Aircraft anti-icing systems of a proposed type would utilize static electric fields to reduce or eliminate the electrostatic forces that bond ice and water to metal surfaces. These would be lightweight, low-power-consumption, inexpensive systems that would be installed on the surfaces of wings and other critical airfoils. These systems would not intrude significantly into the interiors of airfoils; they would also not protrude from airfoil surfaces and thus would not disturb aerodynamics.
Many anti-icing systems now in common use are of the “weeping-wing” type: they mete out deicing fluids over airfoils. The reservoirs needed to store deicing fluids, the plumbing needed to distribute the fluids over the airfoil surfaces, and the fluids themselves impose severe interior-space and weight penalties on aircraft design and operation, and the fluids can exert adverse effects on the environments into which they are released. Some other anti-icing systems now in use are of the electrothermal type; the disadvantage of these systems is that they consume significant amounts of aircraft power. Yet another anti-icing concept that has been tried previously involves the use of such icephobic materials as polytetrafluoroethylene; this concept has met only limited success, and performance can be degraded through erosion of ice-phobic materials.
Three phenomena that contribute to the adhesion of ice are electrostatic attraction, covalent bonding, and the Van der Waals force. The electrostatic force is possibly the most significant. Because water and ice are polar materials, the alignment of their molecules is influenced by an electric field. Water adheres to a metallic surface because the molecular orientation is such that a positive charge exists on the water surface facing the metal and is attracted to a negative charge on the metal surface. On freezing, water molecules reorganize from a liquid to a crystalline structure that remains polar. Thus, ice adheres to the metal surface for the same reason that water does. In principle, the electrostatic part of the bonding force could be eliminated by applying an opposing dc electric field across the interface between the metal surface and the ice. In the proposed systems, the necessary electric fields would be generated by use of electrodes patterned on the airfoil surfaces to be protected. The fundamental research on the reduction of ice adhesion strength using an applied dc electric charge was conducted by Professor Victor Petrenko of Dartmouth’s Thayer School of Engineering. Dartmouth College has patented the technology (U.S. Patent No. 6,027,075).
Systems of the proposed type would be attractive for use on general aviation and commuter aircraft. These systems could provide safety margins for aircraft that inadvertently encounter icing conditions. An electrostatic anti-icing system could be activated prior to entering actual or potential icing conditions, without power or performance penalty. An electrostatic anti-icing system could also enhance the performance of an electro-expulsive or pneumatic-boot deicer by reducing or eliminating residual ice after each activation of the deicer.
This work was done by Jack Edmonds and Richard B. Ingram of Innovative Dynamics, Inc., for Glenn Research Center.
Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Commercial Technology Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-16939.
