This application claims the benefit of Russian Patent Application No. 2010101978, entitled “GAS TURBINE TRANSITION PIECE AIR BYPASS BAND ASSEMBLY”, filed Jan. 15, 2010, which is incorporated herein by reference in its entirety.
The subject matter disclosed herein relates to gas turbine combustors, and, more particularly, to a gas turbine transition piece air bypass band assembly that allows for excess compressor discharge air to be bypassed during certain gas turbine operating conditions.
Gas turbines can be somewhat limited as to the amount that the combustor exit temperature can be reduced by the allowed levels of carbon monoxide (CO) produced by the gas turbine. Typically, the combustor exit temperature remains relatively high to ensure that the gas turbine does not exceed permitted levels of CO emissions. To keep combustor exit temperatures high enough to remain at relatively low CO emission levels requires that the fuel the customer is consuming remain “on-line,” that is, synchronized to the electrical power grid. If a primary contributor to CO production in the individual combustor cans is reduced, this would allow the gas turbine customer to further turn down the load on the gas turbine and, thus, reduce fuel consumption during periods of reduced electricity demand. This can replace the method of shutting down the gas turbine during periods of reduced electricity demand and later turning the gas turbine back on when the demand returns. This method of frequently turning the gas turbine on and off may reduce the reliability of the gas turbine.
In existing turndown regimes, the gas turbine still operates at the speed required to produce electricity at the desired frequency, and the flow rate of fuel and air to the combustors is reduced to reduce the amount of combustion gases generated in the combustors, thereby reducing the power produced by the gas turbine. However, the operating range of typical compressors limits the extent to which the air flow may be reduced, thereby limiting the extent to which the fuel flow may be reduced while maintaining the relatively preferred fuel to air ratio. When the fuel to air ratio is in the relatively preferred position, then the combustor emissions are relatively low and the combustion is stable. Bypassing excess air through the transition piece openings can allow for the preferred fuel to air ratio to be achieved at the combustor head end when the combustion process occurs, thereby reducing CO emissions.
According to one aspect of the invention, an air bypass band assembly includes a transition piece of a gas turbine, the transition piece having at least one opening therein to allow a flow of air to pass through the at least one opening. The air bypass band assembly also includes a band that is movable between at least two positions, a first one of the at least two positions being a closed position where the at least one opening is closed to prevent the flow of air from flowing through the at least one opening, a second one of the at least two positions being an open position where the at least one opening is opened to allow the flow of air to flow through the at least one opening. The air bypass band assembly further includes a mechanism that moves the band between the at least two positions.
According to another aspect of the invention, an air bypass band assembly portion of a gas turbine includes a transition piece, the transition piece having a plurality of openings therein to allow a flow of air to selectively pass through the plurality of opening. The air bypass band assembly also includes a band that is movable between at least two positions, a first one of the at least two positions being a closed position where the plurality of openings are closed to prevent the flow of air from flowing through the plurality of openings, a second one of the at least two positions being an open position where the plurality of openings are opened to allow the flow of air to flow through the plurality of openings. The air bypass band assembly further includes a mechanism that moves the band between the at least two positions.
According to still another aspect of the invention, an air bypass band assembly includes a transition piece of a gas turbine, the transition piece having at least one opening therein to allow a flow of air to pass through the at least one opening. The air bypass band assembly also includes a band located radially around at least a portion of the transition piece, the band being movable between at least two positions, a first one of the at least two positions being a closed position where the at least one opening is closed to prevent the flow of air from flowing through the at least one opening, a second one of the at least two positions being an open position where the at least one opening is opened to allow the flow of air to flow through the at least one opening. The air bypass band assembly further includes a mechanism that moves the band between the at least two positions.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
The air bypass band assembly 16 of embodiments of the present invention being in the open position, as illustrated in
Further, embodiments of the air bypass band assembly 16 of the present invention when utilized at the forward end 18 of the transition piece 14 may omit the transition piece forward ring 32. The flow of bypass air 28 may then instead flow through some other suitable cavity or flow channel.
Embodiments of the present invention allow for the reduction in the production of emissions, such as but not limited to, carbon monoxide (CO) in a gas turbine combustor (e.g., in the individual combustor cans). This allows the gas turbine load to be further turned down, thereby reducing the amount of fuel consumption by the gas turbine, during periods of reduced electricity demand, also providing for increased cost savings. Embodiments of the present invention also allow for a relatively good seal capability of the transition piece openings, thereby providing little or no sensitivity to thermal growth and little or no vibration-caused wear problems. This is because any expansion of the air bypass band is compensated for by actuator load and band spring force.
Embodiments of the air bypass band assembly of the present invention have been described and illustrated herein as being located at the forward end of the transition piece of the gas turbine (i.e., at the forward ring 32 of the transition piece 14). However, embodiments of the air bypass band assembly of the present invention may be located at other gas turbine locations, such as, for example, the combustor head end or the combustor liner aft section. In addition, embodiments of the present invention may be utilized in a gas turbine to modulate cooling airflow through components such as a turbine nozzle and blades. Also, embodiments of the present invention may be utilized to “tune” the combustor exit temperature profile during low load regimes.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Number | Date | Country | Kind |
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2010101978 | Jan 2010 | RU | national |