US970193A - Turbine. - Google Patents

Description

W. G. DODD.

TURBINE.

APPLIUATION FILED AUG.I,1909.

Patented Sept. 13, 1910.

2 BHBETS-BHEIIT l.

INVENTOR' ATTORNEY W. G. DODD. TURBINE. APPLIUATIOH mum no.1. 1909.

Patented Sept. 13, 1910.

2 SHEETS-SHEET 2.

INVENTOR ATTORNEY UNITED STATES PATENT OFFICE.

WILLIS G. DODD, OF SAN FRANCISCO, CALIFORNIA.

TURBINE.

T 0 ct whom it may concern:

Be it known that I, WILLIS G. Donn, a citizen of the United States, residing at San Francisco, in the county of San Francisco and State of California, have invented new and useful Improvements in Turbines, of which the following is a specification.

The object of the invention is to obtain a turbine of low rotative speed and high efliciency. This object is accomplished by transforming the potential energy of steam under high pressure into velocity by means of an expanding nozzle, and conducting this steam in a curvilinear path and compelling it to rotate in a plane tangential to the plane of rotation of the turbine wheel or rotor, and converting the resultant centrifugal force into useful work. The means employed for this purpose is described in the following specification, pointed out in the claim and illustrated in the accompanying drawings, similar letters referring to similar parts, in which,

Figure l is a vertical section of the turbine, showing the relative positions of the rotor, the housing and the casing. Fig. 2 is a vertical cross section of the rotor, showing the relative position of the housing. Fig. 3 is an enlarged cross section of the rotor and housing on the line ab, showing the diverging nozzle, rotor and housing in their relative positions, and also indicating the curvilinear path of the steam. Fig. 4 is an enlarged sectional View of the rotor and housing with the diverging nozzle. Fig. 5 is a plan view of a portion of the rotor rim, showing the fins, guides or semi-partitions which confine or guide the steam in its curvilinear path. Fig. 6 is a sectional view of the rotor and housing in their relative positions on the line (:d of Fig. 4, showlng the fins and circular chamber within which the motive fluid rotates. Fig. 7 "is a vertical cross section throu h the rim of the rotor and housing, in t eir relative positions, on the line e; of Fig. 4, showing the elliptical annular chamber formed by the tangentially inclined circular chambers.

Specification of Letters Patent.

Application filed August 7, 1909.

Patented Sept. 13, 1910.

Serial No. 511,722.

Heretofore the practice has been, in turbine construction, to employ the kinetic energy of the steam, using the impulse or reaction principle, for the conversion of said energy into useful work. But in the present form of turbine there is utilized the centrifugal force generated by steam rotating at high velocity within a curvilinear path of small diameter, and the difference between the two methods may be illustrated as follows: If steam under one hundred pounds pressure is expanded, by means of a diverging nozzle, to atmospheric pressure, the resultant effective velocity is approximately 2244 feet per second, and the kinetic energy contained in one pound of this steam, employing the formula 1,246,600 pounds.

All of this enormous quantity of energy is not available, however, for useful work. The loss due to changing the direction of the steam from linear to curvilinear, including friction etc, is, as near as can be ascertamed 20%, or one-fifth, leaving a balance of 997 ,280 pounds. This ressure is exerted in all directions radially rom the center of the circular path within which the steam is traveling, and it is obvious that, in only a relatively small part of the whole of this circular path, can this force be effectively utilized, this being, in practice, approx1- mately one eighth of the entire circumference. This furnishes 124,672 pounds of energy available for conversion into useful work, which shows a theoretical difference in favor of the application of centrifugal force, as compared with the direct conversion of the kinetic energy, as 100 is to 63. This statement would appear to be erroneous, were it not capable of demonstration that, should the diameter of the curvilinear path be doubled or increased from three inches to six inches in diameter, giving a radius of three inches, or one quarter of a foot, then, by the application of the same formula,

there would be obtained 627,200 pounds. Deducting 20% for change from a linear to a curvilinear path, there would be left 501,760 pounds, which, divided by 8, gives 62,720 pounds of energy as available for conversion into useful work, an amount less than the kinetic energy available by the direct method, whic hresult clearly points out the limits within which the centrifugal method of conversion of the energy is more effective than the direct conversion thereof, which limits may be summarized as follows: The greatest efficiency will be obtained when the circular path of the steam has a radius as small as possible, leaving a neutral axis around which the strata or jet of steam can revolve. The neutral axis referred to should be approximately twice the diameter of the jet.

By referring to the drawings, the con.- struction of the turbine will be readily understood, and is briefly as follows: As only a small portion of the circumference of the tangentially inclined circular path is available for the absorption of energy the guide vanes may be cut away more or less leaving an open space in the center of the annular chamber, which serves as a neutral axis around which the jet of steam revolves, and also provides means for the exit of any dead steam, due to the provision of any excess in the number of chambers actually required as will be explained hereafter.

While it is possible to operate this type of turbine at any low rate of speed desired, it may be observed that the lowest speed at which the turbine should be operated to obtain the highest efiiciency is when the peripheral speed of the rotor is a proximately twelve and a half per cent. of the velocity of the steam leaving the jet, and the number of chambers in the housing required to give the number of cycles, or rotations of the steam, requisite for the absorption of the available energy, by the rotor, is determined in the following manner. For the purpose of illustration, steam under 100 pounds ga e pressure may be taken, and it is desire to operate a wheel or rotor two feet in diameter at a speed of 2670 revolutions per minute, equivalent to a peripheral speed of the rotor of 280 feet per second, and exhausting against a pressure of one pound above atmosphere. Steam at 100 pounds gage pressure contains 1184.4 heat units per pound and has a temperature of 337 .8 degrees F., and at one pound pressure has a temperature of 216.3 degrees. This temperature drop gives us a thermal efficiency of 15.24% or in other words, only 15.24% of the total heat units contained in a pound of this steam is available viz: 180.5 for conversion into useful work, and, as each heat unit is equal to 778 foot pounds, the available potential energy contained in one pound of steam, under the conditions given, would be 1184.4 .1524 778 or 140,429 potential foot pounds. The available velocity at which this steam flows from a diverging nozzle would be V140,429 X 6 2244 feet per second,

and the energy of this pound of steam under a velocity of 2244 feet per second, converted into centrifugal force, using a curvilinear path of three inches having a radius of oneeighth of a foot, would be equal to m 1,246,600 POUIldS.

pounds of energy, which, multiplied by six, gives the available velocity in feet per second and is designated in column marked V The column marked V indicates the peripheral speed, or velocity, in feet per second of the rotors rim. The column marked FAB, indicates the amount of energy in pounds absorbed or converted into Work by the rotor at each cycle or revolution of the steam between the rotor and housing. The column Y indicates the percentage of energy absorbed at each cycle. The column Z indicates the total percentage of energy which has been absorbed by the rotor at any particular cycle. For instance, at cycle No. 8, theoretically, .7 604% of the total available energy which has been put into the turbine has been absorbed and converted into useful work. Upon inspection, the table indicates that, with a rotor two feet in diameter, making 2670 R. P. M. or a peripheral speed of 280 feet per second, it requires, to absorb all the available energy possible, sixteen cycles, showing a recovery of the available energy put into the turbine of ninety-seven per cent, with a residual loss of approximately three per cent.

Centrifugal turb ine-2 ft. wheeL-JOO pounds steam to 1.3 at7n0sphe7-es26'70 R. P. M.:280 ft. 7367 second.

TABLE No. 1.

% absorbed.

N mv v v v FAB Y z W/E If the steam at 100 pounds pressure is exhausted into a vacuum of 26 inches and the same Wheel is run at the same peripheral speed, the results would be somewhat changed, as indicated in table No. 2 as given below. The velocity of the steam would be increased to 2970 feet per second and the number of cycles required to absorb the available energy would be increased to nineteen.

Centrifugal turbne-100203md3 to 26 3'70. vac-2 ft. whack-267.9 .P. M.-280 S. F.

TABLE No. 2.

% absorbed.

N 1 1v v v v FAB Y z W/R The efliciencies here shown are not attainable in actual practice, due to losses which occur, in the way of radiation, windage, leakage, and so forth, but it is no detriment to the machine to provide the number of cycles indicated, as the expended steam readily discharges through the openings between the guide blades of the rotor and the housing.

The construction and application of the device here disclosed produces a simple and reliable prime mover, which requires little attention, and, when intelligently operated, will convert into useful Work a high percentage of the energy available.

I do not wish to be understood as confining myself to the specific construction here shown, but reserve the right to make such changes and modifications as properly come within the spirit and scope of my invention. I Having described my invention, what I claim as new, and desire to secure Letters Patent for, is

A steam turbine comprising a rotating element and a stationary element, said elements between them forming an annular elliptical chamber, within which are located a series of guide vanes, constituting a series of tangential chambers, forming paths of constant deflection for the impelling medium, an expanding nozzle located within the first chamber of the series, a neutral axis or annular space between the stationary and rotating elements, formed by cutting away the guide vanes as and for the purpose specified.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

WILLIS G. DODD. Witnesses:

FRANCIS M. WRIGHT, D. B. RICHARDS.

Images