HONEYCOMB STRUCTURE ASSEMBLIES

Abstract: The present invention relates to honeycomb structure assemblies comprising walled structures (22) which admit fluid such as air for purposes of cooling or heating the walls (21,23) thereof or for other purposes. The assemblies comprise spaced inner and outer walls (23,21) united by means of an internal honeycomb structure (10,11) comprising aligned cells having opposed interior and exterior gaps open to adjacent cells, which causes the admitted fluid to undulate through said gaps into contact with both of the walls (21,23) such as for uniform cooling or heating. The honeycomb structure (10,11) contains flanges (19) which are secured to one or both walls (21,23) for uniform strength and resistance to separation under the stress of use

Description: The present application relates to a honeycomb structure assembly according to the first part of claim 1. Such a structure is known from US-A-4 642 993. The cooling structures or walled heat exchange structures of US-A-4,642,993 represent a substantial advance of the art by providing lightweight, inexpensive efficient structures which are relatively simple to manufacture and which permit inspection for quality control purposes during manufacture. The cooling structures of the Patent comprise opposed walls forming therebetween an interior space containing a honeycomb structure, the walls of which extend substantially perpendicularly or radially relative to the opposed walls, depending upon whether the walls are planar or curved. The honeycomb structure of US-A-4 642 993 is formed by joining narrow undulated metal strips to each other in an alternating down-and-up or stepped configuration to form a unit having a plurality of honeycomb cells, such as hexagonal cells, the walls of each cell which are formed by the "down" undulated strip extending from the base upward but being short of the top surface of the honeycomb structure, and the walls of each cell which are formed by the "up" undulated strip extending from the top surface of the honeycomb structure but being spaced from the base thereof. Thus, when the honeycomb structure is confined between a base wall and a top wall to form a honeycomb structure assembly, each honeycomb cell is open adjacent the base wall by uniform openings in the cell walls formed by the "up" undulated strip, and is open adjacent the top wall by corresponding uniform openings in the cell walls formed by the "down" undulated strip. According to US-A-4,642,993 the base of the honeycomb structure is attached to one wall of the walled cooling structure, such as the interior wall of a combustor liner, by welding or brazing the "down" undulated strips thereto, and the opposed wall, such as the exterior wall of a combustor liner, is wrapped thereover, and fastened to the interior wall by means of spaced spring clips and bolts passing through some of the honeycomb cells. This permits the heat exchange structure to be bent into a curved or annular configuration, prior to insertion of the clips and bolts, to form a unit, or a plurality of arcuate sections which can be assembled as a unit, to form a heating or cooling structure of the desired wall shape. Cooling or heating fluid entering the structure, such as air, is caused to undulate against one wall, such as the interior wall, to enter a honeycomb cell, and then against the other wall, such as the exterior wall, to escape from that honeycomb cell to adjacent cells where the undulation flow pattern is continued to effect cooling or heating of both walls, depending upon the nature and temperature of the fluid. While the novel walled structure of US-A-4,642,993 provides substantial areas of improvement over prior known structures it does have limitations relative to overall strength and reliability which preclude or restrict its use in certain important applications. For example, since only the "down" undulated strips are attached to the interior wall, such as by brazing or welding, the assembly does not have any resistance to high internal pressure. Even if the "up" undulated strips are brazed or welded to the exterior wall, the strength of the assembly is dependent upon the attachment of the "up" and "down" undulated strips to each other and upon the integrity of the weld or braze connecting the edge of each undulated strips to the interior or exterior wall. Moreover, the manufacture of the honeycomb structure of the Patent requires the precise stepped alignment of the undulated strips while they are brazed to each other in order to insure the uniformity of the coolant passagways or gaps, and assembly requires thin line welding or brazing of the strip edges to the interior or exterior walls, which is possible but requires expensive machinery and skilled operators. US-A- 2,910,153 discloses a structural panel of the honeycomb type, with an interior wall, an exterior wall spaced from the interior wall to form a space disposed between said walls, a plurality of pairs of undulated strips which are united to each other and to adjacent pairs of strips to form partitions of the honeycomb structure, the structure comprising a multiplicity of adjacent cells extending from said interior wall to said exterior wall within said space, each said strip comprising a plurality of segments each segment comprising a main portion extending substantially perpendicular to said walls and a flange extending parallel to said walls, each said cell being defined by two opposed partition segments and intermediate segments between them, the opposed partition segments being welded together to form welded segment pairs whose main portions extend substantially perpendicularly from the interior wall to the exterior wall and which unite said strips and strip pairs and which have flanges extending parallel to and in contact with both said walls. The undulated strips are welded to each other and to the interior and exterior walls in a single welding operation performed on the flanges of the strips. It is thus impossible to form a unitary honeycomb structure of the strips before fixing to the walls, and the welding operation is complicated. Furthermore the strips form almost a complete barrier between the walls, leaving only small bleed holes where flanges of adjacent strips start and stop overlapping. There are no apertures between the level of the flanges in contact with the interior walls and the level of the flanges in contact with the exterior walls. The present invention provides an improved structure with the features set out in claim 1. The invention has the advantage that the undulated strips are attached together independently of the walls, allowing pre-assembly; moreover, the flanges of the opposed partition segments could extend in opposite directions - in contrast to the disclosure of US-A-2 910 153 where the flanges extend in the same direction, requiring distortion of the line of flanges along a strip to allow interfitting of the flanges of adjacent strips. Further, the apertures of the invention may be used to cause air to flow alternately inwardly and outwardly, from cell to cell. Further the invention provides novel honeycomb structure assemblies which have the advantages of those of US-A-4 642 993, which are acknowledged in the preamble portion of claim 1, especially the way in which the apertures cause the air to flow alternately inwardly and outwardly, but which are stronger and more reliable under the effects of the conditions of use. In addition, the present invention provides novel honeycomb cooling structure assemblies which are easier and less expensive to manufacture, avoiding some of the precision alignment means and skill required for the manufacture of the products of US-A-4 642 993. The present invention relates to novel honeycomb structure assemblies including walled heat exchange structures such as cooling combustor wall and other spaced walled structures designed to receive heat exchange or other fluid, such as air, into the space therebetween for purposes of cooling or heating the spaced walls efficiently and directing the flow of the heat exchange fluid as desired, or for other purposes such as noise reduction. According to the present invention, the individual undulated strips used to form the honeycomb unit are of sufficient height to extend between the opposed supporting walls, i.e., the interior and exterior walls, and are provided with segmented weld flanges which extend substantially perpendicularly along both the top and bottom edges of the undulated strips to provide a plurality of attachment flange segments, preferably one between each bend or undulation along one edge and one between every other bend or undulation along the other edge, to provide a plurality of flanges which can be welded, brazed or otherwise attached to the adjacent walls of the walled structure, whereby the honeycomb unit is strongly attached to both walls of the assembly for maximum strength and heat transfer. Such strips are provided with fluid gaps by cutting away spaced portions of the strips adjacent said other edge thereof, between every other bend or undulation, i.e., in areas where there are to be no attachment flanges. Such undulated strips are attached to each other in alternating inverted positions to provide a honeycomb unit having attachment flanges at both the upper and lower surfaces and consisting of honeycomb cells having fluid passages adjacent both the upper and lower edges. The flanges of the honeycomb unit are secured to the adjacent surfaces of both of the supporting walls to form a strong honeycomb structure assembly which provides the undulating, dissipating gas flow disclosed in US-A-4,642,993. An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: FIG. 1 is a perspective view of undulated strips for an assembly which is outside the scope of the present invention; FIG. 2 is a perspective view of a portion of a walled honeycomb structure assembly incorporating undulated strips of the type illustrated by FIG. 1; FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 2; FIG. 4 is a perspective view of undulated strips for an assembly according to an embodiment of the present invention; FIG. 5 is a perspective view of a portion of a walled honeycomb structure assembly according to the first embodiment of the present invention, incorporating undulated strips of the type illustrated by FIG. 4, and FIG. 6 is a cross-sectional view taken along the line 6-6 of FIG. 5. Referring to FIG. 1, a pair of undulated elongate strips 10 and 11 are illustrated in spaced relation, one inverted relative to the other in position to be fastened to each other to form a segment of a honeycomb unit, which is advantageous but does not form part of the invention. Strips 10 and 11 are identical elongate metal strips having uniformly spaced transverse folds 12 which divide each strip 10 and 11 into a plurality of uniform-width wall panels including panels 13 which are coplanar with each other, and offset coplanar panels 14 which are also coplanar with each other. The coplanar panels 13 and 14 are connected to each other by means of angular panels 15. In the hexagonal embodiment illustrated, each panel 13 and 14 is connected by means of a singular angular panel 15 bent at an angle of 120° relative to the parallel coplanar panels 13 and 14. Elongate strips 10 and 11 are welded or brazed to each other by aligning the panels 13 of each strip in contact with each other, strip 10 being slightly elevated relative to strip 11 so that the top edges of the panels 13 of strip 11 are at the positions illustrated by means of broken lines 16 on strip 10 and the bottom edges of the panels 13 of strip 10 are at the positions illustrated by means of broken lines 17 on strip 11 in FIG. 1. So positioned, the strips 10 and 11 are welded or brazed at spots 13a to form honeycomb unit sections which are similarly attached to similar honeycomb unit sections to form the honeycomb units of the desired dimensions. A plurality of such sections are welded or brazed together in similar fashion to form a honeycomb unit of the desired dimensions, i.e., the coplanar panels 14 of each strip 10 and 11 of each section formed as discussed are welded or brazed to panels 14 of similar sections of elongate strips 10 and 11 in similar alternating up and down positions to form a honeycomb unit 18 as illustrated in FIG. 2. The elongate undulated strips 10 and 11 of FIG. 1, and of the honeycomb unit 18 of FIG. 2 formed therefrom, has a segmented attachment flange 19 formed along one edge of the strips 10 and 11 by making V-shaped cuts inwardly along one edge of the strip - forming stock at uniformly - spaced locations corresponding to the intended folds 12 and then folding the segmented flange 19 along a longitudinal fold line 20 until the flange segments extend substantially perpendicular to the panels 13 to 16 from which they extend. After the elongate strip stock is folded to form undulated strips 10 and 11 and such strips are welded or brazed at points 13a to form honeycomb units, the attachment flanges 19 of strips 10 provide a plurality of spaced connection points for the upper or exterior wall 21 of the walled structure 22 of FIG. 2 and the attachment flanges 19 of strips 11 provide a plurality of spaced connection points for the lower or interior wall 23 of the walled structure 22 of FIG. 2. Each such connection point is welded or otherwise fastened to form the walled structure 22. As illustrated by the cross-sectional view of FIG. 3, the attachment flanges 19 of strips 10 are welded or brazed to the adjacent surface of the exterior wall 21 and the attachment flanges 19 of strips 11 are welded or brazed to the adjacent surface of the interior wall 23, and the undulated strips 10 and 11 are welded or brazed to each other in a vertically-offset or up-and-down alignment, whereby the parallel walls 21 and 23 are securely fastened to the honeycomb unit at a spaced plurality of locations across substantially the entire surface areas of each. The spacing between the top edges of the angular panels 15 of each strip 11 and the inside surface of the exterior wall 21 provides each honeycomb cell with two spaced upper fluid gaps or passages and the spacing between the lower edges of the angular panels 15 of each strip 10 and the inside surface of the interior wall 23 provides each honeycomb cell with two spaced lower fluid gaps or passages, each of said gaps communicating with adjacent honeycomb cells to cause the flow of air or other gas to undulate between contact with each of the walls 21 and 23, and to dissipate throughout the honeycomb structure 18 causing a uniform cooling of the walled structure 22. According to the present invention, which avoids the necessity of aligning the elongate undulated strips in vertically-offset or up-and-down position and assures the formation of honeycomb structure assemblies having exceptional strength and uniform flow gaps, the elongate undulated strips 24 and 25 have the design illustrated by FIG. 4 of the drawings. Strips 24 and 25 are identical to each other but one is inverted or turned upside down relative to the other so as to provide upper and lower flow gaps, as will be discussed. Each strip 24 and 25 consists of alternate coplanar panels 26 and 27, which extend parallel to each other, and angular connecting panels 28 which terminate inwardly from one edge of the strips 24 and 25 to provide uniform flow gaps 29. Each strip 24 and 25 is provided with a segmented attachment flange 30 along one edge, to which the gaps 29 are adjacent, and a segmented attachment flange 31 along the opposite edge, as illustrated. As in the embodiment of FIG. 1 the attachment flanges 30 and 31 are formed by making uniformly spaced V-cuts inwardly along the edges of the flat strip stock in areas corresponding to the transverse folds to be made between the panels. Then portions of the panels 28 are cut away, inwardly along one edge, to form the gaps 29. The segmented flange 30 is folded or bent in alternating directions into substantially perpendicular position so that the flange portions on panels 26 and 27 extend towards each other. Similarly, the segmented flange 31 along the other edge is bent or folded into perpendicular position so that the flange portions on panels 26 and 27 extend in the same direction as the flange portions 30 on said panels. The direction of extension of the flange portions 31 on angular panels 28 is not important. Elongate undulated strips 24 and 25 are aligned and contacted, with panels 26 of each strip in uniform surface contact, and panels 26 of each strip are welded or brazed together at spots 26a to form a section of the honeycomb unit. Similar sections are formed and united, such as by welding or brazing the planar panels 27 of two such sections to the planar panels 27 of the section of FIG. 1. The directions of extension of the weld flanges 30 and 31 on planar panels 26 and 27 permits the faces of such panels to be placed in intimate surface contact for the welding operation. The formed honeycomb unit 32 is illustrated by FIG. 5. Referring to FIG. 5, the honeycomb unit 32 has upper and lower segmented flanges 30 and 31 which are welded or brazed to the adjacent surfaces of the exterior and interior walls 33 and 34 to form a walled structure 35 of exceptional strength and uniformity of dimensions of the cooling fluid gaps 29. Such a structure is easier to manufacture than those of Patent 4,642,993, avoiding the need for precision alignment equipment, and is exceptionally strong since each of the undulated strips 24 and 25 is fastened to both the interior and exterior walls. FIG. 6 illustrates the cross-sectional interconnection between the parallel walls 33 and 34 and the honeycomb unit 32. The adjacent attachment flanges 30 and 31 of inverted panels 26 (and 27), of strips 24 and 25 extend away from each other so as not to interfere with the surface contact between panels 26, welded at point 13a, and each strip 24 and 25 carries both the upper and lower flanges 30 and 31 which are welded to the walls 33 and 34 for exceptional strength and resistance to separation. The walled structures can be manufactured in a number of different manners, sizes and configurations from a number of different structural materials depending upon the end use to which they are to be put. As disclosed in US-A-4,642,993 the walled structure can be made by attaching individual undulated strips, such as 11 of Fig. 1 and 25 of Fig. 4, to one supporting wall, such as 23 of Fig. 2 and 34 of Fig. 5 and then attaching the individual undulated strips 10 of Fig. 1 and 24 of Fig. 4 to the strips 11 and 25 which are attached to the supporting wall, in order to build up the attached honeycomb structure. Preferably, the honeycomb structure is first formed as a unit and is then attached to the inner and/or outer walls. The walled structures can be assembled in stepped relation, as shown by Figs. 2 and 3 to provide inlet and outlet slots and/or spaced inlet and outlet ports may be provided in the inner and outer walls to admit a fluid, such as air, hydrogen, water or other fluid for circulation through the honeycomb labyrynth to cool or heat both walls and to extract the fluid at one or more remote locations. The present walled structures may be unitary or may be assembled as a plurality of structural units, such as annular units which are attached to or form an annular element having cooling or heating requirements, such as a combustor chamber, reactor, or the like. In an annular configuration the honeycomb cells generally extend radially with respect to the longitudinal axis of the combustor or reactor. In the illustrated assemblies of Figs. 2 and 5, the assembled sections 22 and 35 are radially-offset relative to each other to provide exterior inlet slots 21a and 33a which open to a plurality of exterior honeycomb gaps for the admission of fluid to the honeycomb structures of the upstream end of the structure sections, and interior slots 23a and 34a which open to a plurality interior honeycomb gaps for the discharge of fluid from the honeycomb structure at the downstream end. While the walled honeycomb structure assemblies are well suited for use as combustor liners for gas turbine engines in the manner disclosed by US-A-4,642,993, they are also suitable for a variety of different uses having heat exchange requirements, such as space vehicle wings and bodies, nuclear reactor housings, solar heat panels, heat shields and a variety of other elements which have cooling or heating requirements. Moreover, the walled honeycomb structure assemblies can be fabricated from plastics, laminates, composites and other materials for purposes other than heat exchange purposes, such as muffling or noise reduction purposes, aeration purposes, flow dissipation purposes, gas and/or liquid mixing purposes and other uses which will be apparent to those skilled in the art in the light of the present disclosure. The nature of the materials from which the present assemblies are fabricated will dictate the nature of the means used to fasten the undulated strips to each other to form the honeycomb structure and to fasten the honeycomb structure to the interior and exterior walls.

Claims: A honeycomb structure assembly comprising an interior wall (23; 34); an exterior wall (21; 33) spaced from the interior wall (23, 34) to form a space disposed between said walls (23, 34; 21, 33), and a multiplicity of undulated strips (10, 11; 24, 25) which are welded to each other and are directly attached to at least the interior wall (23; 34) to form partitions of the honeycomb structure, the structure comprising a multiplicity of adjacent cells (18, 32) extending from said interior wall (23, 34) to said exterior wall (21, 33) within said space, each undulated strip comprising a plurality of segments each comprising a partition portion extending substantially perpendicular to said walls, each said cell (18, 32) being defined by the partition portions (14, 15; 27, 28) of an adjacent pair of the undulated strips, of which portions one portion (14; 27) of one strip is opposed to one portion (14, 27) of the other; each of the said opposed partition portions (14; 27) being welded to the corresponding partition portion of a different one of the undulated strips adjacent the said pair thereof; for each of the cells (18; 32), the cell-defining partition portions (15; 28) of one of the strips (10; 24) adjacent the said one partition portion (14; 27) of that strip defining apertures adjacent the exterior wall (21, 33); and the corresponding cell-defining partition portions (15; 28, 29) of the other strip (11; 25) adjacent the said one partition portion (14; 27) thereof, defining apertures (29) adjacent the interior wall (23; 34); characterized in that each of the said segments comprises a narrow flange (19; 30, 31) extending parallel to said walls by means of which the strip is attached to the corresponding wall; in that the flanges (19, 20; 30, 31) to the said opposed partition portions (14; 27) extend in opposite directions with reference to the interface between those portions at which they are welded; and in that each said opposed partition portion (27) of each strip extends from the interior wall to the exterior wall and, of the partition portions (28) of the other segments of that strip, each such portion (28) either stops short of the exterior wall and the segment has a flange (31) in contact with the interior wall, or else it stops short of the interior wall and the segment has a flange in contact with the exterior wall. An assembly as claimed in Claim 1, wherein for each strip some of the said flanges of the said other partition segments (28) are in contact with the interior wall and some with the exterior wall. A heat exchange structure characterized by being formed from a plurality of sections comprising honeycomb structure assemblies as defined in Claim 1 or Claim 2. A heat exchange structure as claimed in Claim 3, each said assembly being generally annular, the interior wall (23, 34) and the exterior wall (21, 33) being generally annular and spaced radially from each other. A structure as claimed in Claim 4, characterized by each said section (13, 14; 26, 27) thereof being radially offset from the section adjacent thereto. A structure as claimed in Claim 4, characterized by each said section including an upstream end and an axially opposed downstream end, each said honeycomb structure having adjacent its upstream end a plurality of said apertures adjacent the exterior wall, and having adjacent its downstream end a plurality of said apertures adjacent the interior wall.

Inventors: SWEET, E. JACK
Applicants: AVCO CORPORATION
Application year: 1988
Main classification: F28F3
IPC codes: B32B3, F28F3, E04C2, F23R3