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

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

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 Lift Drag Relative Wind Leading Edge Trailing Edge

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

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

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

Ice Spectrum 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 Rime IceGlaze IceMixed Ice

Glaze Ice  In general, occurs at temperatures near 32 o F 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 T total =25 O F LWC=0.75 g/m 3 MVD=20  m  =5 minutes

Icing Prevention and Removal Techniques Anti-icing (ice prevention): 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 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

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

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

Baylor University Wind Tunnel 24” by 24” Test SectionTest 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

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

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

Thank you! Questions?