System for cooling and purging exhaust section of gas turbine engine

A system is provided with a turbine exhaust strut configured to provide a bi-directional airflow. The turbine exhaust strut includes a first portion having a first flow passage configured to flow a fluid in a first direction between inner and outer exhaust walls of a turbine exhaust section, and a second portion having a second flow passage configured to flow the fluid in a second direction between the inner and outer exhaust walls of the turbine exhaust section. Furthermore, the first and second directions are opposite from one another.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to gas turbine cooling and more specifically to exhaust section cooling.

A gas turbine engine combusts a mixture of fuel and compressed air to generate hot combustion gases, which drive turbine blades to rotate. The rotation of the turbine blades causes rotation of a shaft supported by bearings. The rotation of the shaft and the hot combustion gases exiting through the turbine exhaust section may generate significant amounts of heat in the bearings and other exhaust section components. Unfortunately, this heat may cause damage to the turbine components, without adequate cooling in the exhaust section.

BRIEF DESCRIPTION OF THE INVENTION

In a first embodiment, a system includes a turbine exhaust strut configured to provide a bi-directional airflow. The turbine exhaust strut includes a first portion having a first flow passage configured to flow a fluid in a first direction between inner and outer exhaust walls of a turbine exhaust section, and a second portion having a second flow passage configured to flow the fluid in a second direction between the inner and outer exhaust walls of the turbine exhaust section. Furthermore, the first and second directions are opposite from one another.

In a second embodiment, a system includes a turbine exhaust section, including an exhaust flow path, an outer structure having an outer exhaust wall disposed along the exhaust flow path, an inner structure having an inner exhaust wall disposed along the exhaust flow path, and an inner cavity disposed between the inner exhaust wall and a rotational axis of a turbine, a bearing assembly disposed in the inner cavity, a lubrication passage disposed in the inner cavity, a strut extending between the outer structure and the inner structure, wherein the strut having a first flow passage configured to flow a fluid through the inner cavity.

In a third embodiment, a system includes a turbine section, and an exhaust section coupled to the turbine section, including an exhaust flow path, an outer structure having an outer exhaust wall disposed along the exhaust flow path, an outer casing, and an outer cavity disposed between the outer exhaust wall and the outer casing, an inner structure having an inner exhaust wall disposed along the exhaust flow path, and an inner cavity disposed between the inner exhaust wall and a rotational axis of a turbine, a first flow passage configured to flow a fluid through the inner cavity, and a second flow passage configured to flow the fluid from the inner cavity to the outer cavity.

DETAILED DESCRIPTION OF THE INVENTION

As discussed below, the disclosed embodiments enable cooling and purging of various components in an exhaust section of a gas turbine engine, e.g., bearings, struts, outer exhaust, inner structure, and so forth. For example, certain embodiments include a strut capable of bi-directional airflow that enables a single cooling air blower to cool the bearings, and other exhaust section components of the gas turbine engine. For example, the strut may include a plurality of separate flow passages. In some embodiments, a first passage of the strut may flow a cooling fluid (e.g., air) from the outer exhaust wall to the inner structure containing the bearings while a second passage may flow the cooling fluid from the inner structure to the outer exhaust wall after cooling the bearings and other exhaust section components. Thus, the first and second passages flow the cooling fluid in opposite directions, while controlling heat in the strut, the inner structure, and an outer structure having the outer exhaust wall. For example, the cooling fluid may transfer heat away from (e.g., cool) the bearings, inner exhaust wall, and aft portion of the inner structure, while adjusting a temperature of the outer structure (e.g., outer exhaust wall) via a combination of the relatively lower temperature cooling fluid entering the first passage and the relatively higher temperature cooling fluid exiting the second passage. In some embodiments, the cooling fluid may vent into the exhaust flow from the inner structure of the outer structure. Furthermore, a variety of insets may be selectively mounted in openings in the inner or outer structure to control an amount of venting. For example, some of the inserts may completely block airflow, while others reduce the amount of airflow into the exhaust flow.

FIG. 1is a schematic flow diagram of an embodiment of a turbine system10having a gas turbine engine12that may employ bi-directional exhaust section cooling. For example, the system10may include a multi-directional cooling system11having a plurality of separate flow rates in an exhaust section strut. In certain embodiments, the system10may include an aircraft, a watercraft, a locomotive, a power generation system, or combinations thereof. The illustrated gas turbine engine12includes an air intake section16, a compressor18, a combustor section20, a turbine22, and an exhaust section24. The turbine22is coupled to the compressor18via a shaft26. As indicated by the arrows, air may enter the gas turbine engine12through the intake section16and flow into the compressor18, which compresses the air prior to entry into the combustor section20. The illustrated combustor section20includes a combustor housing28disposed concentrically or annularly about the shaft26between the compressor18and the turbine22. The compressed air from the compressor18enters combustors30, where the compressed air may mix and combust with fuel within the combustors30to drive the turbine22. From the combustor section20, the hot combustion gases flow through the turbine22, driving the compressor18via the shaft26. For example, the combustion gases may apply motive forces to turbine rotor blades within the turbine22to rotate the shaft26. After flowing through the turbine22, the hot combustion gases may exit the gas turbine engine12through the exhaust section24. As discussed below, the exhaust section24may include a plurality of struts, each having multiple flow paths of the multi-directional cooling system11.

FIG. 2is a sectional view of an embodiment of the gas turbine engine12ofFIG. 1sectioned through the longitudinal axis, illustrating an embodiment of the multi-directional cooling system11. As described above with respect toFIG. 1, air may enter the gas turbine engine12through the air intake section16and may be compressed by the compressor18. The compressed air from the compressor18may then be directed into the combustor section20where the compressed air may be mixed with fuel. The combustion section20includes one or more combustors30. In certain embodiments, the gas turbine engine12may include multiple combustors30disposed in an annular arrangement. Further, each combustor30may include multiple fuel nozzles32attached to or near the head end of each combustor30in an annular or other arrangement. In operation, the fuel nozzles32may inject a fuel-air mixture into the combustors30in a suitable ratio for optimal combustion, emissions, fuel consumption, and power output.

Within the combustion section20, the fuel-air mixture may combust to generate hot, pressurized combustion gases. After combustion, the hot pressurized combustion gases may exit the combustor section20and flow through a transition piece34to the turbine22. Within the turbine22, the pressurized combustion gases may turn blades36that extend radially within the turbine22to rotate the shaft26before exiting through the exhaust section24as exhaust gas.

The exhaust section24may include an inner structure38, at least one strut40, and an outer structure42. The strut40provides the support between the outer structure42and the inner structure38. As the hot combustion gases exit the turbine22and shaft26rotates, the components in exhaust section24may experience high temperature conditions. More specifically, the high temperature conditions may cause thermal stress, wear, and/or damage to the strut40, the inner structure38, and the outer structure42. Accordingly, the multi-directional cooling system11includes a blower44coupled to a controller46, which controls a cooling air flow through the inner structure38, the strut40, and the outer structure42to reduce thermal stress and wear of these components and parts disposed therein.

In the illustrated embodiment, the strut40defines an outer body48and an inner body50. As illustrated, the inner body50defines a first flow passage52(e.g., inner flow passage) and the outer body48defines a second flow passage53(e.g., outer flow passage) of the multi-directional cooling system11. As discussed below, the flow passages52and53are separate from one another to enable bi-directional flow of a cooling fluid (e.g., air) through the strut40. Although the illustrated strut40includes only two separate passages52and53, the strut40may include any number of separate passages to route a cooling fluid (e.g., air) to and from various features in the inner structure38, the outer structure42, and the strut40. As illustrated, the blower44under the control of controller46blows cooling air58through the outer structure42, through the strut40(i.e., passage52of inner body50), and into the inner structure38. The cooling air58circulates in the inner structure38and then exits through the outer body48of the strut40. After flowing through the strut40to and from the inner structure38, the cooling air58flows into the outer structure42for venting into the exhaust flow path56. As discussed in detail below, multi-directional cooling system11enables a single blower44to cool the strut40, while simultaneously purging heat from the inner structure38.

Furthermore, in certain embodiments, the inner body50of the strut40is a load bearing structural support configured to bear a considerable mechanical load between the inner and outer structures38and42of the of the exhaust section24, while the outer body48of the strut40is not a load bearing structural support. For example, the outer body48may be included to protect the inner body50by blocking heat from the inner body50. In particular, the outer body48may be designed to flow cooling air externally along the inner body50to provide a thermal barrier between the inner body50and the hot combustion gases in the exhaust section24. The outer body48also may have greater thermal resistance to the hot combustion gases as compared with the inner body50. For example, the inner body50may have a lower temperature limit than the outer body48. In some embodiments, the inner body50may have a temperature limit lower than the temperature of the hot combustion gases, while the outer body48may have a temperature limit substantially above the temperature of the hot combustion gases. Thus, the outer body48thermally protects the inner body50, such that the inner body50is able to effectively bear the mechanical load between the inner and outer structures38and42of the exhaust section24.

FIG. 3is a sectional view of an embodiment of the gas turbine engine12ofFIG. 2taken within line3-3, illustrating exhaust section cooling by the multi-directional cooling system11. The design of the strut40enables a single blower44to cool the strut40and inner structure38. As illustrated, the inner structure38defines an inner exhaust wall80, a bearing cavity82, bearing assembly84, lubricant (e.g., oil) passage86, baffle (e.g., sleeve)88, baffle (e.g., disc)90, bearing support wall92, and aft shaft rotor cavity94. As explained above, the blower44blows cooling air through the inner body50of the strut40. The cooling air convectively cools the passage52in the inner body50, thus reducing the possibility of damage associated with thermal stress in the strut40.

After passing through the strut40, the cooling air58enters the inner structure38. More specifically, the cooling air58passes through the bearing support wall92and into the bearing cavity82, where it cools the bearing assembly84. The bearing assembly84generates significant amounts of heat as its bearings spin during rotation of shaft26. Accordingly, the cooling airflow convectively cools the bearing assembly84to reduce premature wear or damage caused by the heat.

After contacting the bearing assembly84, the cooling air58separates into two airflows100and102in opposite axial directions as indicated by arrows96and98. The airflow100traveling in axial direction96contacts baffle (e.g., disc)90, which directs the airflow100radially toward the baffle (e.g., sleeve)88. The sleeve88routes the airflow100axially along the lubricant passage86. As illustrated, the baffles88and90focus and restrict (e.g., funnel) the airflow100along the lubricant passage86, thereby enhancing the convective cooling of the lubricant passage86. Upon exiting the sleeve88, the airflow100passes along the inner exhaust wall80at a downstream end portion81of the inner structure38, thereby cooling the downstream end portion81. Again, the baffles88and90may force the airflow to pass along the inner exhaust wall80, thereby enhancing convective cooling of the wall80. Upon reaching the strut40, the airflow100then travels through the passage53of the outer body48and into the outer structure42.

Unlike the airflow100, the airflow102travels in the opposite axial direction of arrow98. While traveling in the direction of arrow98, the airflow102passes through the bearing assembly84and then enters the turbine aft wheel space94. The airflow102then travels toward the inner exhaust wall80, where part of it exits through gap104into the exhaust path56. The rest of the airflow102returns to the strut40, where it enters the outer body48and travels in the passage53to the outer structure42.

The outer structure42includes an outer exhaust wall106and an outer casing108, which define an intermediate outer cavity110(e.g., annular space). As the air100and102exits the strut40, it enters the outer cavity110for controlling the temperature of the outer structure42before venting into the exhaust flow path56. For example, the air100and102vents into the exhaust flow path56through apertures112in the outer exhaust wall106. In some embodiments, the inner exhaust wall80may also include apertures112for venting the airflow into the exhaust flow path56. As illustrated, the outer structure42includes both a cooled airflow58and a warmed airflow100and102, which are separated from one another. These two airflows may be adjusted to control the temperature in the outer structure42. For example, the ratio of these two airflows may be adjusted by varying the sizes of the passages52and53, the number and sizes of the apertures112in the inner and outer exhaust walls80and106and so forth.

FIG. 4is a cross-sectional view of an embodiment of the strut40inFIG. 3taken along line4-4. As described above, the strut40includes the outer body48disposed about the inner body50. As illustrated, the outer body48defines the passage53, leading edge54, and trailing edge55, while the inner body48includes the passage52. In the present embodiment, the outer body48has an oval shape (e.g., an airfoil shape), while the inner body50has a rectangular shape. In other embodiments, the inner and outer bodies48and50may have other shapes, such as rectangular in rectangular, airfoil in airfoil, oval in oval, and so forth. Despite the shapes, the inner and outer bodies48and50are disposed one inside another, such that the passages52and53are isolated one inside another (e.g., coaxial). The two passages52and54provide bi-directional airflow between the inner and outer structures38and42. For example, the passage52may direct the airflow inwardly from the outer structure42to the inner structure38while the passage53directs the airflow from the inner structure38to the outer structure42, or vice versa. However, an embodiment with cooler airflow in the passage52and warmer air in the passage53may reduce a temperature differential between the outer body48of the strut40and the exhaust gas in the exhaust portion56, thereby reducing thermal stress in the strut40. In some embodiments, each passage52and53may be configured to route air to a specific region of the inner structure38. In either embodiment, the passages52and53in the strut40enable a single blower44to cool the strut40, the inner structure38, and the outer structure42. In the inner structure38, the airflow can be directed to various regions to enhance convective cooling before being vented into the exhaust.

FIG. 5is a cross-sectional view of an embodiment of the strut40inFIG. 3taken along line4-4. The strut40defines an outer body140disposed about an inner body142(e.g., coaxial). The outer body140defines a passage143, a leading edge144, and a trailing edge145. The outer body140may form any number of shapes, such as oval, airfoil, teardrop, rectangular, square, circular, or generally elongated. The outer body140receives the inner body142, which is sized smaller than the outer body140to define one passage143. As illustrated, the passage143is subdivided by walls150to form passages146and148. In other embodiments, the passage143may be further subdivided by walls150to define any number of passages (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more passages). Similar to the outer body140, the inner body142may form any number of shapes, such as oval, airfoil, teardrop, rectangular, square, circular, or generally elongated. Although the illustrated inner body142includes a single passage152, the inner body142may include any number of passages (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more passages). As discussed above, the passages146,148, and152enable a single blower44to blow cooling air that cools the strut40and inner structure38, while simultaneously purging the inner structure38of warmed air. Furthermore, the multiple passages may enable dedicated coolant flows (e.g., air flows) to and/or from specific regions of the inner structure38of the exhaust section24. For example, dedicated airflows may be routed to/from the bearing assembly84, the downstream end portion81of the inner structure38, or the turbine aft wheel space94.

FIG. 6is a cross-sectional view of an embodiment of the strut40inFIG. 3taken along line4-4. The strut40defines an outer body170disposed about an inner body172. The outer body170defines a passage173, leading edge174, and trailing edge175. The outer body170may form any number of shapes including oval, airfoil, teardrop, rectangular, square, circular, or generally elongated, and includes a passage173. The outer body170receives the inner body172within the passage173. As illustrated, the inner body172defines two passages176and178separated by a wall180. In other embodiments, more walls180may form additional passages in inner body172, (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more passages). Similar to the outer body170, the inner body172may form any number of shapes, such as oval, airfoil, teardrop, rectangular, square, circular, or generally elongated. As discussed above, the passages174,176, and178enable a single blower to blow cooling air that cools the strut40and inner structure38while simultaneously purging the inner structure38of the warmed air. Furthermore, the multiple passages may enable dedicated coolant flows (e.g., airflows) to and/or from specific regions of the inner structure38of the exhaust section24. For example, dedicated airflows may be routed to/from the bearing assembly84, the downstream end portion81of the inner structure38, or the turbine aft wheel space94.

FIG. 7is a cross-sectional view of an embodiment of the strut40inFIG. 3taken along line4-4. The strut40includes an outer body190, a hollow interior191, and an interior support beam192(e.g., an I-beam). The outer body190may form any number of shapes, such as oval, airfoil, teardrop, rectangular, square, circular, or generally elongated. The support beam192divides the outer body190into two passages194and196. In other embodiments, a plurality of support beams192may divide the outer body190into any number of passages (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more passages). The outer body190may also include a leading edge198and a trailing edge200. The passages194and196enable a single blower44to blow cooling air that cools the strut40and inner structure38, while simultaneously purging the inner structure38of the warmed air. More specifically, the cooling air may cool the strut40and inner structure38by passing through the passage194or196into the inner structure38. After cooling the inner structure38, the air may then be purged through the opposite passage194or196. In certain embodiments, the cool supply airflow may be directed through the passage194along the leading edge198, while the warmed return (purge) airflow may be directed through the passage196along the trailing edge200. In this manner, the cooler supply airflow is focused on the hotter leading edge198of the strut140to improve the cooling and temperature distribution in the strut40.

FIG. 8is a sectional view of the strut40and outer exhaust wall106illustrating venting apertures112taken along line8-8ofFIG. 3. As explained above, the cooling air is purged from the inner structure38, where it flows through the passage53in the strut40to the outer structure42having the wall106. In the outer structure42, the airflow passes through the outer cavity110and then vents into the exhaust flow path56via apertures112. As illustrated, the apertures112are circular in shape and arranged into rows. In other embodiments, the apertures112may form different shapes (e.g., square, triangular, rectangular, oval, elongated, polygonal, or cross-shaped), and may be arranged into other patterns (e.g., staggered, circular, rectangular, or random). Furthermore, the sizes of the apertures112may change depending on their location. For example, the apertures112may progressively change (e.g., increase or decrease) in diameter with distance from the strut40. In some embodiments, the apertures112may be arranged in groups (e.g., 1 to 100 apertures112) that are spaced apart from one another. Furthermore, the apertures112may be arranged between approximately 0 to 180 degrees relative to a rotational axis of the turbine engine12. For example, the apertures112may be angled at 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, or 165 degrees relative to the axis.

FIG. 9is a cross-sectional view of removable inserts202,204, and206that may be inserted into one or more apertures112ofFIG. 8as indicated by line9-9. As illustrated, each aperture112may selectively receive a variety of inserts, such as inserts202,204, and206. The inserts202,204, and206may assist in controlling the amount of air entering the exhaust flow path56ofFIG. 3through the apertures112of the outer exhaust wall106. For example, each insert may provide a different amount of restriction for the aperture112. Thus, a variety of different inserts may be coupled to the apertures112to control a flow distribution through the wall106, thereby controlling a temperature distribution in the wall106.

As illustrated, the insert202includes a body portion208, a ledge portion210, and an aperture212. The body portion208fits within the aperture112, while the ledge portion210rests on the inner surface214or the outer surface216of the outer exhaust wall106. The body portion208may be connected to the wall106by an (interference fit, threads, a weld, bolts, or another fastener). As illustrated, the aperture212defines a diameter218that is smaller than a diameter220of the aperture112. Accordingly, upon insertion, the insert202will reduce the size of the aperture112, which then limits the airflow into the exhaust flow path56. Similar to the insert202, the insert204includes a body portion222and a ledge portion224. The body portion222fits within the aperture220, while the ledge portion224contacts the inner surface214or outer surface216of the outer exhaust wall106. As illustrated, the insert204does not include an aperture and therefore fills the entire aperture112, thereby blocking cooling air from venting into the exhaust flow path56. The insert206likewise includes a body portion226, a ledge portion228, and an aperture230. The body portion226fits within the aperture112, while the ledge228rests on the inner surface214or the outer surface216of the outer exhaust wall106. As illustrated, the aperture230defines a diameter232that is smaller than the diameter220of the aperture112, but larger than diameter218of insert202. Accordingly, upon insertion, the insert206will reduce the size of the aperture112, which then limits the airflow into the exhaust flow path56by an amount less than insert202.

Although the illustrated embodiment includes only three inserts202,204, and206any number of inserts with varying restriction apertures may be employed in the turbine engine12. These inserts202,204, and206control the amount and distribution of airflow through the wall106and into the exhaust flow path56. For example, the inserts202,204, and206may be used in different apertures112to control the cooling of the outer structure42in a more uniform manner. As a result, the selective use of these inserts202,204, and206may reduce temperature gradients and thermal stress in the outer structure42.

FIG. 10is a sectional front view of an exhaust section250with cooling struts252and254in the gas turbine engine12. The exhaust section250includes cooling struts252and254, outer casing256, outer exhaust wall258, blower260, controller262, inner structure264, bearing assembly266, and line268. As illustrated, the controller262controls the blower260to blow cooling air270through the cooling struts252. The cooling air270cools the struts252as it flows inwardly toward the inner structure264. In the inner structure264, the cooling air270cools the bearing assembly266. For example, the cooling air270may flow through the bearing housing272to cool the bearings274. After cooling the bearings274, the air270then exits the inner structure264though the struts254. The struts254route the air270into outer cavity276between the outer casing256and the outer exhaust wall258. As the air270flows through the outer cavity276, the air270may control the temperature (e.g., cool) the outer exhaust wall258and vent into the exhaust flow path280via apertures278. As discussed above, inserts may be placed within the apertures278to control the amount and distribution of airflow exiting the outer cavity276into the exhaust flow path280. Accordingly, the exhaust section250enables a single blower262to cool the inner bearings274and the struts252and254.

Technical effects of the invention include the ability to cool multiple components of a turbine exhaust section with a single blower. In particular, the disclosed embodiments enable cooling of struts, bearings, and other portions of an inner structure of the turbine exhaust section with the single blower. For example, the struts may be configured with one or more passages to direct airflow both into and out of the inner structure to simultaneously cool the struts, the bearings, and so forth. In one embodiment, each strut includes at least two passages to direct airflows in opposite directions into and out of the inner structure. In another embodiment, one strut may include at least one passage to route air into the inner structure, while another strut may include at least one passage to direct air out of the inner structure.