A Test Rig for Evaluation of Thrust Bearings and Face Seals

Transcription

1 TRC-B&C TRC Project 32513/1519F2 May 2015 Year II A Test Rig for Evaluation of Thrust Bearings and Face Seals Luis San Andrés, Michael Rohmer, Scott Wilkinson

2 Justification Compressors, turbochargers, turbo expanders, blowers, etc., rely on thrust bearings as they are the primary means of axial load support and rotor position. Axial loads in turbomachinery are speed and pressure dependent, their prediction is largely empirical. Thrust bearing design relies on validated models, experimental results will benchmark predictive tools for thrust bearings. 2

3 Cross Section of Thrust Bearing Test Rig Thrust Load Mechanism Air Buffer Seals Shaker Aerostatic Bearings Rotor Assembly 0 2 in 4 in Test Thrust Bearing Radial Hydrostatic Bearings Slave Thrust Bearing 3

4 Exploded View of Thrust Bearing Test Rig 4

5 Schematic Thrust Bearing Test Rig TB load shaft + housing (3.4 lb) Thrust Bearings (Test & Slave): Kz, Cz Axial Force Rotor (8.7 (8.5 lb) Radial (air) Bearings: Kxx, Kyy, Cxx, Cyy Radial (water) Bearings: Kxx, Kxy, Kyx, Kyy, Cxx, Cyy, Cxy, Cyx Test Thrust Bearing 5

6 Proposed Work Year II Complete revamping of test rig: alignment of rotor, installation of instrumentation. Measurement film thickness vs. thrust load over a range of rotor speed and supply pressure to 6 bar for a water lubricated hybrid thrust bearing. Compare measurements to predictions from thrust bearing code. 6

7 Summary of Work Complete revamping of test rig: Manufacture new rotor. Repair housing. Align rotor and motor shaft. Design and build static load system. Calibrate and install instrumentation and data acquisition. System analysis & troubleshooting Free-free mode natural frequencies and shapes. Rotor-bearing system natural frequency and damping ratio (without rotor speed). Measurement of clearance vs. thrust load for operation with water at various bearing supply pressure and no shaft rotational speed. 7

8 Water Manifold System Update Purpose: Mitigate pressure drop across the water manifold Increase pipe diameter. 8

9 Rotor Thrust Collar Planicity 9

10 Alignment of Rotor and Motor Shaft L Distance between Hinge Points on Coupling 140 mm M Distance between Coupling Centerline and Measurement 34 mm A Allowable Misalignment mm/mm x L y M A x : total indicated runout on the rim [mm] y : on the face [mm] 10

11 Flexure Pivot Tilting Pad Hybrid Bearings water lubrication Bearing Radial Clearance 89 μm Inner Diameter 38.1 mm Outer Diameter 76.2 mm Length 38.1 mm Pads Number of Pads 4 Arc Length 72 Pivot Offset (dim) 60 % arc length Preload (dim) 0.2 Flexure Stiffness 200 Nm/rad Pockets Axial Length 12.7 mm Arc Length 24 Depth 508 μm Mean Diameter 54.9 mm Pocket/Wetted Area Ratio 0.11 Orifices Diameter 1.7 mm Radial Injection 50% of pocket length 11

12 Hybrid Thrust Bearings water lubrication Bearing Inner Diameter 40.6 mm Outer Diameter 76.2 mm Axial Clearance μm Pockets Number of Pockets 8 Mean Diameter 54.9 mm Radial Length 8.1 mm Arc Length 20 Depth 445/508 μm Pocket/Wetted Area Ratio 0.19 Orifices Diameter 1.8 mm Radius location 27.4 mm 12

13 Rotor-Coupling Free-Free Mode Natural Frequency and Shapes (a) Rotor Quill Shaft Coupling 101 Hz (test) 104 Hz (XLTRC2) (b) Rotor Quill Shaft Coupling 544 Hz (test) 555 Hz (XLTRC2) (c) Rotor Quill Shaft Coupling 1280 Hz (test) 1304 Hz (XLTRC2) Findings: Test rotor and quill shaft must be considered as a single unit. 13

14 Journal Bearing Predictions Load=19 N P S ε Q P R K XX K YY C XX C YY ε = c = Clearance (89 μm) e = Static Eccentricity [μm] = 0 rpm P S ε Q P R K XX K YY C XX C YY Supply Pressure [bar(g)] Static Eccentricity Ratio Flow Rate [LPM] Pocket Pressure [bar(g)] Vertical Direct Stiffness [MN/m] Horizontal Direct Stiffness [MN/m] Vertical Direct Damping [Ns/m] Horizontal Direct Damping [Ns/m] 14

15 Rotor-Coupling-Bearing System Natural Frequency and Damping Ratio (without Rotor Speed) Procedure: Water supplies journal bearings (no rotor speed or active thrust bearings). Impact load exerted on quill shaft, rotor motions used to identify natural frequency and damping ratio of system. Findings: Natural frequency increases little with water supply pressure. Quill shaft flexibility places critical speed and determines low damping ratio. Predictions agree with test data. 15

16 TB clearance and pocket pressure (w/o rotor speed) Findings: Clearance decreases as applied load per unit area increases. Load per unit area is only a fraction of water supply pressure. Area = = Pocket Pressure Ratio P S = Supply Pressure P R = Pocket Pressure P A = Ambient Pressure (0 bar (g)) Findings: As clearance decreases, flow rate decreases and pocket pressure increases. 16

17 Static & Dynamic Load System Purpose: Apply static and/or dynamic loads onto thrust bearing. Design and construction in progress. 17

18 Proposed Work Year III Apply thrust load (max. 670 N [2.0 bar specific load]) over a range of rotor speed (max. 9 krpm) and supply pressure (max. 6 bar (g)) into water-lubricated hybrid thrust bearing: Measure TB clearance, flow and pocket pressure vs. specific thrust load (max. 2.0 bar) Measure axial response from dynamic load with excitation frequency (max. 150 Hz) Estimate experimental thrust bearing force (K,C,M) coefficients. Compare measurements to predictions from XLHYDROTHRUST. Accommodate other thrust bearing configuration Max speed: 9 krpm Bearing OD: 3 inch (76 mm) 18

19 TRC Budget Year III Support for GS (20 h/week) x $2,100 x 12 months $ 25,200 Fringe benefits (2.7%) & medical insurance ($255/month) $ 3,740 Tuition three semesters ($362 credit hour X 24 h/year) $ 8,712 Recirculation pump $ 3,500 Registration and Travel to US Conference $ 1,500 Supplies: piping, cables, etc. $ 900 Total $ 44,952 19

20 Questions (?) TRC-B&C Revamping and Preliminary Operation of a Thrust Bearing Test Rig Luis San Andrés, Michael Rohmer, Scott Wilkinson Acknowledgments Thanks to Turbomachinery Research Consortium and TAMU Turbomachinery Laboratory. Also, thanks to Giovanni Pallini and Maxime Deslandes. 20

21 Background information

22 USET Thrust Bearing Test Rig USET Research Program ( ): $787,300 Test Rig: $288,500 Test Thrust Bearing Radial Bearings Slave Thrust Bearings inch in Rotor 2 2

23 Instrumentation and Data Acquisition Sensor Range Quantity Purpose Turbine Flow Meter Eddy Current Sensor Static Pressure Transducer Strain Gauge Load Cell Optical Tachometer Signal Conditioner LabView DAQ GPM mm psig lbf krpm X ±10 V Measure supply flow rates into journal bearing and test thrust bearing, measure exhaust flow rate through inner diameter of thrust bearing. Measure the lateral position, the axial clearance, and planar orientation of each thrust collar. Measure the supply pressure into each journal bearing, the slave thrust bearing, and the test thrust bearing. Measure the pocket pressures in the test thrust bearing. Measure the axial load applied by the test thrust bearing. 1 Measure the rotor speed. 12 Apply voltage offsets to voltages from eddy current sensors. Amplify voltage from strain gauge load cell. ±10 V 16 Acquire and record voltages or currents from each 0-20 ma 8 sensor. 23

24 Components of Motor Drive System SKF Precision/Gilman Technologies Spindle Motor Drive (D45985) 22KW (30 30,000 RPM Constant torque 0 30,000 RPM (62 lb-in torque) Digital closed-loop speed control with LabView interface Water chiller All subsequent required hardware and software Coupling Corp. of America (CCA), Custom Coupling - FLEXXOR Twin-diaphragm or Quill shaft design with Anderson Locking hub(s) 30,000 RPM Maximum speed rating 825 lb-in max. continuous torque +/ inch Axial Travel allowance (> 8X req d.) Low axial spring rate ( lb/0.001 inches) Weight: lbs. Inertia (Ip): lb-in^2 24

25 Objective and Tasks ( ) Test rig funded by USET (AF) program Design and construction of thrust bearing test rig. Measurements of minimum film thickness, pocket pressures, and flow rates in a water hybrid thrust bearing at various speeds and loads. Comparison of test data to prediction of performance from XLHYDROTHRUST. 25

26 Test Results and Predictions 250 psi TB clearance vs. load at rotor speeds of 7.5 krpm, 12.5 krpm, and 17.5 krpm. San Andres, 2008, JANAFF paper 26