RU2809640C2 - Sound-absorbing spherical panel - Google Patents

Abstract

FIELD: sound-absorbing panels.

SUBSTANCE: invention can be used to absorb noise from machines and aerodynamic devices. The sound-absorbing spherical panel contains a thin solid spherical shell, a three-dimensional honeycomb shell and a thin perforated spherical shell. The shells are rigidly connected along the contact surfaces and form a plurality of acoustic resonators. The volumetric honeycomb shell is made in the form of a honeycomb block with a quadrangular outline. Two opposite sides of a quadrangular contour are formed by segments of parallel lines. The cell block is symmetrical about the line connecting the midpoints of the parallel sides of the contour. The honeycomb block is assembled in rows of elastic wavy tape between the parallel sides of a quadrangular contour. Adjacent rows of wavy tape are mutually offset by half a step and connected at the junction of peaks and valleys. The volumetric honeycomb block is deformed along the contours and spherical contact surfaces of the blind and perforated shells.

EFFECT: improved sound absorption and manufacturability of the perforated shell.

3 cl, 12 dwg

Description

The invention relates to sound-absorbing panels and can be used to absorb noise from machines and aerodynamic devices.

The well-known sound-absorbing panel of an aircraft engine (See utility model patent: NOISE REDUCTION PLATE STRUCTURE USED FOR AIRCRAFT ENGINE, CN203476833U, IPC F04D 29/66, published 03/12/2014), contains a thin blind shell, a voluminous honeycomb shell and a thin perforated shell. The perforated shell is formed from perforated sheet material. The honeycomb shell is installed between the blank and perforated shells. The shells are rigidly connected along the contact surfaces and form a plurality of acoustic resonators that absorb acoustic energy, reducing the noise level of the aircraft engine.

The well-known multilayer sound-absorbing panel of an aircraft engine (See the patent for the invention: MULTI-LAYERED ACOUSTIC LINER, US3948346, IPC, G10K11/172, published 04/06/1976), contains a thin blind shell, at least two voluminous honeycombs and two thin perforated ones shells. Perforated shells are formed from perforated sheet material. The honeycomb shells are separated by perforated shells and installed between the blind shell and the outer perforated shell. The shells are rigidly connected along the contact surfaces and form a plurality of acoustic resonators that absorb acoustic energy, reducing the noise level of the aircraft engine.

Known sound-absorbing panels do not provide for a geometric connection that ensures coaxiality between the axes of the holes of the perforated shell and the axes of the cells of the honeycomb shell. Acoustic resonators have an asymmetrical shape and/or several input holes. The misalignment of the holes of the perforated shell and the cells of the volumetric honeycomb shell leads to an expansion of the absorption spectrum of sound waves. The resonant frequencies of acoustic resonators differ from each other and do not coincide with the frequency of the absorbed sound wave. The sound absorption effect inherent in the Helmholtz acoustic resonator is not fully realized.

Sound-absorbing panel of an aircraft (See invention patent: LINEAR ACOUSTIC LINER, US8196704B2, IPC, B64D33/02;E04B1/84, published 06/12/2012), contains a thin blind shell, a voluminous honeycomb shell, outer and inner perforated shells, between with which a porous layer of adhesive material is introduced. The honeycomb shell is installed between the blind and inner perforated shell. The shells are rigidly connected along the contact surfaces and form many acoustic resonators that absorb acoustic energy and reduce noise levels. Perforated shells are formed from composite materials on a molding pattern and can be made into cylindrical, conical or other non-cylindrical shapes. The molded shells are perforated together by making individual holes using a manual or programmable tool. To maintain hole alignment after final assembly, the perforated shells are tied together with locating pins and holes.

The latest invention does not disclose the geometric relationship that ensures the alignment of the axes of the holes of the perforated shells and the axes of the cells of the volumetric honeycomb shell. In addition, making individual holes on molded shells is a time-consuming operation that does not meet the requirements of mass production.

Selected as a prototype, the sound-absorbing conical panel (See the patent for the invention: SOUND-ABSORBING CONICAL PANEL, RU 2785838, IPC, E04B 1/82, published 12/14/2022), contains a thin blind shell, a voluminous honeycomb shell and a thin perforated shell. The honeycomb shell is installed between the blank and perforated shells. The shells are rigidly connected along the contact surfaces and form many acoustic resonators that absorb acoustic energy and reduce noise levels. The volumetric honeycomb shell is made in the form of a prismatic honeycomb block with a trapezoidal contour. The honeycomb block is made up of rows of elastic wavy tape. The rows of elastic wavy tape are parallel to the bases of the trapezoidal contour. Adjacent rows of wavy tape are offset by half their pitch and connected at the junction of peaks and valleys. The dimensions of the trapezoidal contour of the honeycomb block are equal to the dimensions of the contact surface of the perforated shell. The volumetric honeycomb block is deformed along the contour and conical surfaces of the blind and perforated shells. The pitch and coordinates of the axes of the holes in the perforated shell are related to the geometric parameters of the sound-absorbing conical panel and the honeycomb block by relationships that ensure the coaxiality of the holes of the perforated shell and the cells of the honeycomb shell, as well as the design of the holes in the package of perforated shells.

The prototype creates a sound absorption effect close to the effect of an acoustic Helmholtz resonator, however, the geometric connections and relationships of the conical sound-absorbing panel are unsuitable for the sound-absorbing spherical panel.

The problem solved by the invention is the creation of a sound-absorbing spherical panel in which:

- the holes of the perforated spherical shell and the cells of the honeycomb shell are coaxial;

- the holes of the perforated spherical shells are made in a package of their flat blanks.

Technical result from the use of the invention:

- improvement of sound absorption at the frequency of the absorbed sound wave;

- reducing the duration of perforation of spherical shells.

The invention can be implemented in the following embodiments.

1st performance

The sound-absorbing spherical panel contains a thin solid spherical shell, a three-dimensional honeycomb shell and a thin perforated spherical shell. The volumetric honeycomb shell is installed between the blank and perforated spherical shells. The shells are rigidly connected along the contact surfaces and form many acoustic resonators that absorb acoustic energy and reduce noise levels. The volumetric honeycomb shell is made in the form of a honeycomb block with a quadrangular outline. Two opposite sides of a quadrangular contour are formed by segments of parallel lines. The cell block is symmetrical about the line connecting the midpoints of the parallel sides of the contour. The honeycomb block is assembled in rows of elastic wavy tape between the parallel sides of a quadrangular contour. Adjacent rows of wavy tape are mutually offset by half a step and connected at the junction of peaks and valleys. The volumetric honeycomb block is deformed along the contours and spherical surfaces of the blind and perforated shells.

To solve the problem, the blind and perforated spherical shells are made in the form of concentric spherical belts, and the contour of the honeycomb block is geometrically related to the parameters of the sound-absorbing spherical panel by the ratios:

where: x, y - coordinates of the contour points in the rectangular coordinate system XOY , mm; the origin point O lies on the cell axis in the middle of the segment connecting the midpoints of the parallel sides of the contour, the OY axis is directed along this segment; R is the radius of the contact surface of the outer spherical and honeycomb shells, mm; H - height of the spherical belt, mm, the number of sectors in a closed spherical belt, i = 1 corresponds to an annular spherical belt (see below: Fig. 4, 7).

The coordinates of the axes of the holes in the perforated shell are related to the geometric parameters of the sound-absorbing spherical panel by the following relationships:

Where: - azimuthal and polar coordinate angles of the hole axes in the spherical coordinate system, rad., the origin of the coordinate system coincides with the geometric center of the spherical belt; azimuth angle measured from the symmetry axis of the spherical belt sector;n-number of a row of holes measured from the fundamental plane;m --hole number inn-th row when counting from the axis of symmetry of the sector of the spherical belt; - pitch of the cell axes of the cell block along the axisOX,mm; - pitch of the axes of the holes of the honeycomb block along the axisOY, mm (see below: Fig. 5-10).

Relations (1), (2) are obtained from the following conditions:

- the x- coordinate of the contour of the honeycomb block is equal to half the length of the arc on the contact surface of the outer spherical shell in its section by a plane parallel to the fundamental plane;

- the y- coordinate of the honeycomb block is equal to the length of the arc of the contact surface at the end of the outer spherical shell between the above parallel planes (see below: Fig. 4).

For large radii of the sound-absorbing spherical panel, for example, when R is thirty or more times the width of the elastic wavy tape, the honeycomb block, after installation between thin shells, is elastically deformed. Relations (1), (2) quite accurately ensure the preservation of the shape, size, pitch and position of the cells of the honeycomb block on the contact surface of the outer spherical shell. Relations (3)-(6) determine the spherical angular coordinates of the axes of the holes on the contact surface of the outer spherical shell through steps s and t of the cells of the honeycomb side.

The known position of the cells of the honeycomb block makes it possible to make perforation holes coaxial with them along spherical coordinates on both the outer and inner spherical shells. The acoustic resonators in this design have a symmetrical shape, and the sound absorption effect is improved.

2nd version

Sound-absorbing spherical panel in version 1, characterized in that the holes of the external perforated spherical shells are made in a package of flat blanks. The coordinates of the axes of the holes on the surface of a flat workpiece are determined by the relations:

Where: - coordinates of the axes of the holes in the rectangular XOY coordinate system on the surface of the flat workpiece of the perforated shell, mm; point O of the origin of coordinates coincides with the point of contact between the workpiece and the top of the close-fitting spherical punch of the rigid die (see below: Fig. 11,12).

Relations (7)-(10) were obtained for spherical shells produced by sheet stamping in axisymmetric wrapping operations in rigid dies under the condition of uniform axisymmetric stretching of the workpiece (see Averkiev A.Yu., Averkiev Yu.A., Antonov E.A. Forging and stamping. In 4 volumes. T. 4. Sheet stamping. Page 13, 236-240.). The rectangular coordinates of the axes of the holes in a flat workpiece follow from the spherical angular coordinates (3)-(6) by reducing them to linear values: multiplying by the radiusRcontact surface of the outer spherical shell and dividing by coefficient taking into account the axisymmetric stretching of the workpiece.

Relations (1)-(3) and (7)-(10) determine the coaxial position of the axes of the holes of the outer spherical shell and the cells of the volumetric honeycomb shell after the operations of covering a flat workpiece with a spherical punch and assembling the panel. The acoustic resonators of this design are symmetrical and provide improved sound absorption effect.

3rd version

Sound-absorbing spherical panel in version 1, characterized in that the holes of the internal perforated spherical shells are made in a package of flat blanks. The coordinates of the axes of the holes on the surface of a flat workpiece are determined by the relations:

Where: - coordinates of the hole axes in the rectangular XOY coordinate system on the surface of the flat workpiece of the inner spherical shell, mm; point O of the origin coincides with the point of contact between the workpiece and the top of the close-fitting spherical punch of the rigid die; h is the height of the cells of the cell block, mm (see below: Fig. 11).

The rectangular coordinates of the axes of the holes in a flat workpiece follow from the angular spherical coordinates (3)-(6) by reducing them to linear values: multiplying by the radius (R - h) of the contact surface of the inner spherical shell and dividing by a coefficient that takes into account the axisymmetric stretching of the workpiece.

Making holes in a package of flat blanks reduces the duration of perforation of shells by a multiple of the number of blanks in the package. Relations (1)-(3) and (11)-(14) determine the coaxial position of the axes of the holes of the internal spherical shell and the cells of the volumetric honeycomb shell, after the operations of covering a flat workpiece with a spherical punch and assembling the panel. As in previous versions, the acoustic resonators are symmetrical, and the sound absorption effect is improved.

The rationale for relations (1)-(14) is presented below in the description of the invention.

In fig. 1 shows an annular sound-absorbing spherical panel, in which a thin perforated shell is made in the form of an outer spherical belt; FIG. 2 - annular sound-absorbing spherical panel, in which a thin perforated shell is made in the form of an internal spherical belt, in FIG. 3 - sector of the sound-absorbing spherical panel shown in FIG. 1; in fig. 4 - view A in Fig. 3; in fig. 5 - extension element B in Fig. 4; in fig. 6 - section B-B in Fig. 4; in fig. 7 - contour of a volumetric honeycomb block in a rectangular coordinate system; in fig. 8 - cell block; in fig. 9 - remote element G in Fig. 8; in fig. 10 - perforated spherical shell in a spherical coordinate system; in fig. 11 - diagram of the deformation of a flat workpiece when it is covered with a rigid spherical punch of radius R ; in fig. 12 - a package of flat blanks of perforated shells in a rectangular coordinate system.

Sound-absorbing spherical panel, see fig. 1-3 contains a thin blind spherical shell 1, a voluminous honeycomb shell 2 and a thin perforated spherical shell 3. The voluminous honeycomb shell is installed between the blind and perforated spherical shells. The shells are rigidly connected along the contact surfaces and form a plurality of acoustic resonators. The volumetric honeycomb shell is made in the form of a honeycomb block with a quadrangular outline. Two opposite sides of a quadrangular contour are formed by segments of parallel lines. The cell block is symmetrical about the line connecting the midpoints of the parallel sides of the contour. The honeycomb block is assembled in rows of elastic wavy tape between the parallel sides of a quadrangular contour. Adjacent rows of wavy tape are mutually offset by half a step and connected at the junction of peaks and valleys. The volumetric honeycomb block is deformed along the contours and spherical contact surfaces of the blind and perforated shells.

The blind and perforated spherical shells are made in the form of concentric spherical belts, and the contour of the honeycomb block is connected with the geometric parameters of the sound-absorbing spherical panel by relations (1), (2). After deformation of the honeycomb block along the contour and spherical contact surfaces of thin spherical shells, the prismatic cells of the honeycomb block take the shape of truncated pyramids. Relations (1), (2) ensure the preservation of the shape, size and pitch of the cells of the honeycomb block on the surface adjacent to the outer spherical shell. On the surface adjacent to the inner spherical shell, the shape of the cells of the honeycomb block is preserved, and the dimensions and pitch of the cells are reduced in proportion to the radius of the shell. The sound-absorbing spherical panel can be made detachable from several sectors.

After installing the three-dimensional honeycomb shell, the rows of elastic tape are compressed, which increases the density of the acoustic resonators. The specified contour of the honeycomb block allows the holes of the perforated shell to be made coaxially with the cells of the honeycomb block, obtaining symmetrical acoustic resonators and, as a result, improving the sound absorption effect.

The lengths of the sides of the contour of the honeycomb block are determined by the dimensions of the contact surface of the outer spherical shell. The lengths of the parallel sides of the contour of the honeycomb block are equal to the lengths of the arcs of the bases of the outer spherical belt. The variable distance between the non-parallel sides of the contour is determined by the length of the arc of the contact surface of the outer spherical belt in its current section by a plane parallel to the fundamental plane P.

From the geometric connections in Fig. 4, 10 the length of the parallel sides of the contour of the cell block is equal to the length of the arc LM :

The distance between the parallel sides of the contour of the honeycomb block is equal to the length of the arc CD on the contact surface of the outer spherical shell in its polar section.

The greatest distance between the non-parallel sides of the contour of the honeycomb block is equal to the length of the arc EK on the contact surface of the outer spherical belt in the fundamental plane P.

In the rectangular XOY coordinate system, the contour of the cell block is defined on the segment:

between values:

On the segment:

On segments:

the x values correspond to a constant azimuthal angle equal to half the angle EOK of the sector of the sound-absorbing spherical panel and a variable radius r of circles in planes parallel to the fundamental plane P. For the coincidence of the lateral sides of the contour and the spherical shell after deformation of the honeycomb block, the variable radius and coordinate y are determined by the relations:

where: r is the variable radius of circles in planes parallel to the fundamental plane.

From (15)-(24) relations (1), (2) follow, which ensure the preservation of the shape, size and pitch of the cells on the surface of contact with the outer spherical shell. On the surface adjacent to the inner spherical shell, the shape of the cells of the honeycomb block is preserved, and the dimensions and pitch of the cells are reduced in proportion to the radius of the shell. When the honeycomb block is deformed along the contour and spherical surfaces of the shells, the rows of elastic wave-shaped tape are compressed, and the density of the reliability of their connections improves.

The connection of the contour of the prismatic honeycomb block with the geometric parameters of the sound-absorbing spherical panel determines the shape and position of the cells of the volumetric honeycomb shell, which makes it possible to make holes in the perforated shell coaxially with the cells of the volumetric honeycomb shell, obtain symmetrical acoustic resonators and, as a result, improve the sound absorption effect.

In versions 2 and 3, the holes of the perforated spherical shells are made in a package of several flat blanks along rectangular coordinates, determined respectively by relations (7)-(10) and (11)-(14), see Fig. 12.

In version 2, the rectangular coordinates of the axes of the holes in the flat workpiece follow from the angular spherical coordinates (3)-(6) by reducing them to linear values: multiplying by the radius R of the contact surface of the outer spherical shell and dividing by a coefficient taking into account the axisymmetric stretching of the workpiece, see fig. eleven:

where: k is a coefficient that takes into account the axisymmetric stretching of the workpiece.

In version 3, the rectangular coordinates of the axes of the holes in the flat workpiece follow from the angular spherical coordinates (3)-(6) by reducing them to linear values: multiplying by the radius (R - h) of the contact surface of the inner spherical shell and dividing by a coefficient taking into account axisymmetric tension blanks:

in this case, the steps of the cells of the honeycomb block on the surface adjacent to the inner spherical shell will decrease in proportion to the radius of the inner spherical shell:

Where: - pitch of the cells of the honeycomb block on the contact surface of the inner spherical shell along the axisX. - pitch of the cells of the honeycomb block on the surface adjacent to the inner spherical shell along the axisY.

The sound-absorbing spherical panel is assembled in an assembly jig. The contact surfaces of the shells are coated with organic bonded powder solder. The honeycomb block is installed between thin spherical shells and is deformed along their contour and spherical surfaces. The assembled structure is subjected to heat treatment to form solder joints.

In the preferred design of the sound-absorbing spherical panel, the three-dimensional honeycomb block is assembled with an undulating tape with a trapezoidal waveform forming hexagonal cells. Due to the fact that relations (1) - (6) do not contain cell shape parameters, the elastic honeycomb block can be assembled with a wavy tape with a different waveform and, as a consequence, with a different cell shape.

The production of a sound-absorbing spherical panel is carried out in the production of a metalworking plant.

The industrial applicability of the invention is confirmed by the manufacture and testing of a pilot batch of products.

Claims (12)

1. A sound-absorbing spherical panel containing a thin blind spherical shell, a volumetric honeycomb shell and a thin perforated spherical shell, the volumetric honeycomb shell is installed between the blind and perforated spherical shells, the shells are rigidly connected along the contact surfaces and form a plurality of acoustic resonators, the volumetric honeycomb shell is made in the form honeycomb block with a quadrangular contour, two opposite sides of the quadrangular contour are formed by segments of parallel straight lines, the honeycomb block is symmetrical with respect to the line connecting the midpoints of the parallel sides of the contour, the honeycomb block is assembled in rows of elastic wavy tape between the parallel sides of the quadrangular contour, adjacent rows of wavy tape are mutually offset by half a step and connected at the contact points of the peaks and valleys, the volumetric honeycomb block is deformed along the contours and spherical surfaces of the blind and perforated shells, characterized in that the blind and perforated spherical shells are made in the form of concentric spherical belts, and the contour of the honeycomb block is geometrically connected with the parameters of the sound-absorbing spherical panel ratios: where: x, y – coordinates of the contour points in the rectangular coordinate system XOY , mm; the origin point O lies on the cell axis in the middle of the segment connecting the midpoints of the parallel sides of the contour, the OY axis is directed along this segment; R – radius of the contact surface of the outer spherical and honeycomb shells, mm; H is the height of the spherical belt, mm, i is the number of sectors in a closed spherical belt, i = 1 corresponds to an annular spherical belt, the coordinates of the axes of the holes of the perforated shell are related to the geometric parameters of the sound-absorbing spherical panel by the following relations: Where: – azimuthal and polar angles of the hole axes in a spherical coordinate system, rad.; the origin of the coordinate system coincides with the geometric center of the spherical belt; azimuth angle measured from the symmetry axis OX of the spherical belt sector; n – number of a row of holes measured from the fundamental plane; m is the number of the hole in the nth row when measured from the symmetry axis of the spherical belt sector; s is the pitch of the axes of the cells of the cell block along the OX axis, mm; t – step of the axes of the cells of the cell block along the OY axis, mm. 2. Sound-absorbing spherical panel according to claim 1, characterized in that the holes of the external perforated spherical shells are made in a package of their flat blanks, the coordinates of the axes of the holes on the surface of the flat blank are determined by the relations: Where: – coordinates of the hole axes in the rectangular XOY coordinate system on the surface of the flat workpiece of the perforated shell, mm; point O of the origin coincides with the point of contact between the workpiece and the top of the close-fitting spherical punch of the rigid die. 3. Sound-absorbing spherical panel according to claim 1, characterized in that the holes of the internal perforated spherical shells are made in a package of flat blanks. The coordinates of the axes of the holes on the surface of a flat workpiece are determined by the relations: Where: – coordinates of the hole axes in the rectangular XOY coordinate system on the surface of the flat workpiece of the inner spherical shell, mm; point O of the origin coincides with the point of contact between the workpiece and the top of the close-fitting spherical punch of the rigid die; h – height of the cells of the cell block, mm.