Bolt On Seal Ring

A device to route cooling air to a turbine blade is provided. The device includes a seal ring having an L-shaped cross section configured to abut a turbine disc. The seal ring includes a radial portion extending radially with respect to a rotor and an axial portion extending axially with respect to the rotor. The seal ring also includes a plurality of radial cooling holes disposed within the radial portion of the seal ring and arranged circumferentially around the seal ring. The plurality of cooling holes route cooling air from a device configured to impart tangential momentum to the cooling air to a turbine blade in order to cool the turbine blade. A system and a method to improve a flow of rotor cooling air to a turbine blade are also provided.

BACKGROUND

The present application relates to gas turbines, and more particularly to a device to route cooling air to a turbine blade. A system to improve a flow of rotor cooling air and a method to improve a flow of rotor cooling air to a turbine blade are also provided.

2. Description of the Related Art

During operation of the gas turbine, turbine blades are exposed to extremely high temperatures. Various methods are employed for their cooling, including routing rotor cooling air to the turbine blades. Traditionally, an air separator is used to separate the air into two paths, one leading into the row one turbine disc, also referred to as the turbine disc one, for cooling of the row one blade platform and the other path leading to the rotor for cooling of the rotor discs and turbine blades. After the air separator routes the air to the rotor, the air is then brought up to the rotational speed of the rotor. This process incurs undesirable aerodynamic losses as the work of the rotor associated with bringing the air up to rotational speed is high. A pre-swirler device may be used to impart tangential momentum in order to get the rotor cooling air up to the rotational speed of the rotor quicker than the process used with the air separator. Using the pre-swirler device to swirl the incoming rotor cooling air reduces losses and improves the overall efficiency of the gas turbine which leads to the improved cooling ability of the rotor cooling air to cool the turbine blades.

SUMMARY

Briefly described, aspects of the present disclosure relate to a device to route cooling air to the turbine blade.

A first aspect of provides a device to route cooling air to a turbine blade. The device includes a seal ring having an L-shaped cross section configured to abut a turbine disc. The seal ring comprises a radial portion extending radially with respect to a rotor and an axial portion extending axially with respect to the rotor. The seal ring also comprises a plurality of radial cooling holes disposed within the radial portion of the seal ring and arranged circumferentially around the seal ring. The plurality of cooling holes route cooling air from a device configured to impart tangential momentum to the cooling air to a turbine blade in order to cool the turbine blade.

A second aspect provides a system to improve a flow of rotor cooling air to a turbine blade. The system includes a swirler device configured to swirl a rotor cooling air with a rotation of the gas turbine. The system also includes a turbine disc and an L-shaped seal ring abutting the turbine disc and configured to route the rotor cooling air through a plurality of radial cooling holes within the seal ring from the swirler device to a turbine blade in order to cool the turbine blade.

A third aspect of provides a method to improve a flow or rotor cooling air to a turbine blade. The method includes swirling rotor cooling air such that the cooling air is rotating at the speed of the rotor and routing the swirled cooling air to a turbine blade through a radial hole in an L-shaped ring for cooling.

DETAILED DESCRIPTION

To facilitate an understanding of embodiments, principles, and features of the present disclosure, they are explained hereinafter with reference to implementation in illustrative embodiments. Embodiments of the present disclosure, however, are not limited to use in the described systems or methods.

The pre-swirler device, as described above, would physically replace the air separator in existing gas turbines. In order to integrate the pre-swirler into existing gas turbines, an additional device may be needed to replace the functionality of the air separator; that is to separate the cooling air into the two paths, one path into the row one turbine blade platform and the other path to the turbine rotor discs and turbine blades. Additionally, the additional device may be needed to provide a sealing function for the pre-swirler housing. The additional device and its functionality separating the cooling air into two paths may also be incorporated into the design of a new engine.

FIG. 1illustrates a longitudinal cross section of a mid-section1of a gas turbine including a pre-swirler device30. Additionally,FIG. 1shows a partial longitudinal view of the gas turbine's turbine section2including the turbine one disc20and a proposed seal ring device10. The pre-swirler device30includes a pre-swirler inner and outer housing,80and a pre-swirler nozzle40. The pre-swirler device30is a stationary, non-rotating device, whereas the turbine one disc20and the proposed seal ring device10rotate with respect to a rotor centreline100. The pre-swirler nozzle40imparts a tangential momentum to the rotor cooling air F which enters the pre-swirler device30from the rotor air cooling system of the gas turbine. The pre-swirler nozzle40may also be used to point the rotor cooling air F in a desired direction. After exiting the pre-swirler nozzle40, the rotor cooling air F enters a cavity90disposed between the pre-swirler device30and the turbine disc one20. At least one seal70may be used for sealing the pre-swirler inner housing80against the seal ring device10in order to minimize the loss of rotor cooling air when routing it toward the turbine blades.

The seal ring device10is disposed between the pre-swirler device30and the turbine disc one20and above the cavity90into which the swirled rotor cooling air F enters at the speed of the rotor after being expelled by the pre-swirler nozzle40. The turbine one disc20includes multiple radial cooling passages, of which one is illustrated in the Figures,50through which a portion of the rotor cooling air flows radially to the turbine blade for its cooling. Additionally, an axial cooling passage60exists in the turbine disc one20for a further portion of the rotor cooling air F to flow in order to cool the further stages of turbine discs and turbine blades.

FIG. 2illustrates a longitudinal cross section of the seal ring device10. The seal ring10includes an L-shaped cross section as seen in theFIG. 2. The seal ring10thus comprises a radial portion120extending radially with respect to a rotor centreline100and an axial portion130extending axially with respect to a rotor centreline100. The seal ring10may include a plurality of radial cooling holes110disposed within the radial portion120of the seal ring10. The plurality of radial cooling holes110may be arranged circumferentially around the seal ring10. Each of the plurality of radial cooling holes110route cooling air from the pre-swirler device30to a turbine blade.

A contour of the radially interior surface of the seal ring10may be optimized using computational fluid dynamics such that the pressure loss of the rotor cooling air is reduced and the performance of the rotor cooling air to cool the turbine blades is improved. In the embodiment shown inFIG. 2, the contour of the radially interior surface includes a radially downward inclination. In this embodiment, the contour acts as a nozzle or funnel to collect the air and efficiently point and direct the air to the radial cooling air holes110in the seal ring10and the axial cooling holes60in the turbine disc one20.

A radially exterior surface of the axial portion130may be adapted to accommodate the pre-swirler sealing70. The pre-swirler sealing70may be designed to minimize the leakage of cooling air through the seal70. Additionally, the pre-swirler sealing70keeps the cool air at a higher pressure within the cavity90in order to force the cool air into the turbine blades. In the embodiment shown inFIG. 2, the pre-swirler sealing70includes a plurality of labyrinth seals as well as a brush seal, and a honeycomb seal.

In the embodiment shown inFIG. 3, a partial perspective view of the seal ring10is shown. In this view, only 180 degrees of the seal ring10is shown such that the L-shaped cross section may also be viewed. However, in an embodiment the seal ring10would be constructed as a full 360 degree ring. The advantage of making the seal ring10, 360 degrees would be so that the seal ring10may support itself in the hoop stress direction and therefore have a minimal stress impact on the turbine disc one20. In another embodiment, the seal ring70may be segmented such that ring segments fit together to form a complete 360 degree seal ring70. FromFIG. 3, the circumferential arrangement of the cooling holes110may be seen.

FIG. 4illustrates a close up perspective view of the L-shaped cross section shown in detail A ofFIG. 3. A cross section of a cylindrically-shaped cooling hole110may be seen in the embodiment ofFIG. 4. However, one skilled in the art would understand that cooling holes with different shaped cross sections are also possible. Additionally, in the shown embodiment the axis140of the cooling hole lies perpendicular to the centreline of the rotor100. However, each of the plurality of cooling holes110may be inclined relative to a radial length of the radial portion120of the seal ring10in order to promote a more efficient delivery of rotor cooling air to the turbine blade. As such, the axis140of the cooling hole would be inclined relative to the centreline of the rotor100.FIG. 4also shows an embodiment of the contour of a radially exterior surface of the axial portion130of the seal ring10. The contour may be adapted to accommodate the sealing of the pre-swirler device30.

The seal ring10may comprise the same or similar material as the turbine one disc20. Using the same or similar material for the seal ring10as that of the turbine one disc20would prevent significant differences in the rate of thermal expansion between the two components during operation of the gas turbine. A significant difference in the rate of thermal expansion may cause the misalignment of the radial cooling hole11and the radial cooling hole50of the turbine disc one20such that the amount of the cooling air reaching the turbine1blade would decrease, for example. The seal ring10may thus comprise a low alloy steel which is traditionally used for the turbine disc material.

The seal ring10is configured to abut the turbine disc20such that the cooling passage50of the turbine one disc is aligned with the radial cooling hole110of the seal ring10. The seal ring10may also comprise attachment means to attach the seal ring10to the turbine one disc20. As illustrated inFIG. 4, a hole150may be positioned in the radial portion120of the seal ring10to accommodate a bolt or a sheer pin, for example. The hole150would be positioned such that it would not interfere with any of the plurality of radial cooling holes110. For example, the hole150may be positioned between adjacent radial cooling holes110in the circumferential direction. The attachment means may also include interference fit (shrink fits) or welding the seal ring10to the turbine one disc20. A weld preparation area may include a radially exterior surface of the seal ring10surrounding, but not including, each radial cooling hole110.

Referring toFIGS. 1 and 2, a system to improve a flow of rotor cooling air to a turbine blade is also provided. The system includes a device configured to swirl a rotor cooling air with a rotation of the gas turbine. In an embodiment as shown inFIGS. 1-2, the device is a pre-swirler device30as described above. In a mid-section of a gas turbine1, the pre-swirler device30may physically replace an air separator when retrofitting a gas turbine with the pre-swirler device30. The pre-swirler nozzle40imparts a tangential momentum to the rotor cooling air and expels this swirled cooling air into a cavity90. In an embodiment, the pre-swirler nozzle40may direct the cooling air in a direction of a radial cooling hole110. The pre-swirler nozzle40may direct the cooling air in a direction of an axial cooling hole60. An axial portion130of an L-shaped seal ring device10creates a seal with the pre-swirler device30. A radial portion120of the seal ring device10may abut a turbine disc20. When retrofitting an existing gas turbine with the seal ring10, the turbine disc one20may need a modification in order to accommodate the geometry of the seal ring10. The modification may include machining the turbine disc one20to accommodate the geometry of the seal ring10. The seal ring10may be attached as described above to the turbine disc20.

The seal ring10includes a plurality of radial cooling holes110extending radially through the radial portion120of the seal ring10. These radial cooling holes110may be aligned with radial cooling passages50within the turbine disc one20such that the cooling air F is efficiently routed from the pre-swirler device30to the turbine blade. The turbine disc20may also include an axial cooling passage60which routes cooling air to turbine blades in a flow direction downstream from the turbine disc one20. An example of a cooling air split between the radial cooling passage50and the axial cooling passage60may be 50% through the radial cooling passage50and 48% through the axial cooling passage60with approximately 2% lost through leakage. The turbine blades themselves control the amount of cooling air flow they consume. The more cooling holes110each turbine blade includes, the higher amount of cooling air flow the turbine blade takes in.

Referring toFIGS. 1-4, a method to improve a flow of rotor cooling air F to a turbine blade is also provided. As described above, the pre-swirler device40is described above to swirl the rotor cooling air F to the speed of the rotor and expel this air through a pre-swirler nozzle40into a cavity90. The swirled cooling air is then routed through a seal ring10to the first row turbine blade for its cooling.

In an embodiment, the method includes attaching the seal ring10to a turbine disc one20. The seal ring10may be attached to the turbine disc one20using through bolts, sheer pins, interference fits, or by welding as described above. In an embodiment, a plurality of through holes150may be positioned in a radial portion120of seal ring10through which a bolt or sheer pin may be inserted, for example, and fastened in order to securely attach the seal ring10to the turbine disc one20. In another embodiment, the seal ring10is welded to the turbine disc one20.

The attaching of the seal ring10may include aligning a plurality of radial cooling holes110in the seal ring10with a corresponding cooling passage50in the turbine one disc20such that the flow of cooling air cools the row one turbine blade. An interference fit may be provided between the seal ring10and the turbine disc20by heating up the turbine disc20to center its cooling passage60with the radial cooling hole110of the seal ring10.

In an embodiment, especially when retrofitting an existing gas turbine with a seal ring10, the turbine disc20may need to be machined in order to accommodate the geometry of the seal ring10such that the seal ring10abuts the turbine disc20. The machining would precede the attaching of the seal ring10.