US1854006A - Elastic fluid turbine - Google Patents

Description

April 12,' 1932. D. F. WARNER ELASTIC FLUID TURBINE Filed July 25, 1931 Inventow: Donald F Wawnen M His Attowne Patented Apr. 12, 1932 UNITED STATES PATENT, OFFICE? DONALD IE. wAImEmoF LYnN, 'MAssAoHUsE'r'rs, AssIGNoR' USO GENERAL ELECTRIC COMPANY, AooRroRATIoN 0F NEWJYORK? ELASTIC FLUID TURBINE v r Application filed July 23,

' This invention relates to elastic fluid turbines wherein elastic fluid froman extrac: tion stage or from the exhaust or from both anextraction stage and the exhaust is used for industrial purposes. Turbines of this kind are :known .as'automatic extraction turbines, back pressure turbines and combined automatic extraction and'back pressure turbines respectively. 1 a

In these turbines it is desirable to control the flow of elastic fluid to the-turbine and from an extraction stage to the next lower stage in terms of pressure in the extraction stage and in the exhaust respectively.

The speed of such combined extraction and back pressure turbine maybe maintained constant by external means such as a line of constant frequency to which anelectric genera-tor driven by said turbine is connected in parallel with other electric generators. The mechanical energy which is transferred from such aturbine to the electric generator at a determined speed depends upon theamount of steam extracted from the extraction stage and the amount of steam passing the exhaust.

The electric generator having a;,certain load capacity and being driven by such a.tur-' bine is liable to be overloaded and damaged if the mechanical energy transferred to the generator exceeds a certain sustained value or, in other words, if the demands for extraction and exhaust steam simultaneously reach certain'values, and particularly'if both extraction and exhaust steam demand reach a maximum value at the same time.

. One object of my invention comprises an improved control mechanism which prevents overload of the electric generator driven by such turbine or, in other words, which limits the mechanical load output of such turbine-to a predetermined value so long as initial conditions in the steam or fluid at the throttle are maintained. I 7

Another object of my invention consists in the provision of'means which rendervvalve opening actuation of certain pressure re:- sponsive. means ineffective 1f the mechanlcal load output of the turbine'h'as reachedsuch predetermined maximum value.

My invention accordingly comprises the tion when the mechanical load output of the turbine fhas' reached'v a certain maximum value regardless of therelative demands for extracted and exhausted steam andproviding initial steam or fluid conditions are maintained. My invention also comprises the provision of yieldable-connections between one or more pressure responslve dGVlCGS and a lever mechanism which connects such de-f vices with the valve actuating means. i r

For a better understanding of what I be lieve to be novel-in my invention attention is directed to the following description-and the claims appended thereto. I 'Referring to the drawings,- Fig. 1 illustrates a preferred embodiment of I my invention applied to a combined extraction: and

back pressureturbine; Fig. 2 illustrates a modified arrangement according to my in? vention, and Fig. 3- illustrates a diagrammatic view of a part of Fig. 1 in different operative positions. 7 f T Referring to Fig. 1,1 indicates the casing of an elastic fluid turbine, 2-indicates the shaft, and 3.-indicates' oneof the "bucket wheels. The turbine isillustrated as being viewed from the high; pressure end and is partly broken away at different sections. 4

indicates a conduit for admitting elastic 1 fluid to the high pressure end of theturbine,

the admission of elastic fluid being controlled by a valve means 5. '6 indicates the exhaustconduit for the turbine and 7"indicates'an extraction conduit connected to an interme- 'diate stage of the turbine; In the extraction stage is a valve means 8, a known form of ring valve being illustrated, which serves to.

control the flow of elastic fluid from the extraction stage to the next lower stage. It is provided with a gear segment 9 with which meshes a short rack 10 connected by a rod 11 to the piston 12 of a fluid-actuated motor. The pilot valve for the fluid-actuated motor is indicated at 13. WVhen ring valve 8 is turned in a clockwise direction it serves to shut off the flow of elastic fluid from the extraction stage to the next lower stage while when it is turned in a counterclockwise direction it is opened further to permit of increase in the flow of elastic fluid from the extraction stage to the next lower stage and to the exhaust. The ring valve is illustrated diagrammatically and by way of example, such arrangements being now known in the art. A valve means of this type is more particularly illustrated and described in the pat- 2 ent to Norton 1,091,078, dated March 24,

14 indicates a pressure responsive device here shown as being in the form of a corrugated bellows located in a casing 15. Casing 15 is connected by a pipe 16 to exhaust-conduit 6. Pressure responsive device 14 is thus subjected to the exhaust-conduit pressure.

Connected to the pressure responsive device is a stem 17 which at its upper end is 30 connected to one end of a floating lever 18. The other end oflever 18 is connected to a speed governor 19 driven from the turbine shaft Spring 21 is a tension spring and operates in a direction to oppose the collapsing of corrugated bellows 14. The tension of the spring may be adjusted by turning the nut 20 in sleeve 20. When the pressure in exhaustconduit 6 increases, corrugated bellows 14 is collapsed somewhat moving the left hand end of lever 18 upward, while when the pressure decreases spring 21 serves to lower the left hand end of the lever 18. A rod 22is pivoted at its upper end tolever 18 and has an abutment 22 at its lower end. A lever 23 is slidably secured at its left end to rod22. and is pressed against said abutment by a spring 22. The right end of said lever 23 is pivoted on a fixed fulcrum 24. Pivotally mounted on lever 23 is a bell crank lever comprising arms 25 and 26. Arm 25 is connected by a link 27 to one end of a lever 28. The other end of lever 28 is connected to a suitable fulcrum 29.

Lever 28 is connected by a link 30 to one end of a floating lever 31. The other end of floating lever 31 is connected to the stem 32 of a fluid-actuated motor 33, the stem 34 of the pilot valve of the fluid-actuated motor being connected to floating lever 31 at an intermediate point. The stem 32 is connected to a valve disk 35 of valve means 5.

Lever 23 is connected by a rod 36 to one arm of a bell crank lever 37 pivoted at the end of a bracket 38, the other arm being connected to one end of a floating lever 39. The other end of floating lever 39 is pivotally connected to an intermediate point of a lever arm 40 pivoted at its lower end on bracket 41 and pivotally connected. at its upper end to a rod 42 which forms an extension of piston rod 11. The stem of pilot valve 13 is connected to floating lever 39.

Bell crank lever arm 26 is connected by a link 43 to one arm of the bell crank lever 44 pivoted on a fulcrum common also to lever 23 in line with its pivot 24; The other arm of bell crank lever 44 is pivotally connected to a stem 45 which at its lower end is connected to a corrugated bellows 46 similar to the corrugated'bellows 14. Corrugated bellows 46 is located in a casing 47 which is connected by a pipe 48 to the extraction stage conduit 7. Corrugated bellows 46 is thus subjected to the pressure in the extraction stage. The collapsing of corrugated bellows 46 is opposed by an adjustable tension spring 49 arranged in a manner similar to the spring 21.

Theoperation is as follows:

Assumethat the turbine is running, the speed being fixed by some external means and that valve means 35 and ring valve 8 are positioned so that the pressures in the extraction stage conduit and the exhaust-conduit are of the desired value. If now the pressure inthe exhaust-conduit increases due to'a decrease in fluid demand, for example, corrugated bellows 14 will be collapsed somewhat thereby lifting the left hand end of lever 18 and through link 22 lifting the left hand end of lever 23, the lever 23 turning on its pivot 24. This serves to lift the right hand endof lever 28 thereby lifting the pilotvalve offluid-actuated motor 33 so as to admit actuating fluid to the upper side of the piston of the fluidactuated motor and permitting it to escape from the lower side. This causes the piston to move downward thereby closing valve means 5 somewhat so as to decrease the amount of elastic fluid being admitted to the turbine. When the piston of the fluid-actuated motor moves downward it lowers the right hand end of floating lever 31 thereby restoring the pilot valve to its former position. Also, when lever 23 moves upward, through rod '36 it turns bell crank lever 37, moving pilot valve 13 toward the left. This serves to admit actuating fluid to the left hand side of piston 12 and permits it to escape from the right hand side thereby moving piston 12 toward the right and eifecting a closing movement of the ring valve 8. When piston 12 moves toward the right the pilot valve is restored to its former position through lever arm 40 and the floating lever connection 39.

If the pressure in exhaust conduit 6 decreases then spring 21 eflects downward movement of the left hand end of lever 18 and in a manner similar. to that already described, effects an opening movement ofvalve meansband of the ring valve 8. Thus it will be seen that when the exhaust conduit pressure inoreases, lboth the high pressure valve means and the ring valve means are closed somewhat, while when the exhaust conduit pressure decreases, both the high pressure, valve means and the ring valve means are opened somewhat. 1 V

Upon a change in extracted'steam demand the extraction pressure-governor -457 acts torotate bell crank 44 which in turn rotates bell crank 2526 in a likeirotary direction. A decrease in extracted steam demand causes an increase in stage pressure. The extraction governor bellows travels in a direction toward its high pressure'stop. This causes a clockwise movement of the bell cranks, as shown in the drawings. Upward movement of link27 acts through lever 28, pilot valve 34, piston and rod 32, etc. to move the main controlling valves in a-direction toward closing. The grid valve 8 remainsundi'sturbed by any action of the extraction governor so that if, as assumed in this case, constant demand for exhausted steam exists, the flow and pressure at the exhaust will be unchanged asit should be. The pressure governor 14 etc. therefore holds lever 23 in a fixed 'position'during a change in demand for extracted steam only. Thus it is seen that a change in extracted steam demand can occur without disturbance to the conditions at the exhaust of the turbine.

The mechanism so far described may be taken as typical for the control of a combined extraction and back pressure turbine in which load limiting device and a yieldable connection with respectto one pressure responsive device may be provided for the purpose here'- inafter set forth. ,Whereas I have described such a combined extraction and back pressure turbine as comprising asingle unit, wish to have it understood that such turbine may also comprise two separate units, a high and a'low pressure unit, mechanically cou-' pled and driving the same generator or generators. My'invention also is not limited to steam turbines as it maysimilarly be applied to other. elastic fluid engines, such as mercury vapor turbines. V a i According to my invention I provide a mechanical load-limiting device which, as already pointed out, automatically prevents further valve opening action when the. mechanical load output of the turbine has reached a predetermined value. a

This load-limiting device may be provided with respect to a part of the control mechanism, the movement'of which is a function of the mechanical'load output of theturbine. More particularly I provide the load-limiting device at a definite point of such part of the control mechanism, the movement of whichis a function of the mechanical load output and not to any appreciable degree affected by the ratio of flows from the exhaust and extraction points. U e

The movements of such part have to satisfy certain conditions which will be more readily understood from the following:

Let us assume that an amount ofsteam- (A+B) vbe admitted to the turbine, an

amount of steam A be extracted from an intermediate stage and an amount 1 be passed through the low pressure part the turbine.

Thethermo-dynamic energy of.

the steam passing through the turbine partly transformed into mechanical energy.

steam amount pressure part of the turbine is. proportional to the amount A itself and a constant 0 The mechanical energy M 'obtained from the A passing through the high be a function of the amount A, the pressure drop within the For certain conditions such constant will have a definite numerical value whichmay change if one of said conditions changes." This constantmay also be considered as the efficiency factor or the coefficient of transformation (hereafter termed transformation factor) of the high'pressure part of the turbine.

turbine, temperature, etc..

In a similar manner the mechanical ens ergy M obtainedfromthe steam amountB the entire turbine is,

M B I wherein a is a corresponding constant wit respect to the entire turbine.

passing through The total mechanical load output isequal to the sum ofthe mechanical energies obtained from both amounts of steam A and I B. Thus, M=M +M ,or,' introducing the above equations, M=c A+c B In asimilar manner it can be proven that. V

wherein o and 0 represent the transformation factors of the high pressure and the low pressure part. respectively .and wherein (A+B) is the amount of steam passing the high pressure part and-B is the amount of steam passing the low pressure part.

Referring to the last equation M=0,. A+B +'@1B it will be seen that in the equation c (A+B) represents the output of the ing the extraction opening (M 0 (B) represents the output ofthe stages following the extraction opening (M The equation also indicates a mutual actuation of the lever mechanism under certain conditions. In

stages precedcase the steam demand B of the exhaust changes, it causes an actuation of both the admission valve and the valve before the quired to find that part of the mechanism 7 which acts as a real or imaginary fulcrum during changes in the relative demands for steam at the extraction opening and at the exhaust during which a constant mechanical load output M is being delivered. If now, a point in the lever mechanism can be found such that a motion m corresponds to a mechanical load output change M in the stage or stages preceding the extraction 7 opening, andsuch that a motion m corresponds to a mechanical load output change M in thestage or stages following the extraction opening. Then wherein I0 and are factors of the lever mechanism involving the efliciencies of the stages preceding and following the extraction opening respectively, and physical characteristics of the governing mechanism.

If a definite flow of steam B passing or in another form,

ex k2 C]; A B

or ass This result shows that the part of the lever mechanism where the load limiting device has to be applied must satisfy the condition according to which the ratio &

2 is inversely proportion to the corresponding ratio of the transformation factors.

A point which substantially satisfies this condition is located on the horizontal part 25 of bell crank lever 25, 26under the assumption that the transformation factors 0,, and 0 are linear functions of the steam amounts A and B respectively and the corresponding physical condition which in fact is approximately true within certain limits.

In the present instance I have shown a load-limiting device between said lever 25 in the simplest form as comprising a fixed plate 50 and an adjustable head screw 51. p

It will be understood that there is only one point beneath said lever to which a definite ratio applies. Thus, a displacement of the screw in either direction along the length of the lever would correspond to a change of such ratios. In order to make this important feature clear, attention is directed to Fig. 3 in which I have illustrated a part of the lever mechanism in difierent operative positions with respect to a load-limiting device. AB and CD represent levers corresponding to levers 23 and 25 of Fig. 1' respectively, and S indicates the load-limiting device.

Let us assume that the turning movements are such that in a change of disposition of the levers represented by a ,8 and a ,8 occurs without change in mechanical load output. The levers AB and CD in these positions are indicated by A 13. A B and C D C D In such an event the intersection point along the horizontal arm C-D of the bell crank lever is the proper location for the abutment if the load is to be limited to that value. It is shown as preventing any further downward travel of the lever C-D. It, therefore, limits governor travel in a valve-opening direction. The governor limiting device S as shown in Fig. 3 is properly set as there is no change in mechanical load output caused by rotation of the lever CD about the point of engagement of the lever with the limiting abutment.

In any other application the relative location of S relative to lever CD has to be changed in dependanceupon thetransformation factors of the stages preceding and the stages following the extraction opening, and the physical characteristics of the two valve groups and the design of the interconnecting linkage and lever system.

Only the properly applied load-limiting device maintains the maximum mechanical load output substantially constant regardless of the relative steam demand in the high pressure and low pressure part.

If the total load of the turbine reaches a predetermined value and vital steam conditions being assumed constant, lever 25 engages the screw 51 which prevents further opening of valve and limits thereby auto-- matically the total load of the turbine. This limiting action takes place regardless of the relative demand for extracted and exhaust steam.

At such times when the horizontal arm is in abutment with the load-limiting device (50, 51) it is desired to render further valve opening action of the back pressure governor ineffective. This is achieved bythe yielding connection 22 between the levers 18 and 23.

A decreasingsteam pressure in the exhaust pipe effects the pressure responsive device 14 to move the left end of lever 18 downward- 1y. But this movement is not transferred to lever 27 as rod 22 merely slides downwardly within the end of lever 23, pressing spring 22 together.

In connection with the operation of the mechanism it will be understood that the lever arm and the connections are so chosen relatively to each other that when lever arm 23 is moved valve means 5 and valve means 8 are opened or closed by amounts such that valve means Swill normally efiect an increase or decrease of flow past it corresponding to the change in flow past valve means 5.

If the pressure in the extraction stage conduit increases bellows 46 is collapsed some- I what thereby turning bell crank lever 44 in a clockwise direction and through link 43 turning the bell crank lever comprising arms 25 and 26 in a clockwise direction. This serves to lift the pilot valve of fluid-actuated motor 33 thereby efiecting a closing movement of the valve means 5 to decrease the amount of elastic fluid admitted to the turbine and bring thepressure in the extraction stage back to its equilibrium value, which is V substantially its former value.

If the pressure in the extraction stage decreases then spring 49 serves to turn bell crank lever 44 in a counterclockwise direction, thereby effecting an opening movement of valve means 5 so as to restore the pressure to its equilibrium value. When the pressure in the extraction stage varies, it-willbe'seenthat no adjustment of the stage valve means takes place, the high pressure valve'means only being moved to bring the extraction stage pressure back to normal value. As a result the pressure in the exhaust-conduit will tle and to decrease the flowtoexhaust. The load will be maintained at the limit.- It is,

therefore, seen that the increased extraction demand is satisfied and without an increase in load. It will be further seen that this is acin the extraction" complished by means of reducing further the flow to exhaust, which when the abutment is made is already limited to a value below that necessary to satisfy the existing demand.

A similar action takes place when a depressure rises in the extraction stage, when the lever 25 is in abutment with the governor limit;

Y a In other words, when the yielding link is applied to the link 22extraction demand is satisfied at the expense of exhaust demand when the governor is in abutment.

c crease in extracted steam demand occurs and- In the event that it is .desirable to satisfy a the exhaust demand at the expenseof the extracted steam demands "at times when the governor is in abut-ment'it would be neces sary to apply the yielding connection to the extraction pressure governor element. 1

There are also cases in which yieldable connections may be provided. with respect to both the intermediate stage and the exhaust responsivemeans. In Fig; 2,I have illustrated such an arrangement; like reference I charactersdesignatethe same parts as in Fig. 1. Link 17 which is positioned by' the inter mediate stage responsive device, is slidable in a hole of the left end of lever Band has an abutment normally pressed against lever 18 by the action of a spring 17 6. Link 45, shown at the right side of the drawings, which ispositloned by the extraction responsive device, is similarly slidable in a hold provided in one arm of thebell crank lever 44, andhas an abutment 45a normally pressed against the bell icrank leverby the action .of a spring 455.; The operation of this mechanismislthe.

same as that described above, with the exception that it allows a free positioning of the extraction responsivedevice 46 (see F ig.1 when lever 28 is in abutment position;

In accordance withthelprovisionsof the PatentStatutes', I have describedthelprinciple of. operation ofmy invention, together V I with the apparatus which I now considerto represent the best embodiment thereof, but

I de'sir'eto' have it understood thatthe appara-' tfus'shown is only illustrative and thatthe invention may be carried out by other mean's,

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

1. The combination with an elasticfluid turbine, a conduit connected to an intermediate stage of said turbine, another conduit connected to the exhaust of said turbine, pressure responsive devices connected to said intermediate stage and. said exhaust r'espelc tively, avalve mechanism controlling the ad,- mission of elastic fluid to the turbine,la valve mechanism controlling the flow of elastic fluid to the-exhaust of the turbine, both being adjusted by said pressure responsive devices, 7

and means for limiting the opening action of a both valve mechanisms at such times when the iao Ill

nszseooe mechanical loa'd output of said: turbine: has: able loadrlimiti-ngrmeansis in; abutmenirposie reached av predetermined value.

' 2; The combination with an elastic fluid: turbine, a conduit to an intermediate stage of said turbine, another conduit to the exhaustof said turbine, pressure responsive devicesconnected tosaid intermediate stage and said exhaust respectively, a valve mechanism controlling the admission of elastic fluid to the, turbine, a valve mechanism controlling the flow of elastic fluid to the exhaust of the turbine, both being adjusted by said pressure responsive devices, means for limiting the openingaction of, both valve mechanisms in response to the demands for steam at either tion;

' hand;

the; extraction opening or at the: exhaust of the turbine, said limiting means being provided at a part of the valve. mechanism the motions of which with respect to the mechanical energies obtained from the steam amounts leaving the intermediate stage and exhaust espectively, are inversely proportional to the corresponding transformation factors of the turbine with regard to'said steam. amounts.

The combination with an elastic fluid turbine having a conduitconnectedto an intermediate stage, valve means controllingthe flow of elastic fluid to the turbine, and valve means controlling the flow of elastic fluid' tromsaid intermediate stage to the next lower stage, of means responsive to a condition ap-- purtenant to the exhaust leaving the turbine for effecting adjustment of both said valve.

means in: the same direction, means responsive to a condition appurtenant to elastic fluid flowing in said conduit for efl'ectingadjusu ment of said first-named valve means only, and adjustable means adapted to limit the opening of said valve means controlling the flow of elastic fluid to the turbine in response to demands for elastic fluid at the extraction opening and at the exhaust.

- 4:. The. combination with an'elastic fluid turbine having a conduit connected to an intermediate stage, valve means controlling the flow of elastic fluid to the turbine and valve means controlling the flow of elastic fluid from-said intermediate stage tothe next lower stage, of a lever means connecting both said valve means whereby when said lever is moved both valve means are adjusted in the same direction, means responsive to a condition appurtenant to the exhaust leaving the turbine for moving said lever, means responsive to a condition appurtenant to elastic fluid flowing in said conduit for 'eflecting adjustment of said first-named valve means independently of said second-named valve means, means forming a yieldable connection between said lever and said means responsive to the exhaust conditions, and adjustable means adapted to limit the opening-travel of said lever, said yieldable connecting means being adapted to render the action ofsaid exhaust responsive means ineflective if. said adjust- I-n; witnessgwhereoff I: haveherenntd satiny;

DONALD F. WARNER;

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