US790426A - Elastic-fluid turbine. - Google Patents

Description

No. 790,426' 4 PATENTED MAY23, 1905.

' A. R. nonea ELASTIC FLUID TURBINE.

APPLICATION FILED APR.24, 1903- *Une sss: J 4 In-Yeh'ofi 27 flusbinR.Dodge,

UNITED STATES Patented May 23, 1905.

PATENT OFFICE.

AUSTIN R. DODGE. OF SOHENEOTADY, NEW YORK, ASSIGNOR TO GEN- ERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELASTlC-FLUID TURBINE.

SPECIFICATION forming part of Letters Patent No. 790,426, dated May 23, 1905.

' Application filed April '24, 1903. Serial No. 154,075.

To all whom, it may concern:

Be it known that I, AUsTIN R. DODGE, a citizen of the United States, residing at Schen-. ectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in the Construction of Elastic- Fluid Turbines, of which the following is a specification.

It has heretofore been considered necessary to enlarge the working passage in elastic-fluid turbines of the jet type from the receiving to the discharge end, meaning by working passage the passage formed between the rows of moving and stationary buckets. This enlargement may take place gradually or by a series of steps. In addition to this the nozzle is arranged to enlarge or expand from the throat to the end, so as to largely convert the pressure of the motive fluid into velocity or m'sviva before delivering it in the form of a jet to the wheel. The enlargement in the working passage involves an increased cost in construction both as to material and in the labor and expense involved in cutting the buckets. The expense of cutting buckets with expanding orenlarging passages between them is largelyincreased by the fact that a second out or operation is made necessary where the expansion takes place circumferentially, as is the common practice. The passages between buckets of a given row also commonly increase in radial depth from the inlet to the discharge end, thereby necessitating an inclined peripheral surface, which obviously increases the difliculty of machining besides requiring more metal. In certain instances the enlargement in the working passage forms a very considerable amount of the total area of the passage.

I have determined by a series of tests that the leakage through the clearances between the moving and stationary expanding buckets of the working passage when the clearances are those commonly employed equals theamount of steam which is intended to be, taken care of by the enlargement of the passages. Such being the case, some of the bucket-passages in front of the nozzle are working with less than the necessary amount of steam to fill them. It follows from this that the enlargement is not only unnecessary under the conditions specified, but is a positive objection.

In elastic-fluid turbines there is always considerable condensation of the steam or other motive fluid employed. This is particularly true of jet-machines, where the pressure of the fluid is largely converted into velocity by expanding nozzles before being delivered to the wheels. There is also more or less condensation due to radiation. Obviously the condensation of the steam or other vapor further decreases its volume, which is another reason for not using expanding working passages.

My invention has for its object to reduce the cost and simplify the construction of elastic-fluid turbines and also to render them more efficient.

In the accompanying drawings, which rep resent one embodiment of my invention, Figure 1 is a quarter-section of a turbine, and Fig. 2 is a detail view showing the construction of the buckets and the nozzle.

1 represents a suitable shell or casing for the wheel 2 and having an exhaust-opening disks are provided with spacers 5 and re-- taining bolts 6, which passthrough them. Formed integral with the disks or otherwise secured thereto are peripheral buckets 7,having small projections or tenons 8 for securing the segmental cover 9 in place, and between the buckets in a given row are non-expanding pasages. Situated between the wheelbuckets is a segmental intermediate support 10, having a plurality of radially-extending buckets 11, also having non-expanding passages between them. The intermediate support is provided with a flange 12, by which it is secured to the casing or shell by bolts 13. The arc covered by the intermediates varies with the arc of the wheel covered by the nozzle or nozzle-sections, and the number of nozzles or nozzle sections employed is-determined by the amount of power which the turbine is to deliver. Between the bodies of the bolts and the support is a slight clearance, which permits the intermediates to be adjusted in a direction parallel with the axis of rotation. The left-hand side of the casing is provided with an opening to receive the expanding nozzle 15. The nozzle is provided with an outwardly-extending flange which engages with a finished surface on the casing. Engaging with this flange is a second flange 16, to which the steam-carrying conduit 17 is attached. Bolts 18 are employed to secure both the conduit and the nozzle in place. The nozzle is provided with a well-rounded bowl 19 and a cylindrical restricted throat 20. From the throat to the discharge end of the nozzle the walls diverge, and owing to this divergence the pressure of the steam is converted into velocity or m's m'va prior to being discharged to the bucket-wheels.

The drawings shown may represent a turbine in itself, or theymayrepresent one stage of a turbine comprising a plurality of stages. The nozzle may consist of one orseveral similar expanding passages having the same angle of delivery. In the event of the structure shown beingused alone the pressure in the conduit 17 will be approximately that of the vapor-generator and the pressure at the discharge end of the nozzle will be somewhat above that of the shell pressure. In event of the structure shown being used in connection with another stage or stages the pressure within the conduit 17 will be equal to that of its source of supply, whether it be the boiler or an adjacent stage, and the pressure within the shell or casing will be dependent upon what follows the turbine-that is to say, whether it is connected to a second stage or to acondenser or exhausts into the open air. In any event the pressure within the conduit 17 is partly converted into velocity before being delivered to the bucketwheels. The spaces between the wheelbuekets 8 and the intermediate buckets 11 form a non-expanding working passage for fractionally abstracting the velocity from the motive fluid. In using the term non-expanding passage I do not mean to be restricted to a passage which has absolutely the same cross-section at every point, because a slight variation at one or more points will work no substantial injury.

From Fig. 1 of the drawings it will be seen that the entrance and discharge ends of the passages between the wheel-buckets have the same radial depth. The same is true also of the passages between the intermediate buckets. Referring to Fig. 2, it will be seen that the walls 21 and 22 of the buckets are concentric. Hence the crosssection at all points in the working passage is the same. In this manner a non-expanding working passage is provided for fractionally abstracting the velocity from the motive fluid, which. velocity is due to the expanding nozzle 15. Byhaving the radial depth of allot the buckets the same and making the periphery thereof a cylinder instead of the frustuni of a cone, as is the common practice, I am enabled to materially decrease the cost of cutting the buckets, because they can be cut at a single operation, whereas when the buckets are provided with passages expanding or enlarging circumferentially it is necessary to alter the position of the tool relative to the work before making a second cut. In this latter case the first cut makes the walls concentric, and the second cut gives the necessary enlargement and makes the walls non-concentric. By dispensing with the enlargement the in crease in radial depth of the buckets on their discharge end is obviated, which means a saving in the cost of cutting, because the linear inches out are less, and also means a saving in stock. This latter is advantageous, because it slightly reduces the weight of the wheel. It must be remembered that the wheel is traveling at high peripheral speed and is under tremendous strain, due to centrifugal force. Hence any saving in weight at the periphery is important.

I have stated that the buckets can be made with a single cut; but I do not wish to be understood as excluding a second or finishing cut, if it is found desirable.

As constructed the nozzle imparts a high velocity to the elastic fluid, which may he steam or similar fluid, and the impact of the molecules on the wheel-buckets causes rotation. Where a single row of wheel-buckets is employed, the speed of the wheel is impractical for ordinary commercial use without expensive and specially-formed. speedreducing appliances; but by providing two or more rows of wheel-buckets and intermediates the speed of the wheel relative to the speed of the fluid stream can be made much lower. This reduction in speed is due to the fact that the velocity of the fluid is abstracted in two or more successive oporatioi'is, each operation reducing the speed of the fluid. stream by a certainamount.

In Fig. 2 the clearance 23 between the wheel and intermediate buckets is clearly shown, and it is evident that so long as the pressure in the nozzle is above the shell-pressure steam will escape radially and be lost in so far as the particular shell is concerned. The clearance between parts is necessary for mechanical reasons, and I so proportion or design the working )assages that they are always completely iilled with steam when opposite the nozzle.

In accordance with the provisions of the patent statutes I have described the principle of operation of my invention, together with the apparatus which I now consider to its velocity unimpaired, with rows of wheelbuckets separated by clearances through Which leakage may take place and which are acted upon by the motive fluid for fractionally abstracting the velocity, the said buckets being separated by non-expanding working passages.

2. In an elastic-fluid turbine, the combination of a shell or casing, bucket-wheels hav ing non expanding1 working passages and acting to fractiona y abstract the velocity of the motive fluid, intermediate buckets also having non-expanding passages, the Wheel and intermediate buckets being provided with clearances through which leaka e may take place, and an expanding nozz e which converts the pressure of the motive fluid into velocity and delivers it in the form of a jet to the wheel-buckets.

In witness whereof I have hereunto set 0 hand this 20th day of April, 1903.

AUSTIN R. DODGE.

Witnesses:

FRANK M. KING, J. B FOSTER.

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