Heat Transfer from Ice Accretion

1
Heat Transfer from Ice Accretion
A Study to Better Predict and Prevent Ice Buildup
on Aircraft Wings
Scholars 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
Basic Aerodynamic Definitions
Leading Edge
Trailing Edge

• Chord- Distance between the leading and trailing
  edge of a wing, measured in the direction of the
  normal airflow
• Angle of attack (a)- Angle between the chord line
  and the relative airflow
• Reynolds Number (Re)- Ratio of inertial forces to
  viscous forces

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
V
AIRFOIL
CLOUD OF SUPERCOOLED WATER DROPLETS

• Shape, amount and type of ice determined by
• Velocity
• Temperature
• Liquid Water Concentration (LWC)
• Droplet Size (MVD)
• Ice Accretion Time (t)

7
Ice Spectrum
Rime Ice
Glaze Ice
Mixed 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

V225 mph Ttotal25 OF LWC0.75 g/m3 MVD20 mm
t5 minutes
9
Icing Prevention and Removal Techniques

• Anti-icing (ice prevention)

• Deicing (ice removal)

• 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

• 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

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?