Patent Application
20140130505
The subject matter disclosed herein relates to turbine systems, and more particularly to a cross-fire tube purging arrangement, as well as a method of purging a cross-fire tube.
Adjacent combustors of a gas turbine engine are typically connected by cross fire tubes to ensure substantially simultaneous ignition and equalized pressure in all combustor chambers of the gas turbine engine. It is common for less than all of the combustor chambers to include an ignition component to initiate a flame. In such an arrangement, the cross-fire tube allows a flame to pass from one combustor chamber to an adjacent combustor chamber. The cross-fire tubes may also be required to pass the flame from lighted to unlighted premixing regions of the combustor chambers during a light-off operating condition between a premix operating condition and a steady state operating condition. In the premix condition, the region of the combustor chamber connected by cross-fire tubes has no flame and is used for premixing the fuel and air, while in the light-off operating condition this same region has a flame.
When the cross-fire tubes are not in use, they must resist the unwanted passage of either hot gases from combustion or unburned fuel in the premixing zone from adjoining combustor chambers, which may lead to melting of the cross-fire tube or re-ignition of the premix zone of combustion. Resistance may be imposed by introducing a purge air to the cross-fire tube, however, constant purging is not desirable during all operating conditions, such as during ignition that leads to the light-off condition which requires passage of the flame from one combustor chamber to another.
According to one aspect of the invention, a cross-fire tube purging arrangement includes a cross-fire tube extending from proximate a combustor chamber to proximate an adjacent combustor chamber for fluidly coupling the combustor chamber and the adjacent combustor chamber. Also included is a compressed air supply arrangement for selectively delivering a compressed air to the cross-fire tube, the compressed air supply arrangement comprising a regulating component for controlling delivery of the compressed air to the cross-fire tube.
According to another aspect of the invention, a cross-fire tube purging arrangement includes a cross-fire tube comprising a first portion and a second portion operably coupled to each other and surrounded by a tube casing. Also included is a compressed air supply arrangement comprising one or more pipes extending through the tube casing into close proximity with an annular manifold disposed along a portion of the cross-fire tube. Further included is a regulating component in communication with the compressed air supply arrangement for controlling delivery of a compressed air to the annular manifold, wherein the compressed air is delivered to the annular manifold during a first operating condition and restricted during a second operating condition.
According to yet another aspect of the invention, a method of purging a cross-fire tube is provided. The method includes delivering a compressed air to the cross-fire tube during a first operating condition for purging the cross-fire tube. Also included is restricting a flow of the compressed air to the cross-fire tube during a second operating condition.
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.
Referring to
In operation, air flows into the compressor 12 and is compressed into a high pressure gas. The high pressure gas is supplied to the combustor assembly 14 and mixed with fuel, for example natural gas, fuel oil, process gas and/or synthetic gas (syngas), in the combustor chamber 18. The fuel/air or combustible mixture ignites to form a high pressure, high temperature combustion gas stream. In any event, the combustor assembly 14 channels the combustion gas stream to the turbine 24 which converts thermal energy to mechanical, rotational energy.
Referring now to
The cross-fire tube 33 includes an outer surface 52 and an inner surface 54, with the inner surface 54 defining an interior region 56 that provides the fluid coupling of the combustor chamber 18 and the adjacent combustor chamber 32, which allows the passage of a flame from the combustor chamber 18 to the adjacent combustor chamber 32, or vice versa. Such passage is desirable during light-off of the combustor assemblies of the gas turbine engine 10 and allows for nearly simultaneous ignition or re-ignition of the combustor assemblies.
The cross-fire tube arrangement 34 also includes a tube casing 58 that is spaced radially outwardly of the cross-fire tube 33 and may assist with supporting the cross-fire tube 33, however, fixing of the first end 36 and the second end 42 may be sufficient for supporting purposes. Both the cross-fire tube 33 and the tube casing 58 are made of a material sufficient to withstand the temperatures imposed on the materials during operation of the gas turbine engine 10 and typically include a metal having a melting temperature high enough to function during high temperature operation.
A compressed air supply arrangement 60 comprises a piping or tubing configuration for routing and delivering a compressed air 62 from the compressor 12, typically indirectly from the compressor 12 via a compressor discharge casing region (not illustrated), to the cross-fire tube 33. The piping or tubing configuration of the compressed air supply arrangement 60 may be arranged in numerous configurations, with the illustrated configuration merely a single example. As shown, the compressed air supply arrangement 60 includes a main supply line 64 that routes the compressed air 62 from the compressor 12, or the compressor discharge casing region, to a location proximate the cross-fire tube arrangement 34, and more particularly proximate the tube casing 58. The compressed air supply arrangement 60 may be split to deliver the compressed air 62 to a plurality of locations and in one exemplary embodiment a first line 68 and a second line 70 receive the compressed air 62 from the main supply line 64 for routing to distinct locations. It is to be appreciated that additional lines may be employed for delivery of the compressed air 62 to additional locations. Additionally, a single line comprising the main supply line 64, or simply an extension thereof, may be employed to deliver the compressed air 62 to a single location.
Irrespective of the precise configuration of the compressed air supply arrangement 60, one or more of the lines extend through the tube casing 58 to a location proximate the cross-fire tube 33 for delivery of the compressed air 62. In the illustrated embodiment, the first line 68 and the second line 70 meet with the main supply line 64 at a junction 72 located externally to the tube casing 58, however, an alternate embodiment includes the junction 72 between the tube casing 58 and the cross-fire tube 33. The compressed air supply arrangement 60 delivers the compressed air 62 to an annular manifold 74 that extends circumferentially around the cross-fire tube 33 to achieve a relatively even flow distribution of the compressed air 62 to the interior region 56 for purging of fluid out of the cross-fire tube 33. The annular manifold 74 may include one or more angled injectors 76 for directing the compressed air 62 into close proximity with the inner surface 54 of the cross-fire tube 33. Directing the compressed air 62 along the inner surface 54 enhances purging since any fluid will be concentrated on the inner surface 54. Alternatively, or in combination with the one or more angled injectors 76, at least one baffle 78 may be disposed along the cross-fire tube 33 proximate the annular manifold 74 to redirect the compressed air 62 into close proximity with the inner surface 54.
In the illustrated embodiment, the first line 68 delivers the compressed air 62 to a location along the first portion 48 of the cross-fire tube 33, while the second line 70 delivers the compressed air 62 to a location along the second portion 50. It is to be appreciated that both locations include the annular manifold 74, such that a repetitive description of the annular manifold 74 for each location is not necessary.
The compressed air supply arrangement 60 includes a regulating component 80 for actively controlling a flow rate of the compressed air 62 being supplied to the cross-fire tube 33. Specifically, the regulating component 80 is configured to selectively deliver the compressed air 62 during one or more operating conditions, while restricting or halting flow of the compressed air 62 to the cross-fire tube 33 in other operating conditions. The regulating component 80 comprises any suitable metering component capable of allowing, restricting and halting flow of the compressed air 62, such as a valve, for example. The regulating component 80 may be disposed in the main supply line 64 to control flow throughout all downstream regions of the compressed air supply arrangement 60, including various lines such as the first line 68 and the second line 70. Alternatively, a plurality of regulating components may be disposed in distinct lines to provide control of each line.
Restricting or completely halting the compressed air 62 is imposed when the passage of fluid or a flame throughout the cross-fire tube 33 is desired. Such a condition exists during light-off or re-ignition of the combustor chamber 18 and the adjacent combustor chamber 32. Delivery of the compressed air 62 during such an operating condition would inhibit the ability of the combustion system to fully light-off, such that active control advantageously allows shut-off of purging during this condition. Delivery of the compressed air 62 is advantageous during steady-state operation and during a premix operating condition, for example. In the case of the premix operating condition, purging of the cross-fire tube 33 enables reliable and efficient operation of a combustion system on liquid fuel (e.g., oil fuel) operation, which reduces the need for water to suppress NOx emissions.
As illustrated in the flow diagram of
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.
