US1092972A - Governing low-pressure turbines. - Google Patents

Description

J. G. CALLAN. GOVERNING LOW PRESSURE TURBINES.

APPLIUATION FILED 1030.4, 1912.

1,09%,972. Patented Apr. 14, 1914.

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GDVBRNING'LOW PRESSURE TURBI'YNES.

APPLICATION FILED 1130.4, 1912.

Patented Apr. 14, 1914 2 SHEETS-SHEET 2.

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JOHN G. CALLAN, 013' BOSTON, MASSACHUSETTS, ASSIGNOR TO COMPANY, A CORPORATION OF NEW YORK.

GENERAL ELECTRIC GOVERNING LOW-PRESSURE TURBINES.

' Specification of Letters Patent.

Patented Apr. it, 1914.

Application filed Deeembe? 4, 1912. Serial No. 734,860.

To all whom it may concern:

Be it known that I, JOHN G. CALLAN, a citizen of the United States, residing at Boston, county of Sufi'olk, State of chusetts, have invented certain new and useful Improvements in Governing Low-Pressure Turbines, of which the following is a Specification.

This invention relates to elastic fluid turbines which are driven by low-pressure steam exhausted from high-pressure engines or from industrial apparatus. In the case where the turbine is carrying its own load, independent of the load on the high-pressure engine, it may frequently happen that the latter will drop, causing a decrease in the amount of exhaust steam furnished by said engine, and also a decrease in pressure in the receiver between engine and turbine, while the load requirements on the turbine may continue unchanged at full load. In this event, the turbine will drop a part of its load in spite of the efforts of its speed governor to prevent this by opening up the throttle valve in the low pressure main. This val ve may open its widest and yet because of the failure of the supply the receiver pressure will not be sufiicient to en- 'able the turbine to carry its load.

My invention aims to overcome this difliculty by controlling the receiver pressure and by re-acting through said receiver on the valves of the high-pressure engine so that they will not be closed upon a drop in the load of said engine, but will continue to furnish suiiicicnt steam to run the turbine. I accomplish this by closing successive nozzle valves on the turbine when the steam supply lesscns and thereby keeping up or increasing the receiver pressure by lessening the aggregate nozzle area admitting steam to the turbine. As this receiver pressure increases, the engine, or engines, which exhaust into it will encounter correspondingly higher back-pressure, and will slow down whereupon its governor, or their governors, will in turn admit an increased supply of steam. This action will go on until equi-- librium is again established with the new load division. Two things tend to reestablish this equilibrium; first, the increase of steam supply from the engine, or engines, determined by the increased back-pressure, and second, the increased energy per pound Massaof steam available for mined by the same fact. ment, the total steam always be used by the turbine and each will have the use of this steam through such pressure drop as is required to carry the exact load existing at any moment. The turbine governor will indirectly influence the engine governor to furnish such amount of steam as will do the combined work of the two units, and over a wide range-between a predetermined maximum and a predetermined minimum turbine load no steam and no part of the available energy of the steam will be wasted. The method applies essentially to the types of turbines in which the number of nozzles in operation, or in general the steam area at entrance, can be varied by the action of the governor. This method may be combined with other governing methods in such manner as the circumstances indicate. In fact, I prefer to provide a by-pass around the turbine to the the turbine, deter- With this arrange from the engine will condenser, which will be opened when the pose of reducing the energy per pound of steam which is available to the turbine,

there will be momentary reverse effect, due

to the discharge of stored steam from the receiver, and the partial evaporation of any water which may have accumulated there. This would cause the turbine to show a momentary rise in speed and load, although the governor would be acting to reduce bothv these. Obviously this would cause a further opening of valves and consequently an unstable condition. For this reason, I prefor to arrange the bypass around the turbine so that it is opened by any sudden opening movements of the valve gear and to add a vacuum-breaking device, which is preferably-actuated whenever the governor acts so quickly to increase the area of steam entrance that even the opening of the by-pass is not sutticient. This vacuum breaker may -85 a 7 and8andclosein reverse order. Asimple to e equalizing "also be actuated to preventrrunaway at zero load if required. addition 'to' all this,

1 may arrange. means for admitting liv" steam at high pressurefintothe receiver on the. quickclosing' of the turbine valves, thus promptly raising this pressure when necessary, andmaintaining the s eed on sudden gload increase as on Isudden cad-reduction;

supply any temporary shortage due mixed-pressure machine, I prefer toarrange treme-low load on the engines.

In the accompanying'drawmgs,

Figural ispan end elevation of a lotvressure turbine of the Curtistype, embti ying my infvention; Fig; 2 is aside elevation on a larger scale of the governing end -of sald turblne, A partly in seet1on,-and Fig. 3 is'a sectlonion' 'erates the by-pass.

a 'still'larger' scale ofjthe dash-pot whichop- The, turbine shown-1s a horizontal its:

' ch'ine-receivin 'lowrp ressure steam through a main 1 an through, the pipe 2.. The main conveysthe steam to a chamber 3-.fro1nwhich itis admitted by valves 4; to nozzles 45,, 6, 7 and 8.-

A, fifth nozzle 9, is permanently open. The nozzles 5 and 6 are actuated successively by so. a controlled by a pilot-valve 11.. A similara motor, preferably "a hydraulic cylinder 10 I motor 12,- also controlled by said pilot valve,

actuates the nozzles -7-and 18; the arrangement of the pilot valve and mechanism being such that the nozzles open inthe'ordent), 6,

- form ofv-alve-operating mechanism is illus-v tratedQcoinprising a bar 13 attached to"th e "engaging with its slots. "The-'lowerslot in.

piston rod of the motor and containingcam slots 14,- 15, one for each valve. Qn each valve,stemfll 6 is a head 17 having a 'pii118 each bar opensits valve before the upper s lotyacts and .has an extension. permitting}- sufficient movement I of the bar to opensaid; i upper valvewithout disturbing the already;

, open lower valve.

The pilot valve ste'ni .1!)-is pivoted to a fioating lever 20- linked'to' the. arm 21 of the piston rod 24 ofa ove'rnor 22 and pivoted to an air-23 which is pivoted to the two bars '13. Attached to this' ecjua'lizer. i s valved piston 25,

the speed,

forming one element. -of a dash-potlwhose passBO extending around the turbine-from. the main 1 to the pipe 2. A finger 31' on the."

cylinderorshell 26is supportedi on a rod 27.

-A rock-arm 28 is pivoted to said; rod and serves to actuate" athrottle va'lve 29 in a by-v spindle of the throttle valve, which is preferably 0f the butterfi typefl is.- adapted.

-. to come in contact Withthe stem 32 of a 'vamiu-m-breaking valve in the by-pass on the con'denser sideof the throttle valve.

as Leading into the main 1, preferably -at anis connected by exhausting to fa condenser v d any greater. back-pressure inthe receiverv elbow of theby-pasal is apipe connected 2 rod 27 through suitablemechanism, such as a lever 35- linked tenants: lever 36 whicha spring 31 with the rockamas The ope'ration as follows: With mini-' mum load on thexturbine, the-nozzle 9, which is always open, issupplem ented by thenoz-f' zles 5, ,6, I7, 8, which under these conditions are also open, both cam bars 13 being raised 1 totheirhighcst point. The amountof steam fedto the turbine is determined by some other source, which maybe variable inde pendently' of vthe load on the turbine such for example, as two or three engines vvorkliver, and let out of itjust as muc energy 1 as the fur ine' loa'd requires, while .at the ingon independent loads and all exhaust-j 'ing into a common receiver from which the main 1 leads tojthe' turbine.- The problem is: to take all the steam which the en ines desame time never imposing upon the engines with all'th'e' nozzle valves open, the amount of steam delivered to the turbine willpass through it and to the condenser with arela'- tively smalldrop'of pressure. On the other hand, as the load on the turbine increasedthe resulting drop-in speed causes the speed I governor 22 to lift the pilot valve 11 and 7 start the motor 12, ivliichpull's down its bar 13 and closes the valve 8, thus increasing the 'pressurevdrop through the turbine and con-. .sequently the energy derived by the turbine from a given amount of steam passing. {As

a con'seqr1ence, the pressure ii the, receiver fro1n wh1oh the turbine derives tssupply will be\increased,thus compelling the en;

eratefund er less favorable conditions and causing them to deliver a larger volume of steam. This adds to the. other eiiechsince the turbine now not only derives more en ergy from each pound'of steam which passes through it, but it s also receives more steam.

Asfujrther load vis placed .upon t'he turhine,

the governor will close successively the valves of nozzles-7, (i'and 5. The receiver pressure will of, course be progressively in-- creasedbythis action, and "when all the valves are closed and steam isfadmitted only at' the nozzle-9, which is always open, the turbine is delivering the maximum load it can without resort to additional high :presg sure steamh Under these conditions the pounds above atmosphere pressure.v

" If'the't urbine is not. a-mixed pressure Inagines which exhaust into the-receiverto opf pressure in, the receiver may be several 12s jc'hine, thatdis, has no valves to admit high 1 downward movement of the cam bars 13 the the rod 27 will be forced down against the tension of the spring 37 whose upper end is held stationary by the arm 28. The rod has a collar 38 engaging with the lever 36 which thereby actuated and opens the .valve 34. This admits boiler steam to the recei'v 7 and furnishes the turbine with additional energy to meet the additional load. If it is desired to admit'live steam to the receiver when the turbine valves are closed with unusual.suddenness as explained in a preceding paragraph then the valve 39, Fig.

will not occur. mine whether such a response is desirable 3, is omitted and the by-pass 40 constitutes the only communication between the upper and lower end of the dash pot. Under these conditions a sudden downward motion of the equalizer 23 will act through the liquid in the dash-pot, which cannot instantly escape, to momentarily open the valve 34; but this valve will continually tend to close again under the influence of the spring 37 and the relatively slow flow of liquid through 40 will allow such closure soon after rapid downward motion of 23 ceases. If the valve 39 is provided as shown, then this temporary admission of live steam in response to sudden downward movement of equalizer 23 Circumstances will deteror not. If the load on the low pressure turbine fluctuates violently and the receiver or pi )ing furnishing its steam is of considerab e capacity, then valve 39 should be permanently closed, since under these conditions the action just explained will be highly desirable in maintaining regulation.

Where reverse conditions obtain, valve 39 should be operative in order to minimize the amount of liveeund therefore expensive steam sent di ectly into the receiver. I prefer'to so design valve 39 that it may be thrown out of operation or left in operation as the demands of the service require. This maybe accomphshed by providing a set screw adapted to clamp the valve to its seat or to be backed ofi so that the valve is operative. Now-on the other hand, assume a reduction in. the load on the turbine. The governor at once causes the motors 10 and 12 to open the valves 5, 6, 7, 8 in succession.

The lifting of the bar 23 lifts the plunger '25, and the mass of liquid above said plunger communicates its movement to the shell which rises with it, lifting the rod 27, Sadting off the live steam valve 3-4, and opening the by-pass throttle 29. The dash pot has a controllable and adjustable by-pass 40 so that if the upward movement of the bar 23 is slow and gentle, the rod 27 may not be plying steam thereto,

erate steadily at all times. Now assume that 1 the load on theturbine becomes so light that the opening of all the nozzle valves does not meet the conditions. will by this time have been lifted so far that the plunger 28 will strike the top of the dash pot. Any further lifting of the bar by the action of the governor will cause a positive lift on the rod 27 and an opening of the throttle valve 29in the by-pass 30. This, and the possible breaking of the vacuum also, will meet the situation supposed.

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 represent the best embodiment thereof; but I desire to have it understood 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. The combination with a low pressure turbine connected to receve the exhaust from a high pressure engine, of a source of steam supply connected to said low pressure turbine, a valve controlling said source, valve means for varying the area of admis sion to said low pressure turbine, a speed governor, and means controlled by said governor to first operate said valve means to de crease the effective area of admission upon adecrease of speed, and to then operate said valve to admit steam from said source to said low pressure turbine.

- 2. The combination with a low pressure turbine connected to receive the exhaust from a high pressure engine, of valve means for varying the area. of admission to said low pressure turbine, a normally closed bypass around said turbine, a speed governor, and means controlled by said governor to first operate said valve means to increase the effective jarea of admission upon an increase of speed and to then open said by pass.

3. The combination with a low-pressure turbine, of a connection for supplying steam thereto from the exhaust of a high pressure engine, valve means for varying the area of admission to said low pressure turbine, a

The equalizer bar 23 conduit joined to said connection for supa normally closed valve in said conduit, a speed governor, and means controlled by said governor to first operate said va ve means to decrease the effective" area of admission uponlan. increase in load andto then open said-valve toadmit steam to said connection.

. 4. 'The combination with ailow pressure turbine of a connection for supplying steam thereto from the exhaust of ahigh pressure engine, valve means forjvary-ing the area ofadmission to said low pressure turbine, a normally closed lby-pass around saidtur-bine',

'10 a'speed governor, means controlled by said governor to operate said valve means to increase the effective area of admission upon an increase of speed, and further means 0011-" trolledby said governor to temporarily opensaid by-pa'ss upon a rapi'd operation of said valve means'to increasethe effective area of admission. f '5. The comb1nat1on With. a low pressure jturbine supplied with steam from a receiver connected with. independently loaded en- -gines, of a plurality of nozzle valves, a'speed governor, and mechanism enabling'said gov- -ernor to' close said .valves 'in. succession, as

the speed drops, and vice versa.

6-; The combination with a low pressure turbine supplied with steam from a receiver connected With'independe'ntly loaded en' gines, of a' plurality ofnozzle valves, a speed v "governor,-means Whereby said governor will close saidrvalves in succession as'the speed drops, and meansenabling said governor to admit live steam to the receiver-when all said; nozzle .valves have been closed.

"T. The combination with a low pressure turbine supplied with steam from a receiver '40 on the turbine drops.

. over-nor andjmeans Whereb .said overn'or connected with independently-loaded engine's, of a plurality of nozzle valves, a speed ,goveaiior', and means whereby said governor.

will succe'ssivelyopen said valves as the load 8. The-combination With a low pressure turbine supplied with steam from a receiver connected with; independently loaded engines, of a plurality of nozzle valves,a speed willsuecess'ively open said valves as the load on the-turbine drops, a-by-pass around said turbine, and means whereby said' can-open said by pass when said nozzle valves have allbeen opened.

bars for operating them, motors for actuating said'bars, a speed governor controlling said motors, a by-pass around said turbine, a throttle valve in said by-pass, and a dash I pot having one elementmoving with. said bars, and the other connected to said throttle valve. j l

10. vThe combination with a low pressure turbine supplied with steam from a receiver, of a plurality 'ofnozzle valves, cam bars for 9. The combination with a low pressure turbine, of a plurality ofnozzle valves, cam

overnor 3 operating said valves, motors for actuating "said bars, a speed governor controlling said motors, a valve admlttmg hve steam lDOSEtld receiver, and a dash pot having one elementmoving' with said bars and the other opera tively connected with said live steam valve. 11 The .combination'vvith a lowpressure turbine supplied with steam from a receiver,

of tWo-pairs'of nozzlevalves, a cam bar for successively operating the valves in each pair, a motor .for'- each bar, a pilot valve common toboth motors, a speed governor controlling said pilot valve, an; e ualizer connecting the two cam bars, ay-pass around said turb1ne,a throttle valve. in said by-pass, a valveddash pot plunger attached to said equalizer, a shell cooperating with said-plunger, and a rodsecur'ed'to said shell and adapted to operate said throttle valve.

12. The combination with a low pressure turbine, supplied with steam from a-receiver, .of a permanently open nozzle, a plurality of nozzles provided with valves, and a speed. governor operating to close said valves upon- CAEL F. VVooDs.

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