Document
l l l l l l 1 1 1 1 1 l l 1 1 1 1 1 1 1 1 1 I l l 1 1I l l 1 1 1 1 1 1 1 I l l 1 1 I l l 1 1 I l l 1 1 I l l 1 1 1 1 1 1 1 1 1 1 1 I l l 1 1 1 1 1 1 US005 116158A
ti11 Patent Number: 5,116,158
United States Patent [191
[45] Date of Patent: May 26, 1992
Carruthers et al.
5,011,353 4/1991 Boyd ................................... 411/383 HIGH TEMPERATURE TURBINE ENGINE STRUCTURE FOREIGN PATENT DOCUMENTS Inventors: William D. Carruthers, Mesa; Gary L.
863432 1/1953 Fed. Rep. of Germany .
Boyd, Tempe, both of Ariz.
3302323 1/1984 Fed. Rep. of Germany .
W09006422 6/1990 PCT Int’l Appl. .
Assignee: Allied-Signal Inc., Morris Township, 962057 6/1964 United Kingdom .
Morris County, N.J.
1238405 7/1971 United Kingdom .
Appl. NO.: 439,991 OTHER PUBLICATIONS Filed: Nov. 20, 1989 DOE/NASA/Ol67-82/4 “Advanced Gas Turbine (AGT) Powertrain System Development For Automo- Related U . S . Application Data tive Applications” p. 39, Jul. 1981.
DOE/NASA/Ol67-6 “Advanced Gas Turbine (AGT) Continuation-in-partof Ser. No. 280,760, Dec. 6, 1988, Technology Development” p. 46, Jun. 1983.
Pat. No. 5,011,353.
DOE/NASA/0167-8 “Advanced Gas Turbine (AGT)
Int. ( 3 . 5 .............................................. F16B 35/00
Technology Development” p. 30, Jun. 1984.
US. Cl. ...................................... 403/28; 403/404, DOE/NASA/0167-10 “Advanced Gas Turbine 403/408.1; 411/383; 411/900 (AGT) Technology Development Project” pp. 15, 16, Field of Search .................................... 403/28-30, 25, 38, 100, Jul. 1986.
403/404, 408.1, 179, 286, 168, 167, 388; DOE/NASA/0167-9 “Advanced Gas Turbine (AGT) 411/383, 384, 338, 339, 546, 537, 900-902 Technology Development” pp. 29, 60, 62, Dec. 1984.
DOE/NASA/0167-12 “Advanced Gas Turbine References Cited (AGT) Technology Development Project” pp. 207, U.S. PATENT DOCUMENTS 252, 253, Mar. 1988.
B 563,412 2/1976 Booher .
Ceramic Design Methodology and the AGTlOl Tech.
808,627 ]/I906 Booth .
Paper Mar. 1985 by Gary L. Boyd et al.
845,121 2/1907 Reniff .
Automotive Gas Turbine Ceramic Component Testing 1,370,474 3/1921 Newsom .
L. Boyd.
Tech. Paper by Gary 1,407.548 2/1922 Knouff .
1,750,770 3/1930 Austin .
Primaly Examiner-Peter M. Cuomo 2,429.936 10/1947 Kenney .
L. Miller; Jerry J.
Attorney, Agent, or Firm-Terry 2,538,396 1/1951 Sutin .
Holden; Robert A. Walsh 2,590,175 3/1952 Hajdu .
3,031,049 4/1962 Somville . 1571 ABSTRACT 3,112,547 12/1963 Poe .
A high temperature ceramic/metallic turbine engine 3,208,035 9/1965 Horvath et al. .
includes a metallic housing which journals a rotor mem- 3,316,861 VI967 Dailey .
King, Jr. .......................... 403/408.1 ber of the turbine engine. A ceramic disk-like shroud 3,835,615 9/1974 portion of the engine is supported on the metallic hous- 3,857,649 12/1974 Schaller .
4,122,605 10/1978 Hirabayashi et al. .
ing portion and maintains a close running clearance 4,312,599 1/1982 Darolia ................................. 403/29 with the rotor member. A ceramic spacer assembly 4.391,434 7/1983 LaBate .
maintains the close running clearance of the shroud 4,540,304 9/1985 Pavelka et al. ................... 403/28 X portion and rotor member despite differential thermal 4,834,569 SA989 Foote et al. .................... 403/404 X movements between the shroud portion and metallic 4,861,211 8/1989 Dunsmore ...................... 411/901 X housing portion.
4,925,364 SA990 Das ................................. 41 1/383 X Kapala et al. ................... 41 1/339 X 4,943,013 7/1990 Rufin et a]. .................. 403/408.1 X 9 Claims, 4 Drawing Sheets 4,975,014 12/1990
U.S. Patent May 26, 1992 Sheet 1 of 4 5,116,158
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US. Patent May 26, 1992 Sheet 2 of 4 5,116,158
U.S. Patent May 26, 1992 Sheet 3 of 4 5,116,158
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Sheet 4 of 4 5,116,158
U.S. Patent May 26, 1992
FIG.
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it is a primary object for this invention to provide a hybrid ceramic/metallic structure for use in a high HIGH TEMPERATURE TURBINE ENGINE STRUCTURE temperature turbine engine.
Particularly, it is an object of this invention to pro- The United States Government has rights in the pres- 5 vide a hybrid ceramic/metallic structure wherein a ent invention pursuant to Contract No. DEN3-167, ceramic portion may be disposed in a high temperature issued and fmded by the Department of Energy part of a turbine engine to retain and support another (DOE), and administered by the National Aeronautics ceramic component, and to extend therefrom toward a and Space Administration (NASA).
lower temperature engine part. The metallic portion of This application is a continuation-in-part O f applica- 10 the structure cooperatively interengages with the ce- tion Ser. NO. 280,760, filed Dec. 6 , 1988, now U.S. Pat. ramic portion and includes provision for engaging other No. 5,011,353 and is related to application Ser. Nos.
engine structure, which may be metallic, in order to 28097613 Dee. 19889 now US. Pat- No. allow relative movement between engine structures in 4,934,138 and to application Ser. No. 282,786, filed Dec. response to differential thermal expansion.
1988* now Ues. Pat. No* 590317400 all assigned to 15 More particularly, it is an object for this invention to Allied-Signal Inc.
provide a hybrid ceramic/metallic structure wherein a The present invention is in the field of high tempera- disk-like metallic portion is spaced axially from a mutu- ture turbine engine structure. Particularly, the present ally concentric ceramic portion, the two par- invention is directed to structure of a high temperature tions experiencing differential thermal movement dur- turbine engine composed of both metallic and ceramic 20 ing operation of an engine including the structure, and components.
concentricity of the two portions being maintained A long-recognized need in the turbine engine art has despite such movement.
been to attain higher operating temperatures in order to Still more particularly, this invention has as an object achieve both a greater thermodynamic efficiency and the provision of a ceramic spacer Structurewhich will an increased power output per unit of engine weight. 25 endure both high temperatures and physical loads while Ideally, a turbine engine should operate with stoichio- allowing differential thermal movement between a ce- metric combustion in order to extract the greatest possi- engine component and a engine ble energy value from the fuel consumed. However, the temperatures resulting from stoichiometric and even nent and maintaining a selected geometric relationship near-stoichiometric combustion are beyond the endur- 30 Of these components* Further to the above, the present jnvention provides ante capabilities of metallic turbine engine components.
Consequently, as the turbine engine art has progressed, a hybrid ceramic/metallic structure comprising a radi- an ever greater emphasis has been placed upon both ally extending disk-like metallic first wall member hav- ing a respective Rference centerline extending perpen- enhanced cooling techniques and the development of temperature and oxidation resistant metals for use in 35 dicularly thereof, said first wall member experiencing components of the engine which are exposed to the respective change of radial dimension in response to highest temperatures. That is, cooling techniques and change of temperature thereof: a radially extending high temperature metals have been developed for each disk-like ceramic second wall member having a respec- of combustion chambers, turbine stator nozzles, and tive reference centerline extending perpendicularly turbine blades. This quest has led to the development of 40 thereof coaxially with said first reference centerline, elaborate cooling schemes for all of these components said second wall member experiencing respective as well as to classes of nickel-based **super alloy*’ metals change Of radial dimension in response to respective which may be cast using directionally solidified or sin- change Of temperature thereoe Spacing XmanS for inter- gle crystal techniques. All in all, the quest for higher Posing axially between and engaging said Wall embers operating temperatures in a turbine engine fabricated of 45 to space the latter axially apart in mutually Parallel metallic components has led to a still increasing corn- relationship and maintaining coaxial alignment O f said plexity and expense in the making of the engine. respective reference centerlines despite said tempera- An alternative approach to the attainment of higher ture-related changes of radial dimension; and securing operating temperatures in a turbine engine has been means for clamping said first and said second wall mem- recognized. This approach involves the use of high- 50 bers in engagement with said spacing means.
strength ceramic components in the engine. Ceramic An advantage of the present invention resides in the components are better able than metals to withstand the provision of ceramic/metallic structural portions in a high temperature oxidizing environment of a turbine turbine engine, which portions may intersecure via the engine. However, the term “high strength” in connec- inventive spacer structure, while controlling differential tion with ceramic structures must be viewed in context. 5 5 thermal movements of the portions.
While many ceramic materials exhibit superior high Another advantage of the present invention results temperature strength and oxidation resistance, ceramics from the use of a ceramic component in a region of the have historically been difficult to employ in turbine engine exposed to high temperatures and a metallic engines because of a comparatively low tensile fracture component in a lower temperature region of the engine.
strength and a low defect tolerance. Consequently, a 60 The ceramic and metallic components may be con- long-recognized need has been for the development of trolled in their relative movements resulting from ther- hybrid ceramic/metallic structures which utilize the mal differences to preserve a selected alignment of the characteristics of each material to best advantage in components.
order to allow combustion in a turbine engine to take Additional objects and advantages of the present place closer to or at the stoichiometric level. 65 invention will appear from a reading of the following In view of the deficiencies of the conventional tur- detailed description of a single preferred embodiment of bine engine art, and of the materials of construction and the invention taken in conjunction with the appended structural techniques available for making such engines, drawing figures.
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FIG. 1 provides a longitudinal view, partly in cross what less than 180" of the ceramic regenerator member section of a hybrid ceramic/metallic turbine engine 28 is exposed to the exhaust chamber 58. Consequently, embodying the invention; the flow path 18 leads once again through the regenera- FIG. 2 depicts an enlarged fragmentary cross sec- tor member 28, and to ambient via the outlet 16.
tional view of an encircled portion of the engine pres- 5 In order to complete this description of the engine 10, ented by FIG. 1; it must be noted that in the combustor 30 fuel is added FIG. 3 provides a perspective schematic view of a to the pressurized air flowing from compressor rotor 22 hybrid ceramic/metallic structure embodying the pres- to support combustion. This combustion results in a ent invention:; flow of high temperature pressurized combustion prod- FIG. 4 depicts an exploded assembly view of a hybrid 10 ucts flowing downstream in the combustor 30, and in ceramic/metallic fastener and spacer assembly embody- flow path 18 subsequent to the combustor. Also, the ing the invention in perspective view; and rotor member 20 is journaled in housing 12 by a journal FIG. 5 Presents a fragmentary Cross sectional view bearing 60 disposed between the rotor portions 22 and similar to FIG. 2, but viewing radially inwardly, and 44, and by a rolling element bearing 62 disposed adja- depicting an alternative embodiment of the invention. 15 cent a metallic power output shaft portion 62 of the FIG* 1 depicts a hybrid ceramic and metallic turbine 20. The disk-like metallic wall portion 54 rotor member engine 10. The engine 10 includes a housing 12 which the outer wall car,+es the journal bearing 60, defines an inlet 14, an outlet 16, and a tortuous flow path portion 56 carries the roller bearing 62.
18 communicating the inlet 14 with the outlet 16 for in con,unction, it will be viewing FIGS. 2 through conveying a flow Of fluid therebetween. A hybrid cera- 2o Seen that the fastener and spacer assembly 52 includes a mic/metallic rotor member generally referenced with bolt member 66 extending through aligned apertures 68, the 2o is journaled in the housing l2 and 70, respective1y defined by the turbine shroud member erates therewith to bound the flow path 18. It will be &, and by disk-]ike metallic wall portion 54. The bolt seen that the rotor member 20 includes a compressor member 66 includes a head portion 72 which bears upon rotor portion 22, rotation of which inducts ambient air 25 the turbine shroud member through an intermediate via inlet 14, as indicated by arrow 24, and delivers this ceramic washer 74. Similarly a nut portion 76 of the bolt air pressurized to a flow path section 18' as indicated by member 66 bears upon the wall portion 54 through an arrow 26.
intermediate metallic washer 78. Clamped between the The flow path section 18t leads axially through (view- of 3o ceramic disk-like turbine shroud member 46 and the ing 2 6 ' ) a segment of somewhat less than disk-like metallic wall portion 54 of housing 12, is a a rotary annular regenerator member 28 which is re- 'pacer member 80. The ceramic %'acer ceived in the housing 12. Downstream of the regenera- 66, and bears at its opposite 8o circumscribes the tor 28, the flow path 18 leads through an axially extend- ing combustion structure generally referenced with the ends On the turbine shroud and Won a numeral 30 (viewing arrows 2 6 ' ) . The combustor struc- 35 ceramic jntermediate washer 82.
In order to provide the reader with an overall under- ture 30 is fabricated of ceramic and includes a standing of the turbine engine structure, FIG. 3 shows ceramic outer liner 32 which is supported at one end by schematically that the disk-like ceramic turbine shroud a generally cone-shaped outer transition member 34. A member 46 and metallic disk-like wall portion 54 are ceramic inner combustion liner 36 is coaxially disposed spaced axially apart and intersecured by three of the within the outer liner 32, and is supported at one end on fastener and spacer assemblies 52. The wall portion 54 a ceramic transition duct member 38. The flow path 18 defines a respective groove 84, viewing FIGS. 2 and 4, leads axially toward the one end of the combustion liner which is aligned radially with a centerline 86 of the wall 36, as indicated by arrow 26". Within the transition duct portion 54. The centerline 86 is coincident with the member 38, a ceramic turbine back shroud member 40 45 rotational axis of the rotor 20, as determined by the and a ceramic turbine stator member 42 cooperatively bearings 60 and 62, recalling that these bearings are define the local flow path 18, and lead the latter radially carried by walls 54 and 56. Received into the groove 84 inwardly to a ceramic turbine rotor portion 44 of the are washer 82, and an end portion 88 of the spacer 80, rotor member 20. All of the transition member 34, tran- viewing particularly FIG. 4. The end portion 88 defines sition duct member 38, turbine back shroud 40, and 50 a pair of diametrically opposed flats 90, 92, only one of turbine stator 42, are supported on a disk-like ceramic which is fully visible viewing FIG. 4. The flats 90, 92 turbine shroud member 46. Downstream of the turbine are closely and movably received in the groove 84 so rotor portion 44, the flow path 18 extends axially and that the spacer 80 i s nonrotational relative to the wall radially outwardly between a pair of spaced apart coop- 54. Consequently, the grooves 84 intersecting at center- erative ceramic exhaust duct members, respectively 55 line 86 establish a radial action line 94 for the spacers 80, referenced with the numerals 48 and 50. A plurality of viewing FIG. 3 . That is, each of the spacers 80 are able hybrid ceramic/metallic fastener and spacer members to rock in the grooves 84 in a respective axially extend- generally referenced with the numeral 52 (one of which ing radial plane containing the lines 94. These action is visible in FIG. 1 ) cooperatively engage the turbine line planes intersect at the centerline 86.
shroud 46 and. the housing 12. The exhaust duct mem- bers 48, 50 are cooperatively supported by the turbine Viewing FIGS. 2 and 4, it will be seen that the spac- 60 shroud 46 and fasteners 52. A disk-like metallic wall ers 80 each define opposed end surfaces 96, 98 which portion 54 of housing 12 supports the fasteners 52. Wall are cylindrically crowned about the center of the spacer portion 54, in cooperation with a metallic outer wall 80. That is, the crown surfaces 96,98 present to turbine portion 56 of housing 12, defines the flow path 18' shroud 46 and wall 54 portions of a right circular cylin- downstream of compressor rotor portion 22. 65 drical surface having a diameter equal to the length of Subsequent to the exhaust duct members 48, 50 the spacer 80. The disposition of the crown surfaces 96,98 flow path 18 leads to an exhaust chamber generally is such that the cylindrical centerline of these surfaces is referenced with the numeral 58. A segment of some- perpendicular to the action lines 94.
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Viewing the schematic depiction of FIG. 3 once is expected to be less than the angulation change of again, it is shown that each spacer 80 may be visualized spacer 80. However, the angulation changes of both 66 as a cylindrical roller or rocker 100, depicted in phan- and spacer 80 are in the same direction so that a rela- tom lines, which is disposed between the wall 54 and tively small clearance 108 is sufficient to prevent inter- turbine shroud 46. The line along which each roller will ference between the bolt and spacer.
roll in response to local relative radial movement is the Received closely about the spacer 80 is an annular action line 94. These action lines 94 intersect at the ring-like secondary ceramic spacer member 110. The centerline 86 of both the turbine shroud 46 and wall 54. secondary spacer member 110 spaces apart the exhaust During operation of the turbine engine 10, the ceramic duct members 48 and 50. Cooperatively, the three sec- turbine shroud 46 and metallic wall 54 experience 10 ondary spacer members 110 carried upon the three changes in temperature, and resulting radial growth or fastener and spacer assemblies 52 substantially maintain contraction. These temperature responsive growths and concentricity of the exhaust duct members 48, 50 with contractions may be in phase with one another, possibly both the turbine shroud 46 and wall portion 54. That is, at different rates, or they may be out of phase with one the secondary spacer member 110 includes an axially another. In other words, the members 46, 54 may be 15 extending boss portion 112 which cooperates with the .
expanding or contracting together at different rates, or remainder of the secondary spacer to define a shoulder one may be expanding while the other is contracting. 114. The duct member 48 is circumferentially continu- Consequently, the members 46, 54 experience local ous at its outer perimeter and includes three peripheral 116, only a portion of one portion 116 being relative radial movement during operation of the tur- portions bine engine 10. These local relative radial movements 20 visible in FIG. 2, each radially confronting a boss 112.
are represented by arrows 102. Despite these local ra- The duct member 48 is captured between the turbine dial movements, the centerline 86 of turbine shroud 46 shroud 46 and shoulder 114, and is located concentri- must remain substantially coincident with the centerline cally by the radial cooperation of the three bosses 114 at of wall 54. This coincidence of centerlines must be the three peripheral portions 116 similarly to the turbine preserved because the running clearance between the 25 shroud 46. In a like manner, the exhaust duct member 50 turbine shroud 46 and turbine rotor 44 is very small, and is circumferentially continuous at its outer perimeter the bearings for rotor 20 are carried by the metallic and includes three peripheral portions 118, only a por- walls 54 and 56. Thus, concentricity of these structural tion of one portion 118 being visible in FIG. 2. The elements must be preserved despite the local radial portions 118 respectively confront one of the spacers 80 movements 102. This necessary concentricity is pre- 30 thereby to preserve concentricity of the duct member served by allowing free radial relative movement of the 50. A resilient member 120 urges the duct member 50 members 46,54 at the location of spacers SO along action into engagement with secondary spacer 110 to bias the lines 94 coincidenfwith rolling of the rollers 100 (rock- latter and duct 48 toward turbine shroud 46. Because ing of spacers 80), while preventing relative circumfer- movement of spacers 80 is limited to rocking substan- entia1 movements at these spacers. Viewing FIG. 3, it is 35 tially in an axially extending radial plane in response to easily appreciated that local circumferential relative local relative radial movements between shroud 46 and movements between members 46 and 54 are prevented wall 54, the concentricity of the ducts 48 and 50 is pre- so long as there is no slippage between these members served by the cooperation of the three fastener and and the cylinders 100 (spacers 80). While the spacers 80 spacer assemblies 52 with the peripheral portions 116, are in fact not a full cylinder, like phantom cylinders 40 118.
100, these spaces present cylindrical surfaces at 96,98 to FIG. 5 depicts an alternative embodiment of the in- the members 46, 54, respectively, and function as cylin- vention. In order to obtain reference numerals for use in drical rollers for limited radial relative movements. describing this alternative embodiment of the invention, Viewing once again FIG. 2, it is seen that the bolt features which are analogous in structure or function to member 66 engages members 46 and 54 through the 45 those described above are referenced with the same intermediate washers 74 and 78. Each of these washers numeral used above, and with a prime added thereto.
defines a respective cylindrical crown surface 104, 106, FIG. 5 shows a cross sectional view similar to FIG. 2, having its center at the center of the spacer 80. In other but with the direction of view being radially inwardly.
words, all of the cylindrical surfaces 96, 98, 104, 106, The metal wall 54' of the turbine engine 10' supports a ideally have the same centerline at the center of spacer 50 ceramic turbine shroud 46' through a fastener and 80. Because of the compressive clamping force applied spacer assembly 52'. The bolt 66' and nut portion 7 6 of by the bolt members 66, the ceramic crown surfaces 96, assembly 52' are the same as that described above. Simi- 98 frictionally engage the ceramic turbine shroud 46 larly, the crown washers 74', 78', spacer 80', and washer and ceramic washer 82 for rocking motion substantially 8 2 received in groove 84' are the same as that described without slippage. The spacer member 80 defines a radial 55 above. However, the embodiment of FIG. 5 includes an clearance 108 with the bolt 66 so that binding or inter- advantageous cooperation between the secondary spac- ference does not result from the relative angulation of ers 110 on spacers 80' and the turbine shroud 46' both to the spacer and bolt as the former rocks between the assure retention of concentricity for the turbine shroud, shroud 46 and wall portion 54. On the other hand, the and to allow for manufacturing tolerances in compo- crown surfaces 104, 106 allow the bolt 66 to assume 60 nents of the engine 10.
angulated positions deviating slightly from a perpendic- As depicted in FIG. 5, the ceramic turbine shroud 46' ular between the shroud 46'and wall 54 as these local defines a radially extending groove 122, which parallels features move radially relative to one another. This the groove 84' in wall 54'. The ceramic secondary change in angulation of bolt 66 results in a rocking spacer member 110' includes an axially elongate boss motion at the head 72 on crown surface 96, and at nut 76 65 portion 112' cooperating with the remainder of the on crown surface 98, without slippage therebetween. spacer 110' to define a shoulder 114 upon which sets Because the surfaces 104, 106 are further apart than the duct wall 48'. The boss portion 112' also extends 96, 98, the change in angulation of the bolt 66 into the groove 122 so that outer diametral surfaces 124 surfaces 5,116,158
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of the boss portion 112' movingly engage the turbine second wall members respectively, said end sur- shroud with only a slight clearance. Finally, the boss faces having a cylindrical curvature extending portion 112' is intentionally made eccentric with respect transversely relative to said first and second wall to the bore of spacer llO', whereat the spacer 80' is members; and closely received. That is, the outer diametral surface 5 a plurality of securing means for clamping said first 124 is slightly eccentric with respect to the bore of and said second wall members into contact with spacer llO', and the spacer 80'.
each of said first and second cylindrically curved During assembly of the turbine engine lo', a fixture is end surfaces, whereby said first and second wall employed in place of the rotor 20 to set concentricity of members remain parallel and coaxial while experi- turbine shroud 46' with the bearings 60, 62. As a result 10 encing said respective changes in radial dimension.
O f manUfaCtUriIlg tOkranCeS, the radial grooves 122 in 2 . The invention of claim 1 wherein said individual &roud 46' may not have Perfect cir~mferential align- spacers are tubular and define a central through bore ment with the radial grooves 84 O f the metallic wall 54'.
extending &tween said first and second end surfaces, Minor circumferential misalignments are accommo- one of =id securing passing through said dated by relative rotation of the spacer 110 on spacer 80 15 through bore of each of =id spacers.
until the boss portion 112' is received into its respective 3. The invention of claim 2 wherein said securing groove 122' of shroud 46'. Of course, minor radial mis- an elongate tensile member passing includes are accommodated by the free radia1 rock- through said central bore of each of said spacers and 66' is ing movement Of the 'pacer 80. Once the engaging at opposite ends with respective one of said tightened by operation of nut portion 7 6 ' , the primary 20 wall members, mechanism for retention of alignment and concentricity 4. The invention of claim wherein said securing is rocking contact without slippage, as described above.
includes said wall members each defining a re- However, in the event of a severe transverse accelera- spective aperture generally aligning axially with a cor- tion or G-force such as would shift the shroud 46' rela- responding aperture of the other of said wall members, tive to wall 54, the surfaces 124 cooperate with shroud 25 said elongate tensile member passing through said 46' at grooves 122 to add further retention strength.
apertures and engaging said members to The applicants have built and tested both embodi- urge the latter toward One another* ments of the invention herein described. In both cases 5. The invention of claim 4 wherein each of said acceptable concentricity was maintained between the ceramic turbine shroud and metallic housing during 3o securing means includes a cylindrically crowned mem- thermal cycling. Addjtionally, the embodiment of ber disposed between each of said wall members and the respective opposite end of said elongate tensile XneInber.
FIGS. 1-4 was subjected to lateral acceleration forces on a shaker table up to a level of 8 ~ 9 ~ with satisfactory 6. The invention of claim 1 wherein said first wall member defines a plurality Of extending retention of concentricity. In fact, the test article had no measurable loss of concentricity after the shaker table 35 grooves having Opposed parallel extending episode. It should be apparent to those ordinarily skilled walls and each receiving one of said first end portions, in the pertinent art that the cylinder axes of the rollers said first end portions having a pair of diametrically 100 each define one side of an equilateral triangle. Three opposed flats which movably and nonrotatably engag- rollers is the minimum number necessary to maintain ing said opposed walls of said grooves.
concentricity of the walls 56 and 54. However, a greater 40 7. The invention of claim 6 wherein said spacers are number of cylinder rollers 100 (spacers 80) can be used. disposed circumferentially apart substantially 120" from In this case, each cylinder axis will define one side of a one another and are three in number.
regular plane polygon having a number of sides equal to 8. The invention of claim 1 further iiicluding a sec- ondary annular spacer member rotatably carried upon the number of roller members.
45 each of said spacers, said second wall member defining What is claimed is: a radially extending groove at each of said spacers, said 1. A hybrid ceramic/metallic structure comprising: secondary spacer members each defining an axially a radially extending disk-like metallic first wall mem- extending annular boss which is eccentric with respect ber experiencing respective change of radial di- to the spacer carrying said secondary spacer, and said mension in response to change of temperature thereof; 50 annular eccentric boss being closely received into said radially extending disk-like ceramic second wall groove to engage the walls thereof, whereby engage- member spaced apart in parallel relation and coax- ment of said eccentric annular boss with said second ial with said first wall member, said second wall wall member at said groove thereof further maintains member experiencing respective change of radial coaxial alignment of said second wall member and said dimension in response to respective change of tem- 55 first wall member.
perature thereof; 9. The invention of claim 1 wherein said cylindrical plurality of spacers disposed between said wall curvature is defined by the surface of a cylinder having members and circumferentially spaced apart, each an axis perpendicular to the direction of said respective of said spacers having a first and second end por- changes in radial dimension.
* * * * *
tion having an end surface adjacent said first and 60