Heat Transfer from Ice Accretion

1. A Study to Better Predict and Prevent Ice Buildup on Aircraft Wings Heat Transfer from Ice Accretion Scholar’s Day: Aeronautical & Processing Applications Rogers Engineering Building February 1, 2008 Steven Mart Baylor University

2. Outline • Basic Aerodynamic Definitions • Aircraft Icing Background • The Problems • Ice Formation • Ice Removal • Research Model & Goals • Questions

3. Lift Drag Relative Wind Basic Aerodynamic Definitions • Chord- Distance between the leading and trailing edge of a wing, measured in the direction of the normal airflow • Angle of attack (α)- Angle between the chord line and the relative airflow • Reynolds Number (Re)- Ratio of inertial forces to viscous forces Leading Edge Trailing Edge

4. Why Icing Is A Problem • Icing is serious flight safety concern • Most serious during take-offs and landings (high lift demands) • With ice, must fly at higher angles of attack (higher drag) • Ice causes early separation • Lift drops drastically • Flow no longer in contact with control surfaces

5. Why Icing Is A Problem (cont.) Courtesy: Gent et al. (2000)

6. The Accretion of Ice • Shape, amount and type of ice determined by: • Velocity • Temperature • Liquid Water Concentration (LWC) • Droplet Size (MVD) • Ice Accretion Time (t) V AIRFOIL CLOUD OF SUPERCOOLED WATER DROPLETS

7. Ice Spectrum Rime Ice Mixed Ice Glaze Ice • Rime and glaze ice are the two main varieties of aircraft ice • Mixed ice, a combination of both rime and glaze ice, can also form • Will focus on glaze ice during experimentation due to its tendency to form during take-offs and landings

8. Glaze Ice • In general, occurs at temperatures near 32oF and high LWCs • Drops do not freeze on impact • Ice is clear • Horns may appear • Surface tends to be covered with roughness elements • Physical mechanism of formation not well understood V=225 mph Ttotal=25 OF LWC=0.75 g/m3 MVD=20 mm t=5 minutes

9. Icing Prevention and Removal Techniques Anti-icing (ice prevention): Deicing (ice removal): Pneumatic boots-attached to wings and are inflated with air in order to break off any ice that has accumulated on them If wings have accumulated ice, a heated glycol and water mix is sprayed on the wings to remove it • Heated wings-Hot compressor bleed air is directed into sections of the wing increasing its surface temperature • Weeping wings-Fluid (a water and glycol mix) is pumped through a mesh panel on the wings leading edge • Clean wings can also be sprayed with glycol based fluids to protect against freezing for a limited time

10. Goals of Research • Looking to expand on the research of Henry, Hansman, and Breuer (1995). • Henry et al. was the first to study the heat transfer of a scale roughness element • Assumed conduction through plate and surface radiation to ambient were negligible • Trying to further their findings by considering the effects of conduction through the plate • Establish a better understanding of what physical events are transpiring

11. Research Model • Thin plate with simulated ice accumulation • Use of the Baylor University Subsonic Wind Tunnel to establish a controlled airflow • Measure the heat transfer across the plate with infrared cameras

12. Baylor University Wind Tunnel 24” by 24” Test Section Test Range: 0 – 150 ft/s Open loop tunnel Larger test area will allow for a larger scale model reducing the required velocity of airflow in order to match Reynolds number

13. Potential Impacts • Open the door for further research • Allow for more complex and precise simulations of ice accretion • Capability to better predict and prevent the icing of aircraft

14. Summary • Glaze ice is a serious problem due to its susceptibility to form during take-offs and landings, when lift demands are at their greatest • Looking to expand upon the research of Henry et al. with the consideration of plate conduction • Attempting to gain a better understanding of the heat transfer due to glaze icing

15. Thank you! Questions?