Document
1 1 1 1 1 11 1 1 1 1 1 1 1 111 1 1 1 1 1 I l l 1 1 1 1 1 1 1 I l l 1 1 1 1 1 1 1 1 1 1 1 1 IIIII 1 1 1 l l 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 US00527903 1A
Patent Number: 5,279,031
United States Patent 1193 1111
Carruthers et al. [45] Date of Patent: Jan. 18, 1994
4,975,014 12/1990 Rutin et al. .
HIGH TEMPERATURE TURBINE ENGINE 5,011,353 4/1991 Boyd .
STRUCTURE Inventors: William D. Carruthers, Mesa; Gary L.
FOREIGN PATENT DOCUMENTS Boyd, Tempe, both of Ariz.
863432 VI953 Fed. Rep. of Germany .
Assignee: AlliedSignal Inc., Morris Township, VI984 Fed. Rep. of Germany .
3302323 Morris County, N.J. 6/1990 PCT Int’l Appl. .
WOA9006422 962057 6/1964 United Kingdom .
Appl. No.: 843,814 .
1238405 7/1971 United Kingdom .
Filed: Feb. 27,1992 OTHER PUBLICATIONS . Related U . S . Application Data Ceramic Design Methodology and the AgtlOl Tech.
Division of Ser. No. 439,991, Nov. 20, 1989, Pat. No. Paper Mar. 1985 by Gary L. Boyd et al.
5,116,158, which is a continuation-in-part of Ser. No. Automotive Gas Turbine Ceramic Component Testing 280,760, Dec. 6, 1988, Pat. No. 5,011,353, which is a Tech. Paper by Gary L. Boyd.
continuation-in-part of Ser. No. 280,761. Dec. 6, 1988, DOE/NASA/0167-82/4 “Advanced GAS Turbine Pat. No. 4,934,138, which is a continuation-in-part of (AGT) Powertrain System Development For Automo- Ser. No. 282,786, Dec. 9, 1988, Pat. No. 5.031,400.
tive Applications” p. 39.
Int. CI.5 .............................................. B23P 15/00
DOE/NASA/OI 67-6 “Advanced Gas Turbine (AGT) US. C1. ................................... 29/889.2; 29/525.1 Technology Development” p. 46.
DOE/NASA/0167-8 “Advanced Gas Turbine (AGT) Field of Search ...................... 29/889.2, 434, 436, Technology Development” p. 30.
29/525.1; 403/404, 408.1; 41 1/383, 900; DOE/NASA/OI 67-10 “Advanced Gas Turbine 416/214.1, 241; 60/39.75 (AGT) Technology Development Project” pp. 15, 16, References Cited 25, 38, 100.
U.S. PATENT DOCUMENTS DOE/NASA/0167-9 “Advanced Gas Turbine (AGT) Technology Development” pp. 29, 60, 62.
Booher .
B563,412 2/1976 DOE/NASA/0167-12 “Advanced Gas Turbine 808,627 VI906 Booth .
(AGT) Technology Development Project” pp. 207, 845,121 2/1907 Reniff .
252, 253.
1,370,474 3/1921 Newsom .
1.407.548 2/1922 Knouff .
Primary Examiner-Irene Cuda 1,750,770 3/1930 Austin .
Attorney, Agent, or Firm-Terry L. Miller; Jerry J.
2,429.936 10/1947 Kenney .
Holden; James W. McFarland 2.538,396 1/1951 Sutin .
2590,175 3/1952 Hajdu .
1571 ABSTRACT 3,031,049 4/1962 Somville .
A high temperature ceramic/metallic turbine engine 3,112.547 12/1963 Poe .
3,208,035 9/1965 Horvath et al. . includes a metallic housing which journals a rotor mem-
3,316,861 VI967 Dailey . ber of the turbine engine. A ceramic disk-like shroud 3,835,615 9/1974 King, Jr. .
portion of the engine is supported on the metallic hous- 3,857,649 12/1974 Schaller .
ing portion and maintains a close running clearance 4,122,605 10/1978 Hirabayashi et al.
with the rotor member. A ceramic spacer assembly 4,312,599 1/1982 Davolia .
maintains the close running clearance of the shroud 4,391,434 7/1983 LaBate .
portion and rotor member despite differential thermal 4,540,304 9/1985 Pavelka et al. .
movements between the shroud portion and metallic 4,834,569 5/1989 Foote et al. .
housing portion.
4,861,211 8/1989 Dunsmore .
4,925,364 5/1990 Das .
3 Claims, 4 Drawing Sheets 4,943,013 7/1990 Kapala et al. .
U.S. Patent Jan. 18, 1994 Sheet 1 of 4 5,279,031
Jan. 18, 1994 U S Patent
Sheet 2 of 4 5,279,031
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U.S. Patent Jan. 18, 1994 Sheet 3 of 4 5,279,031
U.S. Patent Jan. 18, 1994
Sheet 4 of 4 5,279,031
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structural techniques available for making such engines, HIGH TEMPERATURE TURBINE ENGINE it is a primary object for this invention to provide a hybrid ceramic/metallic structure for use in a high STRUCTURE temperature turbine engine.
Particularly, it is an object of this invention to pro- The United States Government has rights in the pres- 5 ent invention pursuant to Contract No. DEN3-167, vide a hybrid ceramic/metallic structure wherein a issued and funded by the Department of Energy ceramic portion may be disposed in a high temperature (DOE), and administered by the National Aeronautics part of a turbine engine to retain and support another and Space Administration (NASA). ceramic component, and to extend therefrom toward a This is a division of application Ser. No. 07/439,991 lower temperature engine part. The metallic portion of filed Nov. 20, 1989, now US. Pat. No. 5,116,158, is a the structure cooperatively interengages with the ce- continuation-in-part of application Ser. No. 280,760, ramic portion and includes provision for engaging other filed Dec. 6, 1988, now U.S. Pat. No. 5,011,353 and is engine structure, which may be metallic, in order to related to application Ser. Nos. 280,761, also filed Dec. allow relative movement between engine structures in 6, 1988 now U.S. Pat. No. 4,934,138, and to application 5 response to differential thermal expansion.
Ser. No. 282,786, filed Dec. 9, 1988, now U.S. Pat. No. More particularly, it is an object for this invention to 5,03 1,400 all assigned to Allied-Signal Inc. provide a hybrid ceramic/metallic structure wherein a disk-like metallic portion is spaced axially from a mutu- The present invention is in the field of high tempera- ally concentric disk-like ceramic portion, the two por- ture turbine engine structure. Particularly, the present invention is directed to structure of a high temperature 20 tions experiencing differential thermal movement dur- turbine engine composed of both metallic and ceramic 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 thermal 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 2 5 the provision of a ceramic spacer structure which will an increased power output per unit of engine weight. 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- ramic engine component and a metallic engine compo- ble energy value from the fuel consumed. However, the nent and maintaining a selected geometric relationship temperatures resulting from stoichiometric and even 30 of these components.
near-stoichiometric combustion are beyond the endur- Further to the above, the present invention provides ance capabilities of metallic turbine engine components. a hybrid ceramic/metallic structure comprising a radi- Consequently, as the turbine engine art has progressed, ally extending disk-like metallic first wall member hav- an ever greater emphasis has been placed upon both ing a respective reference centerline extending perpen- enhanced cooling techniques and the development of 35 dicularly thereof, said first wall member experiencing temperature and oxidation resistant metals for use in respective change of radial dimension in response to components of the engine which are exposed to the change of temperature thereof; a radially extending highest temperatures. That is, cooling techniques and disk-like ceramic second wall member having a respec- high temperature metals have been developed for each tive reference centerline extending perpendicularly of combustion chambers, turbine stator nozzles, and 40 thereof coaxially with said first reference centerline, turbine blades. This quest has led to the development of said second wall member experiencing respective elaborate cooling schemes for all of these components change of radial dimension in response to respective as well as to classes of nickel-based "super alloy" metals change of temperature thereof; spacing means for inter- which may be cast using directionally solidified or sin- posing axially between and engaging said wall members gle crystal techniques. All in all, the quest for higher 45 to space the latter axially apart In mutually parallel operating temperatures in a turbine engine fabricated of relationship and maintaining coaxial alignment of said metallic components has led to a still increasing com- respective reference centerlines despite said tempera- plexity and expense in the making of the engine. ture-dated changes of radial dimension; and securing An alternative approach to the attainment of higher means for clamping said first and said second wall mem- operating temperatures in a turbine engine has been 50 bers in engagement with said spacing means.
recognized. This approach involves the use of high- An advantage of the present invention resides in the strength ceramic components in the engine. Ceramic provision of ceramic/metallic structural portions in a components are better able than metals to withstand the turbine engine, which portions may intersecure via the high temperature oxidizing environment of a turbine inventive spacer structure, while controlling differential engine. However, the term high strength in connection 5 5 thermal movements of the portions.
with ceramic structures must be viewed in context. Another advantage of the present invention results While many ceramic materials exhibit superior high from the use of a ceramic component in a region of the temperature strength and oxidation resistance, ceramics engine exposed to high temperatures and a metallic have historically been difficult to employ in turbine component in a lower temperature region of the engine.
engines because of a comparatively low tensile fracture 60 The ceramic and metallic components may be con- strength and a low defect tolerance. Consequently, a trolled in their relative movements resulting from ther- long-recognized need has been for the development of mal differences to preserve a selected alignment of the hybrid ceramic/metallic structures which utilize the components.
characteristics of each material to best advantage in Additional objects and advantages of the present order to allov~ combustion in a turbine engine to take 65 invention will appear from a reading of the following place closer to or at the stoichiometric level. detailed description of a single preferred embodiment of In view of the deficiencies of the conventional tur- the invention taken in conjunction with the appended bine engine art, and of the materials of construction and 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 a 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 ViewofahYbrid 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 4, and by a rolling element bearing 62 disposed adja.
of the invention.
depicting an alternative embodiment 62 of the 15 cent a metallic power output shaft FIG. 1 depicts a hydbrid ceramic and metallic turbine
member 20. ne disk-like metallic wall portion 54
engine 10. The engine 10 includes a housing 12 which wall carries the journal haring 60, while the defines an inlet 14, an outlet 16, and a tortuous flow path portion 56 carries the roller bearing 62.
18 communicating the inlet 1 4 with the outlet 16 for Viewing FIGS. through in conjunction, it will be 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, respectively defined by the turbine shroud member erates therewith to bound the flow path 18. It will be and by disk-like 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.
The flow path section 18' leads axially through (view- intermediate metallic washer 78. Clamped between the 2 6 ' ) a segment of somewhat less than 180" of 30 Ceramic disk-like turbine shroud member 46 and the ing a rotary annular regenerator member 28 which is re. disk-like metallic wall portion 54 of housing 12, is a
ceramic spacer member 80. The ceramic weer
ceived in the housing 12. Downstream of the regenera-
8o circumscribes the bolt 66, and bears at its opposite
tor 28, the flow path 18 leads through an axially extend- a ends On the ceramic turbine shroud 46* and ing combustion structure generally referenced with the numeral 30 (viewing arrows 2 6 ' ) . The combustor struc- 35 ceramic jntermediate washer 82.
ture 30 is fabricated of ceramic material and includes a In order to provide the reader with an overall under- ceramic outer liner 32 which is supported at one end by standing Of the turbine engine structure, FIG. 3 shows schematically that the disk-like ceramic turbine shroud a generally cone-shaped Outer transition member 34. A ceramic inner combustion liner 36 is coaxially disposed member 46 and metallic disk-like wall portion 54 are within the outer liner 32, and is supported at one end on 40 spaced axially apart and intersecured by three of the fastener and spacer assemblies 52. The wall portion 54 a ceramic transition duct member 38. The flow path 18 leads axially toward the one end of the combustion liner defines a respective groove 84, viewing FIGS. 2 and 4, 36, as indicated by arrow 26". Within the transition duct which is aligned radially with a centerline 86 ofthe wall member 38, a ceramic turbine back shroud member 40 Portion 54. The centerline 86 is coincident with the and a ceramic turbine stator member 42 cooperatively 45 rotational axis of the rotor 20, as determined by the define the local flow path 18, and lead the latter radially bearings 60 and 62, recalling that these bearings are inwardly to a ceramic turbine rotor portion 44 of the carried by walls 54 and 56. Received into the groove 84 rotor member 20. All of the transition member 34, tran- are washer 82, and an end portion 88 of the spacer 80, sition duct member 38, turbine back shroud 40, and viewing particularly FIG. 4. The end portion 88 defines turbine stator 42, are supported on a disk-like ceramic 5 0 a Pair of diametrically opposed flats 90,92, only one of turbine shroud member 46. Downstream of the turbine which is fully visible viewing FIG. 4 . The flats 90, 92 rotor portion 44, the flow path 18 extends axially and are closeb and movably received in the groove 84 so radially outwardly between a pair of spaced apart coop- that the spacer 80 is nonrotational relative to the wall erative ceramic exhaust duct members, respectively 54. Consequently, the grooves 84 intersecting at center- referenced with the numerals 48 and 50. A plurality of 55 line 86 establish a radial action line 94 for the spacers 80, hybrid ceramic/metallic fastener and spacer members viewing FIG. 3 . That is, each of the spacers 80 are able generally referenced with the numeral 52 (one of which to rock in the grooves 84 in a respective axially extend- is visible in FIG. 1) cooperatively engage the turbine ing radial plane containing the lines 94. These action shroud 46 and the housing 12. The exhaust duct mem- line planes intersect at the centerline 86.
bers 48, 50 are cooperatively supported by the turbine 60 Viewing FIGS. 2 and 4, it will be seen that the spac- shroud 4 6 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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is expected to be less than the angulation change of Viewing the schematic depiction of FIG. 3 once 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 phantom and spacer 80 are in the same direction so that a rela- lines, which is disposed between the wall 54 and turbine tively small clearance 108 is sufficient to prevent inter- shroud 46. The line along which each roller will roll in 5 ference between the bolt and spacer.
response to local relative radial movement is the action Received closely about the spacer 80 is an annular line 94. These action lines 94 intersect at the centerline ring-like secondary ceramic spacer member 110. The 86 of both the turbine shroud 4 6 and wall 54. During secondary spacer member 110 spaces apart the exhaust 10, the ceramic turbine 48 and 50. Cooperatively, the three sec- operation of the turbine engine duct members 10 ondary spacer members 110 carried upon the three shroud 4 6 and metallic wall 54 experience changes in temperature, and resulting radial growth or contrac- fastener and spacer assemblies 52 substantially maintain tion. These temperature responsive growths and con- concentricity of the exhaust duct members 48, 50 with tractions may be in phase with one another, possibly at both the turbine shroud 4 6 and wall portion 54. That is, 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 relative radial movement during operation of the tur- portions 116, only a portion of one portion 116 being 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 the three peripheral portions 116 similarly to the turbine of wall 54. This coincidence of centerlines must be 25 shroud 46. In a like manner, the exhaust duct member 50 preserved because the running clearance between the is circumferentially continuous at its outer perimeter turbine shroud 46 and turbine rotor 44 is very small, and and includes three peripheral portions 118, only a por- the bearings for rotor 20 are carried by the metallic tion of one portion 118 being visible in FIG. 2. The walls 54 and 56. Thus, concentricity of these structural portions 118 respectively confront one of the spacers 80 elements must be preserved despite the local radial 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 80 along action into engagement with secondary spacer 110 to bias the lines 94 coincident with rolling of the rollers 100 (rock- latter and duct 48 toward turbine shroud 46. Because movement of spacers 80 is limited to rocking substan- ing of spacers 80). while preventing relative circumfer- tially in an axially extending radial plane in response to ential movements at these spacers. Viewing FIG. 3, it is 35 local relative radial movements between shroud 46 and easily appreciated that local circumferential relative movements between members 46 and 54 are prevented wall 54, the concentricity of the ducts 48 and 50 is pre- served by the cooperation of the three fastener and so long as there is no slippage between these members 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- vention. In order to obtain reference numerals for use in the members 46, 54, respectively, and function as cylin- describing this alternative embodiment of the invention, drical rollers for limited radial relative movements.
features which are analogous in structure or function t o Viewing once again FIG. 2, it is seen that the bolt those described above are referenced with the same member 66 engages members 46 and 54 through the 45 numeral used above, and with a prime added thereto.
intermediate washers 74 and 78. Each of these washers FIG. 5 shows a cross sectional view similar to FIG. 2, defines a respective cylindrical crown surface 104, 106, but with the direction of view being radially inwardly.
having its center at the center of the spacer 80. In other 96, 98, 104, 106, The metal wall 5 4 of the turbine engine 10' supports a words, all of the cylindrical surfaces ceramic turbine shroud 46' through a fastener and ideally have the same centerline at the center of spacer 50 spacer assembly 52'. The bolt 6 6 and nut portion 7 6 of 80. Because of the compressive clamping force applied assembly 52' are the same as that described above. Simi- by the bolt members 66, the ceramic crown surfaces 96, larly, the crown washers 74', 78', spacer 80', and washer 98 frictionally engage the ceramic turbine shroud 46 82' received in groove 84' are the same as that described and ceramic washer 82 for rocking motion substantially above. However, the embodiment of FIG. 5 includes an without slippage. The spacer member 80 defines a radial 55 advantageous cooperation between the secondary spac- clearance 108 with the bolt 66 so that binding or inter- ers 110' on spacers 80' and the turbine shroud 46' both ference does not result from the relative angulation of to assure retention of concentricity for the turbine the spacer and bolt as the former rocks between the shroud, and to allow for manufacturing tolerances in shroud 46 and wall portion 54. On the other hand, the components of the engine 10'.
crown surfaces 104, 106 allow the bolt 66 to assume 60 As depicted in FIG. 5, the ceramic turbine shroud 46' angulated positions deviating slightly from a perpendic- defines a radially extending groove 122. which parallels ular between the shroud 46 and wall 54 as these local the groove 84' in wall 54'. The ceramic secondary features move radially relative to one another. This spacer member 110' includes an axially elongate boss change in angulation of bolt 66 results in a rocking portion 112' cooperating with the remainder of the motion at the head 72 on crown surface 96, and at nut 76 65 spacer 110' to define a shoulder 114' upon which sets on crown surface 98, without slippage therebetween.
the duct wall 48'. The boss portion 112' also extends 104, 106 are further apart than Because the surfaces into the groove 122 so that outer diametrical surfaces surfaces 96, 98, the change in angulation of the bolt 66 .. ..
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124 of the boss portion 112' movingly engage the tur- In this case, each cylinder axis will define one side of a bine shroud with only a slight clearance. Finally, the regular plane polygon having a number of sides equal to boss portion 112 is intentionally made eccentric with the number of roller members.
respect to the bore of spacer llO', whereat the spacer What is claimed is: 80' is closely received. That is, the outer diametrical 5 1. A method of maintaining coaxial alignment of a surface 124 is slightly eccentric with respect to the bore disk-like supporting metallic wall member and a mutu- of spacer llO', and the spacer 8 0 ' . ally parallel disk-like ceramic wall member spaced axi- .
During assembly of the turbine engine 1 0 ' . a fixture is ally therefrom despite thermal differential radial move- employed in place of the rotor 20 to set concentricity of ments occasioned by respective temperature changes turbine shroud 46' with the bearings 60, 62. As a result 10 thereof, said method including the steps of: of manufacturing toierances, the radial grooves 122 in employing at least right circular cylindrical roller shroud 46' may not have perfect circumferential align- members interposed axially between and rollingly ment with the radial grooves 84 of the metallic wall 54'. engaging with each of said wall members; Minor circumferential misalignments are accommo- disposing said roller members so that the cylinder axis dated by relative rotation of the spacer 110 on spacer 80 I5 of each defines one side of a respective regular until the boss portion 112' is received into its respective plane polygon having a number of sides equal to groove 122' of shroud 4 6 ' . Of course, minor radial mis- the number of roller members; alignments are accommodated by the free radial rock- establishing a free radial rolling slippage-free engage- of the spacer 8 0 . Once the bolt 66' is ment of said roller members with said wall mem- ing movement tightened by operation of nut portion 76', the primary 20 bers; mechanism for retention of alignment and concentricity employing said slippage-free engagement to posi- is rocking contact without slippage, as described above.
tively prevent local circumferential relative move- However, in the event of a severe transverse accelera- ment of said wall members and maintain said tion or G-force such as would shift the shroud 46' rela- coaxial alignment while accommodating said ther- tive to wall 54, the surfaces 124 cooperate with shroud 25 mal differential radial movements with said free 46' at grooves 122 to add further retention strength. rolling radial engagement.
The applicants have built and tested both embodi- 2. The method of claim 1 further including the step of ments of the invention herein described. In both cases axially penetrating each of said roller members with a acceptable concentricity was maintained between the through passage, and extending a respective bolt mem- ceramic turbine shroud and metallic housing during 30 ber intersecuring said wall members through each pas- of sage of said roller members.
thermal cycling. Additionally, the embodiment FIGS. 1-4 was subjected to lateral acceleration forces 3. The method of claim 2 further including the step of on a shaker table up to a level of 8G's with satisfactory providing one of a pair of cylindrically crowned mern- retention of concentricity. In fact, the test article had no bers at each one of said wall members, and rockingly measurable loss of concentricity after the shaker table 35 engaging said crowned members with abutment sur- episode. It should be apparent to those ordinarily skilled faces defined at respective opposite end-portions of said in the pertinent art that the cylinder axes of the rollers bolt member to transfer tensile forces from said bolt 100 each define one side of an equilateral triangle. Three mepber to said respective wall members to intersecure rollers is the minimum number necessary to maintain said wall members.
concentricity of the walls 56 and 54. However, a greater 40
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number of cylinder rollers 100 (spacers 80) can be used.