阅读说明：本技术 具有可旋转定子叶片的蒸汽涡轮 (Steam turbine with rotatable stator blades ) 是由 L·科西 E·吉斯蒂 A·帕吉尼 D·切卡奇 F·布西亚雷利 M·加利亚诺 M·菲奥里 于 2020-04-03 设计创作，主要内容包括：蒸汽涡轮(200)具有多个膨胀级(261、262、271)以及在膨胀级(261、262、271)中的至少一个膨胀级上游的定子叶片(221、222、231)；为了调节蒸汽涡轮(200)内部的蒸汽流并使涡轮效率最大化,在蒸汽涡轮(200)的操作期间,定子叶片(221、222、231)的角位置例如由外部控制单元通过例如命令杆(289、299)来控制。(The steam turbine (200) has a plurality of expansion stages (261, 262, 271) and stator blades (221, 222, 231) upstream of at least one of the expansion stages (261, 262, 271); in order to regulate the steam flow inside the steam turbine (200) and maximize the turbine efficiency, during operation of the steam turbine (200), the angular position of the stator blades (221, 222, 231) is controlled, for example, by an external control unit through, for example, command levers (289, 299).)

1. A steam turbine (200) having a plurality of expansion stages, the steam turbine (200) comprising:

an inner casing (220) housing at least the at least one expansion stage (261, 262),

an outer housing (210) surrounding the inner housing (220),

-a row of stator blades (221, 222) upstream of said at least one expansion stage (261, 262, 263), said row of stator blades (221, 222) having an angular position controllable during operation of said steam turbine (200), and

an actuation assembly (280) arranged to rotate the stator vanes (221, 222) of the row, the actuation assembly (280, 290) comprising an actuation mechanism (281), a plurality of transmissions (285, 286), and a command lever (289),

wherein the command lever (289) is arranged to command the actuation mechanism (281), wherein the transmission (285, 286) is arranged to transfer a rotational motion from the actuation mechanism (281) to the row of the stator vanes (221, 222),

wherein the actuation mechanism (281) is positioned between the outer housing (210) and the inner housing (220).

2. The steam turbine (200) of claim 1, wherein the row of stator blades (221) is positioned upstream of all expansion stages (261) of the steam turbine (200).

3. The steam turbine (200) of claim 1 or 2, comprising a rotor arranged to rotate about a turbine axis (R), wherein the actuation mechanism (281) comprises a ring (310) extending about the turbine axis (R), the ring (310) being rotatable about the turbine axis (R).

4. The steam turbine (200) of claim 1 or 2 or 3,

wherein the plurality of transmissions (285) comprise a plurality of actuation levers (320),

wherein each of the stator blades (340) has a spanwise direction, and wherein each actuation rod (320) is rigidly coupled to a respective stator blade (340) and extends parallel to the spanwise direction.

5. The steam turbine (200) of claim 4, wherein the plurality of transmissions (285) comprise a plurality of arms (330), wherein each arm (330) has a first end and a second end, wherein each arm (330) is rigidly coupled to a respective actuation lever (320) at the first end (330) and extends transverse to a spanwise dimension of the actuation lever (320), wherein each arm (330) is hinged to the actuation mechanism (281) at the second end.

6. The steam turbine (200) of claim 4,

wherein the plurality of transmissions (285) comprise a plurality of arms (330), wherein each arm (330) has a first end and a second end, wherein each arm (330) is rigidly coupled to a respective actuation rod (320) at the first end and extends transverse to a spanwise dimension of the actuation rod (320),

and wherein the plurality of transmissions (285) comprises a plurality of connecting rods (325), wherein each connecting rod (325) has a first end and a second end, wherein the first end of each connecting rod (325) is hinged to the second end of the respective arm (330) and the second end of each connecting rod (325) is hinged to the actuation mechanism (281).

7. The steam turbine (200) of claim 4,

wherein the plurality of transmissions (285) comprise a plurality of transmission members, wherein each transmission member (335) is rigidly coupled to a respective actuating lever (320) and has a first arcuate surface centered in the spanwise direction,

and wherein the actuation mechanism (281) has a plurality of second arcuate surfaces, each complementary to and abutting a respective first arcuate surface.

8. The steam turbine (200) of any of claims 4 to 7,

wherein each of the plurality of actuating rods (320) has an axial rod bore (323) whereby a first rod end (321) and a second rod end (322) are fluidly connected, wherein each stator vane of the row of the stator vanes (340) has a vane bore (343) whereby a first vane end (341) and a second vane end (342) are fluidly connected, and

wherein the rod aperture (323) is fluidly connected with the blade aperture (343).

9. The steam turbine (200) of any of claims 1 to 8, wherein the plurality of transmissions (285) comprise a plurality of actuating levers (320), and wherein the inner housing (220) has a plurality of holes (225) that receive the plurality of actuating levers (320).

10. The steam turbine (200) of any of claims 1 to 9, wherein the outer casing (210) has a through-hole partially accommodating the command lever (289), and wherein the command lever (289) preferably comprises one or more articulated joints.

11. A steam turbine (200) having a plurality of expansion stages, the steam turbine (200) comprising:

an inner casing (230) housing at least the at least one expansion stage (271, 272, 273),

an outer housing (210) surrounding the inner housing (220),

-a row of stator vanes (231) upstream of the at least one expansion stage (271, 272, 273), the stator vanes (231) of the row having an angular position controllable during operation of the steam turbine (200), and

-an actuation assembly (290) arranged to rotate the row of stator vanes (231), the actuation assembly (290) comprising an actuation mechanism (291), a plurality of transmissions (295) and a command lever (299),

wherein the command lever (299) is arranged to command the actuation mechanism (291), wherein the transmission (295) is arranged to transfer a rotational movement from the actuation mechanism (291) to the row of stator blades (231),

wherein the actuation mechanism (291) is positioned inside the inner housing (230).

12. The steam turbine (200) of claim 11, wherein each of the rows of the stator blades (640) is hinged to the inner casing and has teeth (645) for rotation.

13. The steam turbine according to claim 11 or 12,

wherein the inner housing (230) has a through hole partially accommodating the command rod (299),

wherein the outer case (210) has a through hole partially accommodating the command lever (299), and

wherein the command lever (299) preferably comprises one or more articulated joints.

14. A method of regulating steam flow in a steam turbine (200), comprising the steps of:

-changing at least one row of stator blades (221, 222, b) during operation of the steam turbine,

231) The angular position of (a);

wherein the angular position of the stator vanes (221, 222, 231) is changed by:

-turning (720) a command lever (289, 299) protruding from an outer casing (210) of the steam turbine (200),

-transferring (730) a rotational movement from the command lever (289, 299) to an actuating rotatable ring, the actuating rotatable ring (310, 610) being positioned inside an outer casing (210) of the steam turbine (200), and

-transferring (740) a rotational movement from the actuating rotatable ring (310, 610) to the stator vanes (221, 222, 231).

15. The method of claim 14, wherein the actuating rotatable ring (310) is positioned between an outer casing (210) of the steam turbine (200) and an inner casing (220) of the steam turbine (200) or inside an inner casing (230) of the steam turbine (200).

Technical Field

The subject matter disclosed herein relates to steam turbines, and in particular, to mechanically driven turbines and power generating turbines that require control of steam flow and/or power output.

Background

Steam turbines are turbines with over a hundred year industrial application, with proven design solutions adopted by all manufacturers since decades.

Steam turbine flow and power control are key requirements for mechanically driving a steam turbine (i.e., a steam turbine used to drive a compressor or pump).

Additionally, power generating steam turbines are often required to control the load.

Steam turbine flow and power control is typically achieved by placing a throttle valve upstream of the turbine or in a "partial arc control stage" within the turbine itself.

These devices achieve control by limiting the amount and/or pressure of steam in the turbine. However, these solutions may determine significant voltage drops that result in undesirable energy dissipation.

In view of the increasing demand for efficiency in both design and non-design conditions in industrial steam turbines, it is desirable to find alternative solutions to control the flow and/or power of steam turbines that reduce energy dissipation.

Steam turbines are known in which the angular position of some of the stator vanes is varied in order to control their operation.

If the above-described solution is used in a high-pressure steam turbine, a large leakage of steam occurs through openings in its casing, which is necessary for commanding the stator blades.

Disclosure of Invention

According to one aspect, the subject matter disclosed herein relates to a steam turbine having a plurality of expansion stages; the steam turbine has a row of stator blades upstream of at least one of the expansion stages; the row of stator blades has an angular position that is controlled by an actuation assembly during steam turbine operation. The actuation assembly includes a command lever, an actuation mechanism mechanically coupled to the command lever, and a plurality of transmissions mechanically coupled to the actuation mechanism and the stator vanes. Stator blades inside an inner casing of a steam turbine may be rotated by acting on a command lever at least partially outside the outer casing of the steam turbine.

According to another aspect, the subject matter disclosed herein relates to a method of controlling steam flow and power output of a steam turbine; the method includes the step of changing an angular position of at least one row of stator blades during operation of the steam turbine by a command lever protruding from an outer casing of the steam turbine. A rotatable ring inside the outer casing of the steam turbine is used to transfer motion from the command lever to the stator blades.

Drawings

A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 illustrates a schematic longitudinal cross-sectional view of a known steam turbine;

FIG. 2 illustrates a partial schematic longitudinal cross-sectional view of an embodiment of a steam turbine;

FIG. 3 illustrates a partial schematic front cross-sectional view of a first embodiment of an actuation assembly in the turbine of FIG. 2;

FIG. 4 shows a partial schematic longitudinal cross-sectional view of a first possible implementation of the actuation assembly of FIG. 3;

FIG. 5 illustrates a partial schematic top view of a first possible implementation of the actuation assembly of FIG. 3;

FIG. 6 shows a partial schematic longitudinal cross-sectional view of a second possible implementation of the actuation assembly of FIG. 3;

FIG. 7 illustrates a partial schematic top view of a second possible implementation of the actuation assembly of FIG. 3;

FIG. 8 illustrates a partial schematic top view of a third possible implementation of the actuation assembly of FIG. 3;

FIG. 9 shows a partial schematic longitudinal cross-sectional view of a fourth possible implementation of the actuation assembly of FIG. 3;

FIG. 10 illustrates a partial schematic front cross-sectional view of a command lever in the turbine of FIG. 2; and is

FIG. 11 illustrates a flow diagram of an embodiment of a method of regulating steam flow in a steam turbine.

Detailed Description

Steam turbines for mechanical drive or power generation purposes are required to control mass flow and/or power output for a given steam pressure ratio and inlet conditions (pressure and temperature).

Control of mass flow and power is typically achieved using a throttle or partial arc control stage solution which utilizes their function to vary the pressure ahead of the turbine axial stage and ultimately across the turbine stage. These methods, although widely used in the steam turbine industry, are characterized by low isentropic efficiency outside of their design conditions, since throttling (which is applied in both methods) is a pure mechanical energy dissipation, and partial arc stages are characterized by high aerodynamic losses due to inherent flow non-uniformities and wind effects.

The applicant has conceived a different solution in which the control of the mass flow is achieved by varying the angular position of at least the first row of stator vanes.

Changing the angular position of the stator blades in the rows of the axial stages of the steam turbine allows the operating curve (flow rate versus pressure) of the stages to be modified. In particular, the operating curve changes due to changes in the throat region between the rotatable stator vanes.

This solution achieves a much higher efficiency outside the design operating conditions of the turbine, since it avoids the energy dissipation associated with the use of throttling or partial arcs. In particular, the efficiency of the steam turbine remains close to the design level even outside of the design operating conditions.

In more detail, the applicant has thought of varying the angular position of the stator blades during the operation of the steam turbine by means of a control unit external to the turbine.

It may be advantageous to control one or more of the other rows of stator vanes according to the desired flow variation and efficiency level.

In view of the specific architecture of steam turbines, in particular those used for mechanical driving or power generation applications, the applicant has envisaged a specific and advantageous solution for actuating the stator blades.

Reference now will be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit thereof. Reference throughout this specification to "one embodiment" or "an embodiment" or "some embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" or "in some embodiments" in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

When introducing elements of various embodiments, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

Referring now to the drawings, FIG. 1 is a view of a known steam turbine 100, and FIG. 2 is a (partial) view of an embodiment of a new steam turbine 200 retrofitted from the turbine of FIG. 1; components of the steam turbine 200 and corresponding components of the turbine 100 are identified by reference numerals that differ by one hundred.

The steam turbine 200 of FIG. 2 differs substantially from the steam turbine 100 of FIG. 1 in that the blades of at least one row of blades, and in particular the blades of three rows of blades (i.e., blades 221, 222, and 231), may move during operation of the steam turbine; in particular, the angular position about the axis of the blades may vary during operation of the steam turbine; the axis is radially oriented. Specifically, the high-pressure section of the steam turbine 200 includes at least a first rotor blade stage 260, a first inner casing section 220, blades 221, 261, 222, 262. The low pressure section of the steam turbine 200 includes at least a second rotor blade stage 270, a second inner casing section 230, blades 231 and blades 271.

Typically, all of the blades of a row are movable; however, it is not excluded that only some of the blades of a row may be movable according to some embodiments.

It should be understood that fig. 2 and its relationship to fig. 1 should not be construed as limiting. Many other embodiments are possible, for example with a different number of blade rows and/or a different number of turbine sections.

In fig. 2, the possibilities of movement and the means to allow such possibilities of movement are conceptually illustrated.

In the embodiment of fig. 2, there is a first actuation assembly 280 (see also fig. 3) arranged to rotate the stator vanes 221 and 222, and a second actuation assembly 290 (see also fig. 6) arranged to rotate the stator vanes 231. The first actuation assembly comprises an actuation mechanism and two plurality of actuators and is commanded by a command lever; the actuation mechanism is conceptually illustrated by the dotted circle 281; the first plurality of gears (for the vanes 221) is conceptually illustrated by arrows 285; the second plurality of actuators (for the blades 222) is conceptually illustrated by arrows 286; a command lever operably coupled with the actuation mechanism is conceptually illustrated by the strap 289. The second actuating assembly comprises an actuating mechanism and a plurality of transmissions and is commanded by a command lever; the actuation mechanism is conceptually illustrated by the dotted circle 291; the gearing (for the vanes 231) is conceptually illustrated by arrow 295; a command lever operably coupled with an actuation mechanism is conceptually illustrated by the strap 299.

According to the embodiment of fig. 2, there is at least one row of stator vanes immediately upstream of at least one expansion stage; this applies, for example, to the blades 221 relative to the rotor blades 261, the stator blades 222 relative to the rotor blades 261 and the blades 231 relative to the rotor blades 271. These blades are position controlled blades, in particular, having an angular position that is controllable during operation of the steam turbine.

Preferably, as in the embodiment of FIG. 2, there is a row of position controlled blades just upstream of the first expansion stage of the steam turbine, i.e., blades 261 of turbine 200. The blades 261 belong to a first expansion stage of the steam turbine, which is also the first expansion stage of the high-pressure section of the steam turbine. In the embodiment of FIG. 2, there is also a row of position controlled blades just upstream of the first expansion stage of the low pressure section of the steam turbine, i.e., blades 271 of turbine 200.

In addition to a row of position-controlled blades just upstream of the first expansion stage of the steam turbine, there may advantageously be other rows of position-controlled blades. For example, in the embodiment of FIG. 2, there is a row of position-controlled blades just upstream of the second expansion stage of the steam turbine, i.e., blades 262 of turbine 200.

As already contemplated, the embodiment of fig. 2 includes two actuation assemblies; however, alternative embodiments may include only one actuation assembly or more than two actuation assemblies. Considering fig. 2, according to some preferred embodiments, there is only a first actuation assembly, i.e. an actuation assembly designed to move a first row of stator blades (221 in fig. 2) and possibly one or more subsequent rows of stator blades (222 in fig. 2).

The steam turbine 200 includes an inner casing section 220 housing expansion stages (i.e., blades 261, 262, 263) and an outer casing 210 surrounding the inner casing section 220; it should be noted that the inner casing section 220 is an inner casing. Furthermore, it comprises an actuation assembly 280, i.e. a first actuation assembly (see also fig. 3), arranged to rotate the stator vanes 221 and 222. According to a simpler case, as illustrated in fig. 3, the actuation assembly 280 is arranged to rotate only the stator vanes 221.

The actuation assembly includes an actuation mechanism 281 and a plurality of transmissions 285 and 286; transmissions 285 and 286 are arranged to transfer rotational motion from actuation mechanism 281 to stator vanes 221 and 222, respectively; the actuation mechanism 281 is advantageously positioned between the outer housing 210 and the inner housing 220, more precisely in the gap between the outer housing 210 and the inner housing 220.

Steam turbine 200 also includes a command lever 289 for commanding actuation mechanism 281; additionally, command rod 289 may be considered a component of the first actuation assembly. Advantageously, in this case, the external casing 210 has a through hole that partially houses the command lever 289; in fact, the actuation mechanism (and the position-controlled stator vanes) may be commanded from outside the steam turbine, and the steam leakage is limited to a single-stem hole (at relatively low pressure, i.e., lower than the pressure in the flow path of the steam turbine) between the external environment and the clearance environment; generally, one or more seals are associated with the command lever. Preferably, in this case, the command rod 289 is arranged for translational and/or rotational movement.

Preferably, command lever 289 includes one or more hinged joints for compensating for distortion due to thermal expansion of steam turbine 200 and command lever 289, the thermal expansion being stronger closer to turbine axis "R" of steam turbine 200.

Preferably, the actuation mechanism 281 of the actuation assembly 280 comprises a rotatable ring 310 rotatable around the turbine axis "R" of the steam turbine 200, and the command lever 289 is arranged to actuate the rotation of the rotatable ring 310.

In a first embodiment, as shown in fig. 10, the command lever 289 is arranged tangentially with respect to the rotatable ring 310, and is in particular coupled to the rotatable ring 310 by a hinge. In this first embodiment, command rod 289 is configured to perform a translational movement in order to actuate the rotation of rotatable ring 310 about turbine axis "R".

In the second embodiment, command lever 289 is arranged tangentially with respect to rotatable ring 310, and is coupled to rotatable ring 310, in particular, by a worm gear. In this second embodiment, command lever 289 is configured for rotational movement to actuate rotation of rotatable ring 310 about turbine axis "R".

In the third embodiment, command rod 289 is arranged radially with respect to rotatable ring 310, and is specifically coupled to rotatable ring 310 through a 90 ° gear. In this third embodiment, command lever 289 is configured for rotational movement to actuate rotation of rotatable ring 310 about turbine axis "R".

The steam turbine 200 includes another inner casing section 230 housing the expansion stages (i.e., blades 271, 272, 273) and an outer casing 210 surrounding the inner casing section 230; it should be noted that the inner casing section 230 is an inner casing. Furthermore, it comprises a further actuation assembly 290, i.e. a second actuation assembly (see also fig. 9), arranged to rotate the stator blades 231. According to a more complex scenario, the actuation assembly 290 may be arranged to rotate other stator blades.

The actuation assembly includes an actuation mechanism 291 and a plurality of transmissions 295; the transmission 295 is arranged to transmit the rotational movement from the actuation mechanism 291 to the stator vanes 231 and may be partly integrated into the actuation mechanism 291 and partly integrated into the stator vanes 231; the actuation mechanism 291 is advantageously positioned within the inner housing 230, more precisely in a recessed seat on the inside of the inner housing 230.

The steam turbine 200 further comprises a further command lever 299 for commanding the actuating mechanism 291; command lever 299 may also be considered a component of the second actuating assembly. Advantageously, in this case, the external casing 210 has a through hole that partially houses the command rod 299; in fact, the actuation mechanism (and the position-controlled stator vanes) may be commanded from outside the steam turbine, and the steam leakage is limited to a single-stem hole (at relatively low pressure, i.e., lower than the pressure in the flow path of the steam turbine) between the external environment and the clearance environment; generally, one or more seals are associated with the command lever. Preferably, in this case, command rod 299 is arranged to perform a translational or substantially translational movement. Preferably, the command lever 299 may be arranged according to the implementation described above with reference to command lever 289.

With respect to the actuation assembly 290, the inner housing 230 advantageously has a through hole that partially receives the command rod 299; in fact, steam loss is limited to a single rod orifice between the interstitial environment and the flow path environment.

A first embodiment of the first actuation assembly 280 will now be described with reference to fig. 3.

The plurality of transmissions 285 of the actuation assembly 280 includes a plurality of actuation levers 320 arranged to rotate a plurality of stator vanes 340 (corresponding to vanes 221 in fig. 2) accordingly; the stator vanes 340 may rotate, in particular radially oriented, about respective spanwise directions transverse to the flow direction of the steam. Preferably, each actuation rod 320 is rigidly coupled to a respective stator vane 340 and extends parallel to its spanwise direction.

Preferably, the transmission 285 is arranged to transmit rotational motion from the ring 310 to each of the actuating rods 320. According to the embodiment of fig. 4 and 5, such a transmission 285 comprises a plurality of arms 330 coupled with a ring 310 and a plurality of actuating rods 320. It should be noted that the arm 330 may also be considered as a component of the actuation mechanism 281.

In particular, according to the embodiment of fig. 4 and 5, each arm 330 extends transversely to the spanwise dimension of the respective stator vane 340 and has a first end rigidly connected to the respective actuation lever 320 and a second end hinged to the actuation mechanism 281, in particular to the ring 310. Preferably, each arm is hinged to the actuating mechanism 281, in particular to the ring 310, by means of a simple cylindrical hinge. This means a small axial movement of the ring 310 during rotation of the ring 310.

A second embodiment of the first actuating assembly 280 will now be described with reference to fig. 6 and 7.

The plurality of transmissions 285 of the actuating assembly 280 according to the second embodiment includes a plurality of actuating levers 320 arranged in the same manner as the actuating levers 320 described in the first embodiment. The transmission 285 also includes a plurality of arms 330. Each arm 330 extends transverse to the spanwise dimension of a respective stator vane 340 and has a first end rigidly connected to a respective actuation rod 320 and a second end. It should be noted that the arm 330 may also be considered as a component of the actuation mechanism 281.

The plurality of transmissions 285 of the actuation assembly 280 according to the second embodiment further comprises a plurality of connecting rods 325 having a first end and a second end, the first end of each connecting rod 325 being hinged to the second end of the respective arm 330 and the second end of each connecting rod 325 being hinged to the actuation mechanism 281, in particular to the ring 310. Preferably, each connecting rod 325 is hinged to the respective arm 330 and to the actuating mechanism, in particular to the ring 310, by means of a spherical joint. Advantageously, this prevents axial movement of the ring 310. It should be noted that the connecting rod 325 may also be considered as a component of the actuation mechanism 281.

A third embodiment of the first actuation assembly 280 will now be described with reference to fig. 8.

The plurality of transmissions 285 of the actuating assembly 280 according to the third embodiment includes a plurality of actuating levers 320 arranged in the same manner as the actuating levers 320 described in the first embodiment. The transmission 285 also includes a plurality of transmission members 335. Each transmission member 335 is rigidly connected to the corresponding actuation rod 320 and has a first arcuate surface centered in the spanwise direction of the corresponding stator vane 340. It should be noted that the transmission member 335 may also be considered as a component of the actuation mechanism 281.

The actuation mechanism 281, in particular the ring 310, according to the third embodiment has a plurality of second arcuate surfaces. Each second arcuate surface of the actuation mechanism 281 is complementary to and positioned against a respective first arcuate surface of the transmission member. Advantageously, each pair of first and second arcuate surfaces is configured to slide against each other during rotation of the ring 310 in order to actuate rotation of the actuation rod 320 and the stator vanes 340 connected to the actuation rod 320. Advantageously, this prevents axial movement of the ring 310.

In the first, second and third embodiments, the actuation rod 320 and the stator vane 340 are formed as a single piece or fixedly coupled together with their axes coincident, as shown in fig. 3, 4, 5, 6, 7 and 8.

Preferably, the inner housing 220 may have a plurality of through-holes 225 partially receiving a plurality of actuating rods 320. According to the embodiment of fig. 3, the axis of the vane 340, the axis of the actuator rod 320 and the axis of the bore 225 coincide. In the embodiment of fig. 4 and 6, there may be some vapor leakage from the hole that receives the actuation rod; however, such leakage is internal to the steam turbine, and therefore not really detrimental to the operation of the machine, and is limited due to the relatively small pressure differential between the gap and the flow path; further, one or more seals are associated with the actuator rod.

According to the embodiment of fig. 4 and 6, each of the actuation rods 320 has an axial rod through hole 323, whereby the first and second rod ends 321, 322 are fluidly connected, each of the stator vanes 340 has a vane through hole 343, whereby the first and second vane ends 341, 342 are fluidly connected, and the rod hole 323 is fluidly connected with the vane hole 343. In this case, there is a relatively low pressure differential between the first and second rod ends 321, 322 and between the first and second vane ends 341, 342, such that the components of the actuation assembly 280 must counteract the relatively low pressure.

According to the embodiment of fig. 4 and 6, the first blade end 341 is hinged to the inside of the inner casing 220; advantageously, the second blade end 342 is hinged to a stator member 240 of the steam turbine 200, which may be, for example, an inlet volute of the steam turbine 200 or an extension thereof. It should be noted that according to an alternative embodiment, the vanes 340 may be hinged at only one end.

In general, the actuation mechanism according to the above embodiments may be considered as an assembly of all components of the actuation assembly except for the command and actuation levers. A typical component of the actuation mechanism is an actuating rotatable ring. In other words, the actuation mechanism is an assembly of components that allows the transfer of motion from the command lever to the actuation lever.

An embodiment of the second actuation assembly 290 will now be described with reference to fig. 9.

The actuation mechanism 291 of the actuation assembly 290 includes a rotatable ring 610 rotatable about the axis of the steam turbine 200; preferably, the rotatable ring 610 is positioned in the annular seat 234 of the inner housing 230; more preferably, the annular seat 234 is a groove in the inside of the inner housing 230; in this manner, the ring 610 does not substantially impede the flow of steam. In particular, the ring 610 is connected to the annular seat 234 by a bearing positioned inside the seat 234 so as to allow the ring 610 to rotate.

According to the embodiment of fig. 9, the transmission 295 of the actuation assembly 290 is arranged to transmit a rotational motion from the ring 610 to each of the stator vanes 640 (corresponding to the vanes 231 in fig. 2). In this embodiment, the stator blades 640 may rotate about an axis transverse to the direction of steam flow, particularly in a radial orientation. In this embodiment, the transmission 295 is partially integrated into the actuation ring 610 and partially integrated into the stator vanes 640; for example, the ring 610 has a plurality of teeth that mate with the plurality of teeth 645 of the stator vanes 640. Each stator blade 640 may have only one tooth 645, or preferably a plurality of teeth 645. Preferably, the plurality of teeth 645 are positioned outside of the flow path and move within the groove 236 in the inside of the inner housing 230.

According to the embodiment of fig. 9, the first blade end 641 is hinged to the inside of the inner casing 230; to this end, the stator blades 640 have pivots 643 that fit into the blind holes 237. It should be noted that according to an alternative embodiment, the second blade end 642 may be hinged.

According to the embodiment of fig. 9, the inner housing 230 has a through hole 235 terminating at the groove 234, wherein the command rod 299 is slidable to command the rotation of the ring 610 (see arrow in fig. 6).

It should be noted that the mechanical solutions shown in fig. 3, 4, 5, 6, 7, 8 and 9 may be used elsewhere in the steam turbine to move the stator blades.

The actuating rotatable ring may be positioned a) between an outer casing of the steam turbine and an inner casing of the steam turbine, or B) inside the inner casing of the steam turbine.

The steam turbine just described and other similar embodiments allow for the implementation of a method of conditioning a steam flow.

Embodiments of these methods include the steps of:

-changing the angular position of at least one row of stator blades during operation of the steam turbine;

this step corresponds to blocks 720, 730 and 740 in the flow chart of fig. 7.

During operation of the steam turbine, the angular position may change once or more typically several times. The external control unit may be responsible for deciding when to perform such changes and provide commands to the corresponding actuators, e.g. electric motors.

Preferably, the movable stator vanes are those vanes that are positioned just upstream of the first expansion stage of the steam turbine.

Advantageously, one or more rows of other stator blades, such as the second and/or third rows of stator blades, may be moved.

The movable stator vanes may be those vanes positioned just upstream of the first expansion stage of any expansion section of the steam turbine.

FIG. 7 illustrates a flow diagram of an embodiment of a method of regulating steam flow in a steam turbine. The method has a start step 710 and an end step 790 that may correspond to a start of the steam turbine and a shut down of the steam turbine, respectively.

According to this embodiment, the angular position of the stator vanes is changed by:

-turning (block 720) a command lever protruding from an outer casing of the steam turbine,

-transferring (block 730) the rotational movement from the command lever to an actuating rotatable ring positioned inside the outer casing of the steam turbine, and

-transferring (block 740) a rotational movement from the actuating rotatable ring to the stator vanes.

Repeating the above three steps for each movable stator vane; typically, the movement of all of the movable stator vanes occurs simultaneously. It should be noted that the rotatable ring may act on one or more rows of movable stator vanes.

Although the three steps described above are logically sequential, the time difference between them may be very short or even zero.

Typically, the above three steps are repeated multiple times during operation of the steam turbine for all of the movable stator blades; this is illustrated by the loop L in fig. 7.