Extraction unit for turbine and related method

An extraction unit for a steam turbine includes an end plate mounted downstream of a selected stage of a steam turbine, the end plate sealing the selected stage from the atmosphere, and an extraction pipe passing through the end plate for extracting steam from the selected stage.

BACKGROUND OF THE INVENTION

The invention relates generally to turbine technology. More particularly, the invention relates to an extraction unit for converting a turbine or adding extraction outlets to a turbine.

Two types of steam turbines used in industry are a condensing steam turbine and an extraction steam turbine. A condensing steam turbine exhausts steam in a partly condensed state, while in an extraction steam turbine steam is pulled from various locations and used for other industrial processes such as preheating water boilers, etc. Valves control steam extracted from an extraction steam turbine.

SUMMARY OF THE INVENTION

A first aspect of the disclosure provides an apparatus comprising: an end plate mounted downstream of a selected stage of a steam turbine, the end plate sealing the selected stage from the atmosphere; and an extraction pipe passing through the end plate for extracting steam from the selected stage.

A second aspect of the disclosure provides a steam turbine comprising: a plurality of stages, each stage including a plurality of rotating blades coupled to a rotating shaft; an end plate mounted downstream of a selected stage, the end plate sealing the selected stage from the atmosphere and including a rotating shaft opening allowing the rotating shaft to sealingly pass through the end plate; and an extraction pipe passing through the end plate for extracting steam from the selected stage.

A third aspect of the disclosure provides a method comprising: providing a steam turbine including at least one stage; and adding extraction outlets to the steam turbine by sealingly mounting an end plate downstream of a selected stage of the steam turbine, the end plate including an extraction pipe passing through the end plate for extracting steam from the selected stage.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings,FIG. 1shows a perspective partial cut-away illustration of a double flow, low pressure steam turbine10, which is just one example of the type of steam turbine to which the teachings of the invention may be applied. Steam turbine10includes a rotor12that includes a rotating shaft14and a plurality of axially spaced rotor wheels18. A plurality of rotating blades20are mechanically coupled to each rotor wheel18. More specifically, blades20are arranged in rows that extend circumferentially around each rotor wheel18. A plurality of stationary vanes22extends circumferentially around shaft14, and the vanes are axially positioned between adjacent rows of blades20. Stationary vanes22cooperate with blades20to form a stage and to define a portion of a steam flow path through turbine10.

In operation, steam24enters an inlet26of turbine10and is channeled through stationary vanes22. Note, however, that the steam inlet configurations may vary. Vanes22direct steam24downstream against blades20. Steam24passes through the remaining stages imparting a force on blades20causing shaft14to rotate. At least one end of turbine10may extend axially away from rotor12and may be attached to a load or machinery (not shown) such as, but not limited to, a generator, and/or another turbine.

In one embodiment of the present invention as shown inFIG. 1, turbine10comprises five stages. The five stages are referred to as L0, L1, L2, L3and L4. Stage L4is the first stage and is the smallest (in a radial direction) of the five stages. Stage L3is the second stage and is the next stage in an axial direction. Stage L2is the third stage and is shown in the middle of the five stages. Stage L1is the fourth and next-to-last stage. Stage L0is the last stage and is the largest (in a radial direction). It is to be understood that five stages are shown as one example only, and each turbine may have more or less than five stages. Also, as will be described herein, the teachings of the invention do not require a multiple stage turbine.

FIGS. 2-5show an extraction unit100for converting a non-extraction type steam turbine10to an extraction steam turbine200(FIG. 3) or adding additional extraction outlets to an extraction steam turbine. Generally, extraction unit100converts a condensing type steam turbine10to extraction steam turbine200or adds extraction outlets to an extraction type turbine by providing a seal at the selected stage and extraction pipes through which steam can be extracted. Where steam turbine10is a condensing type system, it would typically allow the steam therein to condense after all desired work had been extrapolated from the steam. Where steam turbine10is already an extraction type steam turbine (other outlets not shown), then extraction unit100may add further outlets for steam. In any event, according to embodiments of the invention, steam extracted may be employed in any other now known or later developed industrial application, e.g., a de-salination process, preheating boiler, etc.

In one embodiment, extraction unit100includes an end plate102mounted downstream of a selected stage (e.g., L0inFIG. 1) of steam turbine10and one or more extraction pipe(s)104passing through the end plate for extracting steam from the selected stage.FIG. 2shows an embodiment including four extraction pipes104;FIG. 3shows an embodiment including three extraction pipes104, with two aligned with the vertical centerline of end plate102; andFIGS. 4-5are devoid of extraction pipes for clarity of illustration. Downstream stages (not shown) from extraction unit100may be removed or adjusted to provide clearance for extraction unit100, perhaps leaving a casing106(FIGS. 3-5) therefor. Casing106may be at atmospheric conditions. As shown best inFIGS. 3-5, end plate102seals the selected stage from the atmosphere. The selected stage may include practically any stage in steam turbine10. Downstream stages may need to be removed or adjusted to provide clearance for extraction unit100. Extraction unit100may be made of any suitable metal alloy capable of withstanding the steam conditions of the selected stage.

As shown best inFIGS. 4-5, end plate102may be mounted in a groove110in a casing112of steam turbine10, i.e., by a flange114on end plate102. Groove110may be machined in casing112using any known technique, or may be provided by the addition of a fixture including the groove. Casing112may include the casing surrounding the selected stage, or any other convenient structure capable of immovably fixing end plate102. In one embodiment, end plate102may be sealed to a casing112using a flexible seal120, which seals a periphery of end plate102and casing112. In one embodiment, flexible seal120is formed from a metal alloy into a U-shaped member122having a first leg124thereof coupled to casing112and a second leg126thereof coupled to the end plate102. Each leg124,126may be coupled to its respective part by, for example, bolting or welding. In an alternative embodiment, not shown, flexible seal120may have a V-shape. Flexible seal120may be formed as one integral piece (FIG. 4) or may include two mating halves (FIG. 5), which may be, for example, bolted or welded together. In an alternative embodiment, shown in phantom inFIG. 5, one leg (e.g.,124) of flexible seal120may be coupled to structure other than casing112such as downstream casing106. In any event, flexible seal120prevents steam leakage from between end plate102and casing112.

Referring toFIGS. 2-3, end plate102may also include a rotating shaft opening150allowing rotating shaft14of steam turbine10to sealingly pass through the end plate. In one embodiment, a rotating shaft collar152may be mounted to end plate102. As illustrated best inFIG. 2, a pair of steam packing seal openings154allowing sealing of collar152with rotating shaft14in a known fashion may be provided. Openings154may include appropriate piping156for delivery or removal of steam, as shown inFIGS. 2-3. In an alternative embodiment, shown inFIG. 6, end plate102may include an end bearing190to support an end of rotating shaft14. In this case, rotating shaft14terminates in end bearing190.

Extraction pipe(s)104may be, for example, welded or bolted to appropriately sized openings130in end plate102. As shown inFIG. 3, extraction pipe(s)104may extend through a casing106downstream and different than casing112in which the selected stage is mounted. This structure may be necessary where casing106is not readily removed from steam turbine10, e.g., because of surrounding structure, costs, safety concerns, etc.

As also shown inFIG. 2, in one embodiment, end plate102may include a pair of mating parts150A,150B. As illustrated, mating parts150A,150B each include a substantially semi-circular plate having a mount160for coupling to one another. Mating parts150A,150B may be, for example, bolted or welded together. Although in the example shown, mating parts are substantially semi-circular, it should be recognized that end plate102may be segmented in a number of different fashions to allow for ease of installation and manufacture. For example, more than two mating parts may be employed such that end plate102is more modular so that it may be installed with a user selected number of extraction pipes104. In this case, the mating parts may be more pie shaped (excluding rotating shaft opening150). In this case, end plate102may include a set number of mating parts, e.g., 6, and a user can select whether a mating part includes an extraction pipe opening130or is blank. Each mating part would include appropriate mounts160(FIG. 2), steam packing openings154(FIG. 2) and flange114(FIGS. 4-5) section.

Another embodiment includes steam turbine200(FIG. 3) as converted. In this embodiment, turbine200includes plurality of stages L4-L0, each stage including plurality of rotating blades20coupled to rotating shaft14. End plate102is mounted downstream of a selected stage, and the end plate seals the selected stage from the atmosphere. A rotating shaft opening150allows rotating shaft14to sealingly pass through the end plate. Extraction pipe(s)104pass through end plate102for extracting steam from the selected stage.

In another embodiment, a method may include providing steam turbine10including at least one stage L4-L0, and adding extraction outlets by sealingly mounting end plate102downstream of the selected stage. End plate102includes an extraction pipe104passing through the end plate for extracting steam from the selected stage. In this fashion, a condensing steam turbine can be converted to an extraction type steam turbine200(FIG. 3).

The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another, and the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context, (e.g., includes the degree of error associated with measurement of the particular quantity). The suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the metal(s) includes one or more metals). Ranges disclosed herein are inclusive and independently combinable (e.g., ranges of “up to about 25 wt %, or, more specifically, about 5 wt % to about 20 wt %”, is inclusive of the endpoints and all intermediate values of the ranges of “about 5 wt % to about 25 wt %,” etc).

While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.