US2479056A - Cooling turbine rotors - Google Patents

Description

Aug-16,1949 W.K; BODGER v 2,479,056

COOLING TURBINE ROTORS Filed Aug. 23, '1944 I 2 Sheets-Sheet l FIG.

ov v a"; Q -n m lNVENTOR 1949- v w. K. BODGER 2,479,056

COOLING TURBINE ROTORS Filed Aug. 23, 1944 2 Sheets-Sheet 2 3 5 Q U D 4 co 5/ O XN D \x 3 2 7 a 4 Z N 6 Z s l. 2 w 9 0 9! g a 8 pg a INVENTOR LUMMW Patented Aug. 16, 1949 UNITED STATES COOLING TURBINE ROTORS Walter Kenneth Bodgcr, South Glastonbury, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application August 23, 1944, Serial No. 550,871

1 Claim. 1

This invention relates to cooling a rotor, particularly in a turbine adapted for operation by hot gases.

The oopending application of Ledwith, Serial No. 550,887, filed August 23, 1944, describes a rotor having an axial bore through which a tube extends for admitting fluid from one end of the rotor to cooling chambers adjacent the bearings at both ends. This arrangement permits the admission of fluid at the center of the rotor to avoid the action of centrifugal force on the fluid being pumped into the rotor. This tube also prevents excessive heating of the fluid as it passes through the power section of the rotor. A feature of the present invention is an alternative construction in which the coolant tube is omitted.

When the rotor is built up of disks carrying blades and end sections held together by a centrally extending through bolt the rotor has a substantial axial expansion when in operation which applies a high stress'to the bolt. Since the allowable bolt stress is reduced as the temperature of the bolt increases the bolt may become too hot to withstand the stresses resulting from the rotor expansion. A feature of this invention is an arrangement for internally cooling the bolt'for its entire length.

Another feature is the cooling of both the bolt and the ends of theturbine rotor by circulating coolant through the bolt from one end through chambers in the rotor adjacent the bearings.

The copending application of Soderberg and Kalitinsky, Serial No. 550,885, filed August '23, 1944, discloses an arrangement for cooling the disks of a built-up turbine rotor and for simultaneously cooling the connecting bolt. ',A feature of this invention is the combination of internal bolt cooling with external cooling of this char acter for maintaining the bolt at such a temperature that the allowable bolt stress will not be exceeded during turbine operation. v

Other objects and advantages will be apparent from the specification and claim and from the accompanying drawings which illustrate an embodiment of the invention. I

Fig. l is a sectional view through the turbine.

Fig. 2 is a fragmentary sectional view on a. larger scale through the central bolt and the end sections of the turbine rotor.

The turbine shown includes a casting l built up of rings l2, l4, l6 and I8 and supported by radial pins 20 in a housing 22, These pins which are all in the same plane and which constitute the support for the casing within the housing engage bores in bosses 24 in one ring IQ of the 65 around each disk thereby reducing the tempera.-v

2 casing. Rotor 26 within the casing has a number of rows of blades 28 alternating with the rows of nozzles 3Bon the casings.

Housing 22 has a cap 34 which forms a part of the housing and supports a bearing sleeve 38 for the front end of rotor 26. At the other end of the turbine the housing 22 supports a mounting 38 within which is a bearing 40 for the rear end of the rotor. Mounting 38 has a number of legs 42 engaging with radial pins 48 which support the mounting within the housing.

Rotor 26 is made up of a number of disks 46, 48, '50 and 52, and shaft-forming end elements 55 and 56. The disks and the shaft elements are all held together by a central bolt 58. The ends of the bolt are positioned within the end elements 54 and 56 and are connected to these elements by threaded sleeves 60 and 62. Each sleeve 60, t2 hasinner and outer threads 64 and 66 engaging respectively with cooperating threads on the bolt and on the end elements. On one of the sleeves (sleeve sq as shown) the inner and outer threads may differ in pitch, the inner thread being of 25 greater pitch, so that as the sleeve is screwed into place a substantial tension may be applied to-the bolt. I

To assist in aligning the disks during assembly and to prevent relative rotation in operation each 30 disk has projecting annular flanges on opposite v sides, these flanges having elements preferably in the form oi.v face splines with similar elements on the adjoining disk. Similarly, the inner ends of shaft elements 54 and 56 have face splines engaging with splines on the end disk.

Gas enters the first stage nozzles of the turbine through an inlet scroll attached to the end of casing Ill. Gas from the turbine discharges through a duct 72 connected to the end casing o ring and surrounding the rear bearing mounting.

The disks which make up the power section of the rotor have central openings 18 slightly larger in diameter than the fastening bolt and the shaft elements 54 and 56 have central openings 80 and -82 also larger in diameter than the fastening bolt. The disks and shaft elements of the rotor are thus free to expand radially without affecting the arrangement of the parts.

The rotor disks and the outside of the central bolt may be cooled by admitting gas under pressure througha passage 88 in the front end element to the opening between this element and the first disk 46. Gas from this space passes through the central openings in the disk and 3 ture of the central parts of the disk and also reducing the temperature of the bolt.

Coolant is admitted to the rearward end of the central bolt through a tube 90 mounted in one of the projecting legs 42 of the bearing mounting 30 and connecting with a passage 92 in bearing 40. A cap 94 on the bearing mounting has a connecting passage '96 by which coolant from rpassage 92 is guided to'a tube 90 extending through a cap I on the end of the bolt. Since coolant enters at the axis of the bolt there are no centrifugal forces acting on the fluid, as a result of the rotation of the rotor, until the fluid'reaches the bolt.

The bolt-has passages I02 adjacent its rearward and which communicate with opening 82 permitting coolant to flow through this opening and discharge through grooves I04 in the end element 56 to the inside of cap 94.

Similarly, at the forward end of the bolt, passages I06 permit coolant to flow into the space 80 within the end element 54. Packing I08 surrounding the bolt and located by a projecting rib IIO on the bolt limits the flow of coolant to the portion of space 80 forward of the passages 88. Coolant in opening 80 discharges through ports H2 in end element 54 and ports H4 in a journal II6 mounted on the end element.

As shown in Figure 2, packing I08 and similar packing II8 within end element 56 may be held in place by sleeves I20 and I22 integral with sleeves 60 and 62 respectively. These sleeves have ports I24 and I26 to permit the flow of coolant from the inside of the sleeve to the outside. Since coolant is continually admitted to the rearward end of the bolt and flows over the inner surface of the bolt for its entire length, the central bolt may be cooled to the desired temperature necessary for withstanding the stresses applied to the bolt. At the same time, the passage through the bolt directs fluid into the cooling spaces surrounding the bolt adjacent the bearings at opposite ends of the rotor. A cap I28 closes the forward end of the rotor.

Under certain extreme conditions it is possible that the turbine might have to operate at approximately full power without opportunity tor the turbine to be heated gradually to the operating temperature. In this event, the rotor disks will be rapidly heated while the bolt remains practically cold and the disk expansion will place a high axial load on the bolt. If the bolt is to be sufliciently strong to withstand this load it may be necessary to make the bolt of a material which, although capable of being heat treated to high strength, loses its strength rapidly at high To maintain the necessary high strength in the bolt the direct cooling of the bolt both internally and externally may be necessary to prevent the bolt from reaching a temperature at which the bolt strength would be less than the temperature.

stress applied to it.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claim.

I claim:

A turbine rotor having blade carrying disks having central openings and end shaft forming elements, a hollow axial bolt extending through said disks and elements and holding them together, each element forming a chamber surrounding said bolt adjacent each end, means for admitting coolant to said bolt, and means for admitting coolant from the bolt to said chambers, in combination with means for circulating another coolant between said bolt and the disks, the

latter having their central openings larger than the bolt to provide for the circulation of the other coolant.

WALTER KENNETH BODGER.

REFERENCES CITED file of this patent:

UNITED STATES PATENTS The following references are of record in the

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