r. phillips, w. straka, a. fontaine (penn state/arl)
DESCRIPTION
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) - PowerPoint PPT PresentationTRANSCRIPT
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
ARLPenn State 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)
Wang [2007] – Turbine cavitation
MHK turbine concepthttp://www.verdantpower.com/
http://www.seageneration.co.uk
ARLPenn State 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
Wang [2007] – Turbine cavitation
MHKF1-180s Tip Section Foil
ARLPenn State 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
508x114mm Rectangular Test Section Three part fin design to minimize end wall effects
203.2mm chord , Re = 1.3M
ARLPenn State
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
ARLPenn State
Test Results:NACA 4412 - Clean 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)
Bubble
Sheet
Gap
NACA 4412 one-part Fin Developed Cavitation
σ=2.0, =10
σi=2.18
NACA 4412 one-part Fin (near inception)
Cavitation Inception
Performance
ARLPenn State
Test Results: MHKF1-180 - Force Data
• 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
Drag performance (clean vs fouled foil)60 grit carborundum roughness applied
Lift performance (clean vs fouled foil)
7%
ARLPenn State
Test Results: MHKF1-180 - Cavitation visualization
• MHKF1-180 – Clean foil
Sigma = 1.1, alpha = 8 deg.
Sigma = 3.9, alpha = 14 deg.
Developed Cavitation Near Inception (bubble/patch)
ARLPenn State
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
ARLPenn State
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
Distributed leading edge roughness
36%
33%
26%
19%
12%
6%
1 to 2.5%Isolated roughness elements
7%
Gap Cavitation
LocalizedPatch Cavitation
MHKF1-180σ=1.15, =4
σi=1.07
ARLPenn State
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
ARLPenn State 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
ARLPenn State
Questions?