US3897171A - Ceramic turbine rotor disc and blade configuration - Google Patents

Abstract

A ceramic gas turbine rotor disc is formed integrally with an array of ceramic airfoil blades. Each blade has an elongated shank portion to reduce thermal and mechanical stresses on the rotor disc. An elongated cavity is disposed between adjacent shank members. Each elongated cavity is filled with undensified unattached silicon nitride plug. The plug acts as a centrifugal force pin, preventing excessive blade vibration. Each plug also helps reduce hot motive fluid leakage between adjacent blade shanks.

Description

United States Patent Stahl July 29, 1975 [5 CERAMIC TURBINE ROTOR DISC AND 3,824,036 7/1974 Penny et al. 416/244 BLADE CONFIGURATION FOREIGN PATENTS OR APPLICATIONS [75] Inventofl William Stahl, Media, 718,939 3/1942 Germany 416/244 [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa. Primary ExaminerEverette A. Powell, Jr. Filed: June 1974 Attorney, Agent, or FlrmF. A. Wmans [21] Appl. No.: 482,913 [57] ABSTRACT A ceramic gas turbine rotor disc is formed integrally [521 416/244; 416/213 416/241 with an array of ceramic airfoil blades. Each blade has [5 Clan elongated Shank p i to reduce thermal and [58] F'eld of Seal-chm 416/244 241 B chanical stresses on the rotor disc. An elongated cavity is disposed between adjacent shank members. Each [56] References C'ted elongated cavity is filled with undensified unattached UNITED STATES PATENTS silicon nitride plug. The plug acts as a centrifugal 2,297,508 9/1942 Sch'litte 416/244 force pin, preventing excessive blade vibration. Each 2,769,611 11/1956 Schwarzkopf 416/213 plug also helps reduce hot motive fluid leakage be- 3,262,676 7/1966 l-luebner et al. tween adjacent blade shanks, 3,664,766 5/1972 Rahnke 3,817,657 6/1974 Hueber 416/244 4 Claims, 3 Drawing Figures Ht l4 I4 .44 4

I I6 1 18 23 v 22 24 22 24 x I l6 I 18; 8 l8 26 2o 2 2| 2o 2| 2/ CERAMIC TURBINE ROTOR DISC AND BLADE CONFIGURATION 1;

BACKGROUND OF THE INVENTION 1. Field of the Invention i This invention relates generally to ceramic articles, and more particularly to integral ceramic rotor blades and discs for gas turbines.

2. Description of the Prior Art In the past few years, intensive effort has been applied to the development of turbine wheels which have blades and the disc integral in one investment casting. Attempts have been made to make an integral array of blades in rotor disc from ceramic material. Silicon carbide and silicon nitride are the candidate materials in this area because of their high strength and good oxidation and thermal shock resistance. The prior art for integral blade and disc arrangement has included US. Pat. No. 2,857,094. Another attempt at integral rotor blade and discs is shown by US. Pat. No. 3,283,377 made from alloy material. A further attempt at integral blade and rotor discs is shown in US. Pat. No. 3,262,676, wherein a plurality of recesses adjacent the rotor rim reduce stresses therein.

An object of the present invention is to define a rotor disc integral with rotor blades, capable of withstanding extremely high motive fluid temperatures with maximum time between failures.

Another object of the present invention is to define an integral rotor disc and blade capable of being manufactured from ceramic material and at minimum cost.

SUMMARY OF THE INVENTION This invention describes an integral rotor disc and blade array comprised of ceramic material. Each blade has an extended shank portion. An elongated cavity is disposed between adjacent extended blade shank members. The cavities are filled with an undensified unattached silicon nitride plug. The plugs acts as centrifugal force pins. The extended shanks reduce thermal and mechanical stresses on the rotor disc. The cavities are shaped so as to restrain the radial motion of the plugs due to centrifugal forces caused by rotor rotation. The plugs act as sealing members to prevent hot motive fluid from leaking out of the hot motive fluid flowpath. The plugs also serve to reduce any vibratory motion of the blade.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the nature and objects of this invention, reference may be had to the following detailed drawings in which:

FIG. 1 is an end view of a portion of a turbine rotor disc constructed in accordance with the principles of this invention;

FIG. 2 is a view taken along lines lI-II of FIG. 1; and,

FIG. 3 is an alternative embodiment of the invention as shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings in detail, and particularly to FIG. 1, there is shown a portion of a turbine rotor wheel 10, or disc. The rotor disc has an array of blades 12 disposed about its rim. The blades 12 are formed integral with the rotor disc 10. Each blade 12 is comprised of an airfoil portion 14 disposed on the radially outer portion of each blade 12, a platform portion 16 disposed on the intermediate portion of each blade 12, and a shank portion 18 comprising the radially inner portion of each blade 12. Each shank portion 18 is integral with the rotor disc 10. Each shank 18 is elongated, and between each adjacent elongated shank 18 there is disposed a radially extending elongated cavity 20. The radially outer portion of each extended cavity 20 has opposing wall members 22 and 24 that generally approach each other acutely. The radially outermost point of each wall member 20 and 24 corresponds to the furthermost edge from the center of the blade platform 16. The rotor disc 10 and blades 12 are comprised of ceramic material, preferably silicon nitride or silicon carbide. Each cavity 20 is filled with silicon powder which is reacted with nitrogen to form a porous or undensified unattached silicon nitride plug 26. The walls of each cavity 20 are coated with a parting material to prevent adherence of the undensified silicon nitride plug 26 thereto.

During rotor wheel 10 rotation, the undensified unattached silicon nitride plugs 26 act as centrifugal force pins to prevent the blades 12 from excessive vibration.

FIG. 2 shows an array of blades 12 having a generally linear gap 28 between adjacent platforms 16. The gap 28 between the adjacent blade platforms 16 permits slight thermal expansion and motion of the blades 12 without interference with one another. The undensified unattached silicon nitride plugs 26 act to seal the gap 28 from leakage of any fluid from the hot motive fluid flowpath to an area radially inwardly of the airfoil portions 14 of the blades 12, further reducing stress buildup from thermal causes.

A further embodiment of this invention is shown in FIG. 3, wherein adjacent blades 12 have platforms 30 which have non-linear or curved gap 32 between one another. The undensified unattached silicon nitride plugs 26 will still act as centrifugal force pins and as sealing members for the curved gaps 32.

There has been shown a high temperature integral ceramic rotor and blade structure capable of withstanding high thermal and vibratory stresses while being capable of being manufactured in an economical manner. The undensified unattached silicon nitride plug 26 acts both as a centrifugal force pin and a sealing element for the gaps 28 between adjacent blade platforms 16. The elongated cavity 20 permitting the elongated shanks l8, and the angularity of the cavity walls 22 and 24 permitting the plug 26 to act as a C.F. pin.

While the invention has been shown basically in one form, it will be recognizable by those skilled in the art, once having the benefit of seeing this disclosure, that it is not so limited, but is susceptable of various other changes and modifications without departing from the scope and spirit thereof.

I claim as my invention:

1. A ceramic rotor disc for gas turbines including:

ceramic airfoil blades integral with said ceramic rotor disc;

each of said airfoil blades having an airfoil portion on their radially outer section an intermediate platform portion, and an elongated shank portion on their radially inner section,

an elongated cavity being disposed between adjacent blade shanks,

each of said cavities having wall portions, said wall portions being coated with a parting material,

said cavity being filled with a ceramic plug, said ceramic plug serving as a centrifugal force pin to help reduce vibratory motion of the airfoil blades during rotor disc rotation.

2. A ceramic rotor disc for a gas turbine as recited in claim 1, wherein the radially outermost opposing wall portions of said elongated cavity generally defines an acute angle with one another, and said ceramic plug is wedged therein due to centrifugal forces generated during rotor disc rotation, each of said ceramic plugs of a generally porous material.

i I II! i

Claims (4)

1. A ceramic rotor disc for gas turbines including: ceramic airfoil blades integral with said ceramic rotor disc; each of said airfoil blades having an airfoil portion on their radially outer section an intermediate platform portion, and an elongated shank portion on their radially inner section, an elongated cavity being disposed between adjacent blade shanks, each of said cavities having wall portions, said wall portions being coated with a parting material, said cavity being filled with a ceramic plug, said ceramic plug serving as a centrifugal force pin to help reduce vibratory motion of the airfoil blades during rotor disc rotation.

2. A ceramic rotor disc for a gas turbine as recited in claim 1, wherein the radially outermost opposing wall portions of said elongated cavity generally defines an acute angle with one another, and said ceramic plug is wedged therein due to ceNtrifugal forces generated during rotor disc rotation, each of said ceramic plugs wedged therein preventing leakage of hot motive fluid from the hot motive fluid flowpath to the blade shank area.

3. A ceramic rotor disc for a gas turbine as recited in claim 1, wherein said ceramic plug in said cavity comprises a silicon powder, disposed therein, said silicon powder disposed therein being reacted with nitrogen to form a silicon nitride plug.

4. A ceramic rotor disc for a gas turbine as recited in claim 3, wherein said silicon nitride plug is comprised of a generally porous material.

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