Patent Application
20130149106
Embodiments of the present invention relate generally to steam turbines and, more specifically, to a stator blade ring for a steam turbine and a method of making a stator blade ring.
A steam turbine is a turbo machine which converts thermal and pressure energy of steam into rotary motion which may be used to perform work. Steam turbines may be used, for example, to drive electrical generators or compressors.
To enhance steam turbine efficiency, steam is often expanded through a number of stages. Each stage typically includes a stator blade diaphragm and a bearing mounted rotor assembly including at least one impeller.
As steam progresses through the latter stages of the steam turbine, sufficient energy may be absorbed from the steam to cause portions of the steam to condense, and thus, to become so called, wet steam. In addition to having a potential corrosive effect, when wet steam impinges against the stator blade diaphragm, the condensate tends to violently impact the stator blades and other parts of the diaphragm. As a result, the stator blades and other portions of each stator blade diaphragm in the latter stages of the steam turbine may be damaged, for example, during prolonged exposure to wet steam having a high proportion of condensate.
In modern steam turbines, the manufacture of stator blade diaphragms represents a significant cost, particularly in multi stage steam turbines having three or more stages each of which may include one or more separate stator blade diaphragms.
If a stator blade diaphragm is damaged, the steam turbine may need to be shut down and the damaged stator diaphragm removed for servicing. If on site repair is not possible, the entire diaphragm may need to be sent for repair or, alternatively, an entire new stator diaphragm must be installed. Worse yet, if a replacement is available, a new stator blade diaphragm must be fabricated. Thus, in addition to the cost of the stator diaphragm, costs associated with the extended downtime of the steam turbine are also incurred.
Accordingly, what is needed is a replacement for the conventional stator blade diaphragm, which is easily serviced and/or replaced, which is capable of successful operation in the presence of wet steam, and which provides a simple design which is easier manufactured.
According to an embodiment of the present invention, there is provided a stator blade ring for a steam turbine. The stator blade ring comprises a plurality of stator blade modules defining an annular chamber. Each of the plurality of stator blade modules comprises an elongated blade portion comprising a first blade shell portion, a second blade shell portion brazed to the first blade shell portion, a longitudinal passageway, and at least one opening extending through at least one of the first blade shell portion and the second blade shell portion to the longitudinal passageway. Each of the plurality of stator blade modules further comprises an inner portion brazed to a first longitudinal end of the elongated blade portion, wherein the inner portion comprises a through hole forming a portion of the annular chamber, and an inner passageway extending from the through hole to the longitudinal passageway, and an outer portion brazed to a second longitudinal end of the elongated blade portion and engaged to the steam turbine, wherein the outer portion comprises an outer passageway open to a surface of the steam turbine and the longitudinal passageway.
According to an embodiment of the present invention, there is provided a multi-stage steam turbine. The multi-stage steam turbine comprises a rotor assembly comprising at least one impeller, a bearing connected to the rotor assembly, wherein the bearing is configured to rotatably support the rotor assembly, and a stator blade ring for the last stage of the steam turbine, wherein the stator blade ring comprises a plurality of stator blade modules defining an annular chamber. Each of the plurality of stator blade modules comprises at least one elongated blade portion comprising a first blade shell portion and a second blade shell portion brazed to the first blade shell portion, an inner portion brazed to a first longitudinal end of the at least one elongated blade portion, wherein the inner portion comprises a through hole forming a portion of the annular chamber, and an outer portion brazed to a second longitudinal end of the at least one elongated blade portion and engaged to a surface of the steam turbine. The at least one elongated blade portion of at least one of the plurality of stator blade modules further comprises a first longitudinal passageway and an opening for steam condensate to enter the first longitudinal passageway. The inner portion of the at least one of the plurality of stator blade modules comprises a first inner passageway extending from the through hole to the first longitudinal passageway for the steam condensate to flow between the annular chamber and the first longitudinal passageway. The at least one elongated blade portion of another of the plurality of stator blade modules comprises a second longitudinal passageway, the inner portion of the another of the plurality of stator blade modules comprising a second inner passageway extending from the through hole to the second longitudinal passageway for allowing the steam condensate to flow between the annular chamber and the second longitudinal passageway. The outer portion of the another of the plurality of stator blade modules comprises an outer passageway extending from the second longitudinal passageway and opening to the surface of the steam turbine for allowing the steam condensate to flow out of the stator blade ring.
According to an embodiment of the present invention, there is provided a method of making a blade module for a stator blade ring in the last stage of a steam turbine, wherein the blade module comprises an elongated blade portion, an inner portion, and an outer portion. The method comprises brazing a first edge and a second edge of a first blade shell portion to a first edge and a second edge of a second blade shell portion to form a longitudinal passageway in the elongated blade portion, forming a through hole in the inner portion, forming an inner passageway in the inner portion extending from a surface of the inner portion to the through hole, brazing a first longitudinal end of the elongated blade portion to the surface of the inner portion such that the longitudinal passageway is open to the inner passageway, forming an outer passageway in the outer portion extending from a first surface of the outer portion to a second surface of the outer portion, and brazing a second longitudinal end of the elongated blade portion to the first surface of the outer portion such that the longitudinal passageway is open to the outer passageway.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:
The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of a turbo machine that has a stator and a rotor. However, the embodiments to be discussed next are not limited to these exemplary systems, but may be applied to other systems.
Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
To provide some context for the subsequent discussion relating to stator blades according to these exemplary embodiments,
During operation, the steam turbine takes a steam input from an inlet 460 through various stages of expansion, to an outlet 470 leading to a condenser. At each turbine stage, steam is directed by a stator diaphragm 430 onto an impeller rotor 440 thereby converting the temperature and pressure energy of the steam into rotating energy available for work at the rotor shaft 450.
Each stator blade module 14a, 14b includes an elongated blade portion 16, as shown in
As further shown in
Each blade module 14 includes an inner portion 38 connected to a first longitudinal end of at least one blade portion 16, as shown in
Each inner portion 38 also includes at least one inner passageway 44, as shown in
Each stator blade module 14 also includes an outer portion 52 connected to a second longitudinal end of at least one blade portion 16, as shown in
In another path, condensate may enter a longitudinal passageway 26 of a blade portion 16 below the rotor shaft of steam turbine 10 and flow out through outer passageway 54 without first travelling through the annular chamber 20 formed by through holes 42.
The removal of condensate from the wet steam progressing through the latter stages of steam turbine 10 may prevent damage to the stator blade ring 12 as well as to the turbine blades 16 and other downstream components of steam turbine 10. Moreover, stator blade ring 12 allows for the collection of condensate which may include residual heat for use in other processes.
Some blade modules, for example, blade modules above the rotor shaft of steam turbine 10, may be provided without an outer passageway 54, for example, to reduce manufacturing costs, since the downward flow of condensate may obviate the need for outer passageways 54 in blade modules 14 above the rotor shaft. Further, some blade modules 14 may be provided with blade portions 16 without slots, for example, to further reduce manufacturing costs. Alternatively, and as shown in the embodiment of
In addition to providing cost savings over stator blade diaphragms which may need to be serviced or replaced as a unit, blade modules 14 provide a simple one piece design which is easier to install and/or replace than conventional stator blade diaphragm rings. As shown in
As shown in
A groove 66 in each inner portion 38 forms a continuous circumferential groove facing a center of stator blade ring 12, as shown in
As further shown in
Brazing platform 72 and brazing platform 74 provide a convenient surface for brazing the longitudinal ends of each blade portion 16 as well as defining a portion of a stage and/or steam flow path within steam turbine 10. Note from
In the embodiment of
Thus, according to an exemplary embodiment shown in
The above-described exemplary embodiments are intended to be illustrative in all respects, rather than restrictive, of the present invention. Thus the present invention is capable of many variations in detailed implementation that can be derived from the description contained herein by a person skilled in the art. All such variations and modifications are considered to be within the scope and spirit of the present invention as defined by the following claims. No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items.
| Number | Date | Country | Kind |
|---|---|---|---|
| CO2011A000060 | Dec 2011 | IT | national |
