Split ring for gas turbine casing

Details Split ring for gas turbine casing Split ring for gas turbine casing

2002-01-14

2003-03-18

Verdier, Christopher (Department: 3745)

Rotary kinetic fluid motors or pumps

Including thermal expansion joint

Circumferentially spaced nozzle or stator segments

C415S173100, C415S178000

Reexamination Certificate

active

06533542

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combustion gas turbine and, specifically, it relates to a split ring disposed on the inner wall surface of a gas turbine casing.
2. Description of the Related Art
A turbine casing of a combustion gas turbine forms a hot gas path through which high temperature combustion gas passes. Therefore, a lining made of a heat resistant material (such as a thermal protection tile) is disposed on the inner wall surface in order to prevent the casing metal surface from directly contacting hot combustion gas. Usually, the thermal protection lining is composed of a plurality of split segments arranged on the inner surface of the turbine casing in a circumferential direction so that the segments form a ring. Therefore, the thermal protection lining of the turbine casing is often called “a split ring”. In order to avoid problems due to thermal expansion at a high temperature, the respective split segments are spaced apart from each other in a circumferential direction.
FIG. 1
shows a cross-section of a turbine casing taken along the center axis thereof which indicates the position of the split ring.
In
FIG. 1
, numeral
1
designates a turbine casing as a whole. The turbine casing
1
has a cylindrical form in which a plurality of annular casing segments
3
made of metal are joined to each other in the axial direction.
Each casing segment is provided with a thermal insulation ring
5
disposed inside the casing segment
3
and spaced apart from the inner surface of the casing segment
3
. Stator blades
9
of the respective turbine stages are fixed to the thermal insulation ring
5
through a stator ring
7
.
Further, a split ring
10
is attached to the inner surface of each thermal insulation ring
5
at the portion between the stator rings
7
in such a manner that the inner surface of the split ring
10
opposes the tips of the rotor blades
8
with a predetermined clearance therebetween.
The split ring
10
is, as explained before, composed of a plurality of split segments made of a heat resistant material and arranged in the circumferencial direction of the casing inner wall. The respective split segments are spaced apart, in the circumferential direction, at a predetermined distance in order to accommodate the thermal expansion of the split segments.
A split ring of this type is disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 2000-257447.
The split segment of the split ring in the '447 publication is provided with an internal cooling air passage for cooling the split segment. Cooling air after cooling the split segment is injected from the outlet of the passage disposed on the end face of the split segment located on the downstream side thereof with respect to the direction of the rotation of the turbine rotor. The cooling air is injected from the above-noted outlet obliquely toward the end face of the adjacent split segment. Further, the comer between the end face located upstream side with respect to the direction of rotation of the rotor and the inner face of the split segment in the '447 publication is cut off so that the cooling air—injected from the adjacent split segment flows along the inclined surface formed at the comer. Thus, the inclined surface between the end face and the inner face is cooled by the film of cooling air.
However, in the split ring composed of the split segments, heat load exerted on the corner of the split segment between the upstream end face and inner surface thereof is very high and, in some case, cooling by the cooling air film is not sufficient.
This problem will be explained with reference to FIG.
9
.
FIG. 9
schematically illustrates a cross-section of the turbine casing perpendicular to its axis.
In
FIG. 9
, numeral
1
designates a turbine casing (more precisely, a thermal insulation ring),
11
designates split segments of the split ring
10
. As explained before, the respective split segments
10
are arranged in the circumferential direction with relatively small clearance
13
therebetween. The rotor blades
8
rotate in the direction indicated by the arrow R with a small clearance between the inner face
11
c
of the split segments
11
and the tips of the rotor blades
8
.
High temperature combustion gas flows through the casing
1
in the axial direction as a whole. However, when combustion gas passes through the rotor blades
8
, a circumferential velocity component is given to combustion gas by the rotor blade rotation and combustion gas flows in the circumferential direction with a velocity substantially the same as the tip velocity of rotor blades in the clearance between the tips of the blades
8
and the split segment
11
.
When this swirl flow of combustion gas passes the clearance
13
between the split segments
11
, turbulence occurs in the swirl flow.
FIG. 10
schematically illustrates the behavior of the swirl flow FR of combustion gas when it passes the rotor blade
8
. As shown in
FIG. 10
, when the swirl flow FR passes through the clearance
13
between the split segments
11
, the swirl flow FR impinges on the lower portion (i.e., the portion near the corner between the end face and the inner face) of the upstream end faces lla of the split segment
11
before it flows into the clearance
13
. Therefore, at the portion where swirl flow FR of combustion gas impinges on the upstream end face
11
a,
heat is transferred from combustion gas to the end face by an impingement heat transfer. This causes the heat transfer rate between the end face
11
a
and combustion gas flow FR to increase largely compared with the case where combustion gas flows along the inner face
11
c
of the split segments
11
.
Due to this increase in the heat transfer rate, the lower portion of the upstream end face
11
a
(i.e., the portion near the corner between the upstream end face
11
a
and the inner face
11
c
) of the split segment
11
receives a large quantity of heat every time the rotor blade
8
passes the clearance
13
. Therefore, the temperature of the corner portion of the upstream end faces
11
a
of the split segments
11
largely increases and, due to sharp increase in the local temperature, burning or cracking occurs at the corner portions of the split segments
11
.
In the above-noted '447 publication, since cooling air is injected and flows along the corner portion of the split segment, the temperature rise of the corner portion is suppressed to some extent. However, in the actual operation, since the flow of cooling air is disturbed by the impinging swirl flow of combustion gas, a cooling air film sufficient for cooling the corner portion is not formed and, thereby, cooling of the corner portion is insufficient even if the cooling air is supplied to the corner portion as disclosed by '447 publication.
SUMMARY OF THE INVENTION
In view of the problems in the related art as set forth above, the objects of the present invention is to provide a split ring of a gas turbine casing capable of preventing the burning of the corner portion of the split segment by reducing the temperature rise caused by the impingement of the swirl flow of combustion gas.
The objects as set forth above is achieved by a split ring for a gas turbine casing, according to the present invention, comprising a plurality of split segments arranged on an inner wall of a gas turbine casing in a circumferential direction at predetermined intervals so that the split segments form a ring disposed between tips of turbine rotors and inner wall casing opposing the tips of the rotor blades, wherein each of the split segments includes two circumferential end faces which oppose the end faces of the adjacent split segments and an inner face substantially perpendicular to the end faces and opposing the tips of the rotors and a transition face formed between at least one of the end faces and the inner face and, wherein the surface of the transition face is formed in such a manner that the clearance between the tips of the rotor blades and

Affiliated with

Also associated with

Rating

Split ring for gas turbine casing does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Split ring for gas turbine casing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Split ring for gas turbine casing will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3055779