A Preliminary Evaluation of Icing Scaling on AAM Propellers

National Aeronautics and Space Administration

A Preliminary Evaluation of Icing Scaling on

AAM Propellers

Jen - Ching Tsao Ohio Aerospace Institute Zaid Sabri, Paul H. von Hardenberg, Curtis A. Flack NASA Glenn Research Center AIAA Aviation Forum, July 21 – 25, 2025 www.nasa.gov 1 This material is a work of the U . S . Government and is not subject to copyright protection in the United States .

National Aeronautics and Space Administration Outline • Background • Test Objective • Test Description • Preliminary Results • Concluding Remarks • Acknowledgments www.nasa.gov 2

National Aeronautics and Space Administration Background • Currently there are no accepted icing scaling methods for the AAM propeller and engine open rotor fan.

• Developing experimental icing simulation capabilities in the NASA Icing Research Tunnel (IRT) for propeller and engine fan icing studies.

• Acquiring ice shape and shedding data on non - proprietary propeller/rotor geometries to support – GlennICE code validation and development.

– Ice shedding prediction capabilities.

NASA UAM - Tiltwing Concept Vehicle NASA AATT PT - Unducted Propulsor Research (cruise configuration) (open - rotor engine architecture) www.nasa.gov 3

National Aeronautics and Space Administration

Background

• Current recommended scaling methods for icing – Unheated surfaces on fixed wings (i.e., straight & swept wings) – Super - cooled water droplets in App - C & SLD regimes • Past studies on rotary wing ice accretion showed – Different ice shape with feather formation features observed on fixed wing and rotating blade surfaces, i.e., surface shear  surface shear + centrifugal force – The fundamental physics of ice accretion appears to be the same www.nasa.gov 4

National Aeronautics and Space Administration

Background

• Current proposed methods for size scaling (details in the full paper)

– Choose scale model size & LWC – Match scale J (advance ratio) to reference ➢ Determine scale propeller rotational speed RPM – Match scale K (or  ) to reference 0 0 ➢ Determine scale MVD – Match scale We to reference L ➢ Determine scale velocity V – Match scale n to reference ➢ Determine scale temperature T ∞ – Match scale A to reference c ➢ Determine scale accretion time τ www.nasa.gov 5

National Aeronautics and Space Administration

Test Objective

• Begin preliminary evaluation of the propos ed scaling methods for AAM propeller ice accretion • Develop ice shape database in the IRT for three geometrically similar propellers of ➢ 24”, 28”, and 36” in diameter ➢ NACA 0012 airfoil profile w twist and chord distributions inspired by the NASA Computationally Optimized Proprotor (COPR)* Ø36” Ø28” Diameter = Ø24” Note: Spinner not scaled with propeller size *Zawodny et al., NASA TM 20220015637, NASA Langley Research Center, 2023 www.nasa.gov 6

National Aeronautics and Space Administration Test Description • NASA Glenn IRT • March 2023 - ARIES I • January 2024 – ARIES II • 24 ”, 28” and 36 ” diameter blades of NACA 0012 profile • J = 2.3 – 2.7 • AoA = 4.5 ° ; 0 ° r/R=0 .75 • n = 0.51 – 1.0 • MVD’s :15 - 80  m • LWC’s : 0.55 - 1.20 g/m • Tunnel Speed : 87 - 130 kt www.nasa.gov 7

National Aeronautics and Space Administration Model and Test Setup • Propeller in axial flow configuration • Constant RPM for duration of spray • High speed imaging for shedding events • Light strobing for ice growth monitorin g • Photographs of final ice shape • 3D ice shape from laser scan • Ice mass measurements • 2D ice shape extraction at r/R = 0.75 www.nasa.gov 8

National Aeronautics and Space Administration

Ice Shape Comparison (1)

Model Size Scaling in ARIES I

Similarity Parameters Target Operating and Cloud Conditions ( c alculated at 𝑟 / 𝑅 = 0.75 ) 𝑡 𝑉 𝛿 LWC 𝜏 RPM D 𝑊𝑒 ∞ , 0 ∞ 𝐿 Run J 𝑛 𝐴 𝛽 0 𝑐 0 3 6 knots °C μm g/m min rev/min in 10 RA3717 95 - 12.0 15 0.55 3.4 1928 24 2.49 1. 0 3.76 0.90 0.15 RA3698 “ “ “ “ 4.0 1657 28 2.49 1. 0 3.78 0.89 0.18 RA3681 “ “ “ “ 5.0 1300 36 2.47 1. 0 3.67 0.86 0.23 www.nasa.gov 9

National Aeronautics and Space Administration

Ice Shape Comparison (2)

LWC Scaling in ARIES I

Similarity Parameters Target Operating and Cloud Conditions ( c alculated at 𝑟 / 𝑅 = 0.75 ) 𝑡 𝑉 𝛿 LWC 𝜏 RPM D 𝑊𝑒 ∞ , 0 ∞ 𝐿 Run J 𝑛 𝐴 𝛽 0 𝑐 0 3 6 knots μm g/m min rev/min in 10 ° C RA3 701 87 - 3.0 15 0.55 3.0 1516 28 2.49 0.51 2.59 0.88 0.15 RA3 690 “ - 6 .0 “ 1.20 1.4 “ “ “ “ 2.64 “ “ www.nasa.gov 10

National Aeronautics and Space Administration

Ice Shape Comparison (3)

LWC Scaling in ARIES II

The n values seemed to be over - estimated based on the resulting ice shapes obtained www.nasa.gov 11

National Aeronautics and Space Administration Concluding Remarks • Limited icing tests were performed in the IRT to evaluate the proposed scaling methods for propeller icing scaling.

• Preliminary results showed good agreement of both size and shape of main ice shapes and feather regions.

• More data is needed to assess the effectiveness of the proposed scaling methods, especially for freezing fractions less than unity.

• Further evaluation of the scaling methods over a wider range of propeller sizes and operating conditions is recommended to assess its applicability for the modern propeller and engine open rotor fan icing scaling analysis .

www.nasa.gov 12

National Aeronautics and Space Administration Acknowledgements • This work was supported by the Propulsion Technologies (PT) sub - project of the NASA Advanced Air Transport Technology (AATT) project .

• The authors would also like to thank the IRT staff for their outstanding support during the test campaigns.

www.nasa.gov 13