Gas guide element with sound-absorbent walls for blocking and damping noise spreading from it into main conduits

A gas guide element with sound absorbent walls for blocking or damping noise spreading into main conduits, the gas guide element comprising a guide element body including a flexible sound absorbent inner hose resistant to mechanical, chemical and caloric load exerted by a gas to be guided; an outer hose; and a soft and flexible sound absorbent intermediate layer of material disposed between said sound absorbent inner and outer hose, said inner hose being composed of a flexible material and having an outer side provided with weighted metal elements, said sound absorbent intermediate layer being composed of a randomly oriented pile of materials, and said guide element body having a gas inlet and a gas outlet and at least one 360.degree. convolution between said gas inlet and said gas outlet.

BACKGROUND OF THE INVENTION
 The invention relates to a gas guide element with sound-absorbent walls for
 blocking and damping noise spreading from it into main conduits, which
 element is made up of a flexible inner hose with a metal element, an outer
 hose, and a soft and likewise flexible intermediate layer of material
 disposed between the hose.
 In a known gas guide element of this kind according to German Patent
 Publication DE-OS 27 49 665, the inner hose is comprised of a wide-mesh
 cloth which is provided on its inner side with a spiral wire as a metal
 element to reinforce it. The outer hose is constituted by a foil, wherein
 a foamed material is inserted between this foil and the cloth as a
 intermediate layer of material. The annular end regions of this gas guide
 element, which is embodied as flexible and linear as well, are closed by
 glued-on end caps. According to the ideas of the inventor of this gas
 guide element, the sound is meant to penetrate the mesh of the cloth of
 the inner hose, into the intermediate layer of material, which is
 comprised of a foamed material body, and be damped there. Because of the
 foamed material body, gas guide elements of this kind are neither
 temperature- nor abrasion-resistant and for this reason are only partially
 suited for sound blocking and damping. This kind of gas guide elements
 does not come into consideration for blocking or damping sound emissions
 of high sound intensity in hot gasses from gas turbines.
 In another gas guide element according to German Patent Publication DE 38
 30 346 C2, the inner hose, is embodied of a base element, which is both
 flexible and perforated, on whose exterior an open-pored foam of polymer
 material is deposited as a sound blocking material, which is encompassed
 on its outer circumference face by a compact skin as an outer hose. This
 gas guide element also does not come into consideration for guiding hot
 gasses and for damping sound intensities connected with them which occur
 in gas turbines. Also, the relative reductions of the sound pressure level
 mentioned in these prior publications allow the conclusion that there is
 only mediocre sound damping, although considered in the absolute, a
 reduction of the sound pressure level by 3 dB(A) already signifies a
 reduction of the sound intensity by half.
 Furthermore, German Patent Publication DE 32 20 023 C3 and the identical
 European Patent Publication EP 0 095 582 disclose a gas guide element
 whose outer layer is comprised of a mainly closed-celled, elastic,
 thermoplastic foamed material, whereas its inner layer, which is
 predominantly intended to take on the task of sound blocking, is embodied
 of an open-celled, soft foamed material, for example a polyurethane soft
 foam. The two layers are connected either by means of flame lamination or
 a bonding agent. An intermediate layer of material between the layers in
 the form of a reinforcing layer is also considered, for example a random
 fiber structure, cloth or knit cloth of textile and/or glass fibers. This
 gas guide element also is considered as a sound damper for hot gasses
 because of its material compositions.
 In gas turbines or air driver pumps to be serviced in large-capacity
 airplanes, for example in those of Boeing aircraft of the type 747; a
 sound intensity at the turbine exit of 150 dB(A) and a gas temperature of
 approximately 200.degree. C. must be expected, and at the main turbines, a
 sound intensity of 165 dB(A) and a core jet temperature of 820.degree. C.
 must be expected. This kind of sound intensity signifies a threat to human
 life. The graphs of this prior publication also disclose little regarding
 the sound intensity reduction in this range.
 And finally, U.S. Pat. No. 3,374,856 discloses a gas guide element of
 another generic type, which is comprised of a corrugated outer hose of
 rubber-impregnated or plastic-impregnated woven cloth, while the inner
 hose is made of a synthetic plastic, e.g. urethane caoutchouc. There is no
 layer of material as an intermediate covering. FIG. 2 of this patent
 document shows a bend of a gas guide element of this kind by 180.degree.
 in order to verify its flexibility. In this prior publication, though, an
 installation position in this bent form is not even mentioned once in
 passing. Also, this gas guide element is not suited to blocking or damping
 sound intensities in hot gasses from gas turbines because of its
 temperature-sensitive materials.
 In addition to these gas guide elements with sound-absorbent walls, there
 are also a number of sound dampers with nonabsorbing walls, for example
 according to U.S. Pat. Nos. 2,886,121, 3,187,835, 3,415,337, 3,227,240,
 European Patent Publications EP 0 346 551 B1, EP 0.493 161 A1, and German
 Patent Publication DE-OS 2 264 354, which are not the subject of the
 instant invention.
 SUMMARY OF THE INVENTION
 Based on this prior art, the object of the invention is to embody a gas
 guide element with sound-absorbing walls, according to the generic type
 mentioned at the beginning, which is inexpensive to manufacture and easy
 to use, in such a way that it assures a considerable reduction of the
 sound intensity of noises, even in hot and chemically aggressive gasses.
 This object is attained in connection with the species mentioned at the
 beginning in such a way that depending upon the mechanical, chemical, or
 caloric load exerted by the gas to e guided, the inner hose is comprised
 of a textile material, a woven cloth made of metal wire, glass fiber,
 synthetic, natural or ceramic, a nonwoven, or a soft, thin foil of
 polyurethane, polyamide, polytetrafluoroethylene, or a combination of
 these materials, which is connected on its outside to weighted metal
 elements, that the intermediate layer of material is made of a randomly
 oriented pile of mineral fibers and/or metal fibers And/or shavings and/or
 chips of entropy-elastic materials and the gas guide element has at least
 one 360.degree. convolution between its gas inlet and its gas outlet.
 The materials from textile to nonwoven in the above list can be uncoated
 or, for the desired gas- and airtightness, can be coated with an
 entropy-elastic material, such as natural caoutchouc, rubber, or a
 plastic, or can be provided with a thin aluminum coating of from 25.mu. to
 50.mu., for example.
 According to a first embodiment, the weighted metal elements are comprised
 of individual rings, which enclose the inner hose or hold together the
 inner hose, which is comprised of tube sections.
 According to a second embodiment, the weighted metal elements are comprised
 of a metal spiral, which holds together the hose on its overlapping
 lateral ends and is comprised of two spiral-shaped material strips.
 According to a third embodiment, the weighted metal elements are comprised
 of metal pieces which are fastened to the outside of the inner hose in a
 regular fashion. These heavy metal pieces can be connected with concrete
 or other heavy, parts, such as ceramic or metal-containing plastic.
 According to a fourth embodiment, the weighted metal elements are comprised
 of a metal spiral which encloses the inner hose and of a pipe or hose
 which in turn encloses this metal spiral, is provided with the same
 convolution form, and is connected to the metal spiral by clamps or
 clipped-in bands, wherein the intermediate space between the inner wall of
 the pipe or hose and the outer wall of the hose covering is filled with
 water, high temperature oil, or a melting metal alloy. The correspondingly
 wound pipe or hose is intended on the one hand to increase the oscillated
 mass and on the other hand to draw off or supply thermal quantities at the
 same time via the filling of the intermediate space with different media,
 for example for cooling or also for heat recovery.
 In the attainment according to the invention, the term "convolution" is in
 no way intended to mean only a "circular convolution". Thus the
 convolution on the one hand can be embodied as a circular, archimedean,
 hyperbolic, or logarithmic spiral or, on the other hand, can be comprised
 of an elliptical or oval loop up to a knotted convolution, and finally can
 also have the shape of a serpentine, in particular the shape of a
 sinusoidal serpentine. Within the concept of the invention, a
 "convolution" is generally intended to be understood as the kind which
 extends from a geometric center point out to the intersecting region of
 its ends through all four quadrants of an imaginary Cartesian coordinate
 system. An exception to this is constituted simply by the serpentine which
 extends through only two quadrants.
 It is advantageous to provide the gas guide element with three convolutions
 between its gas inlet and its gas outlet.
 According to a particularly advantageous improvement of the invention, each
 convolution of the gas guide element is provided with as narrow a
 convolution radius as possible, depending on the flexibility of the
 materials of the hose.
 The first trials with a gas guide element embodied in this way with only
 one circular spiral convolution of 360.degree. of the gas guide element at
 a sound intensity of 150 dB(A) at the gas inlet resulted in a sound
 intensity reduction to 108 dB(A) at the gas outlet. When there were three
 circular spiral convolutions of the gas guide element and a noise
 intensity of 150 dB(A) at the gas inlet, only 89 dB (A) were measured at
 the gas outlet. According to observations made here, this kind of
 surprisingly strong reduction of sound intensity is not possible with any
 conventional and known gas guide elements. This advantageous effect can
 only be explained by the particular construction of the gas guide element
 as well as by a settling of the heavy, weighted metal elements, in
 particular the metal rings or the metal spiral, into the flexible
 intermediate layer of material, by means of which the previously
 demonstrated sound intensity reduction was permitted to be achieved in a
 surprising manner mainly by sound-absorbent and probably less by
 reflection and interference phenomena.
 According to an advantageous improvement of the invention, the outer hose
 is also provided with the same construction as the inner hose, wherein the
 intermediate layer of material is evenly distributed in the intermediate
 space between the inner hose, and the outer hose.
 The outer hose, is advantageously comprised of a gastight and airtight
 plastic such as polytetrafluoroethylene (PTFE), polyamide (PA), polyester
 (PETP), or a textile which is coated on one or both sides with these
 plastics and is made of a wire, glass fiber, synthetic, or natural cloth,
 of nonwoven, of ceramic, or a combination of these materials.
 According to a particularly advantageous improvement of the invention, an
 intermediate hose, is inserted between the inner hose and the outer hose,
 which intermediate hose can have the same construction as the inner hose.
 In a particularly advantageous manner, the inner hose, is made of a
 stainless steel wire cloth, the intermediate and outer hose, are made of a
 glass fiber reinforced cloth, and the intermediate layer of material
 between the inner and intermediate hose, is made of stainless steel wool
 and the intermediate layer of material between the intermediate and outer
 hose is made of mineral fiber wool. A gas guide element embodied in this
 manner is particularly suited for blocking and damping sound of hot gasses
 of 1150.degree. C. and more.
 Advantageously, the hose are made in a known manner of spiral-shaped
 material strips whose overlapping lateral ends enclose a metallic support
 body and are enclosed along with this by a clamping body with a C-shaped
 cross section whose legs, which are disposed opposite each other at the
 opening point, clamp the material strips and their overlapping lateral
 ends at this point. This kind of hose is described in every detail and in
 several variants in German Patent Publication DE 37 20 231 A1. By
 inserting the metallic support body into the metallic clamping body with
 C-shaped cross section, not only is a long-lasting connection achieved
 between the sound absorbent walls and the metal elements, but also the
 latter ate weighted with a considerable mass, which expedites sound
 blocking.
 For a further sound blocking and damping as well as for a cooling of the
 materials, it is particularly advantageous if in an improvement of the
 invention the inner hose is provided with a spray device for injecting
 water into the gas guide conduit.
 To reduce pressure losses, the cross-sectional face of the gas guide
 conduit of the inner hose--and therefore of all other hose enclosing
 it--is enlarged in relation to the cross-sectional face of the gas guide
 conduit upstream of the gas inlet.
 Other exemplary embodiments of the invention are shown in the drawings.
 The novel features which are considered as characteristic for the present
 invention are set forth in particular in the appended claims. The
 invention itself, however, both as to its construction and its method of
 operation, together with additional objects and advantages thereof, will
 be best understood from the following description of specific embodiments
 when read in connection with the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS
 According to FIG. 1, the gas inlet 2 of the gas guide element 1 of the
 invention is connected via a flange connection 4 to a main conduit 3,
 while its-gas outlet 5 is oriented toward the atmosphere.
 According to FIG. 1, the gas guide element 1 is provided with one
 convolution W having the narrowest possible convolution radius r, whereas
 the gas guide element 1 according to FIG. 2 has three convolutions W in
 all. In FIGS. 2 to 5, parts which coincide with parts in FIG. 1 are given
 the same reference numerals.
 The gas guide element 1 according to FIG. 2 is disposed in a carrier 6 and
 can be arbitrarily moved along with this by a hoisting device, not shown.
 This hoisting device can be either a crane or a stacker truck. Its gas
 inlet 2 is provided with a funnel 7 into which the main conduit 3 of a
 symbolically depicted turbine 8 flows. However, a blower or another sound
 emitting machine can take the place of the turbine 8.
 According to FIG. 3, the gas guide element 1 is embodied in the shape of a
 loop, which likewise has a convolution W of 360.degree., because it
 extends through all four quadrants of a Cartesian coordinate system, which
 is indicated with the abscissa axis x, the ordinate axis y, and the Roman
 numerals I to IV. Based on this definition, the loop according to FIG. 3
 can also have other shapes.
 FIG. 4 shows a gas guide element 1 in the form of two sinusoidal
 serpentines of 360.degree. each.
 In FIG. 5, the gas guide element 1 has the shape of a spiral, which can be
 an archimedean, hyperbolic, or logarithmic spiral.
 It is evident from all the embodiments of FIGS. 1 to 5 that the convolution
 radius or curve radius r of the convolutions W is embodied as being as
 narrow or small as possible. It could be determined in experiments that
 the reduction of sound intensity is greater the smaller the convolution
 radius r is. Making a convolution radius which is as narrow as possible is
 limited only by the flexibility of the materials of the hose 9, 11, 14.
 According to FIGS. 6 to 8, depending upon the temperature of the gas to be
 guided, the inner hose 9 is comprised of a textile material, a woven cloth
 made of metal wire, glass fiber, synthetic, natural, or ceramic, a
 nonwoven, or a soft, thin foil of polyurethane, polyamide, or a
 combination of these materials, which is held together either by metal
 rings comprised of individual rings or, according to FIGS. 6 to 8 by a
 spiral 10 as the metal element, which is comprised of spiral strips. The
 intermediate layer of material between the inner hose 9 and the outer hose
 11 is embodied by a randomly oriented pile either of mineral fibers 12
 according to FIGS. 6 and 7 or of stainless steel wool 13 according to FIG.
 8.
 The outer hose 11 is either embodied as smooth according to FIG. 6 or,
 according to FIG. 7, provided with the same construction as the inner hose
 9. The outer hose 11 can be embodied of a gastight and airtight plastic,
 such as polytetrafluoroethylene (PTFE), polyamide (PA), polyester (PETP),
 or of a textile which is uncoated or is coated on one or both sides with
 these plastics and is made of wire or glass fiber, synthetic, natural, or
 ceramic woven cloth, of nonwoven, or of a combination of these materials.
 The exemplary embodiment according to FIG. 8 is intended particularly for
 guiding hot gasses with a temperature of 1150.degree. C. and higher as
 well as for blocking and damping the noise spreading in them. In this
 exemplary embodiment, an intermediate hose 14 is inserted between the
 inner hose 9 and the outer hose II. This intermediate hose 14 has the same
 construction as the inner hose 9. In this instance, the inner hose 9 is
 comprised of a fine stainless steel wire cloth, while the intermediate
 hose 14 and the outer hose 11 are comprised of a glass fiber reinforced
 cloth, however the intermediate layer of material between the intermediate
 hose 14 and the outer hose 11 is embodied of a randomly oriented pile of
 mineral fibers 12.
 Naturally, the principal construction of the gas guide element according to
 the invention according to FIGS. 1 to 5 is only intended to be an example.
 Gas guide elements are also possible which have both fewer than three
 convolutions and more than three convolutions. The choice is made by one
 skilled in the art according to the main employment purpose of the gas
 guide element. If this employment purpose is mainly directed toward
 reducing the sound intensity which exists at the gas entry 2, more than
 only three convolutions can easily be used. The number of convolutions,
 though, is chosen so that not too increased a backpressure to the turbine
 8 or to a different engine is produced by the pressure loss which
 increases with each convolution. For this reason it is advantageous to
 enlarge, for example to double, the cross-sectional faces of the gas guide
 conduit 16 of the inner hose 9 in relation to the cross-sectional face of
 the main conduit 3 upstream of the gas inlet 2.
 For further reduction of sound intensity, the inner hose 9 can also be
 provided with a spray device 15 according to FIG. 2 in order to be able to
 inject water into the guide conduit 16 of the gas guide element 1, by
 means of which the thermal stress on the materials is also reduced. A
 spray device 15 of this kind is provided in FIG. 2 as an annular spray
 nozzle at the gas inlet 2, but can also be disposed differently and at
 several points in the guide conduit 16.
 FIG. 9 shows an enlarged representation of the principal construction of
 the inner hose 9, the intermediate hose 14 according to FIG. 8, and the
 outer hose 11 according to FIGS. 7 and 8.
 In this instance, the hoses 9, 11, and 14 are comprised of two
 spiral-shaped material strips 17, 18, a spiral-shaped support body 19, and
 also a spiral-shaped clamping body 20 with a C-shaped cross section. The
 overlapping lateral ends 21, 22 of the spiral-shaped material strips 17,
 18 enclose the support body 19. The legs 23, 24 of the clamping body 20
 are disposed opposite each other at the opening point 25 and at this point
 clamp the overlapping lateral ends 21, 22 of the material strips 17, 18.
 The edges 26, 27 of the legs 23, 24 are rounded in order to prevent a
 tearing of the material strips 17, 18 at this point. The construction in
 principle of the two material strips 17, 18 in connection with the support
 body 19 and the clamping body 20 is described in every detail with several
 variants in German Patent Publication DE 37 20 231 A1 and is therefore not
 the subject of the current invention.
 By placing a plurality of material strips 17, 18 on top of each other, it
 is possible with these metal elements 19, 20 to clamp them simultaneously,
 and therefore the combinations of these materials, which are for the inner
 hose 9 and are claimed in claim 1, are possible. As a result, the inner
 hose 9 can be embodied alternatively to be gas- and airtight or to be gas-
 and air-permeable.
 Both the clamping body 20 and the support body 19 are comprised of metal
 and form a mass capable of oscillation, which can oscillate into the
 randomly oriented pile of mineral fiber wool 12 or stainless steel wool 13
 and consequently can correspondingly reduce the sound intensity. The
 surprising sound intensity reduction with the gas guide element according
 to the invention appears to rest mainly in the blocking of sound intensity
 by means of the oscillating masses 19, 20 in connection with the randomly
 oriented pile of mineral fiberwool 12 and/or stainless steel wool 13. In
 connection with at least one convolution W with as narrow as possible a
 convolution radius r the sound penetrating into the guide conduit 16 is
 reflected by the inner wall 9a of the inner hose 9, so that a sound
 reduction is also possible by means of corresponding interference
 phenomena. The reduction of experimentally generated sound intensity from
 150 dB(A) at the gas inlet 2 to 89 dB(A) at the gas outlet 5 speaks for
 itself, since this signifies an approximately 20-fold reduction of the
 original sound intensity.
 Naturally, the gas guide element 1 according to the invention can also be
 used for sound blocking and damping at the inlet 8a of this turbine 8.
 In order to reduce unwanted impedances on the aspirating side or the
 exhaust side, which can result in the destruction of the turbine 8 when
 particular limit values are exceeded, flow accelerators, such as
 ventilators, flow pumps, etc., which are also muffled, are then
 advantageously inserted into the flow conduit 16 of the gas guide element
 1, and/or the cross-sectional face of the gas guide element 16 is enlarged
 in relation to the cross-sectional face at the turbine inlet 8a.
 It will be understood that each of the elements described above, or two or
 more together, may also find a useful application in other types of
 constructions differing from the types described above.
 While the invention has been illustrated and described as embodied in gas
 guide element with sound-absorbent walls for blocking and damping noise
 spreading from it into main conduits, it is not intended to be limited to
 the details shown, since various modifications and structural changes may
 be made without departing in any way from the spirit of the present
 invention.
 Without further analysis, the foregoing will so fully reveal the gist of
 the present invention that others can, by applying current knowledge,
 readily adapt it for various applications without omitting features that,
 from the standpoint of prior art, fairly constitute essential
 characteristics of the generic or specific aspects of this invention.
 What is claimed as new and desired to be protected by letters patent is set
 forth in the appended claims.