US3534808A - Regenerator seal support - Google Patents

Description

United States Patent Inventor Hugh C. Carroll LockporLNewYork Appl. No. 774,332 Filed Nov. 8, 1968 Patented Oct. 20, 1970 Assignee General Motors Corporation Detroit, Michigan in corporation of Delaware REGENERATOR SEAL SUPPORT 3 Claims, 5 Drawing Figs.

US. Cl. 165/9, 277/96 Int. Cl ..F28d 19/04, F16j 15/54 Field of Search 165/9; 277/92 References Cited UNITED STATES PATENTS 3,234,999 2/1966 Atwood 165/9 9/ 1966 Chapman et al ABSTRACT: An axial-flow rotary regenerator has fluid seals which extend between the fixed housing of the regenerator and the matrix and define the perimeters 0f the fluid flow paths. The seals can yield to distortions of the matrix or hous ing. Each seal includes a matrix-engaging element, a flexible sealing membrane engaging the housing and welded to the matrix-engaging element, a supporting membrane disposed on the low pressure side of the sealing membrane, and a support plate disposed on the low pressure side of the supporting membrane. The support plate has a hinged connection to the matrix-engaging element through an abutment strip welded to the matrix-engaging element. The support plate is a zigzag strip formed by rolling a corrugated sheet so as to collapse the corrugations together.

HIGHER PRESSURE /fi2 Q, #1

LOWER PRESSURE Patented Oct. 20, 1970 I N VEN TOR. fiayi E far/0% B Y \glHGHER PRESSURE REGENERATOR SEAL SUPPORT My invention relates to improvements in sealing arrangements for rotary regenerators, particularly those of the axialflow type. Such regenerators are devices in which a finely porous metal or ceramic disk is slowly rotated so that each element of the disk passes successively through two gas paths, absorbing heat from the hotter gas and releasing it to the cooler gas.

One application of such regenerators is in preheating the combustion air in gas turbine engines. in this case, there is a large pressure difference between the compressedair which is heated and the turbine exhaust gases which give up heat. in order to prevent leakage of the high pressure fluid into the low pressure fluid path and also to prevent each fluidfrom bypassing the matrix, seals are provided which extend around the perimeter of one or both flow paths on each face of the regenerator, bridging the gap between the regenerator disk and a face of the enclosing housing which is proximate to the matrix. Particularly with metal matrices, sealing problems are aggravated by distortion of the matrix due to the large temperature gradient between the two faces.

Because of the relative warping of the matrix and and the housing and because of the very high temperatures of the regenerator when employed with gas turbines, provision of an adequate, durable, and economically practicable seal has presented difficult problems. The purpose of my invention is to provide a seal between a rotary regenerator matrix and the matrix housing which is exceptionally effective, is durable and reliable, and which can be fabricated at a reasonable cost.

The principal objects of my invention are to advance the art of rotary regenerators, to make such regenerators commercially feasible for applications such as gas turbine engines, and to provide an improved seal for a rotary regenerator. A further object is to provide a simple seal having a minimum of leakage paths. A further object is to provide an economical support for a flexible seal having superior characteristics. I

The nature of my invention and its advantages willbe clear to those skilled in the art from the succeeding detailed description of the preferred embodiment of the invention and the accompanying drawings thereof.

FIG. 1 is a schematic view of a rotary regenerator taken in a plane containing the axis of rotation of the matrix.

FIG. 2 is a sectional view of a regenerator embodying my improved seal taken on a plane perpendicular to the axis of rotation as indicated by the line 2-2 in FIG. 1.

FIG. 3 is an enlarged view of a portion of the seal as illus trated in FIG. 2.

FIG. 4 is a still further enlarged cross-sectional view taken on the plane indicated by the line 4-4 in FIG. 3.

FIG. 5 is an enlarged sectional view taken on the plane indicated by the line 5-5 in FIG. 2.

Before proceeding to the detailed description, it may be mentioned that my invention is described as embodied in an axial-flow regenerator of the type to which Chapman et al. U.S. Pat. No. 3,273,903 for Regenerator Seal for a Gas Turbine Engine, Sept. 20, 1966, Bracken et al. U.S. Pat. No. 3,368,611 for Rotary Regenerator Seal with High Pressure Fluid Recovery, Feb. 13, 1968, and Bracken et al. U.S. Pat. No. 3,476,173 for Rotary Regenerator Matrix Mount and Drive are directed. The particular seal structure is a modification of that described in U.S. Pat. application Ser. No.

r 769,928 filed Oct. 23, 1968 of Joseph. W. Bracken, Jr. for

Regenerator Seal, of common ownership.

Referring first to FIG. 1, the regenerator comprises a housing which is generally drum-shaped and which encloses an annular matrix 11 which is of a structure defining pores or passages 12 (greatly enlarged in FIG. 1) extending from face to face of the matrix generally parallel to the axis of rotation defined by a matrix locating and driving shaft 13. Shaft 13 is mounted in suitable bearings in a boss 15 on the housing and terminates in a spider 17 which is coupled to the matrix by means (not illustrated, which may be of the type described in the abovementioned U.S. Pat. No. 3,476,173) so that the matrix may be rotated slowly. The matrix preferably includes a nonporous inner rim l8 and an outer nonporous rim l9. It is not essential that such rims be provided, however. A generally cylindrical space 21 is defined within-the interior of the matrix and a space 22 extends around the periphery of the matrix within the housing 10. An inlet 23 for cool high pressure air enters one face of the housing and opposite to it an outlet 25 is provided for the heated compressed air. The hot low pressure exhaust gases enter through an inlet 26 and leave the regenerator through an outlet 27, the two streams being thus in counterflow relation, althoughfth'isis not essential to the invention. Also, the hot gas passage is of larger area than the cold air passage because of the difference in density, but this also is merely incidental to the invention.

A sealing means or seal assembly 28 is provided. between each face of the matrix and the housing to confine the cold and hot gases to the desired paths through-the matrix from inlet to outlet and minimize leakage between. the paths. As shown more clearly in FIG. 2, such a seal comprises two arms 30 and 31 extending radially of the matrix face preferably joined at the center of the matrix and joined at the outer rim of the matrix by an arcuate rim or by-pass seal 34 extending around the high pressure path and an arcuate rim seal 35 extending around the low pressure path. The seal assembly thus defines an opening 37 for the heated high pressure air and an opening 38 for the hot low pressure exhaust gases, these openings as shown in FIG. 2 conforming generally to the outline of the ducts 25 and 26. v

The seal arms 30 and 31 together may be termed a cross arm seal, this lying between the high pressure and'low pressure fluid paths and the seal portions 34 and 35 may be termed a rim seal or bypass seal, these being engaged with the matrix adjacent its periphery. The rim seal portion 34 and the cross arm seal surround the high pressure passage and the cross arm seal and rim seal portion 35 surround the low pressure gas passage. It is common practice for the high pressure air to occupy the space 22 radially outward of the matrix, in which case the rim seal portion 34 may be omitted at the entrance 23 to the matrix.

Proceeding now to FIGS. 2 to 5 for a detailed description of preferred structure of the sealing means, these figures are views of the seal at the outlet side of the air path and the inlet side of the gas path. The principal structural element of the seal is a carrier or frame 40 which, in this particular seal, consists of a circular portion forming part of the rim seals 34 and 35 and an angular cross arm portion extending through the cross arm seal portions 30 and 31. Preferably, this is a unitary structure of rather heavy sheet metal so that it is rigid in the direction perpendicular to the axis of rotation of the matrix but is capable of flexing to a certain extent in a direction parallel to the axis of the matrix. In the particular example described here in which theseal is approximately two feet in overall diameter, the carrier 40 is about 0.06 inch thick. This frame 40 is located positively against rotation and translatory movement transverse to the axis of rotation, but is free to move parallel to the axis of rotation of the matrix. This mounting is provided by a number of pins or dowels 41 projecting from the fixed structure of the housing 10 into slots in lugs 43 extending from the frame 40. The slots 42 are elongated to provide for relative radial expansion of the carrier 40 and the regenerator housing 10.

The carrier 40 bears a wear element 45 which is in actual contact with the matrix throughout the circumference of the rim seals and along the length of the cross arm seals. The wear element is composed of a material or materials suited to the requirements of the installation. It may be, for example, a graphite composition or a nickel alloy. The wear element may be attached in any desired manner to the face of the carrier as by brazing, riveting, or other fastening means. The wear element also may be about 0.06 inch thick in the described embodiment. The carrier and the wear element together may be called a matrix-engaging strip or element 44.

The structure to which my invention is particularly directed lies in the means for bridging the gap 46 between the carrier 40 and a plane face 48 of the housing which underlies the strip 44. Because of the dishing or other distortion and expansion of the matrix as it heats up and possible distortions and expansion of the case, the width of gap 46 varies not only with operating conditions of the regenerator but also varies from one area to another along the strip 44. The problem is, therefore, to provide a high temperature resistant seal which adapts itself to variation in the width of the gap 46 and substantially entirely prevents leakage from the higher pressure to the lower pressure through the gap 46.

The structure provided for this purpose, shown most clearly in FIGS. 3, 4, and 5, embodies four elements comprising a seal disposed between the carrier or frame 40 and the housing surface 48 and bridging the gap 46. These parts of the seal, in order from the carrier 40, are a sealing membrane 49, a supporting membrane 50, a support plate 52, and a hinge element or abutment strip 53. Parts 53, 50, and 49 are all welded together and to the carrier 40 by a row of spot welds or a seam weld or, if desired, attached by mutual brazing along the portion or line 54 where all of these pans are stacked together adjacent one edge of carrier 40. This weld or other joint is such as to provide a leak-tight connection between the sealing membrane 49 and the frame. The free edge of the sealing membrane 49 bears against the face 48 of the housing under the influence of the differential of gas pressures. As indicated in H6. 5, the higher pressure is underneath or to the left of the sealing membrane and the lower pressure above or to the right of the membrane. The membrane 49 is of very thin sheet metal so that it is readily deflected by the pressure into close substantially leak-proof sealing engagement with the surface 48. In the particular example, this is of 0.002 inch shim stock. Since such very light weight and flexible material could not act as a piston or diaphragm to withstand the force exerted by the gas pressure differential, the parts 50 and 52 reinforce it and provide the necessary stifiness except at the free edge where the seal is maintained. However, it is necessary that the stiffening structure not unduly resist gradual change in width of the gap 46 from one area of the matrix to another because of torsional stiffness of the support plate.

In the seal of the Bracken U.S. Pat. application Ser. No. 769,928 referred to above, the support plate is slotted to reduce its torsional stiffness. According to my invention, the support plate is a strip made of relatively thin sheet metal in the fonn of overlapping recumbent corrugations, with the corrugations extending in the direction from edge to edge of the strip. Because the metal is thin, there is little torsional stiffness; but because of multiple overlapping, there is sufficient beam strength to resist the gas pressure across the span from edge to edge of the strip.

The preferred form of the corrugations of the support plate 52 is clearly shown in FIG. 4. Deep corrugations are rolled so as to fold them over against each other in a recumbent or leaning relation to provide a readily twisted zigzag strip. in the illustrated example, the material from which plate 52 is formed is about 0.005 inch thick; the overall thickness of the plate is about 0.040 inch.

Notches 56 are cut in the outer edge of plate 52 to vent gas passing the sealing membrane 49 and maintain full pressure differential across the membrane.

One edge of the support plate 52 bears against a flange 58 of the hinge element 53 so that the support plate is free to swing about its right-hand edge, as illustrated in FIG. 5, to accommodate variations in width of gap 46. The flange 58 is broken by closely spaced slots 59 so that it does not unduly stiffen the carrier 40 and thus lessen the ability of the carrier to accommodate to the curvature of the matrix.

The supporting membrane .50 serves two functions; it bridges the unevennesses in the'surface of the stipportplate to prevent undue local loading and wear of the sealing membnane 49 while maintaining the flexibility of the support plate 52. Also, it serves to retain the support plate in position against the hinge element 53. In the partlcu ar example, this membrane is 0.004 inch thick. As shown clearly in FIGS. 3 and 5, the outer edge of the supporting membrane 50 is slotted in line with thenotches 56 to provide tabs 60 which are doubled back over the outer edge of the support plate 52 and are welded 0r brazed to it. Leakage gas can flow to notches 56 between these tabs. Note that this outer edge of plate 52 is tapered or feathered, by sanding or otherwise, to a relatively thin edge so that the sealing membrane 49 is supported down to a point closely adjacent to the surface 48. As will be seen, the structure illustrated provides a seal between the strip 44 and the housing which has but one leakage path. that being at the free edge of the sealing membrane 49, and which has structure of great simplicity.

As indicated in FIG. 2. where the cross arm seal joins'the rim seal the portions or parts 49, 50, 52, and 53 are mitered so as to provide a suitable corner joint. A similar miter is proviiied at the angle between the cross arm seal portions 30 and 3 It will be apparent to those skilled in the art that the preferred structure described provides a sealing structure for a rotary regenerator having superior simplicity, a minimum of leakage, and, in general, a structure of great practicality and usefulness.

The detailed description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be considered as limiting or restricting the invention, since many modifications may be made by the exercise of skill in the art without departing from the scope of the invention.

lclaim:

1. In a rotary regenerator including a housing and a heattransfer matrix rotatable in the housing about an axis, the matrix and a face of the housing defining a gap between them the gap being variable in operation of the regenerator, sealing means bridging the said gap obliquely adaptable to variation of the gap comprising, in combination, a matrix-engaging strip having a rear face confronting the housing face, plate means hinged to the strip bridging the gap between the said faces. the plate means being torsionally yieldable to accommodate convergence of the gap along the strip, and a thin flexible sealing membrane supported by the plate means across the gap and having edges extending beyond the plate means into flexural sealing engagement with the said faces, the sealing means being so disposed that the pressure differential across the sealing means biases the membrane toward the plate means, the plate means being defined by corrugated sheet metal with the corrugations extending in the direction across the gap, the corrugations being deep and recumbent and overlapping to provide a plurality of layers of the sheet metal for sufficient beam strength across the gap.

2. A structure as defined in claim 1 including also a flexible supporting membrane disposed between the sealing mem brane and the plate means bridging the corrugations in the plate means.

3. A structure as defined in claim 2 in which the supporting membrane is fixed to the strip and plate means and retains the plate means on the strip.

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