Flex Seal for Gas Turbine Expansion Joints

United States Patent 6065756

Assigned to GE

Eignor, James Giles (Scotia, NY)

Poccia, Nicholas Philip (Gansevoort, NY)

Tomlinson, Leroy Omar (Schenectady, NY)

1. A flex seal for an expansion joint between a gas turbine exhaust duct and an axially adjacent exhaust ductwork comprising plural axially adjacent layers of flexible seal plates, each layer comprising a plurality of said seal plates each having an arc length such that said seal plates together form a 360° annulus in each layer; and further wherein said plural layers of flexible seal plates are secured at first ends to the gas turbine exhaust duct, with opposite second ends of said seal plates slidably engaged across a free edge of said exhaust ductwork.

2. The expansion joint seal of claim 1 wherein said free edge of said exhaust ductwork comprises a free edge of an annular drainage trough adapted to capture water or fuel running along and within said gas turbine exhaust duct.

3. The expansion joint seal of claim 2 wherein said drainage trough comprises an annular, partially toroid-shaped member having a drainage pipe in a lower portion thereof.

4. The expansion joint seal of claim 1 wherein said plural layers comprise three layers.

5. The expansion joint of claim 1 wherein the flexible seal plates of each layer are circumferentially offset from the flexible seal plates of an adjacent layer.

6. The expansion joint of claim 1 including a hold down bar assembly including a plurality of hold down bar segments clamping said flexible seal plates against a radial flange on said gas turbine exhaust duct.

7. The expansion joint of claim 6 wherein said at least one surface of said exhaust ductwork comprises an edge of an annular draining trough adapted to capture water or fuel running along and within said gas turbine exhaust duct.

8. The expansion joint of claim 1 wherein said turbine exhaust duct and said exhaust ductwork are substantially round in cross section, and wherein said turbine exhaust duct has a diameter less than said exhaust ductwork.

9. A flex seal for an expansion joint between a gas turbine exhaust duct and an axially adjacent exhaust ductwork comprising plural axially adjacent layers of flexible seal plates, each layer comprising a plurality of said seal plates each having an arc length such that said seal plates together form a 360° annulus in each layer; and further wherein said plural layers of flexible seal plates are secured at first ends to the gas turbine exhaust duct, with opposite second ends of said seal plates slidably engaged with at least one surface of said exhaust ductwork, and further wherein said at least one surface of said exhaust ductwork comprises a plurality of axially spaced, circumferentially arranged flanges defining an annular radial groove therebetween in which said opposite ends of said seal plates are slidably received.

10. A flex seal for an expansion joint in a gas turbine exhaust system, the joint including a gas turbine duct and an adjacent exhaust ductwork, the flex seal comprising plural axially adjacent layers of annularly arranged flexible seal plates secured at first ends to an annular mounting flange on the gas turbine duct, with second free ends of the flexible seal plates slidably engaged within an annular radial groove in said exhaust ductwork to thereby accommodate relative axial and radial movement between said gas turbine duct and said exhaust ductwork.

Description:

TECHNICAL FIELD

This invention relates generally to gas turbines and specifically to flex seal arrangement for expansion joints in gas turbine exhaust systems.

BACKGROUND

Current expansion joints in gas turbine exhaust systems with hot flanges are generally designed in one of two ways. The most common design is a flat belt arrangement consisting of a ceramic fiber composite belt and bolster bag. One end of the belt is bolted to a frame attached to the gas turbine and the other end is bolted to a frame on the adjacent exhaust ductwork. The gas seal in the composite belt is provided by a Teflon™ layer, metal foil or metal impregnated cloth. The other most common design, sometimes called a "D" style due to the cross-sectional shape of the belt, is a composite belt and bolster with one end bolted to a bar mounted on the gas turbine flange and the other end bolted to a flange on the exhaust ductwork. The belt acts as a diaphragm.

The first mentioned flat belt arrangement has experienced problems including cracked frames due to thermal transients; burned belts due to frames cracking and bolster bag failure; and leakage during gas turbine water wash cycles which not only allows contaminated water to leak onto the ground, but also damages the ceramic fibers in the belt and bolster bag. Liquid fuel ingestion in the event of a failure to fire on liquid fuel-fired gas turbines damages fibers and binders and burns when gas turbine exhaust temperature increases. Moreover, while this design handles large relative motions (3 or more inches axially), the ceramic fiber, once stretched, does not return to its original shape, thereby resulting in burning and hot gas leaks.

The second mentioned "D" style composite belt and bolster bag arrangement has also proven less than satisfactory in that it is very difficult to install this style belt on the ductwork, and because, over time, the bolster bag will degrade and allow hot gas to damage the belt, possibly also resulting in failure.

A metal bellows arrangement has also been used in similar applications, but requires two bellows separated by several feet to accommodate lateral offset as well as relative axial movement. In some cases, the metal bellows concept requires high quality field welding. Overall, the metal bellows technique for large gas turbines have been susceptible to cracking due to thermal fatigue and is thus also unsatisfactory.

DISCLOSURE OF THE INVENTION

The present invention addresses the problem of flexibly connecting either a hot or cold turbine flange to either a hot or cold exhaust ductwork flange within the context of gas turbine axial flow exhaust systems with substantially round cross-sectional shapes. The present invention also addresses the problem of disposing of water or liquid fuel in a manner which prevents contaminated water from leaking onto the ground.

In one exemplary embodiment of the invention, the relative axial and radial motion of a hot gas turbine duct relative to a cold exhaust ductwork is accommodated by layers of overlapping thin metal plates, with first ends of the plates bolted to a flange mounted on the gas turbine duct, and the other ends of the plates either guided or axially supported by the adjacent exhaust ductwork. The thickness and the arc length of the plates are designed to allow the plates to create a gas seal during all gas turbine operating modes. In this embodiment, the free ends of the plates flexibly engage, and are free to slide on, an annular edge of a drainage trough supported on the exhaust ductwork. In addition, the inherent geometry of this design allows the trough to be integrated into the exhaust ductwork and thereby allow easy removal of water and liquid fuel, as described in further detail herein.

In a second embodiment, the overlapping thin metal plates are adapted for use in a hot-to-hot flange arrangement. In this embodiment, the free edges of the flexible plates are guided for radial and lateral movement between flanges supported by the exhaust ductwork.

Insulation blankets may also be employed in conjunction with the seal plates but which do not inhibit movement of the plates either axially, laterally or radially as required.

Accordingly, in its broader aspects, the present invention relates to a flex seal for an expansion joint between a gas turbine exhaust duct and an axially adjacent exhaust ductwork comprising plural axially adjacent layers of flexible seal plates, each layer comprising a plurality of the seal plates each having an arc length such that the seal plates together form a 360° annulus in each layer; and further wherein the plural layers of flexible seal plates are secured at first ends to the gas turbine exhaust duct, with opposite second ends of the seal plates slidably engaged with at least one surface of the exhaust ductwork.