The Effect of In-Flow and Counter-Rotating Props on the Efficiency - - PowerPoint PPT Presentation

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The Effect of In-Flow and Counter-Rotating Props on the Efficiency - - PowerPoint PPT Presentation

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DYNAMIC POSITIONING CONFERENCE OCTOBER 911, 2017 THRUSTERS The Effect of In-Flow and Counter-Rotating Props on the Efficiency of Azimuthing Thrusters H.A. Reynolds and Wu Zhu Diamond Offshore Drilling The Effect of In-Flow and

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SLIDE 1

DYNAMIC POSITIONING CONFERENCE

OCTOBER 9‐11, 2017

THRUSTERS

The Effect of In-Flow and Counter-Rotating Props

  • n the Efficiency of Azimuthing Thrusters

H.A. Reynolds and Wu Zhu Diamond Offshore Drilling

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SLIDE 2

The Effect of In-Flow and Counter-Rotating Props

  • n the Efficiency of Azimuthing Thrusters

H.A. Reynolds, Director R&D Wu Zhu, Structural Engineering Specialist Diamond Offshore Drilling, Inc.

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SLIDE 3

Floating Factory Drillship Design

LWL 222 Meters Beam 39 Meters Draft 11 Meters Displacement ~80,000 Metric Tons Thrusters (6) 5500 kW, 7-8 deg down-angle Props 4.3M φ, 4 knots in-rush

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SLIDE 4

MARIN Tow Tank & Wave Basin Testing

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SLIDE 5

Thruster Efficiency vs. Heading

(DNV DP Analysis 4020.03 Rev. A)

Thruster Heading T1 T2 T3 T4 T5 T6

0.97 0.97 0.97 0.97 0.97 0.97 30 0.97 0.97 0.97 0.97 0.97 0.97 60 0.97 0.97 0.97 0.97 0.97 0.97 90 0.97 0.97 0.97 0.97 0.97 0.97 120 0.97 0.97 0.97 0.85 0.84 0.89 150 0.97 0.97 0.97 0.79 0.79 0.82 180 0.97 0.97 0.97 0.79 0.79 0.79

  • 150

0.97 0.97 0.97 0.79 0.79 0.82

  • 120

0.97 0.97 0.97 0.84 0.85 0.89

  • 90

0.97 0.97 0.97 0.97 0.97 0.97

  • 60

0.97 0.97 0.97 0.97 0.97 0.97

  • 30

0.97 0.97 0.97 0.97 0.97 0.97

Ref: Norbert Bulten & Petra Stoltenkamp. Improved DP Capability with Tilted Thruster Units and Smart Controls Algorithms. MTS-DP Conference Oct. 2016

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SLIDE 6

Ocean Blackhawk Wake, Transiting Indian Ocean

7 deg down-angle thrusters, ~12 knots at 70% power, CW props

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SLIDE 7

Ocean Blackhawk Wake, Transiting Indian Ocean

7 deg down-angle mechanical thrusters, ~12 knots at 70% power, CW props

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SLIDE 8

Multi-Screw Propellers Rotation (from Astern)

Conventional Twin Screw Counter-Rotation Conventional Thruster Rotation CFD Model Thruster Rotation (A) CFD Model Thruster Rotation (B)

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SLIDE 9

Gear-Drive Thruster

7 Degree Down-Angle Spiral Bevel Gear Set Right-Hand Bull Gear Left-Hand Pinion Gear

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SLIDE 10

Floating Factory Hull Blackship (Gusto P-10000) Hull

Diamond Drillships

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SLIDE 11
  • 2 seats of CCM+ Software (cd-Adapco)
  • Diamond Cluster (200 cores) or TACC (1000-2000 cores)
  • K-Ω Solver
  • Sliding Contact at Propeller-Nozzle interface
  • Convergence Tests on Time-Step and Cell Size
  • Props monitored for cavitation

CFD Thruster Models

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SLIDE 12

Prop & Kort Nozzle “Trimmer” Mesh

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SLIDE 13

Typical Prop-Tip Cavitation

Floating Factory, Zero Degrees, 100% Power

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SLIDE 14

Percent Input Power Prop RPM Thruster Force (Metric Tons) Mfgr. CFD 100% 169 105 104.99 80% 157 90 90.01 60% 142 74 73.70 40% 124 57 56.88

CFD Correlation with Open-Water Thrust

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SLIDE 15

80% 85% 90% 95% 100% 105% DNV Efficiency Floating Factory CFD 80% CW Props T1 T2 T3 T4 T5 T6

Thruster Efficiency: DP Analysis vs. CFD

Zero Degrees Azimuth, 80% Power Clock-Wise (CW) Props

“Wrong-Way” Props

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SLIDE 16

80% 85% 90% 95% 100% 105% DNV Efficiency Floating Factory CFD 80% CW Props Floating Factory CFD 80% Counter Rotation (A) Floating Factory 80% Counter-Rotation (B) T1 T2 T3 T4 T5 T6

Thruster Efficiency: Counter-Rotating Props

Floating Factory, Zero Degrees Azimuth, 80% Power

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SLIDE 17

85% 90% 95% 100% 105% DNV Efficiency Floating Factory CFD 80% Counter Rotation (A) Blackships CFD 80% Counter-Rotaion (A) T1 T2 T3 T4 T5 T6

Thruster Efficiency: Hull Comparison

Zero Degrees Azimuth, 80% Power

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SLIDE 18

70% 80% 90% 100% 110% 120% 130% DNV, 0-60 Degs CFD 10 Degrees CFD 20 Degrees CFD 30 Degrees CFD 60 Degrees T1 T2 T3 T4 T5 T6

Thruster Efficiency: Various Headings

Floating Factory, 80% Power, Counter-Rotation (A)

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SLIDE 19

The Problem with Thruster T6: The Skeg

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SLIDE 20

Velocity Plot, Cross-Section Through Thruster T2

Zero Degrees Heading, 100% Power, 99% efficiency

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SLIDE 21

Velocity Plot, Cross-Section Through Thruster T2

30 Degrees Heading, 100% Power, 117% efficiency

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SLIDE 22

Velocity Vectors, Cross-Section Through Thruster T2

Zero Degrees Heading, 100% Power, 99% efficiency

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SLIDE 23

Velocity Vectors, Cross-Section Through Thruster T2

20 Degrees Heading, 100% Power, 117% efficiency

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SLIDE 24

Velocity Vectors, Cross-Section Through Thruster T2

30 Degrees Heading, 100% Power, 117% efficiency

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SLIDE 25

EfficiencyIncrease, TypicalBiasMode

CFD Models vs. DP Analysis Floating Factory, 80% Power, Counter-Rotation (A)

Thruster

T1 T2 T3 T4 T5 T6

Heading

30 330 150 210 180

Efficiency Increase

0.8% 21.4% 21.4% 30.5% 30.5% 13.8%

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SLIDE 26
  • Down-angle thrusters virtually eliminate Coandă Effect, but make thruster

efficiency highly dependent upon intake flows.

  • Thruster efficiency varies significantly with:

(a) Thruster Heading; generally highest normal to the turn of the bilge. (b) Prop Rotation; generally highest “together at the top”.

  • Thruster efficiency is similar between two hulls at Zero Degrees heading.
  • Previous analytical methods don’t consider intake flows or prop rotation.
  • Use CFD to optimize thruster efficiency on new-build DP vessels, including:
  • Varying thruster position
  • Optimizing hull shape (e.g. bilge radius, skeg design, etc.)

Conclusions

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SLIDE 27

THE END