R. Phillips, W. Straka, A. Fontaine (Penn State/ARL) - PowerPoint PPT Presentation

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R. Phillips, W. Straka, A. Fontaine (Penn State/ARL)

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  1. Cavitation and Hydrodynamic Evaluation of a Uniquely Designed Hydrofoil for Application on Marine Hydrokinetic Turbines R. Phillips, W. Straka, A. Fontaine (Penn State/ARL) M. Barone, E. Johnson (Sandia National Laboratory) C.P. van Dam, H. Shiu (Univ. California, Davis) 8th International Symposium on Cavitation August 14-16, 2012

  2. Motivation of Study • Increased interest in marine renewable energy in US and around the world • Leveraging wind turbine technology • Desire to maximize power output • Underwater environment has unique issue • Maintenance and lifecyle • Bio-fouling • Cavitation and erosion • Environmental/noise concerns (Kermeen 1956) MHK turbine concept http://www.seageneration.co.uk http://www.verdantpower.com/ Wang [2007] – Turbine cavitation

  3. Focus of Present Study • Performance evaluation of hydrofoil designed specifically for marine hydrokinetic (MHK) turbine application • Foil designed by Univ. California-Davis [Shiu, et al (2012)] • Foil design objectives: • High L/D (power output and efficiency) • Designed with extended region of laminar flow • Low roughness sensitivity (bio-fouling resistance) • Well defined stall point (stall controlled turbine) • Resistance to surface cavitation (erosion) • Anti-singing TE (environmental) (Kermeen 1956) Model of 3-bladed MHK turbine blade MHKF1-180s Tip Section Foil Wang [2007] – Turbine cavitation

  4. Experimental Setup • Penn State 12-inch diameter water tunnel (2-dimensional test section) • Two foils tested (clean / fouled) • NACA 4412 – baseline/validate test process • One & three-part foils model tested • MHKF1-180s • Three-part foil • Measurements: • Lift/drag/moments – 6-DOF load cell • Wake profiles and trailing shedding - LDV • Cavitation inception performance • Cavitation breakdown performance 203.2mm chord , Re = 1.3M Three part fin design to minimize end wall effects 508x114mm Rectangular Test Section

  5. Test Results:NACA 4412 - Force data • NACA 4412 – baseline foil used to validate setup / reduction procedure • Clean foil • Force data correction applied • Gap corrections [Kermeen (1956)] • Solid and Wake Blockage [Barlow, Rae and Pope (1999)] • No horizontal buoyancy correction needed • Good agreement with historical data Lift Drag

  6. Test Results:NACA 4412 - Clean Cavitation NACA 4412 one-part Fin Developed Cavitation • NACA 4412 – baseline/validation test • Clean foil • Cavitation inception performance • Desinent cavitation calls • 4.0 ppm air content • Good Agreement with historical data • Minimal hysteresis found (incepient vs. desinent) Cavitation Inception Performance σ=2.0, =10 σi=2.18 NACA 4412 one-part Fin (near inception) Bubble Sheet Gap

  7. Test Results: MHKF1-180 - Force Data Lift performance (clean vs fouled foil) • MHKF1-180 – Clean • Slightly higher lift before stall • Well defined stall • MHKF1-180 - Fouled • 60 grit elements (0-7% Chord) • Trip wire (.4mm) at 7% chord • Foil sensitive to fouling • Effectively de-cambers foil • Decrease both max lift and lift curve slope • Significant drag increase over clean foil • Premature transition 7% 60 grit carborundum roughness applied Drag performance (clean vs fouled foil)

  8. Test Results: MHKF1-180 - Cavitation visualization Sigma = 1.1, alpha = 8 deg. • MHKF1-180 – Clean foil Sigma = 3.9, alpha = 14 deg. Developed Cavitation Near Inception (bubble/patch)

  9. Test Results: MHKF1-180 - Cavitation Performance • MHKF1-180 – Clean foil • Minimal hysteresis found • Improved inception performance compared to 4412 at higher angles of attack • Improvement due to thickness effect Cavitation performance (MHK vs NACA 4412) Incipient vs Desinent Performance

  10. Test Results: Fouled Cavitation Performance • Cavitation performance sensitivity to roughness • Three “fouled” conditions • Distributed: 60 grit [250μm] - 50% coverage over 7% chord • Isolated: 46 grit [350μm] 16 grit [1092μm] • Applied to both NACA 4412 and MHKF1-180 Gap Cavitation 12% 19% MHKF1-180 σ=1.15, =4 26% Localized Patch Cavitation 33% 6% σi=1.07 36% 1 to 2.5% Isolated roughness elements 7% Distributed leading edge roughness

  11. Test Results: Fouled Cavitation Performance • Distributed Roughness • NACA 4412 minimal effect on cavitation inception • MHKF1-180 small degradation • Thickness and turbulent transition effects • Lift curve reduced with roughness • Neither show hysteresis • Isolated Roughness • NACA 4412 Large effect on cavitation performance / size had minimal effect • MHKF1-180 Decreased performance with increase element size Sensitive region located aft along chord - NACA 4412 showed significant hysteresis at higher angles of attack and larger elements NACA 4412 MHKF1-180

  12. Conclusions • Performance evaluations were completed for a new MHKF1-180 tip hydrofoil • Improved clean performance compared to NACA 4412 • Not quite fair comparison (t/c) • MHKF1-180 sensitivity to fouling • Lift/drag performance shows significant changes • Likely due to early transition • Cavitation performance minimally degraded with distributed roughness • Cavitation performance degraded with isolated roughness • MHK applications will require tradeoff between max power and longevity

  13. Questions?