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

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

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

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

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

ARL Penn State Schematic of Cavitation Damage Test Configuration

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

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

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

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

ARL Other Cavitation Damage Test Samples Penn State Other Cavitation Damage Test Samples Propeller bronze- 20 hrs @ 61 m/sec Paint- 5 hrs (top), 8.3 hrs (bottom)

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

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

ARL Penn State

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

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

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

ARL Penn State Heart Valve Cavitation

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

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