US1561835A - Steam turbine - Google Patents

Description

Nov. 17, 1925- I 1,561,835

. J. Y. DAHLSTRAND.

STEAM TURBINE Filed Sept. 11, 1922 8 3 1 A 1% an Hi? 5 k I R I E I F w v M fi a JM atkozn e1 samin 'the flow of steam area of the Patented Nov. 17, 1925.

UNITED STATES PATENT ounce-.

Application fled September To all whom it may comer: Bejt known that Josnr Y. Dnnnsrnnnn,

citizen of the United States, residing at Wellsville in the countyof Allegany and 5 State of ll'ew York, has invented cert-am new and useful Improvements in Steam Turbines, of which the following is a'specification, reference being had therein to the accom anyi-ngdrawing,

T e present invention relates to steam turbines of the impulse type, and more partlcularl to the nozzling 0 steam turbines.

- Tile object of this invention is to produce a steam' turbine havin the capability of be- 1 ing adjusted to suit ifierent conditions of steam pressure and back pressure and satisfy different power requirements.

Turbines of the impulse type utilize the kinetic energy of steam jets impinging on $0 curved blad A fixed to a rotorto convert the potential ener of steam under pressure into mechanica work. Thesejets are produced by expanding the steam in nozzles which extend at an angle to the lane of the u rotor and which have restricted t roats commu'nicat' with the steam under' r'essure.

-and mout opening at points close y adjacent the path of; the rotor blades. As is well understood, in order to expand a0 steam in a nozzle below 58% of the initial pressure, he nozzle must be divergent, that is to say the area of the throat must be smaller than the area of themouth. The

- diver nce or taper of the nozzle is deterby the ratio of the admission steam pressure to the exhaust or back pressure, and

through the nozzle is dependent upon the difference between the admission and back pressures and upon the throat. A turbine operating at a 'ven speed develop a. certain number of orse 1fl ower depending upon the amount of steam owing thro h its nozzles.

- lows, therefore,'that 't e nozzling of a turbine is governed by the steam conditions under which the turbine is designed to op erate and by the d and horse wer which it is intended that the turbine ould- 'develop. V T According to the practice heretofore, in

designing 'aturbine to develop a' certam horse power. .a't-a given speed and under glixzen steam conditions, the throat areas of t nozzles are calculated and then from veand power requirements.

.expanding nozzles of circular power requirements.

It fol.-

CORPORATION OF NEW s-rnm runninn.

11, 1922. Serial 1%. 587,304.

' locity and specific volumesthe aneas of the mouths are obtained. Hence practicallyevery turbine has been different. from every other one, so far as nozzling is concerned.

According to the presentimention, a turbine is built up complete with nozzles reamed straight from end to end, that" is, with nozzles of uniform cross sectional area, and each nozzle is provided with means-for varying its area to satisfy specific steam conditions The particular form of nozzle contemplated b the present .invention 1s a nozzle of circu ar cross secand the particular means for varylng tion the nozzle area-is a needle valve projecting mtothe throatof the nozzle and protruding new roux, assrenon. To sr'annnnn through the turbinecasing so as to be ad-' justable from the outside. It'has been discovered that a turbine equipped with noncombined with needle valves for varying the cross section expansion ratio can be adjusted in area to satisfy widely different steam conditions and The present invention and effects the is based on this discovery,

new result that, instead-of it being necessary to nozzle each turbine according to the specifications of it is possible to build up and kee "in stock a number of completely built tur ines, one or more of which can be adjusted to satisfy the requirements of an ordinary order. 0bviousl his result not only simplifies the manu acturing problem and lowers the cost of production, but also involves the produetion of a machine of great operating flexibility.

a particular order, as heretofore,

Referrin'ggnow to the accompanying drawv ings for a more particular description of the invention: 1 v

Figure 1 is a section on line 1-1 of Figure 2. i a

Figure 2' is a section on line'2-2 of'Figure 1 and illustrates the invention applied to a .sin 1e stage turbine.

igure 3 is a view similar to Figure 2, showing the ap lication of the invention to a'two stage tur ine.

The present invention is not concerned with the design of a turbine as a whole, and hencethe drawings'are more or less fragmentary and diagrammatic. Figure 1 shows a fragment of a simple single stage turbine of the two-row type. The numeral-1 desigfor varying the 'flow of steam nates the casing in which is formed a space or ring 2 for steam under pressure and a space for accommodating the rotor. Communicatingwith 2 are a series'of nozzles 3 through which the steam expands and thereby acquires velocity. The steam issuing from the mouths of the nozzles impinges on the rotor blades4 and stationaryblades 5, and then exhausts to the atmosphere or condenser. As indicated, the nozzles are of ciroular cross section and have a uniform crosssectional area, except for the necessary rounding'of the edges at the bowl. Associated with each nozzle is a needle valve 6 which has a threaded stem tapped through a hole in the-casing. A cap 7 is screwed on the projecting end ofthe needle valve stem and is adapted to bescrewed tight against the wall of a suitable recess formed in the casing: A copper-packing gasket 8 is interposedbetweenthe end of the cap and the wall of the recess to make a steam tight joint.

As stated, each nozzle of the turbine has associated with it aneedle valve. All ofthese valves, or'part of them, can be closed off entirely or else opened entirely with no part of the needle projecting in the throat of-the nozzle. In the former case no steam will flow; in the latter case the maximum amount of steam will flow, and since the socalled expansion ratio would be 1 1, the nozzles would not be con ect except for very low steam pressures, in otherwords, conditions where the back pressure exceeds 58% of the bowl pressure, Obviously the nozzles can be closed off to any desired degree between these two extremes. For example, for 80 lbs. steam pressure and atmospheric exhaust, the needle might project into the. nozzle inch; for 150 lbs. pressure the needle might project 1 inch, etc. machine equipped with nozzles and valves'in accordance with this invention could be built up complete and putin stock, and'it would be possible to care for any horse power and speed within the range of the maximum nozzling by opening a smaller or greater number of nozzles. F urthermore, any conditions of'steam pressure and back pressure could be satisfied the extent to which the nozzles are opened.

' Figure 3 indicates the application of the invention to a multiple stage turbine, As shown, the nozzles of each stage have associated therewith needle valves, thus provid ing for adjustment of turbines of this type and securing correct energy and velocity distribution throughout the turbine.

"Now having fully disclosed the present invention, what is claimed asnew and is desired to secure by Letters Patent is:

1. In a steam turbine, the combination 'ofa rotor having buckets thereon, a plu-- -rality of nozzlesadjacent thereto, and means through, and

"throats of the nozzles short of points. in the for varying the ratio of the throat,and tjlp areas of said nozzles, said means inclu ing adjustable needles and formed to progressively increase the nozzle area from the throat'to points in the nozzle substantially short of the tips thereof, whereby when the needles are moved inwardly the throat areas are decreased and increased when moved outwardly, said needles being fixed in their.

adjusted positions.

2. In asteam turbine, the combination of a rotor having buckets thereon, a plurality of nozzles of uniform circular cross section, means for varying the flow of steam through, and for varying the ratio of the throat and tip areas of, said" nozzles, said means including adjustable needles projecting into the throats of the nozzles and formed to progressively increase the nozzle area from the throat to points inthe nozzle substantially short of the tips needles are moved inwardly the throat areas thereof, whereby when the projecting into the I are decreased and increased when moved outwardly, said needles being fixed in their ad usted positions.

3. In a steam turbine, the combination of a plurality a rotor havin buckets thereon, of nozzles ad acent thereto, for controlling the flow of steam to each nozzle and for varying the ratio of the throat and tip areas thereof, said means including adjustable needles projecting into the throats of the nozzles and formed to progressively increase the nozzle area from the throat to points in the nozzle substan: tially shortcf the tips thereof, whereby when the needles are throat areas, are decreased and increased when moved outwardly, said needles being fixed in their adjustedpositions.

4. In a steam turbine, the combination of a plurality of'nozzle s, means for controlling the flow of steam to some of the nozzles of a given stageyand for yarying the ratio of the throat and tip areas thereof, said means including adjustable needles" projecting into the throats of the nozzles and formed to progressively increase the nozzle area from the throat ,to points in the nozzle. substantially the tips thereof, whereby when the needles are moved inwardly the throat areas are decreased and moved outwardly, in their adjusted positions.

5. In a steam turbine, the combination of a plurality of nozzles, means for controlling separate means saidneedles being fixed the flow of steam to some ofthe nozzles of a glven stage and for varying the ratio of the throat and tip areas thereof independently of each other, said means including adjustable needles projecting into the throats of the nozzles and formed to progressively increase the nozzle area from the throat to increased when nozzle substantiallyshort of moved inwardly the I .the tips thereof, whereby when the needles are moved inwardly the throat areas are decreasd and increased when moved outward- 1y, said needles being fixed in their adjusted positions.

6; In a steam turbine, the combination of a plurality of stages, a plurality of nozzles in one of said stages, means for controlling the flow of, steam to some of the nozzles of said stage and for varying the ratio of the throat and a tip areas thereof, said means including adjustable needles projectinginto the throats of the nozzles and formed to progressively increase the nozzle area from the throat to points in the nozzle substantially shortof the tips thereof, whereby when the needles are moved inwardly the throat areas are decreased and increased controlling the flow of steam to when moved outwardly, said needles being fixed in their'adjusted positions.

' 7. In a steam turbine, the combination ofof stages,a lurality of nozzles an one .of sai stages, means for some of and for a plurality in more t the nozzles of each of said. s varyin the ratio of the throat and tip" areas t ereofggsaid means including adjust-' able needles projecting into the throats of the nozzles and formed .to progressively 1ncrease the nozzle area from the throat'to points in the'nozzle substantially short of the tips thereof, whereby when the needles I to the axis of the needle.

9. In a steam turbine, a nozzle that is circular in CIOSS-SGClilOll and of substantially uniform cross-sectional area throughout,

and an adjustable needle that is circularin cross-section, said needle being located in the nozzle axially thereof and so formed that longitudinal elements of its surface are convex to the axis of the needle.

In testimony whereof I hereunto aflix my signature. j

JOSEF IYNIGVE 'DAIIL'STRAND, v

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