Patent Application
20080060362
Referring now to the drawings, in which like numbers refer to like elements throughout the several views,
As is shown, the flexible element 110 may be attached on one end to a turbine duct 120. The turbine duct 120 may be of conventional design. The flexible element 110 may be attached to the turbine duct 120 at a radial flange 130 or a similar location. The flexible element 110 may be attached to the radial flange 130 by a number of fasteners. The flexible element 110 also may be attached to a diffuser duct 140 at the other end. The diffuser duct 140 may be of conventional design. Other types of exhaust ducts may be used herein. The flexible element 110 may be positioned within a pair of flanges 150 on the diffuser duct 140 or at a similar location. A drainage trough 160 or similar type of structure may be positioned about the pair of flanges 150 of the diffuser duct 140.
The expansion joint 100 further may include a number of segmented plates 170. The plates 170 may be made out of an austenitic steel stabilized by Titanium or Niobium. Examples include 321 and 347 grade stainless steel or similar types of materials. The plates 170 may be manufactured and installed using readily available manufacturing methods and parts. The segmented plates 170 may be bolted on the downstream side of the expansion joint 100. Specifically, the plates 170 may be bolted to the diffuser duct 160. The plates 170 may include a number of oversized apertures 180. The plates 170 may be bolted to the diffusion duct 140 via a number of bolts 190 and with oversized washers 200. Other types of attachment means may be used herein. The plates 170 extend outwardly from the diffusion duct 140 towards the radial flange 130 of the turbine duct 120.
In use, the apertures 180 within the plates 170 allow the plates 170 to grow thermally in the circumferential and axial directions yet remain firmly secured to the diffuser duct 140 via the number of bolts 190. Because the diffuser duct 140 generally is internally insulated, the plates 170 are mounted to a well-damped surface and should not be subject to excessive vibrations due to flow excitation or from similar causes.
When the expansion joint 100 is cold and the turbine is not operating, a gap 210 exists in the flow path between the plates 170 and the radial flange 130. The gap 210 allows for drainage of liquid fuel if a false start should occur. Likewise, water from a turbine wash may drain out. When the gas turbine runs and becomes hot however, the turbine duct 120 will experience thermal growth. As a result, the radial flange of the turbine duct 120 will move aft towards the diffusion duct 140. The gap 210 between the radial flange 130 and the plates 130 thus narrows so as to provide a smooth aerodynamic transition. As the gap 210 closes, the flexible element 110 also is protected from pressure fluctuations.
The gap 210 may be about three (3) to about seven (7) inches (about 76.2 to about 177.8 millimeters) in width when the turbine duct 120 is cold and may be about one-half (0.5) to about one (1) inch (about 12.7 to about 25.4 millimeters) when the turbine duct 120 is hot. Other dimensions may be used herein.
The expansion joint 100 describes herein thus provides a smooth aerodynamic transition. This smooth aerodynamic transition maximizes system pressure recovery while providing protection from pressure pulsations. The plates 170 can accommodate relatively large displacements between the flange 130 of the turbine duct 120 and the diffusion duct 140. The expansion joint 100 as a whole thus can address the large relative axial, vertical, and lateral displacements due to thermal growth between the gas turbine 120 and the diffuser duct 140. The plates 170 also are not susceptible to flow excitation. Further, the gap 210 provides a reliable way to drain all liquids that may enter the diffuser duct 140.
It should be apparent that the foregoing relates only to the preferred embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the generally spirit and scope of the invention as defined by the following claims and equivalents thereof.
