A Test Rig for Evaluation of Thrust Bearings and Face Sealsrotorlab.tamu.edu/tribgroup/2015 TRC San Andres/PDF of... · Cross Section of Thrust Bearing Test Rig Rotor Assembly 0 2

A Test Rig for Evaluation of Thrust Bearings and Face Seals

Luis San Andrés, Michael Rohmer, Scott Wilkinson

TRC Project 32513/1519F2

TRC-B&C-02-2015

May 2015

Year II

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.

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Cross Section of Thrust Bearing Test Rig

Rotor Assembly

0 2 in 4 in

Air Buffer Seals

Slave Thrust Bearing

Radial Hydrostatic Bearings

Aerostatic Bearings

Shaker

Thrust Load Mechanism

Test Thrust

Bearing3

Exploded View of Thrust Bearing Test Rig

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Schematic Thrust Bearing Test Rig

TB load shaft + housing (3.4 lb)

Rotor (8.7 lb)

Thrust Bearings (Test & Slave): Kz, Cz

Radial (water) Bearings: Kxx, Kxy, Kyx, Kyy, Cxx, Cyy, Cxy, CyxRadial (air) Bearings: Kxx, Kyy, Cxx, Cyy

Test Thrust

Bearing

Axial Force

(8.5 lb)

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Proposed Work 2014-2015

• 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.

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Year II

Summary of Work 2014-2015

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• 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.

Water Manifold System Update

Purpose: Mitigate pressure drop across the

water manifold –Increase pipe

diameter.

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Rotor Thrust Collar Planicity

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Alignment of Rotor and Motor Shaft

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x y AL M

L Distance between Hinge Points on Coupling 140 mmM Distance between Coupling Centerline and Measurement 34 mmA Allowable Misalignment 0.0105 mm/mm

x : total indicated runout on the rim [mm]y : “””” on the face [mm]

Flexure Pivot Tilting Pad Hybrid Bearings

water lubrication

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Bearing Radial Clearance 89 μmInner Diameter 38.1 mmOuter Diameter 76.2 mmLength 38.1 mm

Pads Number of Pads 4Arc Length 72°Pivot Offset (dim) 60 % arc lengthPreload (dim) 0.2Flexure Stiffness 200 Nm/rad

Pockets Axial Length 12.7 mmArc Length 24°Depth 508 μmMean Diameter 54.9 mmPocket/Wetted Area Ratio 0.11

Orifices Diameter 1.7 mmRadial Injection 50% of pocket

length

Hybrid Thrust Bearings

water lubrication

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Bearing Inner Diameter 40.6 mmOuter Diameter 76.2 mmAxial Clearance 13 - 140 μm

Pockets Number of Pockets 8Mean Diameter 54.9 mmRadial Length 8.1 mmArc Length 20°Depth 445/508 μmPocket/Wetted Area Ratio 0.19

Orifices Diameter 1.8 mmRadius location 27.4 mm

Rotor-Coupling Free-Free Mode Natural Frequency and Shapes

101 Hz (test)104 Hz (XLTRC2)

544 Hz (test)555 Hz (XLTRC2)

1280 Hz (test)1304 Hz (XLTRC2)

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RotorQuill Shaft

(a)

(b)

(c)

Coupling

RotorQuill Shaft

Coupling

RotorQuill Shaft

Coupling

Findings: Test rotor and quill shaft must be considered as a single unit.

Journal Bearing Predictions Load=19 N

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PS ε Q PR KXX KYY CXX CYY1.38 0.26 5.7 0.86 0.81 0.81 720 7582.07 0.20 7.4 1.06 1.10 1.10 800 8202.76 0.16 8.8 1.26 1.33 1.33 872 8833.45 0.14 10.0 1.44 1.52 1.54 936 9464.14 0.12 11.0 1.62 1.69 1.71 1001 10084.83 0.11 12.0 1.81 1.85 1.87 1063 10665.52 0.10 12.9 2.00 2.01 2.02 1120 11226.21 0.10 13.7 2.20 2.16 2.17 1176 11776.89 0.09 14.5 2.38 2.31 2.32 1229 1228

PS Supply Pressure [bar(g)]ε Static Eccentricity RatioQ Flow Rate [LPM]PR Pocket Pressure [bar(g)]KXX Vertical Direct Stiffness [MN/m]KYY Horizontal Direct Stiffness [MN/m]CXX Vertical Direct Damping [Ns/m]CYY Horizontal Direct Damping [Ns/m]

ε =

c = Clearance (89 μm)e = Static Eccentricity [μm]

= 0 rpm

Rotor-Coupling-Bearing System Natural Frequency and Damping Ratio (without Rotor Speed)

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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.

TB clearance and pocket pressure (w/o rotor speed)

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Findings: As clearance decreases, flow rate decreases and pocket

pressure increases.

Findings: Clearance decreases as applied load per unit area

increases. Load per unit area is only a fraction of water supply

pressure.

PS = Supply Pressure

= Pocket Pressure Ratio

PR = Pocket Pressure

PA = Ambient Pressure (0 bar (g))

Area =

Static & Dynamic Load System

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Purpose: Apply static and/or dynamic loads onto thrust

bearing.

Design and construction in progress.

Proposed Work 2015-2016

• 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 krpmBearing OD: 3 inch (76 mm)

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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:

Year III

TRC Budget 2015-2016Support for GS (20 h/week) x $2,100 x 12 months $ 25,200Fringe benefits (2.7%) & medical insurance ($255/month) $ 3,740Tuition three semesters ($362 credit hour X 24 h/year) $ 8,712Recirculation pump $ 3,500Registration and Travel to US Conference $ 1,500Supplies: piping, cables, etc. $ 900Total $ 44,952

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Year III

Questions (?)TRC-B&C-02-15Revamping and Preliminary Operation of a Thrust Bearing Test Rig Luis San Andrés, Michael Rohmer, Scott Wilkinson

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Thanks to Turbomachinery Research Consortium and TAMU Turbomachinery Laboratory.

Acknowledgments

Also, thanks to Giovanni Palliniand Maxime Deslandes.

Background information

0 6 12inch

USET Thrust Bearing Test Rig

0 2 4 in

Radial Bearings

Test Thrust Bearing

Rotor

Slave ThrustBearings

USET Research Program (2005-2008): $787,300Test Rig: $288,500

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Instrumentation and Data Acquisition

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Sensor Range Quantity Purpose

Turbine Flow Meter

0.25-25 GPM 3

Measure supply flow rates into journal bearing and test thrust bearing, measure exhaust flow rate through inner diameter of thrust bearing.

Eddy Current Sensor 0-2 mm 10 Measure the lateral position, the axial clearance, and

planar orientation of each thrust collar.

Static Pressure Transducer

0-300 psig 5

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.

Strain Gauge Load Cell 0-500 lbf 1 Measure the axial load applied by the test thrust

bearing.Optical Tachometer

1-250 krpm 1 Measure the rotor speed.

SignalConditioner

1-1000X±10 V

12 Apply voltage offsets to voltages from eddy current sensors. Amplify voltage from strain gauge load cell.

LabView DAQ±10 V 16 Acquire and record voltages or currents from each

sensor.0-20 mA 8

Components of Motor Drive System

SKF Precision/Gilman TechnologiesSpindle Motor Drive (D45985)22KW (30 HP) @ 30,000 RPMConstant torque 0 – 30,000 RPM (62 lb-in

torque)Digital closed-loop speed control with

LabView interfaceWater chillerAll 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 rating825 lb-in max. continuous torque+/- 0.024-0.048 inch Axial Travel allowance (> 8X req’d.)Low axial spring rate (0.01 - 0.02 lb/0.001 inches)Weight: 2.1 – 3.5 lbs.Inertia (Ip): 2.6 – 5.3 lb-in^2 24

Objective and Tasks (2005-2008)

• 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.

Test rig funded by USET (AF) program

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Test Results and Predictions

TB clearance vs. load at rotor speeds of 7.5 krpm, 12.5 krpm, and 17.5 krpm.

San Andres, 2008, JANAFF paper

250 psi

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