FLOW RATES IN A SHORT LENGTH WET (BUBBLY) SEAL AND TEST RIG RE-DESIGN

Transcription

1 TRC 32513/1519NS Year II MAKING A WET (FOAMY) SEAL AND ESTIMATING ITS DYNAMIC FORCE COEFFICIENTS FLOW RATES IN A SHORT LENGTH WET (BUBBLY) SEAL AND TEST RIG RE-DESIGN Qing Liu Research Assistant, Ph.D. Luis San Andres Mast-Childs Professor May 2014

2 Motivation Application Subsea compression and pumping Effect of two phase flow on seals Leakage rate Dynamic force Stability Status of current research: Theoretical models available Lack of experimental validation 2

3 Previous Work in Year I Prepare test rig for measurements Seal test rig Center rotor/seal, calibrate instrumentation Prepare motor to run up to 6 krpm Upgrade oil supply/return system Prepare to make air-oil mixtures Fabricate mixing device for supply pressures to 100 psig max. (shop air). 3

4 Overview of work in Year I Improved lubrication system Made air-oil mixtures with gas volume fraction (GVF) > 0.9 Measured flow rates with pure oil, air, and with mixture Designed (manufactured) new test rig 4

5 Test Rig Description Vertical TRC SFD Lubricant supply Supporting bars Bearing cartridge Shaker Diameter Length clearance Seal 127 mm (5in) 25.4 mm (1in) mm (5mil) Lubricant ISO VG 10 Supply pressure 1~3 bar Oil density 846 kg/m 3 viscosity 16.9 cp at 20ºC Air density viscosity 1.2kg/m 3 at 1bar 0.018cP at 20ºC, 1bar 5

6 Test Rig Description Vertical TRC SFD Bearing cartridge Seal Eddy current sensor Rotor Load cell Diameter Length clearance Seal 127 mm (5in) 25.4 mm (1in) mm (5mil) Lubricant ISO VG 10 Supply pressure 1~3 bar Oil density 846 kg/m 3 viscosity 16.9 cp at 20ºC Air density viscosity 1.2kg/m 3 at 1bar 0.018cP at 20ºC, 1bar 6

7 Lubrication System Oil Inlet (ISO VG 10) Air Inlet Valves Air Valves Sparger (mixing) element Oil Test seal section 7

8 Flow Rate Measurement Flow rate of single phase flow (only oil) vs. supply pressure 1.7~3.0 bar (absolute pressure) Rotor speed: ~810 rpm (13.5 Hz) Temperature: ~20º C oil only (GVF=0) Uncertainty: ±0.14 g/s Mass flow rate (kg/s) measurement prediction Supply pressure (bar) Prediction: XLHsealH TM

9 Flow Rate Measurement Flow rate of mixture vs. supply pressure 2.2~3.0bar (absolute pressure) Room temperature ~20ºC Air volume fraction (at supply pressure): ~0.96 GVF= Air mass fraction,, 1 Mass fraction is constant as there is no mass transfer between oil and air. 9

10 Flow Rate Measurement GVF=0.96 Mass flow rate (kg/s) measurement prediction Pressure (bar) Uncertainty: ±0.14 g/s Prediction Hseal_mix2010 TM Differences are due to viscosity of mixture. Mass fraction of air Air mass fraction ~0.1 Small volume content of oil (0.04) but large mass fraction (~0.90) Supply pressure (bar) Max Reynolds number Reynolds number Pressure (bar)

11 Test Rig Re-Design Problems with current test rig (old age): For Ps >3 bar, Leakage between cartridge lid and Plexiglas bearing, Cartridge lid warps. Cartridge displaces sideways: connections between supporting rods and cartridge/test rig frame are lose. Need a new test rig! Cartridge lid Plastic bearing Vertical test rig Test rig frame Support rods 11

12 Test Rig Re-Design Design of casing and seal Option 1: changeable bearing Decision: use Option 2 Option 2: non-changeable bearing Schematic views Advantage Easy to change seal geometry Easy to assemble. Disadvantage Difficulty in alignment. Leakage between the bearing and casing. Re-machine to change seal geometry Cannot resume previous geometry after re-machining 12

13 Test Rig Re-Design Design of support Option 1: four bar support Decision: use Option 2 Option 2: pipe support Schematic views Advantage Experience. Existing this support Easy to install and align. Firm connection, prevents sideway displacement Disadvantage Difficulty in alignment. Pressurization may have effect pipe stiffness 13

14 Test Rig Re-Design Sensor locations Decision: use Option 2 Option 1 Option 2 accelerometer Eddy current sensor accelerometer Schematic view Advantage Disadvantage Load cell Easy to install sensors Easy to (dis)assemble test rig Lid deformation affects displacement measure Accelerometer not on mass center Load cell Eddy current sensor Improve displacement measurement Load cell and accelerometer are on mass center Need additional parts for load cells Need to reinstall eddy current sensor when disassemble test rig 14

15 New Test Rig Features Seal diameter: D=127mm, length: L=45.7mm L/D=0.36, Radial clearance: c=0.127mm Lubricant ISO VG10 Viscosity: 16cP at 20 C Density: 845kg/m 3 Weight: ~9kg 15

16 New Test Rig Designed new parts and assembly Machined new parts and assembly Total cost (new parts + test rig frame modification): $4,887 16

17 Proposed work Assemble new test rig and trouble shoot. Generate mixtures and measure flow rates: With various GVFs supply pressure up to 100 psig Rotor speed up to 6,000 rpm Force coefficients measurement Install shakers and perform single frequency dynamic load measurements Identification of force coefficients Visual inspection of bubbly mixture 17

18 TRC Budget Year II Support for graduate student (20 h/w) x $ 2,200 x 12 months $ 26,400 Fringe benefits (2.4%) and medical insurance ($118/month) $ 2,050 Tuition & fees three semesters ($363/credit hour) $ 8,712 Supplies: motor speed controller $1,200, oil $600, $ 3,800 manufacture odd parts $2,000 Other (PC-DAQ, HD storage) $ 1, Year II $ 42,462 18

19 Questions (?): 19