RU2784218C1 - Blade for aircraft made with possibility of hanging and method for removal of ice from specified blade - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: invention relates to a blade and removal of ice from a blade for an aircraft. Blade (7) for a propeller of an aircraft made with the possibility of hanging contains main case (11) with first outer surface (9) and anti-icing system (10) for removal of ice. Anti-icing system (10) contains first layer (20) formed by material with shape memory, activated so that to change its shape according to a value related to a temperature, which is located on at least one outer surface (9) of main case (11), and second layer (25), which forms at least section (26) of second outer surface (12) of blade (7), on which ice (13) settles. Second layer (25) laid on top of first layer (20), on an opposite side of main case, is made with the possibility of selective movement under the action of first layer (20) so that to exert mechanical impact on ice (13) and remove it from blade (7), and is made with the possibility of protection of first layer (20) from external agents.

EFFECT: increase in safety of an aircraft is achieved.

14 cl, 5 dwg

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the priority of European Patent Application No. 18202975.1 filed 10/26/2018, the full disclosure of which is hereby incorporated by reference.

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention relates to a blade for a hovering aircraft, in particular a tiltrotor or helicopter.

The present invention also relates to a method for removing ice from a blade for a hovering aircraft, in particular a tiltrotor or helicopter.

BACKGROUND OF THE INVENTION

It is known that the formation of ice on the wing and/or control surfaces of helicopter blades can degrade the aerodynamic performance of helicopters and in some cases make them particularly difficult to control.

In general, ice forms on the blades of helicopters when the latter are in flight or stationary on the ground with the blades rotating.

More specifically, ice tends to form at the leading edges of the blades when the blades are at temperatures close to or below zero degrees Celsius.

In order to reduce the risks resulting from the formation of ice on the leading edges of the blades, it is known to use anti-icing systems on helicopters.

An example of anti-icing systems for an aircraft blade tip section is known from US 5,686,003.

In more detail, the anti-icing system shown in US 5,686,003 basically comprises, at the leading edge of the aforementioned blade tip portion:

- layer of material with shape memory:

- a polymer layer deposited on the leading edge of the blade; and

- heat-generating layer located between the layer of material with shape memory and the polymer layer.

The layer of shape memory material forms a portion of the outer surface of the blade.

A shape memory material is able to change its shape and generate force through a martensitic phase change when subjected to an energy source such as, for example, heat.

If ice is detected, the heat generating layer is activated and the shape memory material expands so as to apply force to the ice and break that ice on the outer surface of the blade.

The heat required to thermally activate the shape memory layer is supplied by a layer containing electrical resistances, or by the latent heat of fusion produced by the liquid-to-solid transition.

The industry is recognizing the need to reduce the risk of weather or airborne particles damaging the shape memory material layer, thereby rendering the anti-icing system unusable and risking helicopter flight safety.

This risk is increased by the fact that the blades have tangential velocities close to the speed of sound at their respective risers. These particularly high tangential velocities can accelerate the aforementioned particles, making the collision with the shape memory layer even more violent.

This risk is especially high when the helicopter is hovering at low altitude or on the ground with the propeller running, as the rotation of the blades tends to entrain debris and dust in the rotation.

WO-A-98/24690 discloses a three-dimensional active composite membrane formed from two layers of polymer and a reinforcing wire mesh between them, actuated to take on selected different three-dimensional patterns (shapes) by an external shape memory alloy wire mesh or other types of mechanical actuators. to which it is attached. More specifically, the composite membrane comprises two resilient outer layers and a reinforcing element extending between them. The edges of the reinforcing element are attached through one of the outer layers to the edges of the outer shape memory alloy actuating mesh, which has an area similar to the area of the specified reinforcing element, and less than the area of the said outer layers. The actuating mesh is brought into contraction or tension by direct heating, thereby causing a normal deflection of the reinforcing element and thus said outer layers.

US-A-5,558,304 discloses an outer shell deicing device that contains a shape memory metal element that undergoes a transition from a weaker low temperature form (martensite) to a stronger high temperature form (austenite) when the element is heated to its temperature. transition. The shape change is used to deflect the outer shell, thereby shedding the ice that has accumulated on it.

DISCLOSURE OF THE INVENTION

The object of the present invention is to produce a blade for an aircraft capable of hovering according to claim 1.

The present invention also relates to a method for removing ice from an aircraft propeller blade according to claim 13 of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, a preferred embodiment is described below by way of non-limiting example and with reference to the accompanying drawings, in which:

- Figure 1 shows a top view of an aircraft, in particular a helicopter, containing a propeller with a group of blades made according to the present invention;

- Figure 2 is a highly enlarged plan view of a blade made according to the invention and included in the propeller in Figure 1;

- Figure 3 is a section on a highly enlarged scale along the line III-III in Figure 2;

- Figure 4 shows on a highly enlarged scale some of the details of the blade in Figures 2 and 3 in the first working configuration with parts removed for clarity; and

- Figure 5 shows a highly enlarged detail of the blade in Figure 4 in the second working configuration with parts removed for clarity.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figure 1, reference numeral 1 denotes an aircraft, in particular a hovering aircraft, which in the case shown is a helicopter.

Helicopter 1 basically comprises a fuselage 2, a main rotor 3 located on the upper part of the fuselage 2, and a tail rotor 5.

The fuselage 2 contains at opposite ends the nose 17 and the tail boom 4 supporting the tail rotor 5.

Rotor 3, in turn, contains:

- sleeve 6, rotated around axis A; and

- a group of blades 7, extending from the hub 6 and hinged on the hub 6.

Similarly, the tail rotor 5, in turn, contains a hub 8 rotating about axis B transverse to axis A, and a set of blades 14 extending from the hub 8 and hinged on the hub 8.

With reference to Figure 2, each vane 7 extends along a respective axis C transverse to axis A.

Each blade 7, in turn, contains:

- the main body 11, limited by the surface 9;

- outer surface 12; and

- anti-icing system 10 to remove ice 13 that has settled on the surface 12.

Each blade 7 additionally contains, starting from the sleeve 6 in the direction radial to the axis A and opposite to the axis A:

- root section 15, hinged on the sleeve 6;

- main section 16; and

- end section forming the end 18.

Each blade 7 additionally contains:

- leading edge 40;

- trailing edge 41 (visible only in Figures 1 and 2);

- an upper surface 42 and a lower surface 43 opposite each other and extending between the leading edge 40 and the trailing edge 41.

In particular, as a result of the rotation of the blade 7, the leading edge 40 hits the air before the trailing edge 41 of the same blade 7.

The helicopter 1 also contains a group of systems 10 associated with the respective blades 7 of the propeller 3.

The separate system 10 and the corresponding separate blade 7 are described below in the present description, since the systems 10 and the blade 7 are identical to each other.

In more detail, the anti-icing system 10, in turn, contains:

- a layer 20 of material with a shape memory activated so as to change its shape according to temperature; and

- activation layer 21, which is configured to selectively activate to generate the amount of heat required to activate the layer 20.

Layer 20 is deposited on surface 9 of body 11.

The material forming layer 20 assumes a first undeformed configuration (Figures 3 and 4) when it is at a temperature below a threshold value and assumes a second deformed configuration (Figure 5) when it is at a temperature above the aforementioned threshold.

When placed in an undeformed configuration (Figures 3 and 4), the layer 20 assumes the same shape as the surface 9 of the body 11 and therefore has essentially no effect on the ice 13.

On the other hand, when placed in a deformed configuration (FIG. 5), the layer 20 assumes an undulating configuration formed by an alternating group of protrusions 22 and depressions 23. The protrusions 22 are located at a distance from the surface 9 and protrude towards the surface 12. The protrusions 22 act on the ice 13 causing its fragmentation as shown in Figure 5. The depressions 23 are adjacent to the surface 9.

Layer 21 is embedded in housing 11 in a position adjacent to layer 20 so that the heat it generates raises the temperature of layer 20 and activates it.

In the case shown, the layer 21 is formed by electrical resistances (shown schematically only in Figures 3-5) fed by an electrical generator located on the hub 6 or on the stationary part of the helicopter 1.

The anti-icing system 10 comprises a cover layer 25 which forms a portion 26 of the surface 12 of the blade 7 on which ice 13 settles.

The layer 25 is laid on top of the layer 20 on the opposite side of the body 11, is made with the possibility of selective movement under the influence of the layer 20 so as to exert a mechanical effect on the ice 13 and remove it from the blade 7 (Figure 5), and is made with the possibility of protecting the layer 20 from external agents.

In more detail, layer 25 is movable between:

- the first position (Figure 5), taken when the layer 20 is activated and is in a deformed configuration; and

- the second position (Figure 4), taken when the layer 20 is deactivated and is in an undeformed configuration.

Layer 25 is substantially adjacent to layer 20 throughout its entire length in the second position shown in Figure 4.

Conversely, the layer 25 is adjacent to the protrusions 22 and is therefore located at a distance from the surface 9 of the housing 11 in the first position shown in Figure 5.

Preferably, the layer 25 resiliently moves between the aforementioned first and second configurations.

Layer 25 is made of a material that provides it with at least the following characteristics:

- sufficient rigidity to withstand impacts with external agents, such as sand or dust at the tangential velocity of the blades 7, and with particular reference to the flight mode of the helicopter 1 at low altitude close to the ground; and

- sufficient flexibility to resiliently move between the aforementioned first and second positions following the movements of the layer 20 between the respective undeformed and deformed configurations.

More specifically, layer 25 is made of a superplastic material.

The material of layer 25 has a maximum elastic deformation of 0.5%. In other words, the deformation of this material is 0.5% in relation to the original length when the yield strength is reached.

In particular, this maximum elastic strain value of 0.5% is maintained within a temperature range between 40°C and 70°C.

In addition, the material of layer 25 is capable of maintaining this maximum elastic strain of 0.5% after a predetermined number of fatigue cycles, in particular at least a million cycles.

Layer 25 is made of a superplastic material.

Specific examples of this superplastic material are titanium alloys, other metallic materials, or non-metallic materials that exhibit the above characteristics.

In the embodiment shown in Figure 3, the layers 20, 21 and 25 are located on the leading edge 40.

Layers 20, 21 and 25 are also located on sections of the upper surface 42 and lower surface 43 of the blade 7 adjacent to the leading edge 40 and converging on the leading edge 40.

With reference to Figure 2, the layer 25 is located over the end 18 and the main section 16 of the blade 7.

On the other hand, the layer 25 is not applied over the root section 15.

With reference to Figures 3-5, the layers 20 and 25 are applied directly to the respective areas 30 and 31 of the surface 9 of the housing 11.

Section 30 is located radially outside in relation to section 31 relative to the axis A of rotation of the sleeve 6 and the blades 7.

Section 30 continues on the leading edge 40 of the blade 7 and in areas of the upper surface 42 and lower surface 43 of the blade 7 converging on each other at the leading edge 40.

The section 31 continues in the areas of the upper surface 42 and the lower surface 43 of the blade 7, located at a distance from the leading edge 40. The layer 20 does not continue on the section 31 of the housing 11.

In other words, the layer 25 is applied directly to the body 11 of the blade 7 in the area 31 where the layer 20 is absent.

In particular, the layer 25 is applied directly to the section 31 of the body 11 by means of two adhesive areas 34 and 35 located respectively on the upper surface 42 and on the lower surface 43 of the blade 7.

The layer 20 is separated from the adhesive areas 34 and 35 by the corresponding recesses 32 and 33 located on the upper surface 42 and on the lower surface 43 of the blade 7.

The recesses 32 and 33 have an extension transverse to the axis C of the blade 7.

Notch 33 may be longer than notch 32 if the design requirements of the blade so require.

Helicopter 1 also contains:

one or more sensors 50 (shown schematically in Figure 1 only) configured to detect the presence of ice 13 on the blades 7; and

- a control unit 51 (it is also schematically shown only in Figure 1), which is functionally connected to the sensor 50 and the layer 21 of the anti-icing systems 10 of the blades 7.

In particular, when the sensor 50 detects the presence of ice 13 on the blades 7, the control unit 51 controls the passage of an electric current within the resistances of the layers 21 of the respective blades 7 so as to cause the respective layers 20 to move from the respective undeformed configurations to the respective deformed configurations.

The operation of the helicopter 1 is described below starting from the state in which the layer 20 is in the deactivated configuration and consequently the layer 25 is in the second position shown in Figure 4.

The operation of the screw 3 causes the rotation of the blades 7 around the axis A and relative to the sleeve 6.

During the operation of the helicopter 1, ice 13 forms and settles on the surfaces 12 of the blades 7 under temperature conditions below 0°C, as shown in Figure 4.

Preferably, the ice 13 settles on the area 26 of the surface 12, in particular on the leading edges 40 of the blades 7.

The operation of the helicopter 1 is described below with reference to the individual blade 7 and the associated anti-icing system 10.

If the sensor 50 detects the presence of ice 13, the control unit 51 triggers the activation of the layer 21 of the anti-icing system 10.

This activation causes an electrical current to circulate in the resistances forming layer 21 and a subsequent generation of heat in layer 20.

This heat generation causes layer 20 to move into the deformed configuration in Figure 5 as the material of layer 20 changes its shape according to the temperature to which it is exposed.

As shown in Figure 5, moving the layer 20 into the deformed configuration causes the layer 25 to move away from the body 11 of the blade 7 until it reaches the first position.

Due to its mechanical flexibility properties, the layer 25 maintains contact with the protrusions 22 of the layer 20 and thereby has a mechanical effect on the ice 13.

This mechanical action causes fragmentation of the ice 13 and separation of the ice 13 from the blades 7.

As soon as the atmospheric conditions under which ice 13 is formed cease, the sensor 50 stops detecting the presence of ice 13. The control unit 51 deactivates the layer 21 of the anti-icing system 10.

As a result, the electric current stops circulating in layer 21, layer 20 returns to its undeformed configuration, and layer 25 returns to the second position in Figure 4.

During all the above actions, the layer 25 protects the particularly delicate layer 20 from collisions with the weather, dust and sand.

This protective action is especially important:

- at the ends 18 of the blades 7, where the tangential velocities and hence the intensity of any collision is greater; and/or

- when the helicopter 1 is in low hover or on the ground flight modes with propellers 3 operating, thereby increasing the risk that solid debris on the ground will be caught and hit the blades 7.

From the study of the characteristics of the blade 7 and the method presented according to the present invention, the advantages that can be achieved with them are obvious.

In particular, the anti-icing system 10 of each blade 7 includes a layer 25 lying on top of the layer 20 and forming an area 26 on which ice 13 settles.

Thus, the layer 25 protects the layer 20 from collisions with any debris in the air and atmospheric phenomena. In this way, the risk of damage to the layer 20 is substantially reduced and a long service life is guaranteed for the anti-icing system 10, with obvious advantages relating to the safety of the helicopter 1.

Layer 25 is made of a superplastic material which:

- rigid enough to withstand impacts with external agents, such as sand or dust at the tangential speed of the blades 7, and with particular reference to the mode of flight of the helicopter 1 at low altitude close to the ground or the mode in which the helicopter 1 is on the ground with the propellers in operation 3 and 5; and

flexible enough to move resiliently between the aforementioned first and second configurations following the movements of the layer 20 between the respective undeformed and deformed configurations.

Since it is made of a material with an elastic deformation of up to 0.5%, the layer 21 is able to elastically move between the first and second positions following the movement of the layer 21.

Since these values of maximum deformation in the elastic stage are maintained in a variable temperature range between -40°C and 70°C and/or for a number of fatigue cycles in excess of a million, the layer 25 ensures that the layer 20 is protected over a wide range of operating temperatures for the helicopter 1 and over a period of time of the same order of magnitude as the lifetime of helicopter 1.

The layer 25 is located over the leading edge 40 where the risk of collision and damage to the layer 20 is higher. Thus, the effectiveness of the protective action of the layer 25 is increased.

Finally, it is clear that modifications and changes can be made to the blade 7 and the claimed method without deviating from the scope of the present invention.

In particular, both the blades 7 of the propeller 3 and the blades 14 of the tail rotor 5 can be equipped with respective anti-icing systems 10.

In addition, the aircraft may be a tiltrotor with one or more propellers that rotate from a horizontal position (helicopter mode) to a vertical position (airplane mode).

Claims (62)

1. Blade (7, 14) for the propeller (3, 5) of the aircraft (1), made with the possibility of hovering, including: - the main body (11), limited by the surface (9); and - anti-icing system (10) to remove ice (13); wherein said anti-icing system (10) contains: a first layer (20) formed by a shape memory material capable of changing its shape according to a temperature-related value and located on the surface (9) of said main body (11); and - activation layer (21), made with the possibility of selective activation to generate the amount of heat required to activate the specified first layer (20); wherein said activation layer (21) is built into said main body (11) in a position adjacent to said first layer (20), so that the heat it generates raises the temperature of said first layer (20) in use and activates it using; said anti-icing system (10) comprises: a second layer (25) that forms a portion (26) of the outer surface (12) of said blade (7, 14) on which said ice (13) settles during use; wherein said second layer (25) is laid on top of said first layer (20) on the opposite side of said main body (11), is configured to selectively move under the influence of said first layer (20), exert mechanical action on said ice (13), and removing it from said blade (7, 14) and configured to protect said first layer (20) from external agents; wherein the specified second layer (25) is made with the possibility of elastic movement between: - a first position taken when said first layer (20) is activated in use, in which it is at least partially moved away from said main body to remove said ice (13); and - a second position taken when said first layer (20) is deactivated in use, in which it is at least partially in a position closer to said main body (11) with respect to said first position; wherein said first layer (20) is applied directly to the first area (30) of said surface (9) of said main body (11); said second layer (25) is applied directly to the second region (31) of said outer surface (9) of said main body (11), separate from said first region (30): wherein said second layer (25) is adjacent in use to said first layer (20) throughout its entire length in said second position. 2. The blade according to claim 1, in which the specified first layer (20) takes on the use of the first undeformed configuration when it is at a temperature below the threshold value, and takes on the use of the second deformed configuration when it is at a temperature above the specified threshold value; wherein said first layer (20) takes, in said undeformed configuration, the same shape as said surface (9) of said main body (11); wherein said first layer (20) takes, in said deformed configuration, an undulating configuration formed by an alternating group of protrusions (22) and depressions (23); wherein said protrusions (22) are located at a distance from said surface (9) and are made protruding towards said outer surface (12) to act upon said ice during use, causing its fragmentation, in said deformed configuration; wherein said protrusions (23) are in use against said surface (9) in said deformed configuration; wherein said second layer (25) is adjacent to said protrusions (22) and located at a distance from said surface (9) in said first position. 3. A blade according to any one of the preceding claims, wherein said second layer (25) is made of a superplastic material. 4. A blade according to any one of the preceding claims, wherein said second layer (25) is made of a material having a maximum strain under load of at least 0.5% in the elastic stage. 5. A blade according to claim 4, wherein said second layer (25) exhibits said deformation under a load of 0.5% over a temperature range varying between -40°C and +70°C. 6. A blade according to claim 4 or 5, wherein said second layer (25) is made of a metallic material, such as a titanium alloy or other alloys, or is made of a non-metallic material. 7. The blade according to claim 6, wherein said second layer (25) is glued to said second region (31). 8. Blade according to any one of the preceding claims, which includes: - leading edge (40); - a trailing edge (41) which interacts in use with the air flow after said leading edge (40); and - an upper surface (42) and a lower surface (43) opposite each other and continuing between said leading edge (40) and said trailing edge (41); wherein said second layer (25) continues on said leading edge (40) and portions of said upper surface (42) and said lower surface (43) adjacent to said leading edge (40) and converging on said leading edge (40). 9. The blade according to claim 8, in which the specified first region (30) is located radially outside in relation to the specified second region (31) relative to the axis (A) of rotation of the specified blade (7, 14); wherein said first region (30) continues on said leading edge (40) and said portions of said upper surface (42) and lower surface (43) connecting to each other at said leading edge (40); wherein said second region (31) continues in the region of said upper surface (42) and said lower surface (43) located at a distance from said leading edge (40). 10. Blade according to any one of the preceding paragraphs, which includes: - root section (15) pivotally attached to said screw (3, 5); - free end (18); and - main section (16) located between said root section (15) and said free end (18), continuing in the direction of extension (C) of said blade (7, 14); wherein said second layer (25) continues at said free end (18) and said main section (16). 11. Screw (3, 5) of the aircraft (1), made with the possibility of hovering, including: - bushing (6, 8) and - at least one blade (7, 14) according to any of the previous paragraphs. 12. An aircraft (1) configured to hover, including at least one propeller (3, 5) according to claim 11. 13. Method for removing ice (13) from the blade (7, 14) of the propeller (3, 5) of the aircraft (1) configured to hover; including the steps in which: i) changing the shape of the shape memory material according to a temperature related value; wherein said shape memory material forming the first layer (20) of said blade (7, 14) is placed on at least one outer surface (9) delimiting the main body (11) of said blade (7, 14); ii) selectively move the second layer (25) of the specified blade (7, 14) under the influence of the specified first layer (20) so as to exert a mechanical effect on the specified ice (13) and remove it from at least a portion (26) of the outer surface ( 12) said blade (7, 14); wherein said second layer (25) is laid on top of said first layer (20) on the opposite side of said main body (11); iii) protect the specified first layer (20) from external agents through the specified second layer (25); iv) selectively activating the activation layer (21) to generate the amount of heat necessary to activate said first layer (20); wherein said activation layer (21) is embedded in said main body (11) in a position adjacent to said first layer (20), so that the heat it generates raises the temperature of said first layer (20) in use and activates it using; v) resiliently move said second layer (25) between: - the first position taken when said first layer (20) is activated in use, in which it is at least partially moved away from said main body (11) so as to remove said ice (13); and - a second position taken when said first layer (20) is deactivated in use, in which it is at least partially in a position closer to said main body (11) with respect to said first position; wherein said first layer (20) is applied directly to the first area (30) of said surface (9) of said main body (11); wherein said second layer (25) is applied directly to the second region (31) of said outer surface (9) of said main body (11), separate from said first region (30); wherein said second layer (25) is adjacent in use to said first layer (20) throughout its entire length in said second position. 14. The method according to claim 13, which includes step vi), which sets the specified first layer (20) in the first undeformed configuration when it is at a temperature below the threshold value, and in the second undeformed configuration when it is at a temperature above the specified threshold value; wherein said first layer (20) takes, in said undeformed configuration, the same shape as said surface (9) of said main body (11); wherein said first layer (20) takes, in said deformed configuration, an undulating configuration formed by an alternating group of protrusions (22) and depressions (23); wherein said protrusions (22) are located at a distance from said surface (9) and protrude towards said outer surface (12) so as to act upon said ice during use, causing its fragmentation, in said deformed configuration; wherein said protrusions (23) are in use against said surface (9) in said deformed configuration; wherein said second layer (25) is adjacent to said protrusions (22) and located at a distance from said surface (9) in said first position.

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