US2493509A - Gas turbine plant - Google Patents

Description

Jan. 3, 1950 w, TRAUPEL 2,493,509 GA; TURBINE PLANT i Filed Feb. 2'7, 1945 Patented Jan. 3, 1950 GAS TURBINE rLAN'r 'Walter Traupal, wlnierthur, switzerland, a:- signor to Sulzer Frres Socit Anonyme, Winterthur, Switzerland Application February 27, 1945, Serial No. 57 9,9.68 In Switzerland June 17, 1944 2 Claims. (Cl. 60-49) This invention relates to gas turbine plants having at least two turbines.

In gas turbine plants employng circuits open to the atmosphere, it is known to locate, before the compressor turbine and, if necessary, before the useful output turbine as well, throttling members actuated by circuit conditions, for instance, by pressures, and, if necessary, additionally by hand.

In such plants, the working medium may flow through the two turbines in parallel. Any actuating of the throttle members will then alter the distribution of the stream of working .medium between the two turbines. This has, ofcourse, the desired effect that the outputs of the turbines are changed, but, on the other hand, it has the undesired effect that the pressure ratios at the turbines also change and the efficiencies of the turbines are thereby adversely aifected. This undesired effect is particularly disastrous in the case of the compressor turbine because its output in all gas turbine plants is a multiple of the useful output. The latter is obtained from the plant in the form of a comparatively small surplus output. Consequently, a slight diminution in the efliciency of the compressor turbine means a very consderable reducton in the Overall efficiency of the plant.

To eliminate these disadvantages the present invention proposes a novel combination of a circuit of working medium closed off from atmosphere, from which circuit a partial quantity is continuously extracted and in place thereof a make-up Quantity is introduced, with at least one turbine driven by the working medium fiowing round in the circuit and at least one other turbine driven by the partial Quantity extracted from the circuit, combined with a pressure regulator Lwhich is influenced by the highest (roughly) pressure of the circuit to adjust the extraction of working medium through the turbine driven by the extracted quantity until the actual value of the highest pressure in the circuit is, within the regulating error of the apparatus, equal to the.-

control value, as at the moment set on the regulator.

With a circuit thus closed off from atmosphere, that quantity of the working medium which flows through the circuit turbine returns to the closed circuit, and must, of necessity, subsequently flow through the turbine driven by the extracted med-ium before it can flow successively away to atmosphere. Thus viewed, a major portion of the working medium might be said to flow through thetwo turbines not in parallel, but in series, and

2 this circumstance gives the regulating operation quite another action from the case of the uncomplicated parallel flow of an open circuit. V

Moreover, the regulating operation in the'closed circuit may not, as in the open, alter the quantity of the working medium fed to the turbine driven by the extracted quantity at the expense of the quantity driving the circuit turbine. Apart from a short fiuctuation caused by -the volume-capacity of the circuit, the regulator may not through its own operation produce any effect atv all on the quantity of working medium so fed. For it represents the quantity extracted, and as 'such (after deduction of the very slight quantity of fuel) is always equal' to the make-up quantity and therefore, just like the latter,'depends on the qualities of the particular compressor which draws the make-up quantity from the atmosphere and introduces it into the circuit. But such compressors have a very steep characteristic; their suction fvolum'e therefore alters only little if their final pressure is changed.

Consequently the regulator here adjusts the pressure but not the quantity of the extracted medium, and in particular not the quantity flowing to the turbine working with the extracted medium, as is the case with an open circuit. Because of this it here influences the output of the circuit turbine, in that it changes the pressure level of the circuit, and any change in the pressure ratios at the circuit turbine-which as already explained would be a great drawback-is avoided.

Further advantages offthe arrangement proposed by the invention are that at the turbine working with the extracted medium the heat drop now available is considerably greater, whil'st the temperature on the other hand is essentially lower than at the circuit turbine. A throttle member adjusting the quantity extracted may therefore be designed for a smaller volume, since the specific volumes at lower temperatures are smaller; the lower temperature-also-greatly facilitates the structural design of the valve. Further, because of the greater heat drop a considerable part of the loss arising through the throttling can be recovered again as output, the lower value of the temperature diminishing the risk that the temperatures in the final stages of the turbine working with the extracted medium become too high.

Further, the invention is based on a recognition that pressure changes occur essentially earlier than changes in speed. For, in consequence of -machines subiected to regulating operations.

Therefore, if the regulating impulse for adjusting .he output is derived from a pressure of the working medium, the stability of the system will be greatly increased.

These advantages of the invention are further' not confined either to'a definite pressure-of the. circuit or to a deflnite output 'of the turbine worked with the extractedvmedium, an output corresponding somewhat to that pressure.- 0nthe contrary. it is possible to take 'measures iso that the output of the turbine worked with the extracted medium'can b'e adjusted to different levels by altering the setting of the control value `for the highest circuit pressure. Plant efllciency thus remains without any perceptible diminution over really wide limits.

Further, measures can be adopted to utilize the turbine working with extracted medium as the useful output turbine. In this way the speed of the circuit turbine is made' independent of the speed at which the useful output isrequired. The speed of the circuit machines is then free to follow and to correspond to the adjusted control value of the moment for the highest circuitpressure, whilst the speed of the turbine working with the extracted medium follows and corresponds to the useful output. If the latter is led, for

"instance. to a ship's propeller, any regulating of the circuitzmachinel speeds (with ythe exception' l of safety devices) will be superfluous.

The invention is now explained more fully with the aid of the drawing, in which: z

Fig. 1 shows a gas` turbine plant according to the invention. l

Fig. 2 illustrates the regulating device used in 49 the gas turbine plant shown in Fig. 1. The gas turbine plant shown in Fig. 1. works i with a circuit of air from which a part is continuously extracted, in return for which a makeup quantity is contmuously supplied at another point! The air compressed by the low-pressure' 'compressor l passes through the intermediate cooler 2 into the high-pressure compressor 3. The compressed air then flows through the pipe l into the heat-exchanger 5, in which it is preheated while fiowing through the tubes 6. Through the pipe 'I the air passes further to the point 8, at which it-isdivided up into two parts. A major part passes through the pipe 9 into the gas heater lll, is heated to the highest circuit circult turbine 13 and thus for the useful output' temperature while flowing over the heat exchange tubes ll and is then supplied through the pipe l2 to the turbine l3.

The air expanded in the turbine |3 flows through the pipe ll into the heat exchanger 5 6 and here gives up part of its residual heat by heat transmission to the air flowing through the heat-exchanger tubes 6. Through the pipe |5 the air passes into the cooler IS, in which a .further part of its residual heat is led away in a cooling 65 medium. Through the pipe I'I the air is finally returned to the low-pressure compressor l, where the circuit recommences.

From the circuit of air described a part is continuously extracted at the point 8 and is supplied through the pipe |8 to the burner IQ of the gas heater [O as combustion air.v The combustion gases flow out of .the combustion chamber 20 into the heat exchange tubes H, whose walls give up the heat to the air of the circuit flowing over` the tubes. Afterwards thev combustion gases pass through the pipe 2! into the turbine 22.

To replace the airV extracted from the circuit at the point 8, air from the atmosphere is continuously supplied to the circuit by the compressor 23. This make-up quantity is introduced into the heat-exchanger 5 through the pipe 24 at a point 25 at-which the air flowing over the heatexchanger tubes 6 are approximately at the same temperature and the same pressure as the makeup quantity.

The sequence of pressures of the air in the circuit rises from its lowest value at the entry to the compressor l to its highest value at the outlet from the compressor 3. While the air fiows through the heat-exchangers 5 and |0 and the connecting pipes. a slight drop of the pressure occurs according to the resistance to flow. A

'large drop of pressure occurs in the turbine l3.

The outlet pressure is 'higher than the inlet pressure to the compressor i by the amount required to overcome the resistance to flow, in the heatexchangers 5 and Ill and in the pipes.

The absolute values of the pressure sequence depend On the height of the pressure at entry into the compressor4 l. and this in its turn on the height of the delivery pressure of the compressor 23. When this `inlet pressure is changed. for. instance as a result of a change of speed. the pressures in the whole circuit will change, and the maximum pressure to an even higher extent than V the inlet pressure.

'The turbine l3 operated by the air flowing in the circuit drives the compressors l, 3 and 23,

while the turbine 22, which is operated by the part Quantity extracted from the circuit, acts as a useful output turbine and drives the ship's pro-v peller 21 througha gear 26. The turbine |3 and the compressors I, 3 and 23 are further coupled to an auxiliary electric motor 23 which servesfor starting the plant and for balancing surplus or lacking power.

For the purpose of adjusting the extraction of working medium by 'the extraction turbine, tur- `bine 22 is equipped with albypass pipe 29 which bypasses-its first stage and in Which a ow regulating member 30 is built. The servomotor 3l of this regulating member is influenced by 50 means of the impulse pipe 32 from the regulating device 33.

. The control of the regulating device ls effected by the pressure of the air in the inlet pipe |2 of the turbine l3, transmitted through the pipe 34. With the aid of the lever 3'5 the control value for the pressure in the inlet pipe |2 of the delivered by theturbine 22 working with the extracted medium can be set as required by hand.

A reduction of thecross section lof flow freed 0 by the regulating member 30 diminishes the ab- 4 until the quantity extracted, which fiows through the non-bypassed stages of the turbine 22, has

again become" equal to the quantity continually introduced to the circuit through the compressor 23. The bypassed stages are then flowed through by a larger quantity than before the beginning 'of the operation, so that the output of the turbine 22 has now already increased. Meanwhile the circuit machines l3, l and 3 as well as the compressor 23, begin tcL run faster in consequence of `the higher pressures, andV this' is followed by a further increase the pressures and therefore bine 22 now increases very essentially. `Finally,

when the pressure in the inlet pipe |2 has reached the control value as set at the 1ever '35, the operation comes essentially to rest, but the output of the turbine 22 still continues slowly to increase further until also the temperatures in the plant come to rest.

An initial increasing of the cross-section of fiow freed by the regulating member 30 increases the absorption capacity of the useful output turbine 22 and is therefore followed by an operation in the opposite' sense to that described above. With the V'aid of the 1ever 35 the. output' desired for the drive of tl'e propeller can thus be set by the regulating device; and in this way the speed of the vessel can also be set.

The compressor turbine E3 has a bypass pipe 36 which bypasses the first stage of the turbine. The flow regulating member 31 in the bypass pipe can be opened by means of the regulating device 33 by influencing the servomotor 33 through the impulse pipe 32, 38 for the purpose of temporarily accelerating the increase of the useful output. -By opening the regulating member 31 the absorption capacity of the compressor turbine 13 is increased.

In this way, in as far as at flrst the volumecapacity of the Spaces in the circuit lying between compressor 3 and turbines i3 -and 22 and in as -fl far as further vthe pressure-volume characteristic of the compressors l and 3 allow, the output of the turbine H3 may still be further increased for a short time and thereby theV acceleration of,

the machines i3, l, 3 and 23 be made still greater, and the desired increase of the useful output is hereby attained in a reduced time. p

The regulating device 33 (Fig. 2) is influenced by a pressure responsive bellows 40 and which is connected to the pressure pipe 34. With the aid of the 1ever the control value forv the pressure in the inlet pipe l2 can be Set by hand and with it the output desired for driving the ship's propeller. The expansion of the pressure bellows is A transmitted to the joint 4! of the 1ever 42. The

joint 63 on the opposite side of the 1ever 42 is infiuenced by means of the 1ever 35 through the curved cam 44, the rod 45 and the Spring 46. The positionof the middle joint 41 of the 1ever 42 is thus determined by the position of the 1ever 35.

and the expansion of the pressure bellows 40.

The control valve 49 is connected to the joint 41 through the linkage 48 and by it the supply of pressure medium from the pipe 50 to the servomotor 52 and the discharge from the servomotor to the discharge pipe 5| are controlled. The piston 53 of the servomotor is connected on the one hand through the rod 54 to the drag device 55 and on the other hand through thev Spring 56 to the valve control member 51 in the valve casing 34. The piston 53 of the drag device separats two cylinder Spaces from each other which are connected through a pipe 60 provided with a throttling point 59. The valve 51 contrcls the supply of a pressure medium from the pipe 6| 6 U or its discharge into the pipel 62. The control. space 63 of the valve casing v64 is connected through the control pipe 32 /to the servomotor 3| and through the control pipe 38 to the servomotor 30. J

The servomotor 3| has a piston 65 upon which the forceof the Spring 66 acts from'below and the pressure of the control medium in the Space 01 from above.` Arranged in the servomotor 39 is a piston 68 which the force of the spring. 63 acting from below and the pressure of the control space1 W0 acting from above keep in equilibrium. The springs 66 and 69 are of such dimenslons that the regulating member 31 is only lifted from its seatl when the regulating member 30 is pressed against its seat and completely interrupts the fiow through the pipe 29.

If the 1ever 35 is displaced in the +direction of the arrow 1L, the rod 45 is moved in the +direction of the arrow 12. The Spring 46 is then compressed, so that the joint 43 is also displaced in the +direction of the arrow 12 as far as allowed' by the displacement of the liquid in the drag device from the underside of the piston 58 to the upper side through the throttling point 59. As the joint 4! at first remains at rest the control valve 43 moves in the +direction of the arrow 13. Now pressure medium fiows from the pipe 50 through the' pipe 14 into the space of the cylinder 52 situated below the piston 53. The pi-ston is displacedin the +direction of the arrow 16 and the liquid then subjected to pressure in the upper cylinder spacelis led oil' through the pipe 15 to the discharge pipe 5h' By the displacement of the servomotor piston 53 the already existent tensile stress of the Spring 55 is increased and the control valve is drawn' upwards. A connection .is thus established between the supply pipe 3! and the control space 33. By the supply of pressurefiuid the cohtrol pressure in the space 63 is raised until the increased pressure loading on the valve control member 51 in the valve casing 64 balances the increased tensile stress lof the Spring 56 in the middle position of the valve, the control openings of the pipes Sl and 52 being closed.

II'he increased control pressure in the space 63 is transmitted through the pipe 32 into the control space 31 of the servomotor 3| and through the pipe 38 into the control space 10 of the servomotor 39. The increased control pressure in the space 61 presses the piston 65 downwards, so that the cross-section of fiow freed by the regulatng member 30l is reduced. In this way the resistance to flow through the useful output turbine is increased and its volumetric absorption capacity for working medium is decreased.

If the increase in the control pressure in the plpes 32 and 38'after the complete closing of the.

regulating member 30 is able to overcome the pressure of the Spring 69 in the servomotor 39, the regulating member 31 israised from its seat. The result is an increased absorption capacity of the compressor turbine. The speed of the compressor turbine is raised more rapidly, so that the compressors also raise the sequence of pressures in the circuit more rapidly and thus the useful output is increased in a shorter period of time;

Overregulation and an oscillation of the regu- Iamm iuvalved with this is prevanted' with the aid of the drag vcoupling 55, which takes effect as a yielding returnimeans and at the very beginning of the regulating adjustment begins a return motion. In this way the control value set can bemaintained in actual values without any lasting irregularity. During the displacement of the servomotor piston 58 the drag pistonlt is dispiaced in the +direction of the arrow".v The joint 48 of the lever '42 is thus displaced in the direction opposite to the original direction of displacement, so that the control valve 49 is again moved back toward's its middle position in which the control openings of the pipe 14 and 15 are closed. v 1

The final return of the regulating process is then efiected through the plant itself, while the return motion of the yielding device again ceases to be eifective. When the sequence of pressures in the circuit is raised. th'e `pressure responsive bellows 40 expands; The joint 4| of the lever 42 moves upwards. The opposite joint of the 1ever is forced into the position in which the spring 48 is unloaded.- The regulating device comes to rest when the pressure bellows 40 has brought the control valve 49 into the middle'position with the spring 46 uploaded. The height of the sequence' the eircult through the? pipe 2! dams up the working medium in the circuit, raising the pressure and thus the speedof the compressor turbine and of the compressors until the'pressure.:

has again reached the control value required.

i For diminishing the output the lever 35 is displaced in the -direction of the arrow 11. Corresponding regulating processes then take effect, but .in the opposite direction. The sequenceof pressures in the circuit is lowered, and accordingly the output' of the useful output turbine isdecreasd. V v

The point at which the pressure -impulseds -given for the purpose of malntaining the required state of pressure may also 'be situated at other points in the circuit, at'which the presof pressures in the circuit then corresponds to the control value set by the lever 35. As a result of the yielding return motion a single allotted value for the sequence of pressures and thus also for the useful output corresponds to eachapositionof the lever at any time.

If there is a rise of actual pressure above its control value, by means of the pressure billows 40 the joint 41 is displaced-in the -direction of the arrow 13. The control valve 49 then con- 'nects the pipe 50 to the pipe. 15. The piston 53 of the 'servomotor 52 is displaced in the -direction of the arrow 16 land the Spring 56. is unloaded, so that the control valve 51 also 'slides downwards.l Fluid can escape from the 'control space 63, so that the control pressure in the pipes 32 and 38 is reduced correspondingly. In this way the cross-section of fiow at the valve 30 'is sure has a lower value.A

I claim:

1. In a gas turbine plant having a' circuit for working medium closed oif from the atmosphere lator adjustable over a range of control value' settings including' actuatlng means responsive to the approximatelyhighest pressure of theV circuit and regulating means arranged to adjust increased and a greater quantit'y of working medium is extracted from the circuit. The speed of the compressor turbine and the compressors driven by it is decreased, 'so that the sequence of pressures in the circuit is lowered, until; it again corresponds'to the control value set by the lever 35. 1

If the sequence of pressures in the crcuit falls below the control value, the valve 49`is displaced in the +direction of the arrow 13 with the aid" of the bellows 48, the lever 42 and the linkage 48. The servomotor piston`53 is then raised and the Spring 56 'is loaded to an increased extent. According to the increase of load, an increase of pressure presents itself in the control pipes -32 and 38,' whereupon the cross-section cases the valve 31 is raised from its seat. The decreased extraction of working medium from freed by the valve zo is diminished and in given 'the manner of extraction of the substantially constant quantity of working medium passing through the'turbine driven by the extracted'v quantity, said actuating means causing said regulating means to adjust to bring the actual value of that highest pressure equal to the control value set on said regulator.

2. The vcombination of claim 1 in which the turbine working with the extracted Quantity delivers the plant useful output.

WALTER TRAUPEL.

` REFEBENCES cITED The following references are of record in the flleof this patent:

UNITED STATES PATENTS Number Name Date 2,280,765 Anxionnaz et al. Apr. 21, 1942 2,298,625 Larrecq Oct. .13, 1942 2,371,889 Hermitte Man 20, 1945 2,372,686 Sedille Apr. 3, 1945 2,405,676 Strub Aug. 13, 1946

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