De-icing systems and methods

An de-icing system comprising a shield that is configured to deform in a pre-determined way that de-bonds accreted ice. In some embodiments, the shield has a variable (non-uniform) stiffness across its width and/or length such that it undergoes a twist-like or other suitable deformation when subjected to a force. In some embodiments, the system includes a plurality of electro-mechanical actuators configured to generate the force applied to the shield.

FIELD OF THE INVENTION

Embodiments of the invention generally relate to de-icing systems and methods.

BACKGROUND OF THE INVENTION

While on the ground and during flight, aircrafts may be subjected to weather and other conditions that lead to the accumulation/accretion of ice on components of the aircraft. Ice accretion on the aircraft wings, airfoils, rotors, sensors and other components may affect the aircraft's performance and flight safety by reducing lift, increasing draft and weight, and by disturbing sensors and their ability to take proper measurements. As such, regulations require onboard de-icing and anti-icing systems to prevent the accumulation of ice on the aircraft.

SUMMARY OF THE INVENTION

In certain embodiments there is provided an electro-mechanical de-icing system having a shield configured to deform in a controlled and optimized way to de-bond accreted ice. In some embodiments, the shield has a variable (non-uniform) stiffness across its width such that its deformation may be twist-like (or have another suitable profile) when the shield is subjected to a force.

DETAILED DESCRIPTION OF THE DRAWINGS

Disclosed herein are systems and processes for de-icing aircraft components such as, but not limited to, wings or slats. While the systems disclosed herein are discussed for use in aircrafts, they are by no means so limited and may be used in helicopters, jets, rotorcrafts, or other applications where de-icing is desired.FIG. 1illustrates a cross-section of an aircraft wing or slat structure11. As shown inFIG. 1, one or more electro-mechanical de-icing systems, such as de-icing systems13and14, may be positioned generally along a leading edge15of the wing11. In some cases, ice16is generally prone to ice accretion or runback ice accretion along the leading edge15of the wing. As shown, de-icing systems13and14may be positioned proximate ice accretion16, although they need not be.

In some embodiments, the de-icing system includes at least a portion of shield12, which may be an erosion shield and which substantially covers the leading edge15of the wing11and helps protect the wing against various environmental elements such as, but not limited to, bird strikes, lightning strikes, corrosion, etc. Due to the placement of shield12around the wing11, ice (such as at areas16) may accrete directly on an outer surface of the shield12. In some cases, the shield12is formed of a thin metal sheet such as aluminum or stainless steel or other suitable material. Shield12may be affixed or adhered to the wing11in any suitable way. In some cases, the deicing systems13,14(which may include one or more actuators described below) are integral with the shield12, although they need not be. In some embodiments, the one or more actuators are positioned between the shield12and the wing11.

FIG. 2illustrates an embodiment of a de-icing system29that includes a shield22and one or more actuators21. Actuators21may be electro-magnetic (such as but not limited to coils), piezoelectric or any other suitable electrical actuator and are positioned between an inner surface of the shield22and a support structure25, which in some embodiments is a rigid structure bonded to the wing or slat structure. Actuators21are configured to generate forces, such as forces26, along shield22. As shown inFIG. 2, de-icing system29also includes a discharge unit27that supplies the energy required to drive the one or more actuators21and a control unit28that may be programmed to control the de-icing logic in response to the actual ice conditions. In some embodiments, the system29also includes one or more fixation points23, at which the shield22is affixed to the support structure25. As illustrated inFIG. 2, an ice layer24may accrete on the outer surface of the shield22, as the outer surface of the shield22is external to the aircraft wing and exposed to the elements.

FIG. 3Aillustrates a bottom view of one embodiment of an electro-mechanical de-icing system38, whileFIG. 3Billustrates a cross-sectional view36of system38taken along line37. The amount of deformation and displacement of shield32inFIG. 3Bis over-scaled for illustration purposes.FIGS. 3A-3Billustrate a system38having three actuators31, although any suitable number of actuators may be used. As shown inFIG. 3B, actuators31induce forces35that cause the shield32to deform and help break and/or de-bond the accreted ice layer. The performance of the de-icing system is dependent in part on the amount of displacement and acceleration of the shield32as caused by the forces35of the actuators31, as well as the provided energy and the shape and configuration of the shield deformation. In turn, the deformation of the shield32depends in part on the location of one or more fixation points33(at which the shield is connected to the wing or other structure) and the location of the one or more actuators31and the spacing between the one or more actuators31.

As mentioned, the performance of the de-icing system38is correlated to the shape and magnitude of the shield deformation, which is caused by the actuators31. Specifically, the deformation of the shield generates forces that, if strong enough, de-bond the accreted ice.FIG. 4illustrates two types of ice cohesion forces between the ice and the outer surface of the shield: normal cohesion forces47and tangential cohesions forces48. To counteract the normal cohesion forces47of the accreted ice, a normal traction force44may be applied between the accreted ice42and the shield41, which generates a normal stress43at the shield/ice interface. To counteract the tangential cohesion force48, a lateral traction force45may be applied between the accreted ice42and the shield41, which generates a shear stress46at the shield/ice interface. In some cases, as discussed below, the lateral traction force45and the normal traction force44are generated by the deformation of the shield when it is subjected to the actuator forces.

The shear stresses45and46and/or the normal stresses44and43generated by the deformation of the shield41, along with the resulting flexion, generate break stress inside the ice layer42. However, a sufficient amount of shear stresses46and45and normal stresses44and43must be generated to break the ice cohesion forces and de-bond the accreted ice. To ensure that sufficient stresses are generated, the shield may be configured so that its deformation shape is controllable and optimized as discussed below. Using shear stress generated by the shield deformation to de-bond the ice allows the de-icing process to be more independent of the ice layer thickness. Using shear stress is also advantageous because tangential cohesion forces are generally weaker than normal cohesion forces.

In some embodiments, systems are provided that control and/or optimize the amount of deformation of the shield (and thus the deformation shape of the shield) to control the shear and/or normal stresses along the shield/ice interface and the accreted ice, creating controlled ice breakage zones. To accomplish this, the shield is configured such that it has a variable/non-uniform stiffness across its width W and/or its length L (FIG. 5B). Because it has a variable/non-uniform stiffness across its width and/or length, the shield undergoes a twist-like or other suitable deformation when subjected to a force. A twist-like deformation mode provides for a uniform and distributed shear stress at the shield/ice interface.

FIGS. 5A-5Billustrate an example of a de-icing system55that is configured to control the shield53deformation shape such that the deformation generates sufficient forces to break and/or de-bond the ice layer. Specifically, the shield53is configured such that its stiffness varies across its width W and/or length L, as discussed below.FIG. 5Ashows a bottom view of de-icing system55, whileFIG. 5Bshows a cross-sectional view of the de-icing system taken along line56. As illustrated inFIGS. 5A-5B, shield53may be fixed along one or more fixation points54to an aircraft wing or other structure to help restrain the shield under deformation

As illustrated, the de-icing system55includes one or more stiffeners51and one or more areas of reduced thickness52between each of the one or more stiffeners51along the width W and/or length L of the shield53. The stiffeners51can be any suitable structure that support the shield53and provide increased stiffness (high stiffness zones) along portions of the shield. Some non-limiting examples of stiffeners51include stringers, composite fibers, wire frames, laminated or layered frames, etc. In some embodiments, the stiffeners51are bonded or affixed to the inner surface of the shield53in any suitable way. In some embodiments, the stiffeners51project generally radially from each of the one or more actuators501, as shown inFIG. 5A, although they may have other configurations in other embodiments.

One or more thickness reduction areas52are present between the stiffeners51. The one or more thickness reduction areas52are lower stiffness areas along the shield53. In some embodiments, thickness reduction areas52are simply areas that do not have stiffeners51and in other embodiments may include weakening strips or other structural changes (such as, but not limited to, reductions in the thickness of the shield53along these areas52) that reduce the stiffness of the shield53along areas52. In some embodiments, as illustrated inFIGS. 5A-5B, the thickness reduction areas52are relatively thin areas, particularly when compared with the width of stiffeners51.FIG. 6illustrates an embodiment of a de-icing system having a shield70with a plurality of stringers71that extend generally radially from one or more actuators72and with a plurality of weakening strips73that serve as the thickness reduction areas.

The configuration and placement of the one or more stiffeners51and the one or more thickness reduction areas52along the shield creates variable stiffness along the width W and/or length L of the shield53. In particular, as the shield53is subjected to the forces60generated by the one or more actuators, the bending profile of the shield53is reduced along the portions of the shield53that include the stiffeners51. The reduced bending profile increases the curvature radius of the shield along the stiffeners51and encourages twist deformation59along the portions of the shield53that include stiffeners51. The twisting deformation in turn increases ice de-bonding between the one or more actuators501and the one or more rigid fixation points54.

Along these same lines, the curvature radius along portions57of the deformed shield53corresponding to thickness reduction areas52is reduced because the twist is distributed along the stiffeners51, which in turn concentrates the flexion along the portions57and increases the break stress along these areas, which promotes breakage inside the ice layer. The presence of one or more thickness reductions52also helps reduce the amount of energy needed to reach the required level of displacement to de-bond the ice layer.

The configuration of the shield53, in particular the variable/non-uniform stiffness across the width and/or length of the shield, is such that the forces applied to the shield by the one or more actuators cause a twist-like deformation across the shield, which in turn generates a distributed and uniform shear stress (such as force46inFIG. 4) at the shield/ice interface, with such forces being of sufficient magnitude to break the cohesion bonds of the accreted ice and de-ice the outer surface of the wing. In some cases, the generated shear stresses occur along a wider area than if the shield had a uniform stiffness across its width and/or length.

By controlling and/or optimizing shield deformation as described above, the de-icing performance is improved. Moreover, the required forces to deform the shield can be reduced, as well as the size and/or number of the actuators needed to generate the required forces. As such, the space required between actuators can be increased. In turn, the dimensions and weight of the control units can be decreased, while power consumption can also be decreased.

Shields having variable stiffness as described herein can be formed of any suitable materials including, but not limited to, composites materials with multiple layers and/or any suitable fiber arrangement (including various fiber types and various orientations of such fibers within one or more layers) to reach the desired deformation mode. One non-limiting example of a fiber composite patchwork system is illustrated inFIGS. 7A-7B.FIG. 7Ashows a bottom view of de-icing system85, the left portion of which represents a thickness variation/stiffener system87and the right portion of which represents a fiber composite patchwork system88.FIG. 7Bshows a cross-sectional view of the de-icing system85taken along line86.

Like system55inFIGS. 5A-5B, system87includes a shield83that may be fixed along one or more fixation points92to an aircraft wing or other structure to help restrain the shield under deformation. The system87also includes a plurality of stiffeners81and thickness reduction areas82, as described above, which may be positioned/oriented and modified in any suitable way.

System88includes a fiber composite shield89that may be fixed along one or more fixation points92to an aircraft wing or other structure to help restrain the shield under deformation. System88also includes a plurality of high stiffness areas90(which may be composite patches or areas having fibers or other materials configured such that the areas are relatively stiffer) that generally extend along the direction of arrows91, although stiffness areas90may be positioned/oriented in any suitable way. System88also includes a plurality of low stiffness areas84having fibers or other materials configured such that the areas have a relatively lower stiffness (for example, by using lower density fibers or otherwise). There are many ways of achieving a higher stiffness in the plurality of high stiffness areas90and a lower stiffness in the plurality of low stiffness areas84, such as, but not limited to, by varying the configuration/orientation of the fibers, varying the density or other properties of the fibers used, varying the materials used, varying the layers arrangement of the materials, varying the diameter of the fibers, etc.

As described above, the systems87and88are configured to encourage the shield to undergo a twist-like or other suitable deformation when subjected to forces from actuators801due to the variations in stiffness along the width W and/or length L. The anisotropic behavior and heterogeneous fiber arrangement of system88is configured in some embodiments to give substantially the same mechanical deformation shape and/or profile as the system87, which achieves thickness variation by incorporating stiffeners or the like and areas of reduced thickness or weakening strips or the like. The invention is not limited to the arrangements illustrated and described. Rather, any suitable modification may be made to achieve the desired level of deformation and/or the desired deformation profile.

Other shields having variable stiffness can be formed, for example, by machining a sheet having a plurality of stringers and weakness strips or other suitable structures. In other embodiments, the shield includes a wire frame and/or laminated multi-layer composites and/or a layered frame.

The systems disclosed herein can be used alone or may be used in conjunction with any other suitable de-icing system.