Stacked reaction steam turbine rotor assembly

Disclosed herein is a rotor assembly for a steam turbine. The steam turbine includes a retention portion having a stacked rotor section. The steam turbine further includes a first shaft end disposed at a first end of the retention portion. The steam turbine yet further includes a second shaft end disposed at a second end of the retention portion that is opposite to the first end of the retention portion.

BACKGROUND OF THE INVENTION

The present invention relates to a rotor assembly for a reaction steam turbine and, more particularly, to stacked rotor plates of a rotor assembly of the reaction steam turbine.

Reaction steam turbines typically include multiple stator stages and corresponding rotor stages. Each of the stator stages is disposed proximate to the corresponding rotor stages to direct steam flow toward the rotor stages. The stator stages include nozzle stages that direct the steam flow. The rotor stages include buckets that receive the steam flow from the nozzle stages. The steam flow exerts a force upon the buckets of the rotor stages and causes rotation of a rotor assembly, which is converted to, for example, useful work or electrical energy.

Current integral-cover reaction nozzle stages include large quantities of individual reaction nozzles that are assembled into a machined stator inner casing using individual radial loading pins. Such a construction method increases time and cost of casting a stator assembly. Similarly, current integral-cover reaction bucket stages include large quantities of individual reaction buckets that are assembled into a machined rotor assembly using individual radial loading pins. Such a construction method increases time and cost of casting the machined rotor assembly.

BRIEF DESCRIPTION OF THE INVENTION

Disclosed herein is a rotor assembly for a steam turbine. The steam turbine includes a retention portion having a stacked rotor section. The steam turbine further includes a first shaft end disposed at a first end of the retention portion. The steam turbine yet further includes a second shaft end disposed at a second end of the retention portion that is opposite to the first end of the retention portion.

Further disclosed herein is a steam turbine. The steam turbine includes a stator assembly having nozzles directing steam flow. The steam turbine also includes a rotor assembly having buckets receiving the steam flow. The rotor assembly includes a retention portion having a stacked rotor section. The rotor assembly further includes a first shaft end disposed at a first end of the retention portion. The rotor assembly yet further includes a second shaft end disposed at a second end of the retention portion that is opposite to the first end of the retention portion.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a perspective view of a conventional reaction steam turbine. The conventional reaction steam turbine includes a conventional stator10having stator stages12and a conventional rotor20having rotor stages22. The conventional rotor20is disposed proximate to the conventional stator10such that each of the stator stages12is proximate to a corresponding one of the rotor stages22. Each of the stator stages12includes a plurality of individual airfoils or nozzles14. Each of the rotor stages22includes a plurality of individual airfoils or buckets24. The nozzles14of the stator stages12are disposed proximate to the buckets24of the corresponding one of the rotor stages22to direct flow of a working fluid, for example, steam, toward the buckets24. The buckets24are circumferentially disposed at an outer edge of each of the rotor stages22. The nozzles14are circumferentially disposed at an inner edge of each of the stator stages12. Both the buckets24and the nozzles14are fixed at the conventional rotor and stator stages14and12, respectively, for example, by a dovetail assembly. In the dovetail assembly, a dovetail protrusion disposed at a base of each of the buckets24and nozzles14is disposed, respectively, into a corresponding groove disposed in the outer edge of each of the rotor stages22and the inner edge of each of the stator stages12. Such a means of attachment the buckets24and the nozzles14is referred to as a dovetail assembly process.

Still referring toFIG. 1, the conventional rotor20may include, for example, a forged rotor including a unitary shaft having grooves disposed circumferentially around an external surface of the unitary shaft. Each of the grooves receives a bucket via the dovetail assembly process. Alternatively, the conventional rotor20may include, for example, individual wheels corresponding to one of the rotor stages22, which are disposed proximate to each other and combined together on a shaft26to form a conventional rotor20.

FIG. 2is a perspective view of a rotor plate30according to an exemplary embodiment. The rotor plate30corresponds to a single rotor stage. The rotor plate30may be shaped as a disk. The rotor plate30comprises one unitary piece of metal stock. The metal stock is machined to produce mounting features and airfoils. In other words, unlike the rotor stages22of the conventional rotor20, the rotor plate30does not have joints between a main body31of the rotor plate30and the airfoils. Thus, the rotor plate30includes jointless attachment between the airfoils and the main body31of the rotor plate30. The mounting features include a center bore32, retention holes34and a fitting portion36. In an exemplary embodiment, rotor plates30may be adjacently disposed to form a rotor assembly, which will be described in greater detail below.

The airfoils include buckets38that are circumferentially disposed around a portion of the rotor plate30corresponding to an outer edge of the rotor plate30. The buckets38are machined from the metal stock such that the buckets38are spaced apart from the edge of the rotor plate30and equidistant from an axial center of the rotor plate30. The buckets38are repeatedly formed adjacent to each other to completely extend to form an annular bucket region40extending concentrically around the portion of the rotor plate30corresponding to the outer edge of the rotor plate30. Since the buckets38are machined from the metal stock, each of the buckets38is attached to the main body31of the rotor plate30without a joining mechanism. Thus, each of the buckets38is jointlessly connected to the rotor plate30. Additionally, an outer ring39of the metal stock remains after the buckets38are machined from the metal stock. The outer ring39defines the outer edge of the rotor plate30. Thus, the buckets38are disposed in the annular bucket region40, which is disposed between the outer ring39and the main body31of the rotor plate30.

The center bore32is a circular through hole that passes from a first axial face of each rotor plate30to a second axial face of the rotor plate30. The second axial face is opposite to the first axial face. The center bore32is concentrically disposed with respect to the rotor plate30. The center bore32of each of the rotor plates30is receptive of a shaft of the rotor assembly.

The retention holes34are circular through holes that that pass from the first axial face to the second axial face of the rotor plate30. The retention holes34are disposed at the main body31of the rotor plate30. In other words, the retention holes34are disposed at a portion of the rotor plate30that is between the center bore32and the annular bucket region40. The retention holes34are circumferentially disposed at intervals from each other such that the retention holes34are each equidistant from the axial center of the rotor plate30. In an exemplary embodiment, the retention holes34are equidistant from each other. The retention holes34are receptive of a retention device such as, for example, a holding rod42(seeFIG. 3), which functions to retain adjacent rotor plates30proximate to each other. Additionally, it should be noted that holding rods42may be disposed at an exterior of the rotor plate30.

The fitting portion36includes any suitable means to fix adjacent rotor plates30. In an exemplary embodiment, the fitting portion36includes a rabbet fit in which each of the rotor plates30includes a protrusion136extending into a corresponding recess portion138of an adjacent rotor plate30(see, for example,FIGS. 12 and 13).

FIG. 3is a perspective view of a rotor assembly50according to an exemplary embodiment.FIG. 4is a perspective view of a retention portion54of the rotor assembly50ofFIG. 3. The rotor assembly50includes shaft ends52disposed at opposite ends of the retention portion54. The retention portion54includes end plates56and holding rods42. AlthoughFIGS. 3 and 4show cylindrically shaped holding rods42it should be noted that any suitable shape is envisioned such as, for example, hexagonal or square shaped holding rods42. Additionally, retention means other than the holding rods42are also envisioned. As shown inFIG. 4, the retention portion54includes adjacently disposed rotor plates30having the holding rods42disposed through the retention holes34of each of the adjacently disposed rotor plates30for retention of the rotor plates30. Each of the holding rods42includes, for example, a nut engaged to a threaded portion of each of the holding rods42to permit securing of the rotor plates30to the retention portion54. The shaft ends52extend from the opposite sides of the retention portion54to allow transmission of rotational energy from the buckets38to an external device via rotation of the shaft ends52.

The rotor assembly50shown inFIG. 4includes rotor plates30according to an exemplary embodiment. Alternatively, a mixed rotor may be employed.FIG. 5is a diagram showing a mixed rotor assembly according to an exemplary embodiment.FIG. 6is a diagram showing a mixed rotor assembly according to another exemplary embodiment.

Referring toFIG. 5, a mixed rotor60includes a stacked rotor section62having at least one rotor plate30and a forged rotor section64. The forged rotor section64includes a forged rotor portion66and forged rotor stages68that are fixed onto the forged rotor portion66by the dovetail assembly process. AlthoughFIG. 5shows the forged rotor section64being disposed at a rotor end, it should be noted that the forged rotor section64and the stacked rotor section62may be disposed in any suitable order. Additionally, althoughFIG. 5shows three forged rotor stages68and four rotor plates30, it should be noted that a number of the forged rotor stages68and a number of the rotor plates30may each be varied according to operational and design considerations.

Alternatively, as shown inFIG. 6, a mixed rotor60′ includes the stacked rotor section62including at least one rotor plate30and a rotor wheel section70including at least one rotor wheel72in which buckets of the rotor wheel72are attached by the dovetail assembly process. Each rotor wheel72corresponds to one stage of the mixed rotor60′. AlthoughFIG. 6shows the rotor wheel section70being disposed at the rotor end, it should be noted that the rotor wheel section70and the stacked rotor section62may be disposed in any suitable order. Additionally, althoughFIG. 6shows three rotor wheels72and four rotor plates30, it should be noted that a number of the rotor wheels72and the number of the rotor plates30may each be varied according to operational and design considerations. It should also be noted that any combination of sections including the stacked rotor section62, the rotor wheel section70and the forged rotor section64is also envisioned.

FIG. 7is a side view of a stator plate80according to an exemplary embodiment.FIG. 8is a perspective view of the stator plate inFIG. 7. The stator plate80corresponds to a single stator stage. The stator plate80may be shaped as a disk. The stator plate80comprises one unitary piece of metal stock. The metal stock is machined to produce mounting features and airfoils. In other words, unlike the stator stages12of the conventional stator10, the stator plate80does not have joints between a main body81of the stator plate80and the airfoils. Thus, the stator plate80includes jointless attachment between the airfoils and the main body81of the stator plate80. The mounting features include a central bore82and retention holes84. In an exemplary embodiment stator plates80may be adjacently disposed to form a stator assembly, which will be described in greater detail below. Additionally, the stator plates80may include a fitting portion similar to the fitting portion36described above with reference toFIGS. 2,12and13.

The airfoils include nozzles88that are circumferentially disposed around a portion of the rotor plate30corresponding to an inner edge of the stator plate80. The nozzles88are machined from the metal stock such that the nozzles88are spaced apart from the inner edge of the stator plate80and equidistant from an axial center of the stator plate80. The nozzles88are repeatedly formed adjacent to each other to completely extend to form an annular nozzle region90extending concentrically around the portion of the stator plate80corresponding to the inner edge of the stator plate80. Since the nozzles88are machined from the metal stock, each of the nozzles88is attached to the main body81of the stator plate80without a joining mechanism. Additionally, an inner ring89of the metal stock remains after the nozzles88are machined from the metal stock. The inner ring89defines the inner edge of the stator plate80. Thus, the nozzles88are disposed in the annular nozzle region90, which is disposed between the inner ring89and the main body81of the stator plate80.

The central bore82is a circular through hole that passes from a first axial face of each stator plate80to a second axial face of the stator plate80. The second axial face is opposite to the first axial face. The central bore82is concentrically disposed with respect to the stator plate80. The central bore82of each of the stator plates80is receptive of a shaft of a rotor assembly.

The retention holes84are circular through holes that that pass from the first axial face of the stator plate80to the second axial face of the stator plate80. The retention holes84are disposed at the main body81of the stator plate80. In other words, the retention holes84are disposed at a portion of the stator plate80that is between an outer edge of the stator plate80and the annular nozzle region90. The retention holes84are circumferentially disposed at intervals from each other such that the retention holes84are each equidistant from the axial center of the stator plate80. The retention holes84are receptive of a retention device such as, for example, a holding bolt92(seeFIG. 9), which functions to retain adjacent stator plates80proximate to each other. Additionally, it should be noted that holding bolts92may be disposed at an exterior of the stator plate80.

FIGS. 9-11are each diagrams of a stator assembly according to an exemplary embodiment. Referring toFIG. 9, a stator assembly96includes a stacked stator section98having a plurality of stator plates80. It should be noted that although each of the stator plates80is shown having a step configuration with respect to adjacent stator plates80, a sloped configuration in which each of the stator plates80forms a smooth transition with respect to the adjacent stator plates80is also envisioned. The stator plates80are fixed with respect to each other by the holding bolt92, which is disposed through the retaining hole84of each of the stator plates80. A nut may be provided to engage a threaded portion of the holding bolt92to secure the stator plates80together. AlthoughFIG. 9shows five stator plates80, either a greater or fewer number of the stator plates80may be employed.

Referring toFIG. 10, a mixed stator100includes a stacked stator section98having at least one stator plate80and a cast stator section104. The cast stator section104includes a cast stator portion106and cast stator stages108that are fixed onto the cast stator portion106by the dovetail assembly process. AlthoughFIG. 10shows the stacked stator section98being disposed at a stator end, it should be noted that the stacked stator section98and the cast stator section104may be disposed in any suitable order. Additionally, althoughFIG. 10shows three stator plates80of the stacked stator section98and two cast stator stages108of the cast stator section104, it should be noted that a number of stages of the cast stator section104and a number of the stator plates80may each be varied according to operational and design considerations.

Alternatively, as shown inFIG. 11, a mixed stator100′ includes the stacked stator section98including at least one stator plate80and a stator wheel section110including at least one stator wheel112in which nozzles of the at least one stator wheel112are attached by the dovetail assembly process. AlthoughFIG. 11shows the stator wheel section110being disposed at the stator end, it should be noted that the stator wheel section110and the stacked stator section98may be disposed in any suitable order. Additionally, althoughFIG. 11shows two stator wheels112and three stator plates80, it should be noted that a number of the stator wheels112and the number of the stator plates80may each be varied according to operational and design considerations. It should also be noted that any combination of sections including the stacked stator section98, the stator wheel section110and the cast stator section104is also envisioned.

Additionally, any exemplary embodiment of a rotor design according toFIGS. 2-6may be incorporated with any exemplary embodiment of a stator design according toFIGS. 7-11. Furthermore, any exemplary embodiment of a rotor design according toFIGS. 2-6may be incorporated with the conventional stator10, and any exemplary embodiment of a stator design according toFIGS. 7-11may be incorporated with the conventional rotor20.

In order to prevent an introduction of steam between the rotor plates30of the stacked rotor section62or between the stator plates80of the stacked stator section98, seals may be installed between adjacent rotor plates30or adjacent stator plates80.

FIG. 12is a diagram of an axial face seal according to an exemplary embodiment.FIG. 13is a diagram of an axial face seal according to another exemplary embodiment. In bothFIGS. 12 and 13the airfoils (i.e. the buckets38or the nozzles88) are removed for clarity.

Referring toFIG. 12, a first stage120, a second stage122and a third stage124are shown. The first, second and third stages120,122and124correspond to either three adjacent rotor plates30or three adjacent stator plates80. A circumferential caulk wire seal130, shown in a blown up region126/128ofFIG. 12, is disposed between each of the first, second and third stages120,122and124at an edge of an airfoil base portion160(seeFIGS. 5 and 9) of each of the first, second and third stages120,122and124that is adjacent to the edge of the airfoil base portion160of an adjacent one of the first, second and third stages120,122and124. If the first, second and third stages120,122and124correspond to adjacent rotor plates30, then the circumferential caulk wire seal130is disposed at an intersection of the edges of the airfoil base portions160of the adjacent rotor plates30as shown by blown up region126. If the first, second and third stages120,122and124correspond to adjacent stator plates80, then the circumferential caulk wire seal130is disposed at an intersection of the edges the airfoil base portions160of the adjacent stator plates80at a portion shown by blown up region128. Dotted lines140correspond to the edge of the airfoil base portion160of the stator plates80.

The circumferential caulk wire seal130is disposed at the intersection of the edges of the airfoil base portions160of the adjacent rotor plates30or stator plates80, respectively, after the rotor plates30or stator plates80have been fixed together by the holding rod42or the holding bolt92, respectively. The circumferential caulk wire seal130may be installed using, for example, an A14 or an A15 caulking tool.

As shown inFIG. 12, the first, second and third stages120,122and124each include the protrusion136disposed at a first axial face of each of the first, second and third stages120,122and124and the recess portion138disposed at a second axial face of each of first, second and third stages120,122and124. The protrusion136of one of the first, second and third stages120,122and124is inserted into the recess portion138of an adjacent one of the first, second and third stages120,122and124to form the rabbet fit. For example, the protrusion136of the first stage120is received by the recess portion138of the second stage122and the protrusion136of the second stage122is received by the recess portion138of the third stage124.

Referring toFIG. 13, the first and second stages120and122each include a first annular recess142disposed at the first axial face and a second annular recess144disposed at the second axial face. The first annular recess142of the first axial face of the first stage120is disposed to correspond to the second annular recess144of the second axial face of the second stage122. A circular rope seal150is disposed in a gap between the first and second stages120and122formed by the first and second annular recesses140and142. The circular rope seal150is installed before the rotor plates30or stator plates80have been fixed together by the holding rod42or the holding bolt92, respectively. The circular rope seal150is compressed within the gap and expands to entirely fill the gap.

It should be noted that the circular rope seal150and the circumferential caulk wire130may be used individually or in combination for either of a rotor assembly or a stator assembly. Use of the circular rope seal150and/or the circumferential caulk wire130prevents steam from being exposed to the axial faces of the rotor plates30or the stator plates80, thereby decreasing energy losses in the reaction steam turbine. Furthermore, use of the rotor plates30or the stator plates80reduces cost and time to manufacture a rotor assembly or a stator assembly.