US1093148A - Elastic-fluid turbine. - Google Patents

Description

R. H. RICE. ELASTIC FLUID TURBINE. APPLIGATIONIILBD'DEG. 20, 1913.

' 1,098,148. v Patented Apr.14,1914.

Inventor; Rihar-d l-L. Rice.

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RICHARD H. men,

E TA M OFFICE OF LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, 'A-CORPORATION OF NEW YORK.

ELASTIC-FLUID TURBINE.

Specification of Letters Patent.

Patented Apr. 14, 1914.

Application filed December 20, 1913. Serial No. 807,813.

7 '0 all whom it may concern Be it known that I, RICHARD H. Bron, a citizen of the United States, residing at Lynn, county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Elastic-Fluid Turbines, of which the following isa specification.

This invention relates to 'multi-stage turbines actuated by an expansive fluid such as steam. Two classes or types of multistage steam turbines are now well recog nized, one in which the motive fluid operates by reaction or pressure of which the Parsons machine is typical, and the other converting the steam pressure into velocity and operating by impulse or impact, as in the Curt-is machine. In both types thereis a drop in pressure and increase in volume as the steam progresses through the working passage of the turbine. In the Parsons machine this drop proceeds by rather small increments from one end of said Passage to the other. Inasmuch as the velocity due to a given drop in pressure becomes greater and greater as the lower pressures are reached, it follows that the working passage must be correspondingly enlarged in order to permit the steam to expand and keep the same ratio between the steam velocity and the blade velocity upon which the turbine efliciency depends. This means that in a machine of the Parsons type the blades may be quite short in the high pressure and intermediate portions of the working passages,

but must increase in length very rapidly n the low pressure end, and also change the1r curvature and increase their clearance, in order to accommodate the much greater volume of steam. Owing however, to mechanical reasons, the maximum length of the buckets is limited, so that the lowest pressure cannot be utilized to the best advantage in a Parsons turbine. Furthermore, if a larger drum is used to carry long bucketsin the low pressure end, this necessitates a large balancing drum, all of which adds to the weight and the cost.

The ob'ect of my invention is to overcome these defects and obtain. a'greater amountof work from the energy of the low pressure steam in a turbine of the Parsons type. With this end in view, I add at the low pressure end of the machine one or more stages containing impulse wheels, each carrying preferably but a single row of buckblade at that point.

ets cooperating with nozzles located in diaphragms which inclose' said stages. These impulse wheels can be made of suflicient diameter to give a peripheral speed of rotation approximately correct for the best efficiency, that is to say, about one-half the speed of the steam, which in these low stages is quite high. Moreover, .these impulse wheels require no balancing drums, and are much lighter in weight than blade carrying drums would be. By their use, a far greater proportion of the total energy of the steam can be turned into useful WOI'k.

In the accompanying drawing, Figure 1 isa longitudinal section of a horizontal turbine embodying my invention, and Fig. 2"

is a diagram of steam pressures and volumes.

Referring first to Fig. 2, the horizontal central line represents the length of a working passage in which the steam is expanded from its initialhigh pressure down to absolute zero. The lines at right angles thereto represent the volumes of steam, at consecutive points along said passage, the volume being in inverse ratio to the pressure. From this figure it appears that the volume increases very rapidly and by larger and larger increments as the low pressure end of the working passage is approached so that in the final portions of said passage the volume is immensely greater than in the high pressure end. One pound of steam at 210 pounds absolute pressure occupies a volume of 2.15 cubic feet, while one pound at two pounds absolute pressure occupies 172.08 cubic feet. In order to utilize all the energy in the steam, the turbine blades should increase in length from the high -pressure end of the machine to the low pressure end, in. exactly the same ratio as the volume of the steam increases. In other words, the length of anordinate of the curve m at any point represents thelength. of the It is evident that in the extremelow pressure region the blades would become so long as to give rise to dangerous vibrations, and would be too weak to withstand the centrifugal strains. Hence it is customary, in turbines of the Parsons type, to waste spme energy by restricting the length of the low pressure blades to what is known to be a safe size.

Inv Fig. 1 I have shown a turbine having illt its high pressure blading 1 and intermediatcblading 2 of the Parsons type. Furtherl the pressure or the steam fiowing through more, some of the low them into velocity, though not necessarily of the 'divergingtype; so that the wheel or wheels operate by impact, being, therefore, of the Curtis type. These wheels are considerably larger in diameter than the drums I higher vacuum.

- Copies of this patent may be'obtained so that the proper relation of vane to steam speed will be obtained. As many velocity stages may be used as may be found necessary to extract all the energy of the steam, or at least such as can be extracted down to the'lowes't absolute pressure made available by a condenser. In any event, the addition of these impulse stages to the reaction machine'results in greater efiiciency and economy, and makes it possible to utilize a speed In accordance with the provisions of the for five cents each, by addressing the I Washington, D. 0.

patent statutes, I have described the princlple of operation of my invention together with the apparatuswhich I now consider to represent the best embodiment thereof; but I desire to have itiunderstood that the apparatus shown is only illustrative, and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. A steam turbine having a high pressure portion of the reaction type and its final low pressure portion formed into one or more stages of the impact type.

2. A steam turbine having its high pressure portion of the reaction type, and its low pressure portion of the impact type.

3. The combination with a steam turbine of the Parsons type, of one or more low pressure stages provided with nozzles, and impulse Wheels cooperating therewith.

In witness whereof, I have hereunto set my hand this sixteenth day of December RICHARD H. RICE. Witnesses:

JOHN A. MCMANUS, Jr., Jon J. MoKENNnY.

Commissioner of Patents,

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