Turbine inner shroud and turbine assembly containing such...

Details Turbine inner shroud and turbine assembly containing such... Turbine inner shroud and turbine assembly containing such...

1999-04-27

2001-11-13

Verdier, Christopher (Department: 3745)

Rotary kinetic fluid motors or pumps

Including thermal expansion joint

Resilient

C415S136000, C415S138000, C415S139000, C415S173300, C415S200000

Reexamination Certificate

active

06315519

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to turbines, and more particularly to a turbine inner shroud and a turbine assembly containing an inner shroud.
Turbine assemblies include, without limitation, turbine sections of steam turbines and compressor and/or turbine sections of gas turbines. Steam and gas turbines are used, among other purposes, to power electric generators, and gas turbines also are used, among other purposes, to propel aircraft and ships. A steam turbine has a steam path which typically includes, in serial-flow relationship, a steam inlet, a turbine, and a steam outlet. A gas turbine has a gas path which typically includes, in serial-flow relationship, an air intake (or inlet), a compressor, a combustor, a turbine, and a gas outlet (or exhaust nozzle). Compressor and turbine sections include at least one circumferential row of rotating blades. The free ends or tips of the rotating blades are surrounded by a stator casing. The radial gap between the blade tips and the stator casing is made small for increased efficiency of the turbine.
Typically, as shown in prior-art
FIG. 1
, a metal inner shroud
2
(such as one made of Inconel®), has been attached through mating slots to a circumferential segment of an outer shroud block
4
of the stator casing
6
and is spaced apart from the blade tips
8
. The metal inner shroud
2
is subject to heat distortion because of high thermal gradients in the shroud area of the turbine. Such heat distortion places the inner shroud
2
and the outer shroud block
4
under significant mechanical stresses. What is needed is an inner shroud which is more heat resistant and an attachment for the inner shroud which is subject to less mechanical stress.
BRIEF SUMMARY OF THE INVENTION
Broadly described, an exemplary turbine inner shroud of the present invention is attachable to a circumferential segment of an outer shroud block of a stator of a turbine. The stator has a longitudinal axis. The shroud-block circumferential segment has longitudinally spaced apart, generally opposing, and generally longitudinally outward facing first and second side portions. The inner shroud includes a ceramic material and has spaced apart, generally opposing, and generally inward facing first and second hook portion. When the inner shroud is attached to the shroud-block circumferential segment, the first hook portion longitudinally and radially surrounds the first side portion, and the second hook portion longitudinally and radially surrounds the second side portion.
Broadly described, an exemplary turbine assembly of the present invention has a turbine stator and a ceramic inner shroud. The stator has a longitudinal axis and an outer shroud block. The outer shroud block has a circumferential segment, wherein the circumferential segment has longitudinally spaced apart, generally opposing, and generally longitudinally outward facing first and second sides. The first side has a generally longitudinally outward facing first open slot. The ceramic inner shroud includes a first hook portion having a first end positioned in the first open slot.
Several benefits and advantages are derived from the invention. The ceramic inner shroud is heat resistant. The inward-facing first and second hook portions of the exemplary ceramic inner shroud are easy to manufacture and, when the ceramic is a ceramic matrix composite, provide continuous reinforcing fibers from the hook region to the hot gas path face which is desirable to maintain structural integrity and dimensional stability of the ceramic inner shroud. In the exemplary turbine assembly, the first hook portion, being positioned in the longitudinally outward-facing first open slot of the shroud-block circumferential segment, permits a surrounding compliant member to be used in the first open slot to allow for some relative thermal deformation of the ceramic inner shroud and the shroud-block circumferential segment while preventing substantial mechanical loading of the ceramic inner shroud.


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Concurrently filed patent application by Bharat S. Bagepalli et al., entitled “Turbine Assembly Containing an Inner Shroud,” (RD-27,001).

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