The present application and the resultant patent relate generally to axial flow turbines of any type and more particularly relate to controlled flow guides for steam turbines such as Controlled Flow 2 Next Generation (CF2NG) guides.
Generally described, steam turbines and the like may have a defined steam path that includes a steam inlet, a turbine section, and a steam outlet. Steam leakage, either out of the steam path, or into the steam path from an area of higher pressure to an area of lower pressure, may adversely affect the operating efficiency of the steam turbine. For example, steam path leakage in the steam turbine between a rotating shaft and a circumferentially surrounding turbine casing may lower the overall efficiency of the steam turbine.
Steam generally may flow through a number of turbine stages typically disposed in series through first-stage blades such as guides and runners (or nozzles and buckets) and subsequently through guides and runners of later stages of the turbine. In this manner, the guides may direct the steam toward the respective runners, causing the runners to rotate and drive a load, such as an electrical generator and the like. The steam may be contained by circumferential shrouds surrounding the runners, which also may aid in directing the steam or combustion gases along the path. In this manner, the turbine guides, runners, and shrouds may be subjected to high temperatures resulting from the steam, which may result in the formation of hot spots and high thermal stresses in these components. Because the efficiency of a steam turbine is dependent on its operating temperatures, there is an ongoing demand for components positioned along the steam or hot gas path to be capable of withstanding increasingly higher temperatures without failure or decrease in useful life.
Certain turbine blades may be formed with an airfoil geometry. The blades may be attached to tips and roots, where the roots are used to couple a blade to a disc or drum. The turbine blade geometry and dimensions may result in certain profile losses, secondary losses, leakage losses, mixing losses, and the like that may adversely affect efficiency and/or performance of a steam turbine.
In some cases, e.g., steam delivery on the saturation line from a Pressurized Water Reactor, the turbine may operate with wet steam flows. Such flows may create additional wetness losses via the non-equilibrium expansion of the steam (which generates fine fog) and consequential coarse water losses.
The present application and the resultant patent thus provide a steam turbine. The steam turbine may include a number of controlled flow runners and a number of controlled flow guides. The controlled flow guides may include an upstream passage ratio (Wup/W) of 0.4 to 0.7.
These and other features and improvements of this application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.
Referring now to the drawings, in which like numerals refer to like elements throughout the several views,
During operation, the high pressure steam inlet 45 receives high pressure steam from a steam source. The steam may be routed through the high pressure section 15 such that work is extracted from the steam by rotation of the disc 55. The steam exits the high pressure section 15 and then may be returned to the steam source for reheating. The reheated steam then may be rerouted to the intermediate pressure section inlet 50. The steam may be returned to the intermediate pressure section 20 at a reduced pressure as compared to the steam entering the high pressure section 15 but at a temperature that is approximately equal to the temperature of the steam entering the high pressure section 15. Accordingly, an operating pressure within the high pressure section 15 may be higher than an operating pressure within the intermediary section 20 such that the steam within the high pressure section 15 tends to flow towards the intermediate section 20 through leakage paths that may develop between the high pressure 15 and the intermediate pressure section 20. One such leakage path may extend through the packing casing 75 about the disc shaft 55. Other leaks may develop across the steam seal unit 65 and elsewhere.
The first stage 130 may include a first-stage shroud 190 extending circumferentially and surrounding the first-stage controlled flow runners 150. The first-stage shroud 190 may include a number of shroud segments positioned adjacent one another in an annular arrangement. In a similar manner, a second stage 200 may include a number of second-stage controlled flow guides 210, a number of second-stage controlled flow runners 220, and a second-stage shroud 230 surrounding the second-stage controlled flow runners 220. The controlled flow guides 140 may have an Impulse Technology Blading (ITB) guide design. The controlled flow guides 140 may be original equipment or a retrofit. Any number of stages and corresponding guides and runners may be included. Other embodiments may have different configurations.
Referring to
The design provides a very high suction side acceleration rate. As is shown in
This very high initial acceleration on the suction surface thus gives smaller droplet sizes, reduced thermodynamic wetness losses, and reduced consequential wetness losses. The gain in dry stage efficiency may be about 0.2% and wetness losses may be reduced by about 20% as compared to conventional designs. The overall design may safely approach or even somewhat exceed a conventional boundary layer shape factor and the like.
It should be apparent that the foregoing relates only to certain embodiments of this application and resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
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Entry |
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International Search Report for PCT/US20181063072, dated Mar. 21, 2019 (4 pp.). |
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Number | Date | Country | |
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20190203609 A1 | Jul 2019 | US |