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Publication numberUS3843278 A
Publication typeGrant
Publication dateOct 22, 1974
Filing dateJun 4, 1973
Priority dateJun 4, 1973
Publication numberUS 3843278 A, US 3843278A, US-A-3843278, US3843278 A, US3843278A
InventorsTorell S
Original AssigneeUnited Aircraft Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Abradable seal construction
US 3843278 A
Abstract  available in
Images(1)
Previous page
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Claims  available in
Description  (OCR text may contain errors)

United States Patent Torell 51 Oct. 22, 1974 1 ABRADABLE SEAL CONSTRUCTION Inventor: Spencer 1P. Torell, New Britain,

Conn.

Assignee: United Aircraft Corporation, East Hartford, Conn.

Filed: June 4, 1973 Appl. No.: 366,823

US. Cl 415/174, 277/230, 277/96 lint. C1. lFOld 5/20 Field of Search 415/174; 277/96, DIG. 8,

References Cited UNITED STATES PATENTS 9/1961 Spencer 415/174 3,042,365 7/1962 Curtis et a1. 415/174 3,346,175 10/1967 Wiles 415/174 3,575,427 4/1971 Lapac et a1. 415/174 3,649,033 3/1972 Kondo 415/174 Primary ExaminerHenry F. Radulazo Attorney, Agent, or Firm-Stephen E. Revis An abradable tip seal for a compressor rotor, the seal including closely spaced slots having sleeves of reinforcing material, such as braided fiberglass, embedded therein surrounding each slot to reinforce the thin wall between adjacent slots.

ABSTRACT 3 Claims, 4 Drawing Figures ABRADABLE SEAL CONSTRUCTION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a tip seal for a bladed rotor and more particularly to an abradable tip seal for a compressor rotor.

2. Description of the Prior Art Compressor case liners made from nonmetallic material and used as shrouds or tip seals for rotating compressor blades to improve compressor performance are well known in the art, such as the abradable coating ap' plied to the compressor casing as shown in Wiles, U.S. Pat. No. 3,346,175. A further example of such an abradable casing liner is shown in Lapac et al, U.S. Pat. No. 3,575,427, of common assignee with the present invention. It is also known to provide slots or openings 'in these tip seals in the area over which the blade tips pass to improve performance such as shown in Mikolajczak, U.S. Pat. No. 3,580,692, of common assignee with the present invention.

As is often the case, weight and cost are very important factors in the design of these tip seals. In this respect it is desirable to form the tip seals from relatively lightweight and inexpensive compounds such as a thermosetting epoxy resin or rubber. Even these compounds, however are often heavier than desirable. It is possible to reduce the density and thus the weight of compounds such as a thermosetting epoxy resin by the addition of hollow phenolic or glass spheres of small diameter such as is shown in Moorman U.S. Pat. No. 3,271,222 or in the hereinbefore referred to Lapac patent. While these modified compounds are lightweight, they lack strength and may be very brittle. If it is desirable that the tip seal have a plurality of closely spaced openings, the walls between adjacent openings may become quite thin and might break too easily upon contact with a blade tip or even during handling.

It has been found that forming an abradable tip seal having closely spaced slots separated by thin walls using prior art techniques and materials results in either a liner that is strong enough but is too heavy, or a liner that is light enough but is too weak in the area of the thin wall sections and thus does not abrade properly.

SUMMARY OF THE INVENTION One object of the present invention is an improved tip seal for a compressor rotor. A further object of the present invention is an abradable compressor rotor tip seal which is lightweight yet strong where required.

Accordingly, a compressor rotor tip seal with a plurality of circumferentially spaced slots open at the sealing surface is provided, the tip seal including an individual sleeve of reinforcing material embedded therewithin around each slot to increase the strength of the wall between adjacent slots.

In a preferred embodiment the tip seal is abradable and is made from a molding compound comprising epoxy resin, curing agent, small phenolic hollow spheres and chopped fiberglass particles. The overall specific gravity of the molding compound is approximately 0.8. The sleeves surrounding each slot are made from woven fiberglass material. The tip seal, sleeves included, has a specific gravity ofjust under 1.0, yet the wall sections between adjacent slots have good strength characteristics in that each wall has a double thickness of fiberglass fabric embedded in it.

The foregoing and other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of preferred embodiments thereof as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view of a portion of the fan section of the compressor of a gas turbine engine.

FIG. 2 is a view looking in the direction A of FIG. 1.

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1.

FIG. 4 is a view of a braided fiberglass sleeve used in the construction of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As an exemplary embodiment of the present invention, consider the portion of the compressor 10 of a gas turbine engine shown in FIG. 1. The compressor 10 comprises an annular case 12, a case liner 14 and a plurality of rotor blades 16, only the tip portion of one blade being shown. In this embodiment the blades 16 are first stage fan blades, and the case liner 14 is an abradable tip seal for these fan blades 16.

The liner 14 in this instance is bonded with an epoxy adhesive 24 along its radially outwardly facing surface 18 to the radially inwardly facing surface 20 of an annular groove 22 formed in the case 12; however, any suitable technique for securing the liner 14 to the case 12, such as with rivets or bolts, is contemplated as being within the scope of this invention.

Referring now to FIGS. 2 and 3, the liner 14 is shown as being comprised of a plurality of arcuate segments 26 circumferentially spaced within the groove 22 and in abutting relationship with each other such as at 28 and 30. The radially inwardly facing circumferentially extending surface 32 of each segment 26 forms a portion of the gas flow path wall 33 of the compressor 10. As best shown in FIG. 2, each segment 26 includes a double row of circumferentially spaced slots 34. (These slots are not shown in the cross section of FIG. 1 for the purpose of clarity.) The slots in this embodiment are incorporated to improve aerodynamic performance of the fan, but they might be incorporated in a tip seal for any number of reasons such as to reduce noise. As seen in FIG. 3, the slots 34 in this embodiment, although extending generally radially outwardly, are skewed with respect to a radial line and they do not extend completely through the segment 26. As stated, their size, shape, and spacing is dictated by aerodynamic and abradability considerations. With regard to slot spacing, the wall portions 36 between circumferentially adjacent slots 34 are quite thin, being on the order of 86 mils at their thinnest section which is at the surface 32. In this embodiment the wall portions 36 are straight and their surfaces 37 are parallel to the engine axis which is in the plane of the drawing and runs from right to left in FIG. 1.

According to he present invention, woven fiberglass sleeves 38 are embedded within the segments 26, one sleeve surrounding each slot 34 in order to reinforce the thin wall portions 36. These sleeves provide each wall section 36 with a double layer of fiberglass and reduce the brittleness and increase the strength of the wall section. It was found that liners 14 made without these fiberglass sleeves 38 were too weak and too brittle at the wall portions 36 to provide proper abradability characteristics. As can be seen in FIG. 3, the sleeves 38 in this embodiment extend from the radially inner face 32 to the radially outerface 18; however, the

length of the sleeves 38 and their positions within the segments 26 might vary from design to design according to slot size and spacing and the practical aspects of manufacturing the segments, which in this embodiment are molded.

As stated in the summary of the invention, the preferred material for the liner 14 is a molding compound comprising epoxy resin mixed with small phenolic hollow spheres and chopped fiberglass particles, the overall specific gravity of the molding compound being approximately 0.8. FIG. 4 is a drawing ofa sleeve 38 prior to its being molded into the segments 26. The sleeve of FIG. 4 is cut to shape from a continuous tube of woven fiberglass of the appropriate diameter. The sleeves are cured to their desired shape with an epoxy resin to stiffen them so that they will retain their shape during the molding process for the segment 26. As best shown in FIG. 3, the slots 34 are tapered for ease of molding the individual segments 26, the slot circumferential width W decreasing in a radially outward direction. Although, for ease of manufacturing, the preferred embodiment shows a plurality of segments 26, it is contemplated that the liner 14 could be made from a single annular piece.

Although this invention has been shown and described with respect to a preferred embodiment thereof, it should be understood by those skilled in the art that various changes and omissions in the form and detail thereof may be made therein without departing from the spirit and the scope of the invention.

Having thus described a typical embodiment of my invention that which I claim as new and desire to secure by Letters Patent of the United States is:

l. A compressor case liner for use as an abradable tip seal for a stage of compressor blades in a gas turbine engine, said liner comprised of non-metallic, low density moldable abradable material and having a circumferentially extending radially inwardly facing surface defining a portion of a gas flow path through the engine, said liner including a plurality of closely spaced, radially extending slots circumferentially spaced about said surface, each slot defining an opening in said surface and forming thin wall portions between adjacent slots, said linear including a plurality of separately formed fabric sleeves embedded therein, a sleeve surrounding each one of said slots to strengthen said thin wall portions, said liner having an overall specific gravity of about 1.0 or less.

2. The compressor case liner according to claim 1 wherein said liner comprises a plurality of circumferentially spaced abutting arcuate segments, each segment having a circumferentially extending radially inwardly facing surface, said surfaces of said segments defining, in combination with each other, said inwardly facing surface of said liner, the surfaces of said thin wall portions being parallel to said engine axis, said slots being tapered, decreasing in circumferential width in a radially outward direction.

3. The compressor case liner according to claim 2 wherein said liner material is comprised of phenolic resin hollow spheres in a cured epoxy resin, and said fabric sleeves are comprised of woven fiber glass.

3311 UNITED STATES, PATENT OFFICE filififiliFECATE ()F ("IORRECIION TPatent No. 3,843,278 Dated October 22, 1974 Inventofls) Spencer P. Torel].

It is certified that error appears iii the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column '2, line 64, change "he" to --the--'-.

Column 4, line'l6, change "linear" to --liner-.

Signed and sealed this 17th day of December 1974.

fittest:

' TECCOY 11. GIBSON JR. c.- mRsHALL DANN nrtestlng OffLcer Commissioner of Patents

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4280975 *Oct 12, 1979Jul 28, 1981General Electric CompanyMethod for constructing a turbine shroud
US4289447 *Oct 12, 1979Sep 15, 1981General Electric CompanyMetal-ceramic turbine shroud and method of making the same
US4349313 *Dec 26, 1979Sep 14, 1982United Technologies CorporationAbradable rub strip
US4417848 *Feb 1, 1982Nov 29, 1983United Technologies CorporationContainment shell for a fan section of a gas turbine engine
US4466772 *Jan 27, 1981Aug 21, 1984Okapuu UeloCircumferentially grooved shroud liner
US4526509 *Aug 26, 1983Jul 2, 1985General Electric CompanyRub tolerant shroud
US4645217 *Nov 29, 1985Feb 24, 1987United Technologies CorporationFinger seal assembly
US4652209 *Sep 13, 1985Mar 24, 1987Rockwell International CorporationKnurled turbine tip seal
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US5042823 *Dec 21, 1989Aug 27, 1991Allied-Signal Inc.Laminated finger seal
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US5267828 *Nov 13, 1992Dec 7, 1993General Electric CompanyRemovable fan shroud panel
US5388959 *Aug 23, 1993Feb 14, 1995General Electric CompanySeal including a non-metallic abradable material
US5469591 *Sep 8, 1994Nov 28, 1995Paramount Bed Company LimitedBottom structure for a bed
US5472315 *Nov 9, 1993Dec 5, 1995Sundstrand CorporationAbradable coating in a gas turbine engine
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US6203021 *May 12, 1999Mar 20, 2001Chromalloy Gas Turbine CorporationAbradable seal having a cut pattern
US6231301Dec 10, 1998May 15, 2001United Technologies CorporationCasing treatment for a fluid compressor
US6340286 *Dec 27, 1999Jan 22, 2002General Electric CompanyRotary machine having a seal assembly
US6358002Aug 10, 1999Mar 19, 2002United Technologies CorporationArticle having durable ceramic coating with localized abradable portion
US6905305 *Feb 6, 2003Jun 14, 2005Rolls-Royce PlcEngine casing with slots and abradable lining
US6916529Jan 9, 2003Jul 12, 2005General Electric CompanyAlloy of chromium, aluminum, and yttrium, with either cobalt, nickel or iron; monolithic intermetallic beta NiAl; increases the brittle nature of the metal matrix
US7025356Dec 20, 2004Apr 11, 2006Pratt & Whitney Canada Corp.Air-oil seal
US20100028128 *Oct 29, 2007Feb 4, 2010Marcus FischerComponent with diagonally extending recesses in the surface and process for operating a turbine
US20110241295 *Mar 30, 2010Oct 6, 2011United Technologies CorporationMethod of forming a seal element
CN101275583BMar 28, 2008May 29, 2013诺沃皮尼奥内有限公司Abradable and anti-encrustation coating for rotating fluid machines
DE2703572A1 *Jan 28, 1977Aug 4, 1977SnecmaAbreibbare statordichtung fuer turbotriebwerke
DE102009040299A1 *Sep 4, 2009Mar 10, 2011Mtu Aero Engines GmbhIntake surface for rotor of turbo machine, particularly gas turbine, has profiled upper surface, which has multiple elongated, axially running recesses at distance from one another
EP1081335A2 *Aug 9, 2000Mar 7, 2001United Technologies CorporationStator assembly for a rotary machine and method for making the stator assembly
EP1113146A2 *Dec 22, 2000Jul 4, 2001General Electric CompanyRotatory machine having a seal assembly
EP1510657A1 *Aug 12, 2004Mar 2, 2005Snecma MoteursDevice adradable for the fan casing of a gas turbine
EP1832755A2 *Feb 21, 2007Sep 12, 2007Rolls-Royce plcCompressor casing
Classifications
U.S. Classification415/173.4, 277/415
International ClassificationF01D11/08, F01D11/12, F04D29/66
Cooperative ClassificationF04D29/665, F01D11/125
European ClassificationF04D29/66C4C, F01D11/12B2