US1634894A

US1634894A - Turbine-cooling means

Info

Publication number: US1634894A
Application number: US77419A
Authority: US
Inventors: Robert C Allen
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1925-12-23
Filing date: 1925-12-23
Publication date: 1927-07-05
Anticipated expiration: 1944-07-05

Description

July 5, 1927; 1,634,894

' R. c. ALL EN 'TURBINE COOLING MEANS Filed Dec. 23. 1925 R.C.AHEN

WITNESSES: INVENTOR ATTORN EY Patented July 5, 1927.

UNITED STATES PATENT "OFFICEQVV ROBERT c. ALLEN, or 'SWARTHMORE, PENNSYLVANIA, ASSIGNOR TO W STINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION or PENNSYLVANIA.

TURBINE-COOLING MEANS.

Application filed December 23, 1925. Serial Ito. 77,419.

My invention relates to elastic fluid turbines, more particularly to means for ma1n taming an even CllStIlblllllOll of heat in the rotors. thereof when idle, and has for its object the provision of a method and apparatus wherebysaid even distribution of heat isreadily effected. I

Apparatus embodying features of my invention is illustratedin the accompanying drawing wherein Figurel is a view in eleva tionof a turbine with my invention applied thereto and having certain parts broken away to better show the'apparatus together found to be caused by an unequal distribution of heat-throughout the mass of the turbine rotor. When the turbine is stopped the rotor and blading, or parts thereof, are at a temperature approximating that of the motive fluid which may be as high as 700 F. While standing idle, the conduction of heat through the surrounding casing is the cause of convection currents in the air or mixture of air and steam in the casing. These, in turn, create Zones of higher temperature at the topof the rotor than at the bottom thus causing the top of the rotor to remain temporarily at a higher temperature than at the bottom. As the lower part of the rotor cools, it contracts and becomes shorter than the upper part resulting in a warping of the rotor so that there is an appreciable upward bow or bend therein.- If the turbine is again started with the rotor thus temporarily bent it will be found to be decidedly out of balance so that rubbing of the parts is liable to occur and the turbine be seriously damaged. A

The degree to which a rotor becomes unbalanced is determined by its .mass, its length, thetemperature thereof at the time it is stopped, and the interval oftime it has been stopped. In accordance with my in- .ven oi If det rmine the ma i u p a d warping of the rotor within which the turbine maybe safely started, the time in which the maximum allowable upward warping occurs and within which the turbine may be again safely started, and turn the rotor through a sufficiently wide arc, substantially 180, so that another, cooler part thereof is placed upwards and the hotter part downwards. The placing of the hot part of the rotor downwards and of the cool part upwards cools the lower, hotter part and heats the cooler part and thus effects a straightening of the rotor. Should the lower part again become cooler than. the upper part and the rotor again become Warped upwardly, it maybe turned a second or a third time according to the circumstances.

- In carrying out the invention, I provide gear means associated with the turbine shaft and adapted to turn the rotor when idle,

and I provide a motor for actuating the gear means. A ohronometric device is provided for controlling the motor circuit'so that the motor is started at the proper interval of time after the turbine is stopped, determined by the rate of warping of the rotor. After the turbine shaft is turned through an arc ofapproximately 180, the motor circuit is opened and the motor stopped. Should the turbineremain stopped through another; predetermined interval of time, the motor is again started and the rotor againturned throughlSO". By this means the rotor, never warps sufliciently to prevent the turbines being. started promptly.

Referring now to the drawing for a better understanding of my invention, I show a turbine 10 having a rotor 11 and a; shaft 12. At 13 is shown gear means arranged on the shaft, for example, .in the-turbine coupling housing, shown at 14. Extending transversely of the shaft 12 is a shaft 16 having provided thereon a worm 17 which is adapted to mesh with the gear teeth 13.

The shaft 16 is ,slidable longitudinally to the left of its position shown in Fig. ,1,'to permit disengagement of worm 17 and gear teeth 18. Whenthe turbine is in operation its normal direction of rotation'is in the direction of the arrow at 18, sot-hat the worm 17 is automatically thrown out of engagement with the gear 13 when the turbine is being operated by motive fluid. On

one end of'the shaft 16 is provided manual rings fl? and 3-1- on the Face of the gear means, such as a hand wheel 19, tor engaging the worm 17 with the gear 13 when the turhineis idle and it is desired to turn the rotor thereof. This is done by rotating the shaft 16 which screws the worm 1? into engagement with gear teeth A squared end is also provided on the shaft 16 for the attachment of a suitable tool for manually turning the turbine rotor 11 when desired.

As before pointed out when the turbine is first stopped and its rotor is heated, it cools faster at. the bottom than at the top and ellectsnn upward warping or bending oi the rotor. \Vithin certain limits, the upward bending of the rotor may be unob ject-ionable, but ljieyond said limits, dcpending on the time the rotor has been stopped, ditiiculties are encountered in again starting the turbine. In order to determine the rate o'l. up *ard bending of the rotor l l, l. show a measuring device E12 adapted to indicate the clearance between the casing and the rotor. By taliing readings when the rotor has normal clearance and at intervals while cool ing. the rate of upward distortion due to unequal distribution ol heat in the mass thereof may be ascertained. For example, it

it is found that at the termination oi? a period of two hours: after shutting down, the rotor has been bent upwardly as tar as allowable limits, 1 then turn the same by means of the shaft lb and worm 1? through an are of 180 so that the better part placed downwardly and the cooler part upwardly. With the rotor turned in this manner, the heat thereof. is carried upwardly by conduction and convection, the hotter part becomes cooler and. it straightens. it the continued cooling in the new position again ausea an upward warping ol the rotor to unsafe limits it may again be turned through 180.

In order that the above doacribral action may be carried out automatically. I ehow a motor 211; connected to the shalt It) by a sliding coupling 2h so that the worm li' may be readily disengaged :lrorn the gear 123. Driven from the opposite end oi the motor shaft a worm 2T engaging with a gear wlththe same gear ratio as the worm 1T andthe gear 12- so that the gear 2? makes a complete revolution in the same time as the gear 1 and the worm 1? when in mesh.

The motor 124- is controlled by an electrical circuit embodying two brauchee Fill and 3h] which have included therein two brushes 81 and 32 which bear on concentric 5Z8. Approaimatch. halt ol" each ot' the rings in) and Eli OOll'ipliSES conducting material and the other halt insulating material. It third brush 36 bears on both of the rings 3?) and 2MT and connects to one of the motor leads. -L- source ol? electrical energy is unheated at and is connected to the other motor lead through a :ontrolling awitch 38 ot the oscillating, double snap, double contaettype.

lt will be apparent from the drawing that with the switch BS in the ponition shown and the brush 32 hearing on the comlueting rnaterial ol. the ring- 38, the motor circuit is complete and the motor will operate until the

gears

28 and 13 have each. completed a haltrevolution or until the brush 32 is hearing against. the insulating material of the ring It the switch :58 be nowturned 5)). to connect with the branch 30 the motor eircult will then be completed through brush Ell, ring ll and brush 3b and the motor again UPQlfltUS until the

gears

28 and 13 have nch turned a halt revolution.

The switch 38 is controllcdby a chronometric device 259 which has an indicating element 4:0 included in an=electrioal circuit -l-l having a solenoid winding -12 incorporated therein. The moving element 1t?) ol the solenoid is biased upwardly by a spring i land has depending therefrom a flexible member ill. \v'heu the circuit il is (111- er ized, the flexible element-2th moves downwardly, striking the switch 38, whereupon it is turned to the right onto the left, as the case may be, con'uileting tliemotorcircnit through the branchesil!) or ill). In order that the circuit it]. maybe energized at pe riods of time determined by the rate ot warping of the rotor 11 I show branches shi -lo leading to equal divisions of time on the (.lll'Ol'lOinGtl'h'i device 39 so that, when the moving element it) touches at the points indicated, the circuit 41 is completed.

The operation (it the apparatusis as 'lol-- lowe: .l e rate ol? upward bending or warp in;- ot the rotor 11. is lirst determined by means ot the n'lcasuring device Eiland the maximum allowable warping within which the turbine may be safely tarted is determined. .lhe leads all olfthe electrical circuit; --l-l are next distributed,around the dial ot the chronometric device so as to cause the electrical circuit 41) to be con'iplcted at reguar intervals within which t heu'otor is to be nrucd. When the turbine is stopped, the ahal't .l(l is pushed towardthc grarllil by means ot the hand whee]v 1t and is screwed in until the worm 1.7 is in mesh with the gear t l. The clnrononictric device Ill) is then started and the moving element it] is turned. to contact with one oi the leads io -45 whereupon the motor starts and isturned until stopped by reason of one oi the brushes St or 3'3 moving oll' otl'fthewconducting material ol the rings 3? or it. i

The rotor now stands idle until theinorlug element 40 again contacts withoiie o l? the leads whereupon liliQm-ll'ltitOhlSStarted and. the rotor is turned through on arc of 180 as previously described. The rotor again stands idle througlr the period of time determined by its rate of warping when the moving element again energizes the electrical circuit 41, completes the motor circuit and the rotor is again turned through an arc of 180. In the manner described the proper distribution of heat in the rotor 11 is maintained so that the turbine may be started at any time after being stopped without danger of rubbing of the parts or excessive vibration.

From the foregoing it will be apparent that I have devised a method and apparatus for maintaining an even distribution of heat in a turbine rotor when idle.

WVhat I claim is 1. The combination with an idle turbine having a heated rotor, of means other than motive fluid for turning the rotor, and means determined by the rate of cooling of the mass of the rotor for periodically stopping and starting the turning means.

2. The combination with an elastic fluid turbine havinga rotor, of means adapted to operatively engage with the rotor and turn it during idle periods, and means including a chronometric device adapted to start and stop said turning means at predetermined periods of time, said periods of time being in accordance with the distribution of heat in the rotor mass.

3. The combination with an elastic fluid turbine having a rotor with a shaft, of an electric motor, gearing means between the electric motor and the shaft whereby the motor is adapted to turn the rotor during idle periods, an electric circuit for controlling the.

motor, a chronometric device adapted to close the motor circuit at predetermined intervals of time, and means responsive to a predetermined arc of revolution of the rotor for opening the motor circuit.

at. The combination with an elastic fluid turbine having a rotor with a shaft, of gear means arranged on the shaft, a worm adapted to engage with the gear means for rotating the shaft when the turbine is idle and adapted to disengage when the turbine is being operated, a motor for driving the worm, and means responsive to time cooperating with a predetermined arc of revolution of the shaft forstarting and Stopping the rotor.

5. The combination with an elastic. fluid turbine having a rotor with a shaft, of gear means arranged on the shaft, a worm adapted to engage with the gear means for rotating the shaft when the turbine is idle and adapted to disengage when the turbine is being operated, a motor for driving the worm,

other gear means associated with the motor,

a worm engaging with the other gear means rotor during intermittently idle periods comprising determining the rate of warping of the rotor due to unequal cooling thereof when idle, and turning said rotor through 180 deg. before it has warped sufliciently to entail undesirable unbalance if started.

7. The method of offsetting the warping of a turbine rotor due to an uneven distribution of heat throughout its mass when cooling during intermittently idle periods com prising, determining the period of time within which the maximum allowable Warping of the rotor occurs, and turning the rotor through 180 deg. within said period of time.

8. The method of offsetting the warping of a turbine rotor due to an uneven distribution of heat throughout its mass when cooling during intermittently idle periods comprising, determining the period of time within which the maximum allowable Warping of the rotor occurs, and turning the rotor through 180 deg. at the termination of said period of time.

9. The method of maintaining a turbine rotor within safe limits of balance during intermittently idle periods where warping of the rotor occurs in an upward direction due to unequal distribution of heat within its mass-comprising, determining the rate of warping of the rotor per unit of time, and turning said rotor sufiiciently to place a different portion of its mass upward before it warps beyond safe limits.

10. The method of maintaining a turbine rotor Within safe limits of balance during in termittently idle periods where warping of the rotor occurs in an upward direction due to unequal distribution of heat within its mass, comprising, determining the rate of warping of the rotor per unit of time, and turning said rotor to place a cooler portion of its mass upwards before it warps beyond safe limits.

In testimony whereof, I have hereunto subscribed my name this 21st day of Decem- R'OBERT G. ALLEN.

,ber, 1925.