Icing Physics Studies Using the 3D SIDRM Test Article: Ice Crystal Icing Analysis

National Aeronautics and Space Administration Icing Physics Studies Using the 3D SIDRM Test Article:

Ice Crystal Icing Analysis

Tadas P. Bartkus – Ohio Aerospace Institute Sam Lee – HX5 AIAA AVIATION Forum and Exposition July 29 – August 2, 2024 This material is a work of the U.S. Government and is not subject to copyright protection in the United States www.nasa.gov

1. Intro 2. Ice Crystal Cloud Characterization Tests 3. Ice Crystal Accretion Tests 4. General Icing Observations 5. Leading Edge Icing Threshold 6. Surface Heat Flux Impact 7. LE Melt Contribution and Resulting Accretion Downstream 8. Conclusions and Acknowledgements

Introduction – Why Study Engine Icing

• Numerous events of power - loss and engine damage reported since the 1990’s (Bravin, 2019) • Engine icing (ice crystal icing) studied at NASA (and elsewhere) • Full scale engine icing tests (Honeywell LF01, LF11 , HURE) • Component level fundamental icing physics studies • Goal : Gather data to develop and validate computational icing tools (like GlennICE) to predictively assess the onset and growth of ice in current and future engines during flight, to aid certification

21.7 in SIDRM

Testing General Details

schematic 71.8 in 62.6 in Flow • Conducted icing tests in the NASA Icing Research Tunnel (IRT) in 2022 • Ice accretion tests used Simulated Inter - compressor Duct Research Model (SIDRM) • 3D geometrical features of an inter - compressor duct and strut region of a turbofan engine (curved surface w/ strut) • Heated surfaces SIDRM • BUT did not fully simulate conditions profile • Different cloud: glaciated vs mixed phase view • Different air temp: subfreezing vs heated compressed air • Different pressures: ~1 atm vs altitude/compressed • Different flow field: open vs ducted • Tests conducted Generic • Supercooled liquid ice accretion tests engine • Ice crystal (IC) accretion tests schematic • Complementary IC cloud characterization tests (new capability)

1. Intro 2. Ice Crystal Cloud Characterization Tests 3. Ice Crystal Accretion Tests 4. General Icing Observations 5. Leading Edge Icing Threshold 6. Surface Heat Flux Impact 7. LE Melt Contribution and Resulting Accretion Downstream 8. Conclusions and Acknowledgements

Ice Crystal Cloud Characterization Instruments

Instrument Measurement MW : Multiwire Melt ratio and recirculation IKP 2 : Isokinetic Probe Version 2 Total water content RFP : Rearward Facing Probe Air temperature and humidity RFP BHBT PI - IC : Particle Imaging - Ice Crystal Particle size distribution TAT : Total Air Temperature Air temperature ID : Ice Detector (not shown) Glaciation (liquid presence) BHBT : Background Humidity Bent Tube Humidity IKP2 TAT MW 12 Icing clouds characterized • Total Water Content (TWC) • Particle Size Distribution (PSD) PI - IC MW MW

Cloud Recirculation and Continuation

1 1.8 1.6 ) 1.4 1.2 MW_HP 0.8 MW_083 0.6 Spray On/Off 0.4 0.2 Ice Water Content (g/m Spray On = 1, Off = 0 0 0 -500 0 500 1000 1500 2000 2500 3000 Time (s) Thaw resolved issue → Tunnel raised to 10 ° C for ~30 min to melt ice

1. Intro 2. Ice Crystal Cloud Characterization Tests 3. Ice Crystal Accretion Tests 4. General Icing Observations 5. Leading Edge Icing Threshold 6. Surface Heat Flux Impact 7. LE Melt Contribution and Resulting Accretion Downstream 8. Conclusions and Acknowledgements

Ice Accretion Test Objectives

Objectives: • Identify test parameter’s impact on ice accretion mass, location, and characteristics : • Surface heat flux • AOA • MVD + TWC • Airspeed • Investigate leading edge icing heat flux threshold • Investigate leading edge melt contribution • G enerate accretions without shedding Key Measurements: • 3D laser scans (end of test) • Ice mass (end of test) • Heat flux (and heater power measurements) • Surface t emperature • Video to observe icing behavior 20 test runs presented in paper Heater Overlay

1. Intro 2. Ice Crystal Cloud Characterization Tests 3. Ice Crystal Accretion Tests 4. General Icing Observations 5. Leading Edge Icing Threshold 6. Surface Heat Flux Impact 7. LE Melt Contribution and Resulting Accretion Downstream 8. Conclusions and Acknowledgements

Icing Observations

o Negligible strut influence o Primary accretions near ramp base o Amorphous runback ice vs structured sharkteeth ice

Transient Icing Behavior

ID# UG3580 LE Flow t = 10 min t = 1 min t = 5 min t = 3 min t = 7 min T201 - Zn 1 T401 - Zn 1 C) ° T302 - Zn 2 o All IC accretions T303 - Zn 2 exhibited transient T304 - Zn 2 Upstream TCs behavior T305 - Zn 2 T306 - Zn 3 o But reached steady state 5 Spray On/Off once a surface reached subfreezing Downstream TCs temperatures -5 Surface Temperature ( Spray On = 1 , Spray Off = 0 0 -10 -2 0 2 4 6 8 10 12 Time (min)

1. Intro 2. Ice Crystal Cloud Characterization Tests 3. Ice Crystal Accretion Tests 4. General Icing Observations 5. Leading Edge Icing Threshold 6. Surface Heat Flux Impact 7. LE Melt Contribution and Resulting Accretion Downstream 8. Conclusions and Acknowledgements

For Reference

Leading Edge Icing Heat Flux Threshold

Spray Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Run ID Duration T U AOA MVD TWC Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux 3 2 2 2 2 2 2 # min ° C knots ° μm g/m W/in W/in W/in W/in W/in W/in UG3575 N/A - 15 200 0 27.9 1.98 3.1 - 14.2 2.9 - 4.6 0.0 0.0 0.0 0.0 • Insufficient heat, no ice Secondary • Runback ice and Runback Splash Splash ice Ice Band Ice Band • First ice at Heater First melt Setting #5 • Decrease in downstream temps with increased Zone 1 heat flux (Heater Settings # 8, 11 - 13) ID# UG3575

1. Intro 2. Ice Crystal Cloud Characterization Tests 3. Ice Crystal Accretion Tests 4. General Icing Observations 5. Leading Edge Icing Threshold 6. Surface Heat Flux Impact 7. LE Melt Contribution and Resulting Accretion Downstream 8. Conclusions and Acknowledgements

For Reference

Heated Zone 3 Impact on Ice Mass and Location

Spray Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 South North Leading Run ID Duration T U AOA MVD TWC Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux Casing Casing Edge Total 3 2 2 2 2 2 2 # min ° C knots ° μm g/m W/in W/in W/in W/in W/in W/in g g g g UG3565 10 - 15 150 0 26.6 1.93 8.9 3.4 0.0 0.0 0.0 0.0 25 24 49 UG3564 10 - 15 150 0 26.6 1.93 9.5 3.6 3.9 0.0 0.0 0.0 67 22 (sh) 89 • By heating Zone 3, the runback remains liquid into Zone 3 • Greater collision efficiency in Zone 3 (near ramp base) • L iquid runback helps capture the incoming ice crystals, which increases the UG3565 UG3564 collection efficiency Zn 1 - 2 heated Zn 1 - 3 heated • Greater ice mass heating 25 g 67 g Zone 3

For Reference

Elevated Zone 3 Heat Flux Impact on Location

Spray Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 South North Leading Run ID Duration T U AOA MVD TWC Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux Casing Casing Edge Total 3 2 2 2 2 2 2 # min ° C knots ° μm g/m W/in W/in W/in W/in W/in W/in g g g g UG3553 10 - 20 150 0 26.3 2.16 8.9 3.7 4.3 4.0 7.5 4.5 32 33 65 UG3554 10 - 20 150 0 26.3 2.16 8.9 3.7 5.6 4.0 7.5 4.5 29 (sh) 35 (sh) 64 (sh) • Higher Zone 3 heat flux moved accretion farther downstream • H igher heat flux setting resulted in multiple ice build and sheds • Honeywell LF11 full scale icing test: Increased fan speed increased the temperature in the core flowpath and suppressed accretion and suppressed engine rollback UG3553 UG3554 Zn 3 = 3.8 W/in Zn 3 = 5.0 W/in

For Reference

Warm Leading Edge Impact on Ice Mass

Spray Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 South North Leading Run ID Duration T U AOA MVD TWC Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux Casing Casing Edge Total 3 2 2 2 2 2 2 # min ° C knots ° μm g/m W/in W/in W/in W/in W/in W/in g g g g UG3559 10 - 20 150 4 26.3 2.16 8.9 3.1 3.3 4.0 7.5 4.5 18 14 (sh) 32 (sh) UG3558 10 - 20 150 4 26.3 2.16 8.9 3.7 3.3 4.0 7.5 4.5 39 (sh) 2 41 (sh) • H igher heat flux setting kept the leading edge warm and clear of ice, providing a continues supply of liquid melt to the ramp base, resulting in greater ice mass accretion • Honeywell LF11 full scale icing test: Upstream heat sources provided additional melt, promoting accretion within the compressor core and quicker UG3559 UG3558 engine rollback Cooler Zn 2 Warmer Zn 2 18 g 39 g

1. Intro 2. Ice Crystal Cloud Characterization Tests 3. Ice Crystal Accretion Tests 4. General Icing Observations 5. Leading Edge Icing Threshold 6. Surface Heat Flux Impact 7. LE Melt Contribution and Resulting Accretion Downstream 8. Conclusions and Acknowledgements

Runback Dominated Melt

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Run ID Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux 2 2 2 2 2 2 # W/in W/in W/in W/in W/in W/in UG3565 8.9 3.4 0.0 0.0 0.0 0.0 UG3560 7.1 2.8 3.3 3.2 6.0 3.9

• Isolated LE melt contribution test suggests runback

dominant melt

• Red boxes show ice accretion moved upstream or grew in

greater amounts in the same location at the front edge.

• Upstream ice stopped ice growth just aft (blue oval)

Splash Dominated Melt

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Run ID Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux Heat Flux 2 2 2 2 2 2 # W/in W/in W/in W/in W/in W/in UG3574 9.9 3.1 0.0 0.0 0.0 0.0 UG3573 9.9 3.1 3.3 4.3 7.2 5.1

• Isolated LE melt contribution test suggests splash

dominant melt (no prominent runback band)

• Despite upstream ice, the ice within red boxes grew

• Sharkteeth grew longer and pointier throughout test

• L ocally higher collection eff. reinforces pointier shape

(Evidence of) Runback Dominated Melt

• Pointy sharktooth • Limited sharktooth • Flat ridge inside the • Plateau - shaped ridge • Blunt sharktooth • Upstream is fully covered growth from red box • Small ice forming • More ice forming with ice potentially limited • Upstream is clear upstream along the upstream along the • No more liquid runback splash melt • Uniform access to sides of red box, sides of red box reaching the ridge/teeth liquid runback corresponding to • Liquid runback pinched valleys of the plateau off even more limited • Liquid runback to narrow channel limited to peak of creating pointy peak plateau

1. Intro 2. Ice Crystal Cloud Characterization Tests 3. Ice Crystal Accretion Tests 4. General Icing Observations 5. Leading Edge Icing Threshold 6. Surface Heat Flux Impact 7. LE Melt Contribution and Resulting Accretion Downstream 8. Conclusions and Acknowledgements

Conclusions

• Ice crystal cloud characterization tests conducted • T unnel thaws reduced the impact of particle recirculation • S uccessfully generated ice accretions on a test article in a fully glaciated cloud • P rovided insight into icing physics observed • Produced quantitative dataset for model development and validation • Explored minimum surface heat flux required to melt impinging IC near LE • Discussed how surface heat flux impacted ice mass, location, and accretion characteristics • L iquid melt generated at LE transported downstream via runback and splash • Discussed how runback melt and splash melt impacted accretion behavior downstream • Discussed mechanisms that generated sharkteeth ice, but likely different than full scale engine icing tests

Acknowledgments

The authors would like to thank : • Quentin Schwinn and Jordan Salkin for ice scanning, video recording, and post - processing support • Emily Timko for leading ice crystal cloud recirculation and spatial uniformity test efforts • IRT staff for testing support • I ntern Emma Nagy from the Georgia Institute of Technology for data analysis support • T he financial support of the Propulsion Technologies sub - project of the Advanced Air Transport Technology project (AATT) under NASA's Advanced Air Vehicles Program (AAVP) .

Contact Information: Tadas Bartkus tadas.p.bartkus@nasa.gov