revamp test rig for operation at higher rotor speeds to reach a tip surface speed of 120 m/s (15 krpm). Thermal and centrifugal growth at high speeds is expected to further decrease leakage
b) Perform clearance and leakage measurements with a three teeth labyrinth seal and the HALOTM seal operating with pressure ratios as high as 8, temperatures to 300ºC, and tip surface speeds to 120 m/s
c) Compare the labyrinth seal measured leakage with XLLaby® predictions at high temperature. The benchmarking is essential to trust, modify or discard current predictive models
TRC funded project (2 years)TRC members benefit from existing high temperature test rig
(a) Learn operation of test rig and DAQ system(b) Install two seals (labyrinth and HALO) and perform
leakage measurements with air for:
(c) Revamp test rig for high speed operation
Non-rotating and centered rotor
Inlet temperature (30ºC-300ºC)
Supply pressure (1 bar- 7 bar)
Work to date for TRC funded project
TEST LABYRINTH SEAL
LEAKAGE: Labyrinth Seal
Flow rate increases with supply pressure and decreases with inlet temperature due to changes in seal clearance and gas density.
TESTS for low pressure ratios to 3.5 (> choking)
30C
300C
Modified Flow Factor
lDP
Tm
s
Modified flow factor: Labyrinth Seal
Flow factor allows comparison of different types of seals. For labyrinth seal, it removes effect of supply pressure and temperature.
30C
300C
Hydrostatic Advanced Low Leakage Seal All metal (no bristles) non-contacting seal
TEST HALOTM Seal
0 2010
mm
Direction of flow
Direction of flow
http://www.atgi.us
TEST CONDITIONS (HALOTM SEAL)
Hydrostatic Advance Low Leakage (HALO) Seal
*Clearance between seal pad and disc not to scale.
Axial profile of a resilient pad in HALO™ seal (Courtesy of ATG)
Direction of flow
Exhaust Pressure
Supply pressure
Seal pad
Disc 0 1 mm
2 3
0
0.05
0.1
0.15
0.2
0.25
1 1.2 1.4 1.6 1.8
Pressure Ratio [Ps/Pe]
Ra
dia
l C
lea
ran
ce
[m
m]
PR: upstream pressure /ambient (exit) pressure
HALO™ seal clearance closes with pressurization.
Measurements at room temperature (30 °C) and no shaft rotation
LEAKAGE: HALOTM Seal
Flow rate increases with supply pressure and decreases with air inlet temperature. TESTS conducted with much higher pressure ratios
30C
300C
Modified Flow Factor
lDP
Tm
s
Modified flow factor: HALOTM Seal
Modified flow factor much lower than for labyrinth seal
30C300C
Leakage Comparison: Labyrinth & HALO)
LABYRINTH
HALO seal
The HALOTM seal leaks 50% or less than the labyrinth seal. For pressure ratios (Ps/Pa) > 3.0, the HALOseal leaks ~¼ the flow rate of the labyrinth seal
Flow factor (Labyrinth & HALO) 300 C
Labyrinth seals are an outdated technology. Industries seeking to increase efficiency by reducing (parasitic) secondary leakage losses will benefit greatly from a change in seal technology
LABYRINTH
HALO seal
REVAMP TEST RIG
Issues
• Large vibrations of cantilevered rotor
• Critical speeds too low& air temperature too high
• Safety: containment at high speeds
• Drive motor speed limitations
Solutions• Balance rotor
• For high temperature, use a metal mesh foil bearing (MMFB) as a support.
• Use high speed router motor & construct containment guard.
For operation at higher rotor speeds to reach a tip surface speed of 120 m/s (15 krpm)
REVAMP TEST RIGXLTRC2 rotordynamic analysis
f=5953.2 cpmd=.0602 zetaN=10000 rpm
forwardbackward
Metal mesh bearing support adds stiffness and damping to original cantilevered rotor.
Bearing Cartridge Metal mesh
donut
Formed top foil
XLTRC2 imbalance response predictions
0.000
0.040
0.080
0.120
0.160
0.200
0 5000 10000 15000 20000
rotor speed (krpm)
amp
litu
de
mic
ro-m
0-p
k
thin shaft 0.5 inch (current rotor)
shaft 1 inch diam
shaft 1.5 inch
shaft 2.0 inch
original (0.5 inch) - no MMFB
original 0.5 in OD shaft- no MMFB
shaft OD increases(0.5 in to 2.0 in)OD=0.5 in
rotor supported on MMFBs
MMFB increases critical speed and determines a well damped system
With MMFB
Amplitude of motion at disc
Shaft13430
25
2015
105Shaft11
-0.12
-0.08
-0.04
0
0.04
0.08
0.12
0 0.08 0.16 0.24 0.32 0.4 0.48
Axial Location, meters
Sh
aft
Rad
ius,
met
ers
rolling bearings
connecting rod to drive
Disc
Shaft (1/2 inch)
Metal mesh bearing& rods support
journal
Test gas seal
TRC Budget
Year IISupport for graduate student (20 h/week) x $ 1,700 x 12 months $ 20,400
Fringe benefits (0.6%) and medical insurance ($191/month) $ 2,412
Travel to (US) technical conference $ 1,500
Tuition three semesters ($3,802 x 3) $ 10,138
Equipment and supplies for test rig $ 550
Year II $ 35,000Year I $ 39,863
High Temperature Seals
Research will quantify the leakage performance of a novel gas seal for high temperature gas turbines and steam turbines.
RESEARCH PRODUCTS•Reliable leakage database•ASME journal publication•Technical report (M.S. thesis)
Questions (?)
[1] San Andrés, L., and Ashton, Z., 2010, "Comparison of LeakagePerformance in Three Types of Gas Annular Seals Operating at a High Temperature (300°C)," Tribol. Trans., 53(3), pp. 463-471.
Learn more athttp://rotorlab.tamu.edu
References
[2] Justak, J., and Doux, C., 2009, “Self-Acting Clearance Control forTurbine Blade Outer Air Seals,” ASME Paper GT2009-59683.
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