US1678065A - Turbine - Google Patents

Description

July 24, 1928. 1,678,065

c. J. LAMB TURBINE Filed June 1'7, 1925 I U as :5 Wham v ATTORNEY WITNESSES:

Patented July 24, 1928.

warren STATES PATENT OFFICE.

CARL J. LAMB, 0F PHILADELPHIA, PENNSYLVANIA, ASSIGNOR T0 WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

TURBINE.

Application filed June 17,

My invention relates to elastic fluid turbines and it has for its object the provision of a method and apparatus for minimizing the time required for starting up a steam turbine after it is shut down.

More specifically, my object is to prevent distortion and to prevent rubbing of the turbine parts by minimizing the temperature differences between the upper and lower parts of the turbine casing and rotor.

In the accompanying drawings forming a part of this specification Fig. 1 is a view, partly in section, of a multi-stage elastic fluid turbine to which my invention is especially applicable; Fig. 2 is a similar view showing a modified form of my invention.

In the operation of power. plants,as is well known, there is ordinarily a variation of power demand in a days operation. During certain hours of the day more power units must be put in service to supply the power demandthan during otherhours. It follows therefore that in a days operation one or more units are operated for a part time only and are shut down the other part of the time.

IVhere elastic fluid turbines are employed as prime movers under the circumstances mentioned, dificulties have been encountered due to the unequal distribution of heat within the turbine casing during idle periods. When the turbine is in operation, the rotor and the casing become heated by the motive .fluid; and, as motive fluids having tempera tures of 7 00 F., or more, are frequently admitted to steam turbines, it will be apparent that the rotor and the casing become highly heated. When the turbine is shut down and remains idle for several hours the temperature within the casing becomes greater at the top than at the bottom and the idle rotor and the casing cool off to a greater extent at the bottom than at the top. The lower parts of the rotor and the casing being cooler than the upper. parts thereof. such lower parts contract to a greater degree so that the rotor and the casing are caused to bow or bend somewhat due to the differences in temstatute the. '11 car and lower 1925. Serial No. 37,732.

If now the turbine is again started it will be found to be decidedly out of balance and rubbing of the parts is liable to occur ifit is brought up to its designed speed before the heat of the rotor has again become evenly distributed throughout its mass. This difficulty is especially encountered in a turbine having a long rotor of the drum type.

Various expedients have been resorted to in order to overcome the before-mentioned difficulty; that most commonly employed being the provision of a separate motor with suitable gearing to keep the rotor of the idle turbine slowly rotating during its idle periods. This and other expedients known to me are obviously expensive and cumbersome.

Another deleterious effect on the turbine which has been found to follow intermittent periods of operation is that considerable condensation occurs within the casing during ldle periods. Inasmuch as this condensation takes place in the presence of air, serious corrosion of the turbine passages and blading follows, particularly when formed of iron or steel, entailing overhauling and reblading before it would otherwise be necessary.

In accordance with my invention I overmay be necessary to introduce the gaseous medium at a plurality of points in order to insure an even distribution of heat within the casing.

Practically, the invention has been carried out by connecting a suitable number of conduits with a source of air under pressure and conveying the air under pressure through the conduits to selected points in the turbine casing. I have found that intermittently operated turbines equipped with apparatus in accordance with my invention may be started and brought up to full speed in one-third the time of other turbines not similarly equipped. I have also found that the circulation of air through the turbine prevents condensation therein during idle periods, thus preventing its corrosion.

Referring now to the drawings for a better understanding of my invention I show in Fig. l at 10 anelastic tluid turbine having a motive fluid inlet 11 and an exhaust outlet at 12, said exhaust outlet being'connected to a condenser at 13. At 1 1 is shown part of the turbine rotor in section, said rotor being of the drum type and provided with a plurality of rows of moving blades 1616. The turbine casing is shown at 17 and provided with a plurality of rows of stationary blades 1818 all as is well understood in the art to which my invention relates.

VVherea turbine such as is illustrated is intermittently operated and no provision is made for maintaining an even distribution of heat within the turbine casing when the turbine is idle, the lower parts of the rotor lt and the casing become cooler than the upper parts thereof causing them to bend. and

the rotor to become unbalanced. It the turof the turbine in the upper part of the tur- The conduits 19-19 are con hine easing. nected to a manifold 21 which 15 in turn conneeted to a source of air under pressure 22,

such, for example, as the usual air pressure systemfound in modern power plants.

Each of the conduits 19-19 is provided. with a valve 23 adapted to be'closed' when the turbine is being operated and to be "opened tor theadmission of air under pres sure to the casing when the turbine is idle. A valve 24- in the conduit 22 is also provided which shuts off air tromi the manifold 21 when the apparatus is not in operation. A gauge 26 in the conduit 22 may also be provided for determining the pressure at which the apparatus is operating.- By manipulating the valve 241 the operating pressure may At 27 I show a valve leading be varied. from the lower part of the interior of the casing, at the exhaust endthereoit, to the at mosphere. \Vhen the turbine is shut down,

I the valve 27 is opened so that there may be a free circulation of air therethrough.

The operation of apparatus in accordance with thisn'iodification of the invention will be apparent. lVhen the turbine is shutdown. the valve 27 is'opened, also the valve 2st and the valves 23. Air from the conduit 22 and manifold 21 now passes through the conduits wardly around the rotor 141 and out through from whence it flowsdownwardly around the valve 27. Inasmuch as the heat within the turbine casing has a natural tendency to rise, the incoming air under pressure flowing downwardly sets up a flow opposite to the natural flow tendency and causes the turbine rotor to be maintained at an even temperature throughout its mass. In addition to maintaining the turbine rotor at an even temperature the air entering through the conduits 19-19 drivesall moisture out otthe turbine casing" and prevents corrosion, by means of mechanical displacement.

It will be apparent that by disposing the conduits longitudinally of the turbine, I provide for an even distribution of air along the rotor and thereby maintain an even distributionofheat longitudinally of the rotor... Air is admitted over a period sufficient to maintain the temperature differences be" tween the upper and lower portions of the I casing and of the rotor at such. low values that, after shut down, a minimum time is required for restarting.

Referring now to Fig. 2I 7 form of my invention. Instead of introduc ing pressure from an outside source, air within the turbine casing is kept; in circulation during idle periods of the turbine. In aeshow' a modified cordance with this modification I provide a blowing apparatus 28 having an inlet conduit 29 connected to the bottom part of the turbine casing and a discharge conduittl connected to the upper part of the turbine casing. During idle periods of the turbine 10 the valve 27 is opened, admitting air to the interior of the turbine casing and the blower 28 is put in operation. Air is then sucked trom'the bottom part of the turbine casingthrough the blower and discharged into the upper part of the turbine casing the turbine rotor to the blowersuction 29 thus maintaining a circulation of air downwardly around the rotor.

While I have illustrated my invention as employing. air for the circulating medium through the turbine during idle periods, this has been done solelybecause air is, at the moment, the'most available medium to be employed. It will be obvious however, that any other gaseous medium might be em ployed so long as it is circulated in the man-:

ner herein set forth for maintaining an even distribution of heatand preventing condensation within the turbine during'idle periods.

From the foregoing it. will be apparent that .I have invented an improved method of securing an even distribution of heat within an idle turbine which is simple and easy of application, and which. also prevents corrosion withinthe interior of th turbine.

While I have shown my invention in but two forms, it will be obvious to those skilled in the art that it is not so limited, but is' susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

hat I claim is: i

1. The combination with a multi-stage turbine having a rotor and a casing, of means for securing an even distribution of heat through the turbine along the rotor when idle, comprising a distributing manifold adapted to be connected to a source of gaseous medium under pressure, conduits leading from the manifold to the'various turbine stages in the upper part of the turbine casing, and means for withdrawingthe gaseous medium from the lower part of the casing.

2. The combination with a multi-stage turbine having a rotor and a casing, of means for insuring an even distribution of heat through the turbine along the rotor and preventing corrosion of the interior thereof when idle, comprising a pluralityof conduits adapted to be connected to a source of gaseous medium under pressure and communicating with the interior of the turbine casing at selected points in a longitudinal row in the upper part thereot, and means for exhausting the gaseous medium from the turbine casing.

3. The method of effecting an even distribution of heat and preventing corrosion within an idle multi-stage turbine, said turbine having a casing, a rotor and a valve in the lower part of the casing adapted to be opened when the turbine is standing idle, comprising opening the valve at the lower part of the casing, and introducing air under pressure into the interior of the casing at a plurality of points longitudinally of the turbine and in the upper part thereof, whereby it circulates downwardly around the rotor and out through the valve.

a. The method of effecting a distribution of heat and preventing corrosion within an idle multi-stage turbine, said turbine having a casing, a rotor and a valve in the lower part or" the casing at the exhaust end thereof adapted to be opened when the turbine is standing idle, comprising opening the valve at the exhaust end of the casing, introducing air under pressure into the interior of the casing at various selected stages in the upper part of the turbine whereby it circulates downwardly around the rotor and out through the valve.

5. The combination with a multi-stage turbine having a rotor and a casing, of means for securing an even distribution of heat along the rotor when idle, comprising a plurality of conduits adapted to be connected to a source of gaseous medium under pressure and communicating with the interior of the turbine at a number oi points eXtending longitudinally of the casing, and

means located in the casingoopposite said points for discharging gaseous medium from of the casing, and means located in the easing opposite said row for discharging gaseous medium from the turbine casing.

7. The combination with a multi-stage turbine having rotor and a casing, of means for securing-an even distribution of heat along the rotor when idle, comprising a plurality of conduits adapted to be connectedto a source of gaseous medium under pressure and comn'iunicating with the interior ot' the casing at various stages throughout the length of the turbine includthe high-pressure stage, and means communicating with the interior of the casing oppositely of said conduits for discharging gaseous medium from the turbine casing.

8. The combination with a multi-stage turbine having arotor and a casing having an exhaust end, oi means for insuring an even distribution of heat along the rotor, comprising a plurality of conduits connected to a source of gaseous medium under pressure and communicating with the interior of the turbine at a number of points in a row extending longitudinally of the casing at the top thereof, and means located in the lower part of the casing at the exhaust endtor discharging gaseous medium from the turbine casing.

9. The method of minimizing distortion of a turbine rotor and casing in order to reduce the time required for starting after shut down which consists in maintaining minimum temperature differences between upper and lower parts of the turbine casing and rotor after shunt down and until the turbine is re-started by passing a gaseous medium through the space between the casing and the rotor, continuing said operation after the moisture has been removed from said space, in order to prevent the accumulation of heat at the upper portions of the casing and rotor.

10. The method of maintaining an even distribution of heat in the stator and the rotor of a turbine when standing idle, which embodies passing a current of fluid through said turbine, uniformly distributing said fluid among the spaces within the turbine, and discharging said fluid from the turbine.

11. The combination with a multi-stage turbine having a rotor and a casing, of

means/for insuring an even distribution of heat along the rotor, comprising at least one conduit connected to it soui ce of gaseous medium under pressure and'eommunicating With the interior of the'turbine at an intermediate stage thereof and) at the top of the casing, and means at the lower part of the casing for' discharging gaseous medi'um' therefrom.

In testimony whereof, I have I subscribed my name thisseeond'duy of J une 1925. I I s 1 CARL J: LAMB.

hereunto 10

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