US2911789A - Regulating system for steam-gas turbine powerplant - Google Patents

Description

Nov. 10, 1959 Filed Aug. 27, 1958 .dtates Patent 2,911,789 Patented Nov. l0, 1959 ice REGULATFNG SYSTEM FOR lS'IEAtMeGAS TURBNE POWERPLANT Jack M. Baker, Schenectady, NX., assigner to General Electric Company, a corporation of New York Application August '27, 1958, lSerial No. 757,487

7 Claims. (Cl. (l0-39.18)

This invention relates to steam generating plants, pan

ticularly to a plant of the so-called Velox-boiler ty e in which the combustion space is supercharged by a cornpressor driven by a gas turbine, the motive fluid for which is the hot gases discharged from the combustion space. The invention particularly relates to an improved regulating system for a steam generating plant of this type.

Many years ago, the development ofthe Velox-boiler demonstrated the advantages of a steam generator having apressurized combustion system. These advantages include improved thermal etliciency due to the increased effectiveness of the heat transferfrom the high density hot gases in the combustion space, the very substantially reduced size required for the combustion space, and the reduction in total size, Weight, and capital investment required for a steam generating plant of given capacity. Successful commercial exploitation of a steam generating plant of this type depends in large part on a practicable solution to the `problem oi properly coordinating the air ilow requirements of the combustion chamber with the motive lluid requirements of the turbine which drives the supercharging compressor, particularly during the starting cycle and during transition periods of significant load change. The gas turbine is ordinarily directly Vconnected to the compressor rotor, which will usually be of the axial lflow type, having a substantial number of stages. The result is that the compressor-turbine rotor has a very substantial rotational inertia, rendering it rather insensitive to rapid changes in motive iluid llow. That is, ir" the boiler suddenly requires a substantially increased rate of combustion air supply, it requires a signicant time in terval for the increased flow of motive fluid to the turbine to accelerate the compressor-turbine rotor to the new speed required to supply the air called for. in certain ranges of operation, the het gas discharged from the su'- percharged'combustion space ,may be inadequate to provide the gas turbine with sufficient available energy to drive the compressor at the new speed called for. lConversely, when the boiler experiences a suddenly reduced load, Vthe rotational inertia of the compressor-turbine rotor will tend to maintm'n the rate of air supply constant, although the boiler controls will cause 4a sudden reduction of fuel supply, with a consequent reduction in the temperature of the gases discharged from the combustion chamber and a resultant decrease in energy available -to the gas turbine. ri'he net result is an 'inherent sluggishness in response of this type of powerplant to changes in load output.

Accordingly, an object vof the present invention is to provide an improved steam generating plantof the supercharged boiler type having auxiliary motor means Vto assist in .starting and accelerating the compressor rotory to obtain quick response and to provide extra powerneeded when .the .energy available to the gas turbine is 'insuicient to generate the power required by the compressor.

Another object is to provide a.supercharged 'boiler plant of the type described with improved means for coordinating the control of the boiler ,air requirements with 2 the energy made available to Lthe gas turbine ,and Vthat required from the auxiliary motor means.

A still further object is to provide a superchargedboiler plant specially adapted tfor service as a marine powerplant and capable of rapid change inload 4as required in maneuvering a ship around-port.

A still further object istoprovide an ,improved-regulating system for a supercharged boiler plant in which a single speed governor effectively controls both the power output of the gas turbine and the power `required from the auxiliary prime mover means.

`Other objects and advantages will become apparent from the following Vdescription taken in connection'with the accompanying drawing in whichthe single gure'represents diagrammatically a superchargedboilerplanthaving an improved regulating system in accordance with the invention.

Generally stated, the invention is practiced by providing a governor responsive-to compressor speed anda controller producing a signal representing the steam generators demand forcombustion air, which jointly operate to position a bypass valve which diverts a variable amount of hot gas from the gas turbine and an auxiliary control device which varies the energy supplied to an auxiliary prime mover for furnishing extra power when the energy available to the gas turbine is insuiicient to supply the demand for air.

Referring now more particularly to the drawing, the invention is `shown as applied to a supercharged boiler type steam generator shown generally at l, supplied with air from a supercharging compressor 2 driven by a gas turbine El. The auxiliary prime mover is represented by the steam turbine 4, vwhich is also connected to directly drive the air compressor 2. For starting, an additional means shown as an electric motor S may also be coupled to the turbine-compressor rotor. A suitable load device, shown at 6i, may be used to absorb any excess power developed by the gas turbine 3, steam turbine 4 combination when the thermodynamic cycle of the powerplant justifies its installation.

The steam generator l supplies a principal consumer, represented by the steam turbine 7, connected to a load device suchas the generator 8, the output of which represents the primary end product of the powerplant.

The steam generator comprises a combustion space la supplied with air under pressure from a plenum chamber 1b by way of a plurality of air inlet ports 1c. A suitable fuel is injected by nozzle 1d supplied through conduit le containing suitable fuel -control valve means lf, which is controlled by a signal from the boiler controller 16, by way of conduit 16a. Water 'is supplied by the eed'pump vlg to appropriate heating coils 1h. The steam is discharged through conduit lk. Conduit ln delivers motive lluid to the steam turbine 7, at a rate determined by the stop and throttle valve gear of this turbine, represented diagrammatically by the valve means 1p. Condensate from turbine 7 is returned Ato the boiler feed pump 1g by conduit 7a.

The air compressor 2 takes in lair from the ambient atmosphere and delivers it Aunder pressure to the regenerator or air preheater 9. Conduit 9a delivers combustion air to the plenum chamber lb of the steam generator 1. The hot gases discharged from the `steam generator through the dischargeeonduit 1m are delivered to the inlet of the gas turbine 3'. The still `hot motive iluid exhausted `from gas turbine 5 is delivered by conduit 3a to the preheater 9 and then discharged to atmosphere through the stack9'b.

The energy made available to the gas turbine 3 is regulated by diverting a variable amount of lthe 'hot gas from conduit lm through a bypass conduit 16a yto the bypass valve y10. So as to Aconserve the Aenergy in the hot tluid bypassed by valve 10, it may be returned by way of conduit b to the gas turbine exhaust conduit 3a so that the energy thereof will be recovered in the air preheater 9.

Steam is supplied to the auxiliary prime mover 4.by conduit 1]' which contains a suitable stop valve lq. From conduit 1j, steam is conveyed to the inlet of the auxiliary steam turbine 4 by way of conduit 1r, as controlled by the auxiliary throttle valve 11.

For supplying an additional increment of available energy to the turbines driving the air compressor, an additional steam injection valve 12 is disposed in conduit 12f which communicates from conduit 1j and discharges steam into the hot gas conduit 1m, as for instance by a suitable nozzle 12g. This injected steam adds to the weight flow of hot motive uid supplied to the gas turbine 3 and thereby increases the energy made available thereto.

In accordance with the invention, integrated control of the bypass valve 10, the auxiliary throttle valve 11, and the steam injection valve 12 is effected by only two condition-responsive devices, namely the single speed governor 13, and a combustion air demand-responsive device, represented as a bellows 14 supplied with a pressure signal by way of conduit 14a from the boiler controller 16. The nature of the boiler control 16 need not be described here since this is a conventional device which senses the temperature and/or pressure of the steam in conduit 1k and delivers an appropriate pressure signal to conduit 14a similar to the signal sent to fuel valve 1f previously described. For example, if steam pressure is the condition measured, increased demand for steam by steam turbine 7 will cause the pressure to fall. This represents an immediate demand for increased air to the combustion chamber in order to increase the heat supplied to the steam coils 1h. The signals for air and fuel may be coordinated to maintain a given fuel-air ratio. As indicated by the legend in the drawing, an increase in the pressure signal supplied to bellows 14 represents a decrease in demand for combustion air while a reduction in this pressure signal corresponds to an increase required in the air ilow. The speed governor 13 is driven at a speed proportional to that of the air compressor rotor, and is arranged to position its output rod 13a upwardly upon a decrease in speed and downwardly with an increase in speed. Although conditions other than those of the steam in conduit 1k could be sensed to give a signal representing the demand for air, such as the temperature in combustion chamber 1a, the embodiment shown is preferable as it rapidly senses an increase in demand for air.

The details of the control valves 10, 11, 12 will now be noted more particularly.

The bypass valve 10 has a fluid control disk member 10c carried on rod 10d and biased upwardly by a coil spring 10e. At its upper end, rod 10d has an abutment member 10f adapted to be engaged by the main control lever in a manner described more particularly in connection with the method of operation. The air demand control rod 14b is pivoted to the lever 15 at 14C, and the speed governor control rod 13a is pivoted to the lever 15 at 13b.

The auxiliary throttle valve 11 and steam injection valve 12 are both arranged to be actuated by the left-hand end portion 15b of the main control lever 15.

The auxiliary throttle valve 11 has a flow control member 11a carried on rod 11b, the upperend of which is provided with an abutment member 11c biased downwardly by spring 11d. The upper end portion of rod l11b is provided with a threaded portion r11e on which is an adjustable abutment member 11j adapted to be engaged by an abutment ring member 15e which is formed integral with the lever 15. It is to be understood that the rod 11b and the threaded portion 11e project freely through the abutment ring 15c for all positions of the lever 15. With this arrangement, the abutment ring member 15c engages the adjustable abutment 111 so as to raise the valve stem 11b only after the left-hand end portion 4 15b of the lever has moved upwardly a preselected amount, determined by the adjustment of abutment 11f.

Likewise, the steam injection valve 12 has a flow control member 12a carried on a stem 12b which has a threaded portion 12e carrying an adjustable abutment 12d. The valve stem is biased downwardly by a coil spring 12e. The forked end portion of lever 15b is adapted to engage the abutment 12d so as to raise the valve stem 12b only after the lever portion 15b has moved upwardly a preselected distance, determined by the adjustment of abutment 12d. It will be observed that, as shown in the drawing, upward movement of the lever portion 15b will result first in opening the auxiliary throttle valve 11 and subsequently open the steam injection valve 12.

Thus it will be seen that an exceedingly simple interconnecting linkage is employed to connect the two condition- responsive devices 13, 14 so as to position the three motive fluid control valves 10, 11, 12. The method in which this operation is effected will be seen from the following description of the method of operation.

To start the Powerplant, the electric motor 5 is energized to turn the air compressor 2 at the speed necessary to furnish the combustion air required for initiating combustion in the steam generator 1. When the air Supply is adequate, the fuel control valve 1f is actuated to admit fuel, and a suitable sparking device (not shown) ignites the fuel-air mixture. As the combustion rate increases, the feedwater supplied by pump 1g is vaporized and the steam pressure in conduit 1k rises to the rated value which is established by the requirements of the principal consumer steam turbine 7, for example, 1450 p.s.i.g.- 950 F. When sufficient steam pressure and temperature is available, the boiler operator manually initiates acceleration of the unit through the boiler controller 16 by calling for an increase in combustion air flow. This decreases the pressure signal delivered to bellows 14, causing the pivot 14o to descend in the increase air direction. Lever 15 pivots clockwise about the point 13b so that bypass valve 10 is closed, and the abutment 15c engages the adjustable abutment 11f and opens the auxiliary throttle valve 11, so as to admit steam to the turbine 4. 'Ihe auxiliary steam turbine now drives the air compressor, and the electric starting motor 5 may be de-energized, or disengaged by suitable clutch means (not shown). By way of example, it may be noted that the starting motor 5 may be designed to drive the compressor at about 10% of rated speed, which is found adequate to furnish the air required to initiate combustion in the steam generator 1. The auxiliary steam turbine 4 now brings the air compressor 2 up to the desired speed, as determined by the characteristics of speed governor 13 and the speed setting demand for air established by the position of pivot 14C. Increasing speed of the governor 13 causes the pivot 13b to descend so as to partly close the steam throttle valve 11. The governor 13 will now control the steam valve 11 to keep the compressor speed at the value determined by the setting of the air demand pivot 14e.

If now the boiler controller 16 calls for a greater air supply, as occasioned for instance by opening the valve 1p to admit steam to the consumer 7, the pressure signal supplied to bellows 14 will cause the pivot point 14e to descend still further to a new speed setting and open the steam valve 11 wider. This increases the speed of compressor 2, and the resulting increased ilow of hot gases to the gas turbine 3 will decrease the power required from the auxiliary steam turbine 4; and any tendency of the compressor rotor to rise above the speed setting determined by the position of pivot 14c will cause the speed governor 13 to move the pivot 13b downwardly so as to close steam valve 11. If valve 11 closes completely, and the speed governor 13 is still calling for a decrease in speed, further downward movement of pivot 13b will cause lever 15 to pivot counter-clockwise about point 14e so the right-hand portion 15a of lever 15 rises and spring e moves valve stem 10d upwardly andopens' the bypass valve disk member 10c. This permits some of the ho't gas to be diverted from the gas turbine 3 through the bypass conduit 10b. This diverted flow is discharged into the exhaust conduit 3a so that the thermal energy of this gas is not wasted but is recovered in heat exchanger 9.

Thus the bypass valve 19 acts to control the gas turbine 3 when the power output thereof is sufficient that no power is required from the auxiliary prime mover 4, and the demand for air from the boiler controller 16 is such that the hot gas generated is in excess of that required to drive the compressor 2. This will be the normal operating condition, with the bypass valve 10 control ling the gas turbine 3 and the auxiliary steam turbine 4 inactive. lt is, of course, possible to provide an overrunning clutch (not shown) between the auxiliary steam turbine 4 and the air compressor 2 so that the starting motor and auxiliary steam turbine are mechanically disengaged from the compressor shaft except when they are delivering torque to the compressor rotor.

The plant is now operating at normal cruising" condition. If a sudden demand is made on the plant for maximum delivery of steam to the turbine 7, the boiler controller 16 quickly delivers an increase air signal, which is also an increase speed setting, to the bellows 14, causing the pivot 14C to descend rapidly. The resulting clockwise rotation of lever about pivot 13b causes the bypass valve 10 to close, andthe auxiliary steam valve 11 to open. If the power now delivered to the air compressor is still not adequate to supply the demand for air (with valve 11 wide open), the bellows 14 continues t'o pull down on pivot 14e and lever 15 pivots further about the point 13b so the left-hand end 15b of the lever engages the adjustable abutment 12d and opens the steam injection valve 12. This admits steam to conduit 1m, and this additional weight ow of hot motive iluid furnishes the Vadditional energy to the gas turbine required to accelerate the unit to supply the air demand called for.

|Thus in the event of a transient call for maximum air ow, the throttle valve 11 andthe steam injection valve 12 cooperate to increase the flow of motive fluid to the steam and gas turbines so as to provide the compressor power required. When this transient demand is satisfied, the speed governor 13 causes pivot 13b to descend, causing lever 15 to pivot counterclockwise about point 14e. This rst closes the steam injection valve'12, then progressively closes the auxiliary throttle valve 11, and finally returns the plant to the normal condition in which the bypass valve 10 is lpartly opened and controlling the gas turbine, which again furnishes the entire power for driving the compressor at the new steady-state condition.

Conversely, when the boiler controller 16 calls for a reduction in air flow, which means a reduction in speed of the compressor, the lbellows 14 will cause the pivot 14C to rise, opening the gas turbine bypass valve 10, without any effect on the auxiliary valve 11 and steam injection valve 12 since the left-hand end of lever 15 mere- 1y moves downwardly away from the abutments 11), 12d. If the cycle is thermodynamically self-sustaining at this reduced air flow, the gas turbine bypass valve 10 will remain open sufficiently to maintain the energy balance and drive the gas turbine 3 at the new speed called for by the air demand bellows 14. If, however, the cycle iis not now self-sustaining, the gas turbine rotor will decelerate, with the result that speed governor 13 will cause pivot 13b to rise, tending to close the gas turbine bypass valve 10 so as to increase the energy available to the gas turbine. If, with the entire oW of hot gas from conduit 1m going to the gas turbine 3, the power output is still not sufficient to drive the air compressor, the continuing decrease in speed will cause pivot 13b to rise so that the auxiliary steam valve 11 is progressively opened until the combined output of the steam turbine 4 and the gas turbine 3 satisfy the energy requirements of the air compressor 2.

It will, of course, be appreciated that the regulating system` will include suitable emergency overspeed trip governors and other safety devices which are conventional and not necessary to an understanding of the' present invention. Accordingly, these conventional components are not shown in the drawings. f

It' will be seen that the invention provides a very simple regulating mechanism employing only a single speed governor and a single air demand responsive device coordinated in a simple but effective manner for controlling the energy made available to the gas turbine and for supplying additional power from an auxiliary prime mover when the ilow of hot `gas to the turbine 3 is insumcient to furnish the compressor power requirements. The arf rangement provides maximum flexibility of operation of the supercharged steam generator, rendering it extremely responsive to calls: for sudden changes in air flow, making possible rapid acceleration and deceleration as required for maneuvering in a marine powerplant. Thus the invention helps to overcome the inherent sluggishness of the supercharged boiler type of steam generator, giving it such flexibility as to make it readily adaptable for marine propulsion as well as for supplying steam for power generation or industrial process purposes.

While this invention has been illustrated specificallyV as applied to a steam generating plant with a supercharged combustion chamber, it will be obvious to those skilled in the art that the regulating system may be used in any industrial process where there is a demand for air, and in which heat is added either by the process or by combustion before the air enters the gas turbine, and a separate source of energy is available for the auxiliary prime mover. It will also be obvious that the regulating system may be used in other powerplants where the power requirements of load device 6 and the air compressor 2 may be at times greater than the gas turbine 3 can produce alone, and a separate auxiliary prime mover is provided to supply the extra rpower required.

While only one preferred embodiment of the inventionv has been illustrated specifically herein, it will be obvious fto those skilled in the art that many modifications and substitutions of equivalents may be made without departing from the invention. The components illustrated in the drawing are of course intended to be purely diagrammatic and may take many alternate forms. Instead of having the lever 15 act directly to operate the bypass valve 1), the steam valve 11, and the steam injection valve 12, it` will be appreciated that suitable power amplifying means such as electric, pneumatic, or hydraulic servo-mechanisms could be employed to furnish the mechanical power required-to position these valves. It will also be obvious that the electric starting motor 5 may be dispensed with if an auxiliary source of steam other than the steam generator 1 is available to furnish steam to turbine 4 so that it can also serve as the starting motor. Likewise, the auxiliary prime mover 4 could take the form of an electric motor, diesel engine, etc.

It is, of course, intended to cover by the appended claims all such modifications as fall within the true spirit and scope of the invention.

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

l. Regulating means for use in a combined steam generating and gas turbine powerplant having a steam generator including a supercharged combustion chamber, an

air compressor connected to supply combustion air under pressure to the combustion chamber, a gas turbine connected to drive the compressor and to be driven by hot gas discharged from the combustion chamber, and auxiliary motor means also connected to drive the compressor, the regulating means comprising speed governor means responsive to compressor speed, bypass valve means connected to divert from the gas turbine a portion of the total lflow of hot gas discharged from the combustion chamber, first means connected to said bypass valve means to control the supply of motive uid to the gas turbine as a function of combustion air required by the steam generator, second means connected to control said auxiliary motor means to supply additional power to the compressor when gas turbine power is inadequate to furnish the air flow required by the steam generator and to accelerate the compressor to secure desired rate of response upon change in load, and linkage means interconnecting the speed governor with said lirst bypass valve control means and said second auxiliary motor control means to rst progressively close the bypass valve means and then to regulate said auxiliary motor means to increase the power output thereof, upon demand for increased air ow to the steam generator.

2. Regulating means for a combined steam-gas turbine powerplant having a steam generator with a pressurized combustion chamber, an air compressor connected to supply combustion air under pressure to the combustion chamber, a gas turbine driving the compressor and driven by hot gas discharged from the combustion chamber, and at least one auxiliary motor means also connected to drive the compressor when the gas turbine power is insufficient to supply the air demands of the steam generator, the regulating means comprising speed governor means responsive to compressor speed, bypass valve means connected to divert from the gas turbine inlet conduit a portion of the total hot gas discharged from the combustion chamber to vary the motive fluid input to the gas turbine, lrst control means connected to said bypass valve to control the supply of motive fluid to the gas turbine as a function of combustion air required by the steam generator, second control means connected to vary the power output of said auxiliary motor means to regulate the supply of additional power to the compressor when gas turbine power is insufiicient to furnish the air flow required by the steam generator, a steam injection valve connected to supply steam to the gas turbine inlet, and linkage means interconnecting `the speed governor with said bypass valve control means and said second control means and said steam injection valve to iirst progressively close the bypass valve means and then to increase the power output of said auxiliary motor means and then to open said steam injection valve progressively as the demand for air from the compressor increases.

3. In a combined steam-gas turbine powerplant, the combination of a steam generator having a supercharged combustion chamber, a compressor connected to supply air under pressure to the combustion chamber, a gas turbine connected to drive the compressor and to be driven by hot gas discharged from the combustion chamber, variable power output auxiliary motor means also connected to drive the compressor, boiler control means connected to emit a signal as a function of load on the steam generator, and regulating means comprising speed governor means responsive to compressor speed, bypass valve means connected to divert hot gas from the gm turbine inlet to vary the motive iiuid supply to the gas turbine, a main control lever member, first control means connected to position said lever member in accordance with the signal from the boiler control means, second control means connected to position a spaced portion of saidl lever member in accordance with compressor shaft speed, said lever member having 4a rst portion disposed to V'regulate said bypass valve means to control the supply of hot gas to the gas turbine to lieep compressor speed constant at a value determined by said first control means, said lever member having a second spaced portion connected to adjust the power output of said auxiliary motor means, said control lever-being connected to iirst close the bypass valve upon a demand for increased load, and then to increase the power output of the auxiliary motor means.

4. Steam-gas turbine powerplant in accordance with claim 3 and including variable means for injecting steam under pressure into the gas turbine inlet, the main control lever member having also a portion adapted to control said variable steam injection means to supply steam to the gas turbine to increase the power output thereof after the bypass valve is completely closed and the auxiliary motor means is delivering maximum power.

5.V Steam-gas turbine powerplant in accordance with claim 3 and including air-preheater means for transferring heat from the exhaust gas discharged from the gas turbine to the compressed airdischarged from the compressor, and conduit means for discharging the diverted hot gas from the vbypass valve to the air-preheater whereby the thermalenergy of the bypassed gas is transferred to the heated air supplied to the combustion chamber.

6. Regulating means for use with a gas turbine powerplant having a compressor connected to supply gas under pressure to a heating device, a gas turbine connected to drive the compressor and to be driven by hot gas discharged from thelheating device, and auxiliary motor means also connected to drive the compressor, the regulating-,means comprising speed governor means responsive to compressor speed, rst valve means connected to control the quantity of hot gas discharged from the heating device to the gas turbine, second means connected to said iirst valve means to control the supply of hot gas to the gas turbine as a function of desired rate of gas ow to the heating device, third means connected to control the auxiliary motor means to supply additional power when the output of the gas turbine is insufficient to drive the compressor, and linkage means connecting the speed governor with said second control means and with said third auxiliary motor control means to progressively regulate the first valve means and then to regulate the third control means to increase the power output of the auxiliary motor means, upon demand for increased gas flow to the heating device.

,7. Regulating means for use with a gas turbine powerplant having a compressor connected to supply gas under pressure to a heating device, a gas turbine connected to drive the compressor and to be driven by hot gas discharged from .the heating device, load means utilizing a portion of the energy in said compressed gas, and auxiliary motor means also connected to drive the compressor, the regulating -means comprising speed governor means responsive to compressor speed, rst means connected to control the available thermal energy of the hot gas discharged from the heating device tothe gas turbine, second means connected to said first means to control the available thermal energy supplied to the gas turbine as a function of the load on said -load means, third means connected to control the auxiliary motor means to supply additional power when the output of the gas turbine is insuiiicient to drive the compressor, and linkage means connecting the speed governor with said second control means and with said third auxiliary motor control means to progressively regulate the iirst control means and then to regulate the third control means to increase the power output of the auxiliarymotor means, upon increased load on the load means.

. No references cited.

Images