Patent Application
20190203606
The disclosure relates generally to systems and methods for assembling flow path components of turbomachines, and particularly, to systems and methods for sealing the flow path components for example, nozzles in gas turbines.
A turbomachine, such as an industrial, aircraft or marine gas turbine generally includes, in serial flow order, a compressor, a combustor and a turbine. The turbine has multiple stages with each stage including a row of turbine nozzles and an adjacent row of turbine rotor blades disposed downstream from the turbine nozzles. The turbine nozzles are held stationary within the turbine and the turbine rotor blades rotate with a rotor shaft. The various turbine stages define a hot gas path through the turbine.
During operation, the compressor provides compressed air to the combustor. The compressed air is mixed with fuel and burned in a combustion chamber or reaction zone defined within the combustor to produce a high velocity stream of hot gases. The hot gases flow from the combustor into the hot gas path of the turbine via a turbine inlet. As the hot gases flow through each successive stage, kinetic energy from the high velocity hot gases is transferred to the rows of turbine rotor blades, thus causing the rotor shaft to rotate and produce mechanical work.
A first stage of turbine nozzles and turbine rotor blades is positioned closest to the turbine inlet and is thus exposed to the highest hot gas temperatures. The first stage turbine nozzle includes an airfoil that extends in span between an inner band or shroud and an outer band or shroud. The inner band and the outer band define inner and outer flow boundaries of the hot gas path and are exposed to the hot gases. While assembling adjacent turbine nozzles, the resulting assembly may include small gaps between the shrouds of adjacent turbine nozzles, which could provide an undesirable fluid leak path. This has been a challenge sealing potential leak paths between adjacent turbine nozzles and doing so in a way that makes the assembly efficient and reliable.
One aspect of the disclosure provides an assembly of a turbomachine. The assembly includes a plurality of flow path components disposed adjacent to one another, each flow path component of the plurality of flow path components having a forward surface, an aft surface, a pressure side surface, and a suction side surface and a seal channel defined by the pressure side surface of a first flow path component of the plurality of flow path components and the suction side surface of a second flow path component of the plurality of flow path components and extending from the forward surfaces to the aft surfaces of the first and second flow path components, where the seal channel has an open forward end proximate to the forward surfaces and at least two rear ends proximate to the aft surfaces of the first and second flow path components and a plurality of seal layers disposed within the seal channel such that one or more seal layers of the plurality of seal layers extend from the open forward end to a rear end of the at least two rear ends and one or more other seal layers of the plurality of seal layers extend from the open forward end to another rear end of the at least two rear ends.
In one aspect of the disclosure, a method for assembling adjacent flow path components to form an assembly of a turbomachine is provided. The method includes the step of disposing a plurality of flow path components adjacent to each other, each flow path component of the plurality of flow path components having a forward surface, an aft surface, a pressure side surface, and a suction side surface such that a seal channel is defined by the pressure side surface of a first flow path component of the plurality of flow path components and the suction side surface of a second flow path component of the plurality of flow path components, which extends from the forward surfaces to the aft surfaces of the first and second flow path components and the seal channel has an open forward end proximate to the forward surfaces and at least two rear ends proximate to the aft surfaces of the first and second flow path components, inserting one or more seal layers into the seal channel through the open forward end to dispose the one or more seal layers extending from the open forward end to a rear end of the at least two rear ends and inserting a one or more other seal layers into the seal channel through the open forward end to dispose the one or more other seal layers extending from the open forward end to another rear end of the at least two rear ends.
These and other features, embodiments, and advantages of the present disclosure may be understood more readily by reference to the following detailed description.
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
It is noted that the drawings of the disclosure are not to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure.
Embodiments provided herein are directed to systems and methods for sealing adjacent flow path components to form an assembly for a turbomachine. The systems for sealing such as seal layers and methods of sealing, as described herein, advantageously provide improved ease and efficiency for installing the seal layers between flow path components and assembling an assembly, and desirable mechanical properties such as creep resistance, shear/torsional strength and thermal shock resistance at high temperatures in turbomachines. As discussed in detail below, some embodiments relate to an assembly such as a stator assembly of a gas turbine that includes a plurality of flow path components such as turbine nozzles disposed adjacent to one another.
Although exemplary embodiments of the present invention will be described generally in the context of a stator assembly for a land based power generating gas turbine for purposes of illustration, one of ordinary skill in the art will readily appreciate that embodiments of the present invention may be applied to any style or type of gas turbine and are not limited to land based power generating gas turbines unless specifically recited in the claims.
In the following specification and the claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. As used herein, the term “or” is not meant to be exclusive and refers to at least one of the referenced components being present and includes instances in which a combination of the referenced components may be present, unless the context clearly dictates otherwise.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially”, is not limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value.
Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this disclosure belongs. The terms “comprising,” “including,” and “having” are intended to be inclusive, and mean that there may be additional elements other than the listed elements. The terms “first”, “second”, and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. The term “radially” refers to the relative direction that is substantially perpendicular to an axial centerline of a particular component, and the term “axially” refers to the relative direction that is substantially parallel and/or coaxially aligned to an axial centerline of a particular component.
In some embodiments, an assembly of a gas turbine including a plurality of flow path components disposed adjacent to one another and a method of sealing adjacent flow path components for forming the assembly are described with reference to
Referring now to the drawings,
Each turbine stage (30, 31, 32) includes a corresponding stator assembly and a corresponding rotor assembly axially spaced along the axis 28 (
In operation, as shown in
As shown in
Each inner band 200 includes a gas-side surface 202 and a back-side surface 204 that is oriented radially inwardly from the gas-side surface 202. Each outer band 300 includes a gas-side surface 302 and a back-side surface 304 that is oriented radially outwardly from the gas-side surface 302. As shown in
The outer band 300 has a length measured in the general direction of the flow path 25 from the forward most feature of the forward surface 312 to the aft most feature of the aft surface 314. Note that this body length includes projecting surface features that may not be considered integral to the outer band 300. The body length may be defined as the distance from the forward most portion of a theoretically planar forward surface (extending from the forward edge of the back-side surface 304 to the forward edge of the gas-side surface 302) to the aft most portion of a theoretically planar aft surface (extending from the aft edge of the back-side surface 304 to the aft edge of the gas-side surface 302) on a line parallel with the axis 28. The outer band 300 has a body height substantially perpendicular to the body length. The body height can be measured from the back-side surface 304 to the gas-side surface 302 of the outer band 300.
The outer band 300 in
As illustrated in
As shown in illustrated embodiment, the seal channel 320 extends substantially along both the body length and the body height of the outer band 300. In this context, extending substantially along means that the seal channel 320 traverses the majority of the body length and the majority of the body height. In one embodiment, the seal channel 320 extends along at least 85% of the body length and at least 85% of the body height.
Referring to
In some embodiments, as illustrated, the rear portion 340 splits into two rear sections: a first rear section 344 extending from the lateral portion 336 to the first rear end 324 and a second rear section 346 extending from the lateral portion 336 to the second rear end 326. The first and second rear sections (344, 346) may terminate at blind ends or include open ends. As illustrated, the first rear section 344 extends in continuation with the lateral portion 336 substantially parallel to the lateral portion 336. That is, the first rear section 344 extends substantially along the body length. The second rear section 346 extends in continuation with the lateral portion 336 and diverges with the first rear section 344. The first rear section 344 and the second rear section 346 diverge at an angle of at least 1 degree. In some embodiments, the angle of divergence is in a range from about 3 degrees to about 90 degrees. In some embodiments, the angle of divergence is in a range from about 10 degrees to about 70 degrees. In some embodiments, the second rear section 346 may be curved for example, as shown in
In some embodiments, the seal channel 320 defined between the outer band 300 and an adjacent outer band may have a uniform thickness throughout its length. The thickness of the seal channel 320 can be defined as a width of the recess, and is shown as ‘d’ in
As alluded previously, the plurality of seal layers 350 can be inserted through the open forward end 322, travel through the vertical portion 332, the connecting portion 334, and the lateral portion 336, and guided to the first rear section 344 and the second rear section 346 to be terminated at the corresponding first and second rear ends 324 and 326.
In
A seal layer of the plurality of seal layer 350 may be a shim or laminated spline. For example, each seal layer may include a thin rectangular body for example, a strip, sheet or foil of a material, such as an alloy with a desired width, length, and thickness. Suitable materials for the plurality of seal layers 350 may be selected based upon their elastic properties, temperature tolerance, and other physical characteristics compatible with the environment in the flow path 25 of the turbomachine. Some examples of suitable materials include, but are not limited to, cobalt-based alloys such as Haynes® 188 alloy or Haynes® 25 alloy.
Individual seal layers of the plurality of seal layers 350 may be same or different in their thicknesses, lengths, materials, or may incorporate same or different desired characteristics such as elastic properties, flexibility, yield strength, oxidation resistance, or sealing characteristics to facilitate lamination, insertion, and retention. The elastic properties of a seal layer may depend; in part, on the material and the thickness of the seal layer. In some embodiments, individual seal layers of the plurality of seal layers 350 include same or different materials. In some embodiments, individual seal layers of the plurality of seal layers 350 have same or different thicknesses. Each seal layer of the plurality of seal layers 350 may have a thickness in a range from about 0.1 millimeter to about 1 millimeter, for example, depending on desired elastic properties of the individual seal layers. In some embodiments, each seal layer has a thickness in a range from about 0.2 millimeter to about 0.6 millimeter. In some embodiments, the one or more seal layers 352 has a thickness greater than a thickness of the one or more other seal layers 354. In some embodiments, the thickness of a seal layer of the plurality of seal layer 350 may vary along its length.
In some embodiments, the plurality of seal layers 350 may be flexible enough to follow a curved path of the seal channel 320 as shown in
Moreover, it may also be desirable that the one or more seal layers 352 have different oxidation resistance than that of the one or more other seal layers 354 depending on their locations in the gas turbine. The oxidation resistance of a seal layer may depend, in part, on the material of the seal layer. In some embodiments, the one or more seal layers 352 have higher oxidation resistance than that of the one or more other seal layers 354.
The numbers of the seal layers in the first rear section 344 and the second rear section 346 may depend on various parameters such as the thicknesses of seal layers, the flexibilities of seal layers, the thickness of the first rear section 344 and the second rear section 346, and the thickness of the forward portion 330 etc. In some embodiments, the total thickness of the plurality of seal layers 350 (the portions of the plurality of seal layers 350 that are disposed in forward portion 330) matches with the thickness of the forward portion 330. In some embodiments, the total thickness of the one or more seal layers 352 (the portions of the one or more seal layers 352 that are disposed in the first rear section 344) matches with the thickness of the first rear section 344. In some embodiments, the total thickness of the one or more other seal layers 354 (the portions of the one or more other seal layers 354 that are disposed in the second rear section 346) matches with the thickness of the second rear section 346.
In some embodiments, a seal layer of the one or more seal layers 352 has a discontinuity at a position such that the discontinuity is located in the lateral portion 336 of the seal channel 320 when installed in the seal channel 320. As used herein, the term “discontinuity” refers to an interruption in the normal physical structure or configuration of a seal layer. The discontinuity may include a change in surface structure of the seal layer. For example, the discontinuity may be a gap, a cut, a bump, or an external feature add to the surface of the seal layer. For example, a seal layer 352 having a bump 355 on a surface 351 of the seal layer 352 is shown in
The one or more seal layers 352 and the one or more other seal layers 354 may be connected to one another for retention. In some embodiments, the plurality of seal layers 350 may be connected at their front ends that are located near the open forward end 322 of the seal channel 320. The plurality of seal layers 350 may be connected for example, by welding prior to or after insertion of the plurality of seal layers 350 in the seal channel 320. For example, the front ends of the plurality of seal layer 350 may be connected after insertion. Other shapes, configurations, attachment between the seal layers, number of seal layers, and shaping of one or both ends of the seal layers may also be desirable for specific embodiments and retention of the plurality of seal layer.
The step 520 includes a sub-step 530 of inserting one or more seal layers 352 of the plurality of seal layers 350 into the seal channel 320 through the open forward end 322 to dispose the one or more seal layers 352 extending from the open forward end 322 to the first rear end 324. The step 520 further includes another sub-step 540 of inserting one or more other seal layers 354 of the plurality of seal layers 350 into the seal channel 320 through the open forward end 322 to dispose the one or more other seal layers 354 extending from the open forward end 322 to the second rear end 326.
In some embodiments, the step 520 of disposing includes subsequently inserting the one or more seal layers 352 and the one or more other seal layers 354. In some embodiments, the sub-step 530 of inserting the one or more seal layers 352 is performed prior to the sub-step 540 of inserting the one or more other seal layers 354. In some embodiments, each seal layer the plurality of seal layers 350 may be inserted one by one. For example, the method 500 first includes inserting a seal layer of the plurality of seal layers 350 through the open forward end 322, moving through the forward portion 330, moving through the first rear section 344 until the inserted end of the seal layer reaches the first rear end 324 of the seal channel 320. The method 500 may include repeating this step of inserting a seal layer at least one more time depending on the desirable number of seal layers inserted in the first rear section 344. Continuing this example, after the seal layer or layers 352 are inserted into the first rear end 344, a seal layer 354 is then inserted through the open forward end 322 that moves through the forward portion 330, moves through the second rear section 346 until the inserted end of the seal layer 354 reaches the second rear end 326 of the seal channel 320. In some embodiments, in this step, the seal layer 354 may be guided into the second rear section 346 (after travelling the forward portion 330) by using a discontinuity in the previously inserted seal layer 352 into the first rear section 344. The discontinuity in the previously inserted seal layer 352 may guide a subsequent seal layer (i.e., the seal layer 354) to move into the second rear section 346 (as shown in
The plurality of seal layers 350 substantially seals the potential leak path between two adjacent outer bands. Being substantially sealed reduces the total potential leak path between the outer bands by at least 85% compared to the leak path between outer bands without the seal. A substantially complete outer band seal reduces the leak path between the outer bands of adjacent turbine nozzles by at least 99%. In some embodiments, the method may further include connecting the plurality of seal layers at their front ends (that are located at the open forward end 322) after insertion of the plurality of seal layers 350. This may help in securely retaining the plurality of seal layers 350 in place during operation of the gas turbine in which they are installed. A similar process could be achieved between the inner bands of the turbine nozzles and other flow path components that are installed in segments and leave a seam in need of sealing.
In conventional sealing arrangements, several rigid seals such as rigid seal sheets are joined end to end to be installed along a curved seal channel between the outer bands of turbine nozzles when a plurality of turbine nozzles are assembled circumferentially adjacent to one another in a stator assembly. There are several disadvantages in using these straight seals including complex assembly process and chances of disengagement of several joints at different time during the operation. In addition, these rigid seals cannot be removed easily without disassembling the stator assembly and there is risk of falling out a small seal such as a discourager seal. In contrast to those conventional arrangements, embodiments of the present disclosure provide simple and improved installation of flexible seals between the flow path components of a turbomachine. The adjacent flow path components are designed to define an opening at an open forward end of the seal channel between them for receiving and removing the flexible seal layers. This provides ease of installing and removing the seal layers from a curved seal channel without disassembling the stator assembly. The use of flexible seal layers advantageously reduces (i) the number of rigid seals (i.e. number of pieces) inserted in the seal channel along the seal length and (ii) reduces the chances of missing a leak path between the flow path components such as outer bands while manufacturing. In addition, a distance between the flow path of a turbomachine and a bottom side of a seal channel of a flow path component can be reduced by having the seal channel curved. The use of flexible seal layer(s) enables sealing of curved seal channels and thus allows to have curved seal channels in the flow path components such as the inner and outer bands of turbine nozzles. A reduction in the distance between the flow path and the bottom side of a seal channel of a flow path component allows to minimize purge air requirement to cool it.
The foregoing drawings show some of the operational processing associated according to several embodiments of this disclosure. It should be noted that in some alternative implementations, the acts described may occur out of the order described or may in fact be executed substantially concurrently or in the reverse order, depending upon the act involved.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
