This invention is directed generally to gas turbine engines, and more particularly, to an active bypass flow control system controlling the bypass of compressed air around one or more seals between a stator and a first stage rotor assembly to provide purge air to a rim cavity
Industrial gas turbine engines often have a rotor with a first stage turbine rotor blade and a stator with a first stage stator vane located downstream from a combustor A seal is typically positioned between the stator and the adjacent rotor to form a seal for a rim cavity that exists between the stator and rotor. Purge air is provided to the rim cavity via a bypass channel and via leakage past the seal A major problem with this structure is that the seal wears, and thus the leakage flow increases The discharge through the bypass channel is constant as long as the supply pressure remains the same. Thus, as the leakage flow across the seals increases, the cooling air from both pathways into the rim cavity, past the seal and from the bypass channel, increases A need thus exists to account for seal wear and extra leakage flow into the rim cavity so that the total cooling air flow to the rim cavity is not excessive
An active bypass flow control system for controlling bypass compressed air based upon leakage flow of compressed air flowing past an outer balance seal positioned between a stator and rotor of a first stage of a gas turbine in a gas turbine engine is disclosed The active bypass flow control system is an adjustable system in which one or more metering devices may be used to control the flow of bypass compressed air as the flow of compressed air past changes over time as the outer balance seals between the rim cavity and the cooling cavity wear In at least one embodiment, the metering device may include an annular ring having at least one metering orifice extending therethrough. The metering device may be positioned at the outlet of the bypass channel and may be adjustable such that alignment of the metering orifice with the outlet is adjustable to change a cross-sectional area of an opening of aligned portions of the outlet of the bypass channel and the metering orifice reducing or increasing the opening of aligned portions changing the flow of compressed air through the metering device.
In at least one embodiment, the active bypass flow control system may include a stator assembly positioned in proximity to a first stage rotor whereby a compressed air channel is positioned between a portion of the stator assembly and a rotor shaft. One or more outer balance seals may be configured to at least reduce a portion of hot gases from flowing into a cooling cavity In at least one embodiment, the outer balance seal may be a labyrinth seal formed from a plurality of teeth combined with a brush seal sealing a rim cavity from the cooling cavity. The outer balance seal may be positioned on a radially inward end of the rim cavity between the rim cavity and the cooling cavity
One or more bypass channels may extend from an inlet in fluid communication with the compressed air channel upstream of the outer balance seal to an outlet in fluid communication with the compressed air channel downstream from the outer balance seal The active bypass flow control system may also include one or more metering devices that is adjustable to adjust the flow of cooling fluids through the bypass channel to accommodate a changing flow of compressed air past the outer balance seal as the outer balance seal wears during turbine engine operation.
The metering device may be formed from an annular ring having one or more metering orifices extending therethrough The metering device may be positioned at the outlet of the bypass channel and may be adjustable such that alignment of the metering orifice with the outlet is adjustable to change a cross-sectional area of opening of aligned portions of the outlet of the bypass channel and the metering orifice of the metering device In at least one embodiment, the metering device may include a plurality of metering orifices extending through the at least one metering device. In one embodiment, the plurality of metering orifices may be positioned equidistant from each other The plurality of metering orifices may be positioned in the metering device such that each of the metering orifices is aligned with a bypass channel in an open state
The active bypass flow control system may also include a position control system for controlling position of the metering device relative to the outlet of the bypass channel. In at least one embodiment, the position control system may include a cam adjustor having an internal slot for receiving a post that retains the metering device relative to the outlet of the bypass channel The post may be capable of being moved within the slot to change the position of the metering device relative to the outlet of the bypass channel In at least one embodiment, the position control system may also include one or more control levers for changing alignment of the metering device relative to the outlet of the bypass channel The position control system may also include one or more motors usable to change alignment of the metering device relative to the outlet of the bypass channel The position control system may include one or more sensors configured to measure an amount of leakage flow occurring across the metering device In other embodiments, one or more sensors may be used to measure a pressure ratio across the metering device The position control system may include a controller in communication with the sensor and with the motor such that the controller controls operation of the motor to control alignment of the metering device relative to the outlet of the bypass channel based upon data derived from the sensor
In yet another embodiment, the active bypass flow control system for an outer balance seal may include a stator assembly positioned in proximity to a first stage rotor whereby a compressed air channel is positioned between a portion of the stator assembly and a rotor shaft The active bypass flow control system may also include one or more outer balance seals configured to at least reduce a portion of hot gases from flowing into a cooling cavity One or more bypass channels may extend from an inlet in fluid communication with the compressed air channel upstream of the outer balance seal to an outlet in fluid communication with the compressed air channel downstream from the outer balance seal The active bypass flow control system may include one or more metering devices that is adjustable to adjust the flow of cooling fluids through the bypass channel to accommodate a changing flow of compressed air past the outer balance seal as the outer balance seal wears during turbine engine operation.
The metering device may include one or more valves formed from one or more pins movable between open and closed positions in which the pin at least partially bisects the bypass channel The metering device may also include one or more cams engaged to the pin to move the pin between open and closed positions In at least one embodiment, the cam may be formed from a collar positioned in contact with a head of the pin. The pin may also include one or more orifices located in the shaft of the pin and positioned such that the orifice is aligned with the bypass channel when the pin is in the open position The active bypass flow control system may also include a sync ring in communication with the pin via one or more valve arms extending from the pin to the sync ring The valve arm may be pivotably attached to the sync ring The sync ring may be attached to one or more cams engaged to the pin to move the pin between open and closed positions via at least one valve arm The sync ring may be cylindrical with a plurality of valve arms pivotably attached thereto. In another embodiment, the sync ring may also include a plurality of cams formed from slots contained within the sync ring The plurality of cams may be nonparallel and nonorthogonal to an axis tangential to curved midline of the sync ring These and other embodiments are described in more detail below
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention
As shown in
As shown in
The active bypass flow control system 10 may also include one or more bypass channels 28 extending from an inlet 40 in fluid communication with the compressed air channel 16 upstream of the outer balance seal 12 to an outlet 26 in fluid communication with the compressed air channel 16 downstream from the outer balance seal 12 In at least one embodiment, the bypass channel 28 may be positioned within a portion of the stator assembly 18. As shown in
The active bypass flow control system 10 may also include one or more metering devices 14 that is adjustable to adjust the flow of cooling fluids through the bypass channel 28 to accommodate a changing flow of compressed air past the outer balance seal 12 as the outer balance seal 12 wears during turbine engine operation. In at least one embodiment, the metering device 14 may be an annular ring 22 having one or more metering orifices 24 extending therethrough. The metering device 14 may be positioned at the outlet 26 of the bypass channel 28 and may be adjustable such that alignment of the metering orifice 24 with the outlet 26 is adjustable to change a cross-sectional area of an opening 44 of aligned portions of the outlet 26 of the bypass channel 28 and the metering orifice 24 of the metering device 14. In at least one embodiment, the metering device 14 may include a plurality of metering orifices 24 extending through the metering device 14. In at least one embodiment, the plurality of metering orifices 24 may be positioned equidistant from each other, and, in other embodiments, the plurality of metering orifices 24 may be positioned in other configurations relative to each other. The plurality of metering orifices 24 may be positioned in the metering device 14 such that each of the metering orifices 24 is aligned with a bypass channel 28 in an open state, as shown in
In at least one embodiment, the metering orifices 24 may be skewed or angled, as shown in
The active bypass flow control system 10 may also include a position control system 46 for controlling position of the metering device 14 relative to the outlet 26 of the bypass channel 28. The position control system 46 may be, but is not limited to being, a manual system, a motor driven system, and an automatically adjustable system In at least one embodiment, as shown in
The position control system 46 may also include one or more sensors 58 configured to measure an amount of leakage flow occurring across the metering device 14 The sensor 58 may be any appropriate sensor 58 configured to detect pressure, such as, but not limited to, downstream preswirler pressure The sensor 58 may measure a pressure ratio across the metering device 14 or mass flow. In at least one embodiment of the active bypass flow control system 10, the position control system 46 may also include a controller 60 in communication with the sensor 58 and with the motor 56 such that the controller 60 controls operation of the motor 56 to control alignment of the metering device 14 relative to the outlet 26 of the bypass channel 28 based, at least in part, upon data derived from the sensor 58 The controller 60 may be, but is not limited to being, the turbine engine logic control system, a component within the turbine engine logic control system, any microcontroller, programmable controller, computer, personal computer (PC), server computer, a client user computer, a tablet computer, a laptop computer, a desktop computer, a control system, or any machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by the controller 60 Further, while a single controller 60 is illustrated, the term “controller” shall also be taken to include any collection of controllers that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein
During use, compressed air is passed from a compressor into the compressed air channel 16 The compressed air is substantially prevented from entering the rim cavity 62 via the outer balance seal 12 and hot gas is substantially prevented from being ingested into the cooling cavity 25 from the rim cavity 62 The metering device 14 may be used to divert compressed air into the rim cavity 62 to purge hot gas from the rim cavity 62 when the outer balance seal 12 is preventing flow of the hot gas into the cooling cavity 25 and the compressed air channel 16 As the outer balance seal 12 wears and becomes less effective with greater compressed air leakage, the metering device 14 may be adjusted to exhaust less compressed air from the outlet 26 The flow of compressed air through the metering device 14 may be adjusted by adjusting the metering device 14 such that less of the metering orifices 24 is aligned with the outlet 26 of the bypass channel 28 The position of the metering device 14 may be adjusted when the turbine engine is operating or during an outage when the engine is shutdown The position of the metering device 14 may be adjusted manually, such as using the control lever 54 and cam adjustor 48, via one or more motors 56, via an automatic system as described above with the controller 60, motor 56 and sensor 58, or any combination of these systems
In another embodiment, as shown in
The pin 72 may include one or more orifices 80. The orifice 80 may be positioned and the pin 72 rotated such that in the open position, as shown in
In another embodiment, the active bypass flow control system 10 may include a metering device 14 formed from one or more valves 70 formed from one or more pins 72 that are each controlled by a cam 74, as shown in
As shown in
In another embodiment, as shown in
In at least one embodiment, the active bypass flow control system 10 may be used to control a portion of the bypass channels 28 positioned circumferentially about an engine For example, and not by way of limitation, the active bypass flow control system 10 may control the flow through a collection of bypass channels 28 on either side of a gas turbine 21 but not control the flow of gases through bypass channels on the top and bottom of the gas turbine 21
The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention
This application claims the benefit of U.S. Provisional Patent Application No. 61/771,151, filed Mar. 1, 2013, the entirety of which is incorporated herein.
Development of this invention was supported in part by the United States Department of Energy, Advanced Turbine Development Program, Contract No. DE-FC26-05NT42644 Accordingly, the United States Government may have certain rights in this invention.
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