Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
1998-10-06
2001-01-30
Lopez, F. Daniel (Department: 3745)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
C415S190000, C415S138000, C415S139000, C416S095000
Reexamination Certificate
active
06179555
ABSTRACT:
TECHNICAL FIELD
The invention is directed to a novel sealing device for sealing joints utilizing a cylindrical dowel disposed in semi-cylindrical grooves in the joint surfaces, and specifically applied to sealing a T.O.B.I. (Tangential On Board Injection) feed plenum defined with an inner shroud separated into shroud segments with radially extending joints, the joints being sealed with axially extending dowels and fasteners.
BACKGROUND OF THE ART
Gas turbine engines include several compressed air plenums and ducts for conducting pressurized air for cooling over various engine components. The complexity of manufacturing and assembly of various components represents a significant cost factor in the production and maintenance of aircraft engines. In general, it is preferable to replace multiple parts with single cast or machined parts to reduce the complexity of manufacturing.
The present invention is directed to the manufacture and assembly of a circumferential array of stator blades with outer shroud and inner shroud. The stator array is positioned between the high pressure compressor turbine and the low pressure compressor turbine immediately downstream of the combustor. Between these two turbines is the circumferential array of stator blades which include a radially inwardly directed conduit to conduct cooling air from a plenum surrounding the combustor into the interior of the engine for accumulation in a T.O.B.I. feed plenum. From the T.O.B.I. plenum, cooling air is directed toward the cover plate and body of the low pressure compressor turbine. The T.O.B.I. plenum includes nozzles directed toward the cover plate and turbine to direct cooling air on and through the cover plate and turbine.
Conventional designs of stator arrays generally include multiple components which are assembled together into a ring like structure. Individual stator blades are machined and assembled together into a ring structure during manufacture. In general, if any machined components can be manufactured in a single unit, costs and labour savings result. Recently the capability of accurately machining large metal parts has increased through use of computer-aided manufacturing and computer numerical controlled machining. CAD and CNC enable designers to combine extremely complex components together into a single part. The complex geometry of blade shapes and geometry of the hot gas path have in the past resulted in manufacturing procedures which include individually machining each stator blade then brazing the blades together with the outer and inner shrouds to define the hot gas path.
It is desirable to produce a stator blade assembly in a single ring-like unit. For ease of manufacture and maintenance of structural integrity, it is desirable to produce a single ring-like structure utilizing the outer shroud as a continuous hoop member, whereas the blades and attached inner shrouds are split apart. Splitting the inner shroud allows for relieving of internal stresses, facilitates fabrication of the ring structure, facilitates inspection and simplifies maintenance. Fabrication can involve unitary casting of the one-piece outer shroud together with split inner shroud and radial stator blades, or machining individual stator blades then brazing the individual stator blades to form an integral outer shroud and split inner shroud.
The individual stator blades with attached inner shroud segments must be joined together into an inner annular shroud in a manner which maintains the seal of the inner shroud preventing air from escaping from the T.O.B.I. plenum into the hot gas path. Leakage of cooling air would result in a significant decrease in the efficiency of the engine cooling system.
Therefore, it is very desirable to provide a split inner shroud that can be efficiently sealed to prevent migration between the hot gas path and the cooling air within the plenum. It is also highly desirable to produce a plenum from easily assembled and disassembled components that can be inspected, replaced or repaired during routine maintenance.
DISCLOSURE OF THE INVENTION
The invention provides a novel plenum assembly particularly adapted for forming a plenum inwardly of a circumferential stator blade array in a gas turbine engine. Typically, a gas turbine engine has an air compressor, combustor, and an annular hot gas path axially ducting hot gas past a circumferentially spaced apart array of stator blades upstream of a turbine rotor.
Each stator blade has an internal bore for ducting cooling air between a radially outward shroud and a T.O.B.I. plenum (i.e.: Tangential On Board Injection) that accumulates cooling air for expulsion through T.O.B.I. nozzles. The T.O.B.I. plenum is defined by: a forward plate; a rearward plate; and an inner shroud disposed between the forward and rearward plates.
The inventive improvement relates to a novel inner shroud comprising a circumferential assembly of inner shroud segments with radially extending joints between adjacent inner shroud segments. The outer shroud is a one-piece hoop with stator blades and segmented inner shroud. To assemble the inner shroud to contain compressed air in the T.O.B.I. plenum, the plenum enclosure includes releasable elongate fasteners engaging the forward and rearward plates and clamping the inner shroud segments between the plates. Each fastener is disposed axially within an associated joint between adjacent inner shroud segments and each fastener includes a sealing sheath disposed about the fastener for sealing the associated joint.
In broad aspect, the invention provides a sealing device for sealing any joint in a structure between two adjacent joint surfaces. The sealing device being an elongate cylindrical dowel disposed in sealing contact within two opposing generally semi-cylindrical grooves in each adjacent joint surface. Preferably the dowel comprises an outer annular sheath and an inner cylindrical core. Application of the sealing device is advantageous in structures subject to thermal expansion where providing joints allows stress relief. The cylindrical dowels in semi-cylindrical grooves allow for thermally induced movement while retaining an effective seal in the joints. The cylindrical shape can be easily bored during manufacture with commonly available machine tools, and if necessary larger sized bores and dowels can be fitted during maintenance operations if leaks develop.
A preferred sealing device includes an outer annular sheath and an inner core member. The core can be a releasable fastener used in conjunction with plates or other structural components to construct annular rings or hollow plenum structures if desired.
Further details of the invention and its advantages will be apparent from the detailed description and drawings included below.
REFERENCES:
patent: 3393894 (1968-07-01), Redsell
patent: 3788767 (1974-01-01), Bednarczyk et al.
patent: 4526511 (1985-07-01), Levine
patent: 4756153 (1988-07-01), Roberts et al.
patent: 5597286 (1997-01-01), Dawson et al.
patent: 5772401 (1998-06-01), Canova
patent: 5800124 (1998-09-01), Zelesky
Astle Jeffrey W.
Lopez F. Daniel
Pratt & Whitney Canada Corp.
Woo Richard
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