1. Cavitation Damage Research at ARL Penn State
Presented to:
Cavitation Erosion Workshop
Presented by:
David R. Stinebring and Michael L. Billet
27 May 2004

2. Outline of Presentation
ARL
Penn State
Outline of Presentation
Ultra High-Speed Cavitation Tunnel
Cavitation damage test samples and sample holder design
Erosion resistant coating design and testing
Examples of test samples
Application to full-scale and erosion scaling
Other cavitation damage testing at ARL

3. Cavitation Damage Background
ARL
Penn State
David R. Stinebring
Cavitation Damage Background
“Scaling of Cavitation Damage”- Masters Thesis (AIAA National Student Award- Graduate Division
Cavitation/ damage in the Space Shuttle High- Pressure Oxidizer Pump
Analysis of flow, related damage, and design recommendations (reduced damage and increased pump efficiency)
Navy program- Tests of over 150 samples- in Ultra- High Speed Cavitation Tunnel
“Scaled acceptance criteria” – 20 hours at 195 fps at maximum cavitation intensity
Acceptance of coating and item “as fabricated”
Manufacturing procedures, thickness tolerances, adhesion criteria, imperfection tests, damage tests, repair tests, sea-soaked samples
Navy program- similar to above but different application, scaling
Navy program- Surface ship rudder cavitation erosion resistant coatings
Total of over 300 samples tested in Ultra- High Speed Cavitation Tunnel for Navy and private companies
Cavitation/ damage in automobile power steering pumps- Delphi Saginaw
Six contracts- proprietary improvements to system
Cavitation/ damage in diesel engines near fuel injectors- Cummins Engine
Developed diagnostics to solve problem
Cavitation/ damage in locomotive diesel engines- fuel lines/ fuel injectors- General Motors Electromotive Division- Developed technique to solve problem
Cavitation/ damage in prosthetic heart valves- in-vivo & in-vitro
Developed methodology for analyzing cavitation performance

4. ARL Ultra-High-Speed Cavitation Tunnel
Penn State
Ultra-High-Speed Cavitation Tunnel
Test section velocities to 13.7 to 94 m/sec and pressures to 8.3 MPa
All stainless steel
Heat exchanger
Variable air content
Test Section

5. ARL
Penn State
Schematic of ARL Penn State Ultra-High-Speed Cavitation Tunnel for Testing Erosion Resistant Coatings and Materials

6. ARL
Penn State
Schematic of Cavitation Damage Test Configuration

7. ARL Test Sample, Sample Holder Design, and Test Procedure
Penn State
Test Sample, Sample Holder Design, and Test Procedure
Flow
Sample holder is designed for a cycling cavity where the collapse is on the sample
Size and shape of leading edge is designed for maximum erosion
Sample fits within SS mount tight to edges
Typical cavitation erosion test- 61 m/sec for 20 hours at 66% air saturation
Cavity cycling frequency- approximately 500 Hz
Sample holder leading edge
Sample
SS sample mounts
Erosion pattern on aluminum

8. ARL Large Scale Dynamic Behavior of Cavity
Penn State
Large Scale Dynamic Behavior of Cavity
Cavity Cycling- Developed Cavitation
5000 Frames per second
Continuous lighting
Stroboscopic lighting

9. ARL Testing Erosion Resistant Coatings
Penn State
Testing Erosion Resistant Coatings
Test in tunnel has two size scales (frequency)- cavity shedding (approximately 2 cm) and cloud collapse (under 1 mm)
For “compliant” coatings must include dynamic behavior of coating- size scale and frequency of cavitation
For full scale application estimate size and frequency of cavitation
Low hardness and/or thicker compliant coatings’ -erosion resistance is dominated by the cavity shedding exciting the dynamic oscillation of the coating
Harder materials erode based on the cloud cavity collapse
Coating adhesion
Must match primer(s) between coating and substrate
For full-scale applications must consider impressed current for corrosion control
Test adhesion- PLI test
Recommended coating procedure
Qualify a coating, primer, thickness tolerance
Qualify a coating procedure- layers, layer thickness, application procedure
Spray test panels during full scale coating- test samples in tunnel
Test imperfections in coating- run test based on location of imperfection
Devise and test coating repair

10. ARL Coating Test Samples Delamination between coating layers
Penn State
Coating Test Samples
Delamination between
coating layers
Failure due to cavity cycling excitation of coating- internal failure
Failure between coating and substrate
20 hours at 61 m/sec-note damage to SS

11. ARL Other Cavitation Damage Test Samples
Penn State
Other Cavitation Damage Test Samples
Propeller bronze m/sec
Paint- 5 hrs (top), 8.3 hrs (bottom)

12. Cavitation Damage Prediction
ARL
Penn State
Cavitation Damage Prediction
(Why the problem is so difficult)
Cavity Volume
Bubble cavitation
Blade surface- shed volume
Vortex
Collapse location
Statistical variation
Inflow variations
Cavity cycling
Hydrodynamic Scaling
Volume of cavities
Cavity formation rate
Cavity collapse location wrt surface
Collapse location pressure and gradient
Cavity transport velocity to surface
Collapse efficiency
Collapse Efficiency
Angle of flow
Shape of boundary
Surface roughness
Cavity Formation Rate
Bubble formation rate
Blade surface- cycling frequency
and inflow variations
Vortex-area, velocity
Collapse location pressure and gradient
Steady/unsteady- cycling cavity
Material Response
Cavity Transport Velocity to Surface

13. ARL Rudder Cavitation Damage Scaling between tunnel and full-scale
Penn State
Rudder Cavitation Damage
Scaling between tunnel and full-scale
Tunnel test is maximized intensity (damage/area) for cavity length
Assuming similar cavity size scales- tip vortex core size
Same materials and substrates
- water tunnel test time
- full-scale time
- full-scale reference velocity
- water tunnel velocity
- full-scale air content
- water tunnel air content

14. ARL
Penn State

15. High Pressure Oxidizer Pump
NASA Space Shuttle
High Pressure Oxidizer Pump
ARL
Penn State
Inlet
casing
Drive turbine
Low
pressure
pump
Outlet

16. ARL Delphi-Saginaw Power Steering Pump Pump outlet Pump inlet Drive
Penn State
Pump outlet
Pump inlet
Drive
shaft
Schematic of flow control region
Cavitation
viewing window
Photograph of pump

17. ARL Cavitation in the Supercharge Port 300 psig pump outlet pressure
Penn State
Cavitation in the Supercharge Port
300 psig pump outlet pressure
1525 rpm
600 psig pump outlet pressure
1513 rpm

18. ARL
Penn State
Heart Valve Cavitation

19. ARL
Penn State
In Vivo Testing
Calf with ventricular assist device and cavitation monitoring instrumentation

20. ARL Summary ARL Approach: Identify full-scale cavitation patterns
Penn State
Summary
ARL Approach:
Identify full-scale cavitation patterns
Determine those situations where erosion could be an issue (experience- can be difficult)
Determine exposure time
Conduct erosion test on specific material (apply scaling relationships)
Provide estimates of erosion