The subject matter disclosed herein relates to turbomachines and, more particularly, to turbomachines having clearance control capability.
A typical turbomachine, such as a gas turbine engine, a steam turbine engine and a compressor, includes a compressor section, a combustor section and a turbine section. The compressor section compresses inlet air and transmits the compressed inlet air to the combustor section. The combustor section combusts the compressed inlet air along with fuel to produce high energy fluids, which are transferred to the turbine section where they are expanded in power generation operations. During these power generation operations, the high energy fluids aerodynamically interact with successive stages of turbine blades, which are encompassed within a turbine casing with clearances provided between the casing and the tips of the blades.
At each stage, the high energy fluids impinge upon the turbine blades and induce rotation of the turbine blades about a rotor. Since the high energy fluids have high temperatures and pressures, the turbine blades and the casing often undergo thermal deformation (i.e., expansion or contraction) based on a type of turbine operation being conducted. Such deformation can be accounted for by setting the clearances in accordance with worst case scenarios. Under normal operating conditions, however, clearances set in accordance with worst case scenarios may be excessive and could lead to degraded performance due to leakages between the casing and the tips of the blades.
According to one aspect of the invention, a turbomachine having clearance control capability is provided and includes a turbine stage including a blade configured to rotate around a centerline, a movable portion of a casing circumferentially surrounding the turbine stage and a rotatable cam operably coupled to the movable portion and thereby configured to control an axial position of the movable portion. A radially outermost tip of the blade and an interior surface of the movable portion are sloped with respect to the centerline such that the controlled axial position of the movable portion is determinative of a clearance between the blade and the movable portion.
According to another aspect of the invention, a turbomachine having clearance control capability is provided and includes a turbine stage including a blade configured to rotate around a centerline, a casing circumferentially surrounding the turbine stage and including forward, aft and movable portions, the movable portion being axially interposed and secured between the forward and aft portions and defining a cam seat in a radially exterior surface thereof and a rotatable cam received within and operably coupled to the cam seat of the movable portion, the rotatable cam being thereby configured to control an axial position of the movable portion in accordance with rotation thereof. A radially outermost tip of the blade and an interior surface of the movable portion are sloped with respect to the centerline such that the controlled axial position of the movable portion is determinative of a clearance between the blade and the movable portion.
According to yet another aspect of the invention, a system providing a turbomachine with clearance control capability is provided and includes at least one or more turbine stages, each of the at least one or more turbine stages including a blade configured to rotate around a centerline, a movable portion of a casing circumferentially surrounding the at least one or more turbine stages, a rotatable cam operably coupled to the movable portion and thereby configured to control an axial position of the movable portion and a controller. A radially outermost tip of the blade of each of the at least one or more turbine stages and an interior surface of the movable portion are sloped with respect to the centerline such that the controlled axial position of the movable portion is determinative of a clearance between the blade of each of the at least one or more turbine stages and the movable portion. The controller is operably coupled to the rotatable cam and thereby configured to control operations of the rotatable cam.
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.
With reference to
As the turbine stage 20 may be unshrouded, the casing 40 is provided to circumferentially surround the turbine stage 20 and, in some cases, additional stages as shown in
The first annular flange 45 extends in a forward axial direction from the annular central body 44 and is movably receivable within the aft facing recess 410. The second annular flange 46 extends in an aft axial direction from the annular central body 44 and is movably receivable in the forward facing recess 420. As the annular movable portion 43 moves axially forwardly, the first annular flange 45 penetrates relatively deeply into the aft facing recess 410 while the second annular flange 46 recedes from but does not exit the forward facing recess 420. By contrast, as the annular movable portion 43 moves axially aft, the first annular flange 45 recedes from but does not exit the aft facing recess 410 while the second annular flange 46 penetrates relatively deeply into the forward facing recess 420.
Anti-rotation features, such as annularly discrete tabs 49 may be disposed on the movable portion 43 at, for example, either or both of the first annular flange 45 and the second annular flange 46. Such annularly discrete tabs 49 are receivable in secondary recesses 430 defined in the annular forward portion 41 and the annular aft portion 42. As described above, as the annular movable portion 43 moves axially forward or aft, the annularly discrete tabs 49 penetrate relatively deeply into and recede from the secondary recesses 430. While receding, the annularly discrete tabs 49 do not exit the secondary recesses 430.
The sloped interior facing surface 47 of the annular movable portion 43 is disposable radially outwardly from the sloped tip 23 of the blade 21 at a distance that is defined by the controlled clearance between the blade 21 and the annular movable portion 43. The sloped tip 23 and the sloped interior facing surface 47 may be provided substantially in parallel with one another and slope away from the centerline 22 with increasing distance in the aft axial direction, D. The sloped tip 23 provides for improved boundary layer conditions downstream from the turbine stage 20 and thereby allows for relatively aggressive exhaust diffuser performance.
The rotatable cam 60 is operably coupled to the annular movable portion 43 and is thereby configured to control an axial position of the annular movable portion 43. With the sloped tip 23 and the sloped interior facing surface 47 being mutually sloped with respect to the centerline 22, the controlled axial position of the annular movable portion 43 is determinative of a controlled amount of clearance between the blade 21 and the annular movable portion 43 or, more specifically, between the sloped tip 23 and the sloped interior facing surface 47. This control allows for improved efficiency and output for the turbine stage 20 in the unshrouded condition and could be similarly applicable and useful for shrouded turbine stages as well.
The rotatable cam 60 includes a drive shaft 61, which may be operably coupled to the controller 80 to be described in greater detail below, and a head portion 62. The head portion 62 may be generally circular, for example, and may be coupled in an off-center condition to the drive shaft 61. As the drive shaft 61 rotates about longitudinal axis 610, the head portion 62 bobs back and forth on either side of the drive shaft 61.
The radially exterior surface 48 of the annular movable portion 43 is formed to define a cam seat 90. The cam seat 90 is receptive of the head portion 62 of the rotatable cam 60 such that the drive shaft 61 appears to extend, for example, radially outwardly from the annular movable portion 43. The cam seat 90 is configured to mechanically interfere with the head portion 62 such that, as the rotatable cam 60 rotates in first or second opposite directions about the longitudinal axis 610, the annular movable portion 43 correspondingly moves in first or second opposite axial directions, respectively. To this end, in accordance with embodiments, the cam seat 90 may include a recess 91 formed in the radially exterior surface 48, which is bounded on forward and aft sides by a pair of substantially parallel circumferential wall surfaces 92.
The head portion 62 sits tightly within the recess 91 such that its sidewalls abut each of the wall surfaces 92 in opposite directions. As the rotatable cam 60 rotates about the longitudinal axis 610, the forward and aft sides of the head portion 62 impinge upon the wall surfaces 92 and, therefore, force the annular movable portion 43 to movably reciprocate in forward and aft directions.
Although the head portion 62 and the cam seat 90 are described above as being a generally circular element and as a recess 91 that is bounded by wall surfaces 92, it is to be understood that this is merely exemplary and that other embodiments exist. For example, where the head portion 62 is generally circular, the cam seat 90 may also be provided as a circular or polygonal recess defined within the radially exterior surface 48.
The controller 80 is provided as a component of a system for providing the turbomachine 10 with clearance control capability. The controller 80 is operably coupled to the rotatable cam 60 and is configured to control operations of the rotatable cam 60. That is, the controller 80 could cause the rotatable cam 60 to rotate about the longitudinal axis 610 such that, at various operational conditions such as start-up conditions, turn-down conditions, transient conditions and base-load condition, the controlled amount of clearance between the blade 21 and the annular movable portion 43 has various predefined and/or appropriate values. In addition, the controller 80 may be further configured to sense or otherwise measure current clearance amounts and, if such current clearance amounts are excessive or decreased given current operational conditions, to correct the current clearance amounts by selectively operating the rotatable cam 60 accordingly.
In accordance with embodiments, the features described above could be provided as single components or as multiple components. In the latter case, multiple rotatable cams 60 may each be operably coupled to the controller 80 and disposed circumferentially about the centerline 22. With such a configuration, each rotatable cam 60 may be jointly or separately operable based on current conditions.
With reference to
With reference to
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.