US2187788A - Elastic fluid turbine - Google Patents

Description

Jan. 23, 1940. H. KRAFT ELASTIC FLUID TURBINE Filed March 26, 1959 Inventor:

H an s KraF t,

His Attorney.

"1 stage.

Patented Jan. 23, 1940 t me amt-S ewe ELASTIC FLUID TURBINE i H HansKraft, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York - AppIication March 26, 1938, Serial No. 198,279

7. Claims.

The present invention relates to'elastic fiuid turbines, more specifically to the kind of' turbines 'in which elastic fluid discharged froma' bucket wheel with large diameter flows into a 5 nozzle diaphragm of a succeeding stage of small diameter as is the case, for instance, where the first turbine stage includes a Curtis type bucket 1 wheel of large diameter as compared with the ;diameter of the diaphragm of the succeeding It has been found that'a substantial amount of the available energy of the elastic fluid is destroyed on'its path from the exit edge of the buckets of a large diameter bucket wheel to the inlet edge of the diaphragm of the succeeding stage, particularly so at low load with partial admission of elastic fluid to the large diameter bucket wheel.

The object of my invention is to provide an whereby the .5 improved turbine construction it) aforementioned loss of available energy with the resulting low efiiciencyis considerably reduced. I t

- For a consideration of what I believe to be novel and my invention, attentionis directed 2B t'othe following description and the claims appended thereto in-connection with the accom panying drawing.

" In the drawing, Fig.1 illustrates diagrammati cally a turbine embodying my invention; Fig. 2

is a section along line 2-4 of Fig. l; and Fig. 1

is a section along lines l! of Fig. 2.--

The arrangement comprises a turbine casing I0 with an inlet valve H for controlling the flow of elastic fluid to. the turbine. 86%. a rotor with a shaft! 2- and a plurality of bucket Wheels l3, i4, i5, etc..secured thereto. The elastic fiuid is conducted to the first stage bucket Wheel i3 by a. plurality of nozzles l6.' Inthe present instance I have shown four nozzleasee. In other words, all of the elastic fluid conducted through the valve H to the turbine flows through the four nozzles IE to the first bucket wheel i3; it being immaterial as far as thein'vention is concerned whetheror not other i 16-? valves are provided for directing elastic fluid to other parts 'o f 'th e first bucket wheel. An arrangement in which elastic fluid is admitted only along a part of the circumference of the first bucket wheel is known as a partial admission 7 50 arrangement. The elastic fiuiddischarged from the bucket wheel l3 flows into a space H, whence it is directed through a row of nozzles l8 into the succeeding bucket wheel l4. The row. of nozzles I8 is formed by a diaphragm l9 ahead so of the second'stage bucket wheel M. Similar The turbine has diaphragms andZl are provided aheadoi'the succeeding bucket wheels. 'It will be noted that the bucket wheel l3 and the diaphragm I9 are spaced considerably in axial direction and that the diameter of the exit edge of the bucket wheel 5 is designated with D is larger than the diame ter of the outer inlet edge of the nozzles l8 de signated with d. The elastic fluid discharged from the'bucket wheel l3 therefore has to travel radially inward on its path to the nozzles 18 10 charged from the bucket wheel i3 is indicated by" 2 short arrows 23. The axial width of the space I1 formed between the bucket wheel l3 and the diaphragm i9 is necessitated by the great-difference' between the diameters D and d of the bucket wheel of the first stage and of the diaphragm of the second stage respectively to pro-- vide space for the elastic fluid to flow fromv the first stage bucket wheel to thesecondstage nozzles. 'As'stated above, the elastic fluid on its path from the bucket wheel i3 to the diaphragm I!) has a component in the direction opposite the direction of rotation of the bucket wheel l3 and another component directed radially inward.

Thus the elastic fluid flows spirally from the 1 bucket wheel !3 towards the diaphragm l9. This 3 5 condition in a turbine with partialadmission, particularly during low load condition, causes the elastic fluid to whirl in the space H which leads to considerable friction losses. I

The'losses ordinarily thus caused between'the exit edge of the first bucket wheel I 3 and" the entrance edgeof the diaphragm nozzles of the" succeedingstage are reduced in accordance with my invention by the provision of means for re-- ducing rotational low or whirling of the elastic 455i:

fluid discharged from the large diameter bucket wheel l3. Specifically, thisvis accomplished in the present arrangement by a dam 24 in the chamber or annular space H extending axially across the entire width of the space I! and in 59 the present instance by a weld. This dam is provided on the upstream side of the elastic miner orslcsj j .Letters Patent of the United States, is:

fluid jet discharged from the bucket wheel I3. The direction of fluid, as shown in Fig. 2 by short arrows 23 is from the right towards the left, that is, counterclockwise, as viewed in Fig. 2, and the term upstream is to be interpreted with reference to this direction of flow. The elastic fluid discharged from the bucket wheel [3 enters the nozzles i8 formed by the diaphragm [9 along the entire circumference thereof, that is, the dam 24 permits rotational flow of the fluid over a path of 360. By thus limiting the rotational flow of fluid the dam 24 breaks the whirling ordinarily caused and in doing so regains energy of the whirl by impact of the fluid onto the dam 24, building up its pressure and increasing its temperature. From another viewpoint, the dam limits the length of the rotational flow with regard to a portion of the fluid because without the dam a certain amount of the fluid may rotate three or four times about the shaft beforeit. reaches the inlet of the diaphragm nozzles l8. Theentire friction loss of the fluid caused during this second and third rotation is regained by the dam. Actual tests have shown that in certain cases the energy thus regained is of the order of 3% of the total turbine efflciency during low load condition on the turbine.

Thus, with my invention I have provided an improved turbine arrangement whereby loss of. available energy of elastic fluid on its path between a large diameter bucket wheel and a small diameter diaphragm is considerably reduced.

Having described the method of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by 1. An elastic fluid turbine including the con1- binat-ion of a casing, a rotor having a shaft and a first and second bucket wheel secured thereto, adiaphragm intermediate the bucket wheels and held on the casing, the diaphragm having nozzle openings spaced considerably in radial and axial direction from the nozzles of the first bucket wheel. and means substantially completely splitting the ring space formed between the bucket wheel and the diaphragm to reduce loss of avail able energy of elastic fluid on its flow from the exit of the first bucket wheel nozzles to the inlet of the diaphragm nozzles.

2. An elastic fluid. turbine including the combination of a casing, a first stage with a bucket wheel of large diameter and nozzles for directing elastic fluid to an angularly limited area of the first wheel, a second stage including a nozzle diaphragm with an inlet edge of small diameter compared with the exit edge of said bucket wheel, and means arranged near the upstream side of the elastic fluid jet discharged from the bucket wheel and substantially completely splitting the ring space formed between the bucket wheel and the diaphragm to reduce whirling of elastic fluid on its path from the first stage bucket wheel tothe second stage nozzle diaphragm.

3. An elastic fluid turbine comprising a casing, a first stage bucket wheel with means for admitting fluid along a limited arc of the bucket wheels, a second stage including a diaphragm axially considerably spaced from the bucket wheel and forming nozzle openings with an inlet diameter much smaller than the exit diameter of the bucket wheel, and means for directing the flow of fluid from the first stage bucket wheel to the second stage diaphragm and to reduce rotational flow of the fluid intermediate the first stage bucket wheel and the second stage diaphragm, said means being arranged near the upstream side of the elastic fluid jet discharged from the bucket wheel and substantially completely splitting the ring space formed between the bucket wheel and the diaphragm.

4. An elastic fluid turbine comprising a first stage with a bucket wheel and nozzles for admitting fluid along a limited arc to the bucket wheel, a second stage including a diaphragm considerably axially spaced from the bucket wheel and having nozzles with an inlet diameter much smaller than the exit diameter of the bucket wheel, and a dam on the upstream side of the elastic fluid jet discharged from the bucket wheel and substantially completely'splitting the ring space formed between the bucket wheel and the diaphragm to reduce whirling of the fluid discharged fromthe bucket wheel.

5. An elastic fluid turbine comprising a first stage with a bucket wheel and nozzles for admitting fluid along a limited arc to thebucket wheel, a second stage including a diaphragm considerably axially spaced from the bucket wheel and having nozzles with an inlet diameter much smaller than the exit diameter of the bucket wheel, an annular space being formed between the bucket wheel and the diaphragm, and a dam secured to the diaphragm and extending radially through the entire space and having close clearance with the bucket wheel.

6. An elastic fluid turbine comprising a bucket wheel and a nozzle diaphragm axially considerably spaced from the bucket wheel and arranged to receive elastic fluid therefrom, and dam means interposed in the ring space formed between the bucket wheel and the nozzle diaphragm and substantially completely splitting said ring space to reduce rotational movement of elastic fluid in such space.

'7. An elastic fluid turbine comprising a first stage having a bucket wheel and partial elastic fluid admission means therefor, a second stage with a diaphragm considerably axially spaced from said bucket wheel to form a ring space between them for distributing elastic fluid discharged from the bucket wheel during partial admission operation, and means for reducing loss of available energy of elastic fluid due to rotational movement in said space, said means comprising a dam extending radially from the shaft to the outer casing and axially from the bucket wheel to the diaphragm.

HANS KRAFT.

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