1. GT2009-59072 Hybrid Brush Seal Force Coefficients R OTORDYNAMIC F ORCE C OEFFICIENTS OF A HYBRID BRUSH SEAL: M EASUREMENTS AND P REDICTIONS Luis San Andres Jose Baker Mast-Childs Professor Project Engineer Texas A&M University KBR, Inc. Adolfo Delgado Mechanical 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

2. GT2009-59072 Hybrid Brush Seal Force Coefficients Justification Improved Brush Seal Technology Offers: Higher engine performance with less parasitic leakage Improved engine stability and reduced engine vibration Lower 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

3. GT2009-59072 Hybrid Brush Seal Force Coefficients 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 1 st generation SBS Reduced leakage (~36%) over 1 st 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

4. GT2009-59072 Hybrid Brush Seal Force Coefficients 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.

5. GT2009-59072 Hybrid Brush Seal Force Coefficients Structural parameters K shaft = 243 lb f /in (42.5 kN/m) M s+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 RotorStinger Electromagnetic Shaker DC Motor Supporting springs Roller bearing assembly Eddy current sensor Spring Ball bearing Shaft Disk High pressure air Flow Flexible coupling to motor Hybrid brush seal Detail of brush seal test rig Experimental Facility Disc PsPs PePe Seal Flow

6. GT2009-59072 Hybrid Brush Seal Force Coefficients Test Hybrid Brush Seal (HBS) Spring Lever Mechanism * Close-up courtesy of Advanced Technologies Group, Inc. Courtesy of Advanced Technologies Group® Disc PsPs PePe Seal Flow

7. GT2009-59072 Hybrid Brush Seal Force Coefficients Identification of Rotordynamic Force Coefficients K xx, C xx K xy, C xy K yx, C yx K yy, C yy X Y For rotor centered operation:

8. GT2009-59072 Hybrid Brush Seal Force Coefficients Identification of HBS rotordynamic force Coefficients Identification at excitation frequency (ω) ≠ rotor speed (Ω) System ImpedancesImpedance Function and

9. GT2009-59072 Hybrid Brush Seal Force Coefficients Effect of rotor speed on rotor-HBS natural frequency Gyroscopic effects negligible for test rotor speeds (600 and 1,200 rpm [20 Hz]) Rotor Speed [RPM] 1 st Backward Nat. Frequency, [Hz] 1 st Forward Nat. Frequency, [Hz] 2 nd Forward Nat. Frequency, [Hz] 3rd Forward Nat. Frequency, [Hz] 030.5 1461351 60029.731.41541351 120028.832.21631351 Axial Location, z [m] Shaft Radius [m]

10. GT2009-59072 Hybrid Brush Seal Force Coefficients 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 N 600 rpm Frequency [Hz] X-displacement [  m] Y-displacement [  m] Frequency [Hz] X Y

11. GT2009-59072 Hybrid Brush Seal Force Coefficients K xx -  2 M xx Dynamic Stiffness vs. Frequency Load = 22 N, frequency 25-80Hz Model reproduces the measured real part of impedance. Little effect of pressurization Model TESTs Frequency [Hz] Re (Zxx) [kN/m]

12. GT2009-59072 Hybrid Brush Seal Force Coefficients Cross-coupled Stiffness vs. Frequency Load = 22 N, frequency 20-80Hz Identified cross-coupled mass is nearly 0 kg. Identified cross-coupled stiffness (K xx = -K yx ) is estimated as a constant independent of excitation frequency. K xy doubles as rotor speed increases from 600 and 1,200 rpm for both pressure conditions Pressure ratio P r =1.7P r =2.4 Rotor Speed [rpm], Ω 60012006001200 Stiffness [kN/m], K xy 8.8152.76.6 Mass [kg.], M xy 0000

13. GT2009-59072 Hybrid Brush Seal Force Coefficients Equivalent Viscous Damping (C xx ~C eq ) vs. Frequency Damping decreases with frequency, with little effect of supply pressure. Minimum value at test system natural frequency (~32 Hz) P r =1.7 600 rpm P r =2.4 1200 rpm Supply Pressure/Exhaust Pressure

14. GT2009-59072 Hybrid Brush Seal Force Coefficients Force coefficiensts: system & seal Load = 22 N, frequency 25-80Hz No rotation Tests with rotor spinning Pressure ratio P r = 1.0P r =1.7P r =2.4 Rotor Speed [rpm], Ω 0 60012006001200 Stiffness [kN/m], K xx 120 10898130124 Mass [kg.], M xx 2.11 2.622.542.432.39 R 2 (correlation factor) Dynamic stiffness (K xx – M xx ω 2 ) 0.970.98 HBS stiffness[kN/m], K s 93 10389135128 HBS Dry Friction coefficient, μ 0.66 0.390.360.370.38 HBS Loss Factor coefficient,  0.420.290.260.330.34

15. GT2009-59072 Hybrid Brush Seal Force Coefficients HBS predicted stiffness vs. frequency Frequency 25-100 Hz Predicted HBS stiffness (K sxx ) drops slightly in range from 20- 100 Hz. Tests show nearly constant K sxx Pressure (P r = P s /P d ) has negligible effect on seal direct stiffness, K sxx 600 rpm 1,200 rpm HBS Measured Stiffness, Ks Code: XL TPGASBEAR® Frequency [Hz] Stiffness Coefficients [kN/m] ASME GT2004-53614

16. GT2009-59072 Hybrid Brush Seal Force Coefficients HBS viscous damping coeff. vs. frequency Frequency 25-100 Hz HBS direct damping (C sxx ) decreases with excitation frequency. Loss factor coefficient (  ) represents physically seal structural (hysteresis) damping Pr = 2.4  Pr = 1.7  1,200 rpm Pr = 1.7  Pr = 2.4  600 rpm Increasing loss factor (  )

17. GT2009-59072 Hybrid Brush Seal Force Coefficients 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 (K sxx = K syy ) decreases minimally with rotor increasing rotor speed for P r = 1.7 and 2.4. HBS cross-coupled stiffness (K sxy = -K syx ) is one order of magnitude smaller than direct stiffnesses. HBS direct viscous damping coefficients decrease with increasing excitation frequency.

18. GT2009-59072 Hybrid Brush Seal Force Coefficients Thanks to Siemens Power Generation, Advanced Technologies Group (Mr. John Justak) www.advancedtg.com www.advancedtg.com Acknowledgments Questions ? Learn more at http://phn.tamu.edu/TRIBGrouphttp://phn.tamu.edu/TRIBGroup

19. GT2009-59072 Hybrid Brush Seal Force Coefficients HIGH TEMPERATURE SEAL FACILITY 8 3 2 3 4 6 1 7 Flow in (supply pressure) Flow out (ambient pressure) P e =101 kPa 0 1020 cm 2009 STLE Annual Meeting, May 2009

20. GT2009-59072 Hybrid Brush Seal Force Coefficients Max. air temperature (300ºC) & rotor speed (3 krpm) Compare Leakage from Three Seals 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 2009 STLE Annual Meeting, May 2009

21. GT2009-59072 Hybrid Brush Seal Force Coefficients Backup slides

22. GT2009-59072 Hybrid Brush Seal Force Coefficients HPLP ROTOR Pad profile Back plate Cantilever beam 4.445 mm 0.254mm 7.750 mm Front plate Bristle pack Back plate 16.674 mm Hybrid brush seal profile section HBS Pad Lift Off upon Pressurization PsPs P d ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505

23. GT2009-59072 Hybrid Brush Seal Force Coefficients HBS Leakage (No Shaft Rotation) Measured HBS leakage is ~ 36% less than that for a 1 st generation SBS over the test supply pressure range SBS HBS Supply Pressure = 5 to 30 psig Pressure ratio, Pr Leakage [g/s] ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505

24. GT2009-59072 Hybrid Brush Seal Force Coefficients Calculated Effective Clearance Effective clearance (C E ) as if one tooth laby seal SBS HBS Supply Pressure = 5 to 30 psig Pressure ratio, Pr Clearance [mm] ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505

25. GT2009-59072 Hybrid Brush Seal Force Coefficients Seal leakage is proportional to pressure ratio (discharge/exit ). Little dependency on rotor speed. HBS Leakage vs. Pressure Drop Pressure ratio, Pr Leakage [g/s] Supply Pressure = 5 to 30 psig ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505

26. GT2009-59072 Hybrid Brush Seal Force Coefficients 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 HBS Drag Torque [N-m] ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505

27. GT2009-59072 Hybrid Brush Seal Force Coefficients 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 Pr = 1.0 (No external pressurization) Pr = 1.7 Pr = 2.4 ΔP + Rotor Speed [RPM] HBS Power Loss [W] ASME Journal of Engineering for Gas Turbines and Power, 2009, 131(1), pp. 012505

28. GT2009-59072 Hybrid Brush Seal Force Coefficients Dynamic Load Tests (no shaft rotation) Equivalent Test System ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655

29. GT2009-59072 Hybrid Brush Seal Force Coefficients Harmonic force & displacements Impedance FunctionWork ExternalViscous Dissipation dtdt Parameter Identification (no shaft rotation) DRY FRICTION & STRUCTURAL DAMPING ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655

30. GT2009-59072 Hybrid Brush Seal Force Coefficients HBS Structural Coefficients Load = 63 N, frequency: 20-100 Hz (no shaft rotation) *: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 ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655

31. GT2009-59072 Hybrid Brush Seal Force Coefficients HBS Dynamic Stiffness vs. Frequency (no shaft rotation) Model TESTs Load = 63 N, frequency: 20-100Hz Model reproduces real part of the impedance under the given supply pressure conditions. Frequency [Hz] Re (F/x) [kN/m] ASME Journal of Vibrations & Acoustics, 2007, 129, pp. 648-655

32. GT2009-59072 Hybrid Brush Seal Force Coefficients Load = 63 N, frequency 20-110Hz 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) Frequency [Hz] Log (Ceq) [N-s/m]