US2432315A

US2432315A - Bladed rotor

Info

Publication number: US2432315A
Application number: US498643A
Authority: US
Inventors: Howard Alan
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1943-08-14
Filing date: 1943-08-14
Publication date: 1947-12-09
Anticipated expiration: 1964-12-09

Description

Dec.9,1947.

Driven: Al n Howard,

His Attorney Patented Dec. 9, 1947 BLADE!) ROTOR Alan Howard, Schenectady, N. Y., assignor to General Electric Company,

New York a.

a corporation of Application August 14, 1943, Serial No. 498,643 1 Claim. (Cl. 253--39) The present invention relates to bladed rotors such asare used in turbines. It finds especial utility in rotors -for gas turbines such as, for example, turbosuperchargers wherein the rotors operate at high speeds and are subjected to high temperatures at the rim and are strongly cooled at the web. It is this application of my invention which I have elected to specifically illustrate and describe. It is to be understood, however, that this is only by way of example and that my invention may be used whereverfound applicable in high temperature, high speed rotors.

- The object of my invention is to provide an improved rotor of the type referred to and for a consideration of what I believe to be novel and my invention, attention is directed to the following specification and to the claim appended thereto.

In the drawing, Fig. 1 is an end view of a part of a turbine wheel embodying my invention and Fig. 2 is a. sectional view taken on line 2-2 of Fig. l.

Referring to the drawing, i indicates the hub, 2 the web, 3 the rim and 4 the blades of a turbine wheel. In the present instance a shaft 5 is shown as bein formed integral with the hub.

According to my invention, I provide a wheel wherein the rim for the wheel, which rim carries the buckets, is formed from an alloy having good high temperature properties, particularly as regards strength, and the web and hub are formed from an alloy having good low temperature properties, particularly as regards strength, the rim and web being united to each other by fused metal. In this connection, it is pointed out that in high' temperature turbines such as gas turbines receiving motive fluid at temperatures well above 1000 F. it is customary to strongly cool the web and hub portions of the bucket wheels by a blast of cooling air or other cooling medium 50 that they operate at temperatures relatively low compared to that at which the rim and buckets operate. With such a cooling arrangement, the buckets are cooled by conduction of heat to the comparatively cooler web portion of the disk. In such turbines, the temperature of the fluid entering the buckets may be in the neighborhood of 1250 F., the temperature of the buckets around 1200 the temperature of the rim portion 1150 F., while the central web portion of the bucket wheel is maintained somewhere around 600 or 700 F. by the cooling medium. According to my invention, I utilize for the rim and for the web and hub alloys best suited for the operating conditions met with in. each instance.

The high-temperature rim material may be any one of several known alloys of a type which show,

no allotropic transformation when heated and cooled and are nonmagnetic. The most common high-temperature alloys of this type are those known generally in the metallurgical art as austenitics. It is desired to call attention however to the fact that this term has been generally, and somewhat loosely, applied to many high-temperature alloys having the same general characteristics as'the true austenitics, but having only a very few percent of iron, or in some cases no iron at all. One of these "non-ferrous austenitics" which may be used for the high-temperature rim has the following composition:

Percent CO Ni 20 Cr 25 WC 5 1 I desire it to be understood that the term austenitic" as used hereinafter is intended to include such austenitic-like alloys.

One suitable material for the hub and web is SAE 4140. steel. Another is an alloy comprising iron and about the given percentages of the following metals:

In the illustrated embodiment of my invention,

I provide buckets having rectangular bucket cover sections 6 and having bases which may be attached to the rim in any suitable manner, such as by welding, by dovetailed connections or the like.

In the present instance, the bases are shown as comprising a bottom plate 1, a neck 8 and a head 9, the plates 1. being rectangular and fitting against each other in .a completed wheel, and the necks 8 and heads 9 being located in suitable transverse slots formed in rim 3. Thus there is provided a rim in the form of a ring to which the bases of the buckets are fixed by dovetail connections, the rim being formed of a suitable high-temperature alloyv as pointed out above. The rim is attached to the web and hub by welding as is indicated at In in Fi 2. It may be attached to the web either before or after the blades has good tensile strength and life at the elevated temperatures encountered in gas turbine operation. but unfortunately it is difiicult to forge. In the present state of the art it would be difllcult, if possible at all, to make an entire turbine disk, of the sizes needed for gas turbines, wholly of this material. Even if such a disk were fabricated, it would have but a limited life because incapable of enduring for any length of time the great temperature gradients from the central portion of the web to the rim which are encountered n .gas turbine service. Therefore, in order to readily fabricate a rim portion which will have adequate strength and life, it is desirable to keep the radial width of the high temperature rim portion as small, as possible. and preferably substantially less than the radius of the combined hub and web portions. v 7

By my invention, I provide a rotor which is capable of being manufactured readily and which, due to the rim and the web and hub being formed from materials suited particularly to the operating conditions met with, gives superior service.

bodiment thereof. burr desire to have i't'understood that the apparatus shown is only illustrativeand that the invention may be carried out by other means.

WhatI claim as new and desire to secure by tion. a web portion fabricated of a ferrous alloy In accordance with the provisions of the patent material which is easily worked and has good strength properties at operating temperatures below 1000 F., an annular rim portion welded to the outer circumference of the web portion, and an annular row of buckets secured to the rim portion, the rim portion being fabricated of an austenitic material having good strength properties above 1000 F. .and being of a radial width substantially less than the radius of the combined hub and web portions.

ALAN HOWARD.

REFERENCES CITED The following references are file of this patent:

UNITED STATES PATENTS of record in the Number Name Date 2,058,479 Lysholm Oct. 27, 1936 2,174,380 Doran Sept. 26, 1939