US2479057A - Turbine rotor - Google Patents

Description

W. K. BODGER TURBINE ROTOR Aug. 16, 1949;

Filed March 27, 1945 FIG.2

INVENTOR Wm Mfl 55 FIG.I v

FIG.3

Patented Aug. 16, 1949 Walter Kenneth Bodger,

assignor to United Aircraft Corpora- Conn.,

South Glastonbury,

tion, East Hartford, Conn, a corporation of Delaware Application March 27, 1945, Serial 310,525,162

1 Claim. (01. 253-") This invention relates to turbine rotors and particularly to rotor disks for gas turbines in which the blade is a ceramic material.

The operating temperatures of turbines are limited by the materials available which for the most part rapidly lose strength at the high temperatures desirable for emcient operation. The metals commonly used are also subject to creep at high temperatures and may grow, during operation at elevated temperatures, to such a dimension that further satisfactory operation is impossible. A feature of this invention is a turbine rotor the surfaces of which are of ceramic material.

The rotational speed of the rotor is limited by the permissible stress in the blades. If the blade can be kept at a suillciently low temperature the strength of the blade may be kept high enough to withstand the centrifugal stresses resulting from high speeds. A feature of the invention is an arrangement for cooling the structural part of the turbine blades.

Since many ceramics do not have a high tensile strength they are not entirely satisfactory in turbine blades because of the high tensile stresses resulting from the centrifugal loads. A feature of this invention is a turbine rotor so arranged that the ceramic turbine blade may be compressively loaded. Another feature is the positioning of thehollow ceramic blade over posts on the rotor in such a manner that the ceramic blades are supported by the post and the loading on the blades is compressive. Another feature is the circulation of a coolant through the post.

One feature is the supplying of the coolant from the center of the rotor through the posts and the discharge of the coolant at the periphery of the rotor,

A feature of the invention is the arrangement of the posts so that the cross sectional area decreases toward the periphery of the rotor in order to reduce the stresses in the post, and the ceramic blade has its cross sectional area increasing toward the periphery of the rotor in order to reduce the stresses in the blade.

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

Fig. 1 is a sectional view through the rotor Fig. 2 is an enlarged sectional view showing the manner of mounting the turbine blade.

Fig. 3 is a fragmentary elevation of the periphery of the disk.

Fig. 4 is a transverse sectional view through one form of blade.

The turbine disk may be used in a single stage turbine or may form one stage of a multi-stage turbine of the type shown in the copending appiication of Bodger, Serial No. 550,872, filed August 23, 1944, although its use is not limited to this particular type of turbine.

As shown, the rotor includes a disk section ll having a number of radially extending posts or pegs l2 projecting from its outer edge and preferably structurally integral with the disk. ,Each post preferably tapers toward the outer end in order that the tensile stress developed in this post during the rotation of the disk may be approximately uniform throughout the length of the post.

Fitting over the post II, which may be circular in cross section, is a ceramic blade it having a similarly shaped central opening. This blade has its cross-sectional area increasing toward the periphery of the rotor in order that the stress may be approximately uniform throughout the blade. Mounted at the outer end of east post and connected to the post as by welding it is a shroud segment it which engages a shoulder 20 on the ceramic blade to hold the latter in place on the post. In this manner, the shroud segment supports the blade at its outer end and the blade is thus loaded in compression when the disk is rotating.

In order that the rotor may operate at high temperatures without overheating, coolant, preferably in the form of relatively cold air, is sup-- plied to the central opening 22 in the disk, and passes through radially extending ducts 24 in the disk and'in each of the posts i2. With coolant flowing through ducts 24 the posts are kept at a relatively low temperature so that the posts will not be overstressed during the turbine rotation. It will be apparent that the ceramic blade shields the post from direct contact with the hot fluid that drives the turbine. The ducts 24 are open at their outer ends and the coolant is allowed to discharge from the rotor at this point.

Coolant may be delivered to the central opening 22 of the disk by any desired mechanism such as that shown, for example, in the Bodger application, Serial No. 550,872, above referred to.

The blade may be held in the desired position with respect to the turbine rotor by the shroud segments it which engage with flanges 28 on the ceramic blades, as shown in Fig. 3. Each the shroud segments on adjacent posts.

I! desired, the post may be other than circular in cross section, as shown, for example, in Fig. 4 in which the post 28 corresponding to the post I! of Figs. 1 and 8 is approximately oval shaped in cross section to fit a correspondingly shaped opening II in the ceramic blade 82.

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 a row of blades on its periphery, each blade including a central post integral with the rotor, and a ceramic blade element mounted on said post, and a shroud segment on the outer end of the post having substantially circumferentially extending side surfaces, said blade element having radially extendirig flanges at the outer end thereof engaging with the Side surfaces of the shroud segment to prevent turning of the blade element onthe post.

WALTER-KENNETH BODGER.

REFERENCES CITED The followins references are of record in the file of this patent:

5 UNI'I'ED BTATES PATEN'IS Number Name Date 649,014 Terry May 8, 1910 1,266,889 Wait May 21, 1918 1,362,858 Darling Dec. 21, 1920 1,864,448 Lorenzen June 21,1932 1,966,104 Noack July 10, 1934 2,010,022 Holzworth Aug. 6, 1935 2,141,401 Martinka Dec. 27, 1938 2,297,508 Schutte Sept. 29, 1942 15 2,304,259 Karrer Dec. 8, 1942 2,308,233 Schutte Jan. 12, v1943 2,341,664 Bchutte Feb. 15, 1944 FOREIGN PATENTS 20 Number Country Date 390,391 Italy May 11, 1940 383,508 Germany Oct. 13, 1923 384,301 Great Britain Feb. 2'7, 1931 512,301 Great Britain Aug. 31, 1939 711,421 France 1 Sept. 9, 1931

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