RU2575969C2 - Helicopter tail assembly - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to aircraft engineering, particularly to design of helicopters. Helicopter tail comprises fan-in-fin rotor with propeller (4) with blades (3) and, if required, the vertical fins (1.2). Flow-straightening fixed blades stators (5) are star-configured parallel with the propeller plane and upstream of the propeller (4). Fan-in-fin rotor ring (2.1) is enclosed in comprises stricture composed of external erosion-proof surface ply (7.1, 8.1) made of hard plastic of plastic composite and at least one next ply (7.2, 8.2) of elastomer damping material. Fan-in-fin rotor ring comprises alternating two plies of hard plastic and two plies of said elastomer damping material.

EFFECT: lower noise of tail assembly.

10 cl, 9 dwg

Description

FIELD OF THE INVENTION

The present invention relates to the design of the tail / fairing of a helicopter with a fenestron with the signs of the restrictive part of paragraph 1 of the formula.

State of the art

The tail rotor systems in the helicopter ring consist essentially of a tail assembly comprising a fairing with an air flow channel and a screw assembly mounted coaxially in the air flow channel. It is a fact that all helicopter tail rotor systems generate noise in addition to the rotor noise. While the well-known tail rotors for helicopters are often complex, fragile and require large rotor diameters, the tail rotors hidden in the cowl / ring are smaller due to their better aerodynamic efficiency and eliminate the risk of accidents, as they are protected from impact by the cowl.

The steering screw in the ring contains the design of the Central sleeve, many support racks for installing the design of the sleeve in the air channel. The support legs are usually elliptical to improve aerodynamic performance and can be made in the form of stators to straighten the flow and thereby to utilize the energy of rotation of the air flow.

The acoustic energy emitted by such devices essentially depends on the processes of leakage, the phenomena of the flow of bodies around bodies and rotating pressure fields. The tail rotors in the ring may have additional sources of noise created by the fuselage resonance and cavity effects. Although the propeller noise is shielded by the helicopter cowl in the direction of flight, non-optimized tail rotors in the ring nevertheless emit significant noise directed back and to the sides of the helicopter.

A significant source of acoustic energy emitted by the tail rotor in the ring may be turbulence between the ends of the blades and the fairing. The greater the distance between the ends of the blades and the fairing, the greater the acoustic energy generated by this turbulence. This so-called “clearance noise” is commonly known as a moderate but wideband increase in noise. Frank Kameier in "Experimentelle Untersuchung zur Entstehung und Minderung des Blattspitzen-Wirbellärms axialer Strömungsmaschinen, Diss. TU Berlin, Hermann-Föttinger Institut für Thermo- und Fluiddinamik. Berlin, 1994 ”showed that if the clearance exceeds 0.003 screw diameters, a significant increase in noise occurs in certain narrow frequency ranges.

Various methods have been proposed to reduce the level of troubling and tiring noise of the tail rotors:

1. Documents US 5588618; EP680873 respectively describe aerodynamic optimization of support columns and stators to reduce turbulence separation;

2. Documents EP562527; EP680871 respectively describe uneven angular intervals between the rotor blades for distributing acoustic noise over a greater number of fundamental frequencies, and

3. Documents US 5634611; US 8061962 respectively describe the harmonization of the number and arrangement of propeller blades and stators to reduce interference between the blades and stators.

Due to the increase in the number of fundamental frequencies and their harmonics, the noise of the tail structure of the helicopter has the nature of broadband noise, which is able to excite many resonances of the fuselage and cavities. In fact, the tail structure of the helicopter, especially the plumage, has become a kind of “musical instrument” similar to a guitar, which enhances the wide range of remaining audible sound.

Document WO 2010 118860 describes composite components and thermosetting resins and elastomers and relates to a plastic composite component, which is formed by a thin solid plastic outer layer adjacent to it from the inside by at least one elastomeric layer, and at least one metal and / or plastic layer carrier adjacent to this elastomeric layer from the inside and made of fiber reinforced plastic (carbon fiber or glass fiber). This component, among other things, should work as a part that protects against impacts, splinters, or as a part that protects against vibrations, damage caused by vibrations, resonance for vibration damping, or for acoustic damping, among other things, of propeller blades and parts of an aircraft.

EP2071561 discloses a noise absorption structure of a screw and a screw channel. This design has a separation unit for placing the porous wall at a fixed distance from the rigid ring, made of fiberglass, by determining the cavities at a certain height between the porous wall and the ring, where the height is determined to obtain maximum absorption of acoustic waves emitted at the fundamental frequency. An additional porous wall is located in the cavities at an intermediate height for maximum absorption of another fundamental frequency. Porous walls have an absorbent layer made of a fine mesh structure and another absorbent layer of fibrous felt. The use of Helmholtz resonators to absorb noise and reduce the sound level of the tail rotor in the ring allows one to reduce the amplitudes of specific frequencies, i.e. frequencies to which the resonators are tuned, as well as their harmonics. However, it is very difficult — if at all possible — to completely reduce broadband noise by stochastic frequencies when it occurs as a result of the operation of the tail rotor in the ring.

US2009014581 A1 describes a tail rotor in a helicopter ring with a transverse channel and a tail rotor mounted in the channel. The steering screw contains a screw mounted rotatably in the channel, and a stator fixedly mounted in the channel further downstream of the screw. The screw comprises a screw hub having an axis of the screw and screw blades extending from the hub. The propeller blades have a modulated angular distribution around the axis of the propeller. The stator comprises a stator sleeve and a plurality of stator vanes distributed around the stator sleeve. The stator vanes have a modulated angular distribution around the stator sleeve.

No. 6,206,136 B1 describes an absorbing acoustic screen in which a perforated faceplate is coated with an erosion resistant material. This coating can be applied by a simple spraying process. The acoustic screen can be easily adjusted by adjusting the thickness of the coating.

Disclosure of invention

The objective of the present invention is to reduce the overall noise level of the tail of the helicopter.

This goal is achieved due to the tail unit of the helicopter having the features listed in paragraph 1 of the formula. Preferred embodiments of the invention are defined in the dependent claims.

According to the present invention, the tail unit of the helicopter comprises a tail rotor in a ring with a multi-blade propeller with rotor blades and, if necessary, vertical keels. The screw is driven by a drive shaft running along the tail boom of the helicopter. The flow-straightening stators of the fixed vanes are distributed in a substantially star-shaped configuration parallel to the plane of the screw by screw. The ring with the tail rotor enclosed in the channel is enclosed in a composite structure consisting of an external erosion-protective surface layer made of hard plastic or plastic composite material, at least one next layer of elastomeric damping material and at least one load-bearing structural layer, coming after at least one elastomeric layer. The tail unit of the present invention reduces the parasitic broadband noise of the tail rotor in the ring and prevents cavity and fuselage resonance in the tail unit and tail boom structure with minimal weight gain and without affecting aerodynamic drag. The tail unit of the present invention can be applied without loosening the tail elements. The present invention preferably enhances the jamming effect created by the ring to reduce the reinforcing effect of the tail and tail rotor design in the ring as much as possible using the specific composition of the composite materials used for the tail design and, in particular, the tail. The proposed composition of the material effectively damps the sound and vibrations of the tail, drowning out the sound and vibrations of the ring, and, thereby, significantly reduces the excitation of resonances of the fuselage and cavities due to the damping of elements that create, propagate and amplify spurious wideband noise on the inner periphery of the ring, on the blades themselves screw and straightening the flow of the stators in the channel downstream in relation to the screw. This solution is modular, i.e. Depending on the need, various noise reduction levels can be implemented.

According to a preferred embodiment of the invention, at least one more layer of plastic composite material or metal with an intermediate layer of elastomeric material follows behind a layer of elastomeric material which is located after an external erosion-resistant surface layer made of hard plastic or plastic composite material. This at least one additional layer of plastic composite material or metal is a load-bearing structural layer designed to hold the emerging mechanical and aerodynamic loads. The composite material proposed for damping the tail rotor noise of the present invention consists essentially of one or a plurality of layers of elastomeric material with an intermediate or metal sheet or with a plastic matrix material, reducing the broadband noise of the tail rotor in the ring.

According to a preferred embodiment of the invention, the elastomeric material is treated with a crosslinking agent, for example, materials from the group of peroxides, amines or biphenols, the exact choice of material depending on the specific elastomer used and crosslinked by heat treatment into the matrix material using a thermosetting resin, for example epoxy resin, phenol formaldehyde resin, polyester resin or acrylate resin. The elastomeric material consists of a material such as ethylene propylene diene rubber (EPDM), ethylene acrylate rubber (EAM), fluorocarbon rubber (FKM), natural rubber (NR), or elastomeric polyurethane (PU).

According to another preferred embodiment of the invention, the outer layer of the ring, as well as the surfaces of the rotor blades and stators, can preferably consist of layers of hard plastic with a thickness of 0.02 to 0.4 mm and with an impact toughness of the specimen with an notch of at least 40 kJ / m ² preferably more than 60 to 40 kJ / m ² , to protect the composite structure from erosion. This outer layer may consist, for example, of solid polyurethane (PU), or preferably of high molecular weight (HMW) polyethylene (HMW-PE), or even more preferably of ultra high molecular weight (UHMW) polyethylene (UHMW-PE).

Brief Description of the Drawings

The following is a detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 is a side view of the tail unit of the helicopter of the present invention.

FIG. 2 is a side view of an alternative embodiment of the tail unit of a helicopter of the present invention.

FIG. 3 is a perspective view of the details of the tail unit of the helicopter of the present invention.

FIG. 4a is a perspective view of a tail rotor blade of the present invention.

FIG. 4b is a cross section of the rotor blade of FIG. 4a.

FIG. 5a is a composite structure applied to the tail of the helicopter of the present invention

FIG. 5b is an alternative composite construction applied to the tail of the helicopter of the present invention.

FIG. 5c is a sectional view of a stator element of the tail unit of a helicopter of the present invention, and

FIG. 5d is a sectional view of an alternative stator element of the tail / fairing structure of the helicopter of the present invention.

The implementation of the invention

As shown in FIG. 1, the tail boom 1 of the helicopter has a plumage 1.1, consisting of fenestrone with a multi-blade propeller 4 with blades 3 inside the ring 2.1. Plumage 1.1 further contains vertical keels 1.2 mounted on the ring to help control yaw. The screw 4 is driven by a drive shaft 6 mounted in the tail boom 1. Two horizontal stabilizers 1.3 are located to the left and right of the tail boom 1 to control the pitch. The flow-straightening stators 5 consist of stationary blades arranged essentially in a star-shaped configuration parallel to the plane of the screw 4.

Ring 2.1, in which the screw 4 is installed, is enclosed in a composite structure (see Fig. 5b) to damp vibrations and broadband noise generated by the working screw 4.

In FIG. 2, corresponding elements are denoted by the same reference numbers as in FIG. 1. In addition to the composite structure, in which the ring 2.1 is enclosed, containing the screw 4, the tail unit 1.1, the tail unit 1.1 with vertical tail keels 1.2 is enclosed in the composite structure of FIG. 5a or 5b, which is a structure that dampens vibrations and sound and enhances the damping effect of vibrations and sound created by a working screw 4.

In FIG. 3, the corresponding elements are denoted by the same reference numbers as in FIG. 1 and 2. The tail unit 1.1 with a screw 4 and having an aerodynamic shape and having a lining with vertical tail keels 1.2 is enclosed in a composite structure. The outer wall 2.2 of the tail unit 1.1 has outer layers 7 containing an external erosion-protective surface layer 7.1 made of hard plastic, one elastomeric layer 7.2 and the first layer 7.3 of the structure. The inner periphery of the ring 2.1 has a top layer structure 8 containing an external erosion-protective surface layer 8.1 made of hard plastic, followed by two elastomeric layers 8.2 and 8.4, between which there is a plastic composite structure 8.3, and all these layers are attached to the first layer 8.5 design (see Fig. 5b).

In FIG. 4a, the corresponding elements are denoted by the same reference numbers as in FIG. 1-3. The rotor blade 3 with an aerodynamic profile and with a cross section varying along its span is enclosed in an elastomeric layer (see Fig. 4b) between the radial external cross section aa and the radial internal cross section bb to optimize the effect of sound suppression and damping of vibrations.

In FIG. 4b, the corresponding elements are denoted by the same reference numbers as in FIG. 1-4a. Section aa shows a core 3.1 made either of metal, for example aluminum, or of a plastic composite. The core 3.1 as a structural element, bearing the load, serves to accept the loads on the blade 3 of the screw. The elastomeric layer 3.2, used to damp vibrations caused by mechanical and aerodynamic loads, is adapted to the aerodynamic profile of the outer erosion-protective layer 3.3, which has a smooth surface that is necessary for the minimum aerodynamic resistance of the 3 screw blades.

In FIG. 5a, the corresponding elements are denoted by the same reference numbers as in FIG. 1-4b. The composite structure 7 forming the outer wall 2.2 of the tail unit 1.1 has an external erosion protection layer 7.1 made of hard plastic, for example polyurethane, or preferably high molecular weight (HMW) polyethylene, or even more preferably ultra high molecular weight (UHMW) polyethylene. Alternatively, it may be a plastic composite material. The next layer 7.2 is an elastomeric damping element made of a material such as ethylene propylene diene rubber (EPDM), ethylene acrylate rubber (EAM), fluorine carbon rubber (FKM), natural rubber (NR) or elastomeric polyurethane (PU). This elastomeric material is treated with a crosslinking agent, for example, materials from the group of peroxides, amines or biphenols.

This layer 7.2 is followed by a layer 7.3 of the structure of the composite structure 7, designed to accept any emerging loads. An elastomeric material is bonded to layers 7.1 and 7.3 by a thermal process using a thermosetting resin, such as epoxy resin, phenol formaldehyde resin, polyester resin or acrylate resin.

In FIG. 5b, the corresponding elements are denoted by the same reference numbers as in FIG. 1-5a. Composite structure 8 for the inner periphery of ring 2.1 contains an external erosion-resistant surface layer 8.1 made of hard plastic or plastic composite material, followed by an elastomeric layer 8.2, followed by a plastic composite structure 8.3. Behind this layer of plastic composite construction 8.3 is another elastomeric layer 8.4 to enhance the killing effect on the inner periphery of the ring 2.1. The subsequent layer 8.5 is made of either a plastic composite or metal. This subsequent layer 8.5 is able to withstand emerging mechanical or aerodynamic loads acting on the inner periphery of the ring 2.1. Layers 8.1, 8.3 and 8.5 are connected to the elastomeric layers 8.2 and 8.4 by a thermal process using a thermosetting resin such as epoxy resin, phenol formaldehyde resin, polyester resin or acrylate resin.

As shown in FIG. 5c, the composite design of the flow-straightening stator elements 5 consists of a load-receiving component 5.4 of the structure facing side 5.1, which is directly affected by a rotating vortex, and side 5.2, experiencing a reduced aerodynamic load, consists of a layer 5.3 of elastomeric material to damp arising vibrations and silencing the resulting sound. Component 5.4 of the construction of the stator element 5 on side 5.1 consists of metal or a plastic composite material.

In FIG. 5d, the corresponding elements are denoted by the same reference numbers as in FIG. 1-5s. The composite structure of the stator flow straightening elements 5 contains an additional outer layer 5.5 of polished hard plastic to protect against erosion and reduce aerodynamic drag. An additional outer layer 5.5 surrounds a structural component 5.4 made of metal or a plastic composite material and a layer 5.3 of elastomeric material.

List of Reference Items

1 - tail boom

1.1 - plumage

1.2 - keels

1.3 - horizontal stabilizers

2.1 - ring

2.2 - external wall

3 - propeller blade

3.1 - core

3.2 - elastomeric layer

3.3 - a layer that protects against erosion with a smooth surface

4 - screw with a sleeve

5 - stators

5.1 - stream receiving side

5.2 - side with reduced aerodynamic load

5.3 - layer of elastomeric material

5.4 - load bearing stator component

5.5 - outer layer of polished hard plastic to protect against erosion

6 - a power shaft

7, 8 - composite construction

7.1, 8.1 - surface layer for protection against erosion

7.2, 8.2, 84 - subsequent elastomeric layer

7.3, 8.5 - load-bearing structural layer

8.3 - plastic composite construction (made of one or more structural layers).

Claims (10)

1. The tail unit (1.1) of the helicopter, containing:
- a fenestron with a multi-blade screw (4) with blades (3) of the screw and, if necessary, vertical keels (1.2), the screw being driven by a drive shaft (6) installed along the tail boom, and
- flow-straightening stators (5) of fixed vanes are arranged essentially in a star-shaped configuration parallel to the plane of the screw downstream of the screw (4) inside the fenestrone ring (2.1), characterized in that at least the fenestrone ring (2.1) is enclosed in a composite structure, comprising an external erosion-protective surface layer (7.1, 8.1) made of hard plastic or a plastic composite material and at least one subsequent layer (7.2, 8.2) made of an elastomeric damping material,
moreover, the fenestrone ring (2.1) contains a composite structure of the external erosion-protective surface layer (8.1) made of hard plastic or a layer of plastic composite material, followed by one layer (8.2) of an elastomeric damping element, followed by a layer of plastic composite material ( 8.3), followed by a layer (8.4) of elastomeric damping material, followed by another layer (8.5) made of a plastic composite material or metal. 2. The tail unit according to claim 1, characterized in that after at least one subsequent layer (7.2, 8.2) there is at least one load-bearing layer (7.3, 8.5) of the structure. 3. The tail unit according to claim 1, characterized in that the outer walls (2.2) are at least partially enclosed in a composite structure of:
- at least one outer surface layer protecting from erosion (7.1) made of hard plastic or plastic composite material,
- at least one subsequent layer (7.2) of elastomeric damping material, and
- load-bearing layers (7.3) of the structure following said at least one subsequent layer (7.2). 4. The tail unit according to claim 1, characterized in that the blades (3) of the fenestrone screw are enclosed in a composite structure consisting of:
- at least one outer surface layer protecting against erosion (3.3) made of hard plastic or plastic composite material, and
- at least one subsequent layer (3.2) of elastomeric damping material. 5. The tail unit according to claim 1, characterized in that the fixed blades of the straightening flow of the stator (5) fenestrone are enclosed in a composite structure consisting of:
- at least one surface layer protecting from erosion (5.5) made of hard plastic or plastic composite material, and
at least one subsequent layer (5.3) of elastomeric damping material attached to the stator structure component (5.4). 6. The tail unit according to claim 1, characterized in that the solid plastic is made of polyurethane, or preferably high molecular weight (HMW) polyethylene, and / or more preferably of ultra high molecular weight (UHMW) polyethylene. 7. The tail unit according to claim 1, wherein the elastomeric damping material is made of ethylene propylene diene rubber (EPDM), ethylene acrylate rubber (EAM), fluorocarbon rubber (FKM), natural rubber (NR) and / or elastomeric polyurethane (PU). 8. The tail unit according to claim 1, characterized in that the composite structure (8) contains essentially one or more layers of elastomeric material (8.2, 8.4), between which there are either metal sheets or material (8.3) of the plastic matrix. 9. The tail unit according to claim 1, characterized in that the elastomeric material is treated with a crosslinking agent, for example, materials from the group of peroxides, amines or biphenols. 10. The tail unit according to claim 1, characterized in that the layer of elastomeric material is bonded to the matrix material by a thermal process using a thermosetting resin, for example, epoxy resin, phenol-formaldehyde resin, polyester resin or acrylate resin.

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