Fluid reaction surfaces (i.e. – impellers) – Rotor having flow confining or deflecting web – shroud or... – Axially extending shroud ring or casing
Reexamination Certificate
2000-10-31
2002-09-24
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Rotor having flow confining or deflecting web, shroud or...
Axially extending shroud ring or casing
C416S234000, C416S203000
Reexamination Certificate
active
06454535
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to integrally formed bladed disks or “blisks” for turbine engines, and more particularly to a blisk having an integral splitter.
A conventional gas turbine engine includes a high pressure compressor for compressing air traveling through the engine, a combustor downstream from the compressor for heating the compressed air, and a high pressure turbine downstream from the combustor for driving the high pressure compressor. One type of engine, known as a bypass turbofan engine, also has a low pressure turbine downstream from the high pressure turbine for driving a fan upstream from the high pressure compressor. In a variable cycle engine, the first stage of the high pressure compressor is a core driven fan stage. The flowpath of the variable cycle engine is split at the core driven fan stage so it has concentric inner and outer ducts. The amount of air passing through the outer duct can be adjusted to change the thrust and fuel consumption of the engine.
As disclosed in U.S. Pat. No. 5,988,980, which is hereby incorporated by reference, a core driven fan stage includes inner and outer airfoils positioned in the inner and outer ducts, respectively. A generally cylindrical splitter positioned between the inner and outer airfoils forms part of the inner flowpath surface of the outer duct and part of the outer flowpath surface of the inner duct. Some prior art core driven fans are formed from a single piece of material so the inner and outer airfoils, the splitter and a disk are integral. Such an integrally bladed disk is commonly referred to as a “blisk”.
In the past, core driven fan stage blisks have been made with an equal number of inner and outer airfoils so each outer airfoil is radially aligned with a corresponding inner airfoil. Further, each outer airfoil of the prior art blisks has a midspan chord length which is almost as long as (i.e., greater than 80 percent of) the midspan chord length of the inner airfoils. As those skilled in the art will appreciate, the midspan chord length is a straight line distance measured from a point at a leading edge of the airfoil halfway along its span (i.e., radial height) to a point at a trailing edge of the airfoil halfway along its span. Because the outer airfoil chord lengths of the prior art blisks are so long relative to the inner airfoil chord lengths, the leading and trailing edges of the inner airfoils have high stresses, particularly at the tips of the inner airfoils. Previous attempts to reduce these stresses have included forming a groove in the leading and trailing edges of the splitter as disclosed in U.S. Pat. No. 5,988,980.
SUMMARY OF THE INVENTION
Among the several features of the present invention may be noted the provision of a blisk for use in a turbine engine. The blisk includes an annular disk having a hub surrounding a central opening, a web extending generally radially outward from the hub and a rim surrounding the web. In addition, the blisk comprises an inner row of blades including a plurality of circumferentially spaced airfoils integrally formed with the disk. Each of the airfoils of the inner row of blades extends generally radially outward from a root positioned adjacent the rim of the disk to a tip opposite the root. Further, the blisk includes an annular splitter integrally formed with the inner row of blades and surrounding the tips of the plurality of airfoils thereof. The splitter has an inner surface facing the tips of the plurality of airfoils of the inner row of blades and an outer surface opposite the inner surface. Still further, the blisk includes an outer row of blades including a plurality of circumferentially spaced airfoils integrally formed with the splitter. Each of the airfoils of the outer row of blades extends generally radially outward from a root positioned adjacent the outer surface of the splitter to a tip opposite the root. There are more airfoils in the outer row of blades than in the inner row of blades.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.
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Crall David William
Goshorn David Andrew
General Electric Company
Look Edward K.
McCoy Kimya N
Sonnenschein Nath & Rosenthal
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