US 2912824 A
Description (OCR text may contain errors)
Nv. 17, 1959 F. H. VAN NEsT ETAL GOVERNINGPPARATUS FOR MARINE GAS TURBINE POWERPLANT Filed Oct. l5. 1956 SE :ai .Bumm 12x..
United States Patent C) f' GOVERNING APPARATUS FOR MARINE GAS TURBINE POWERPLANT Francis H. Van Nest and Robert J. Brown, Schenectady,
N.Y., assignors to General Electric Company, a corporation of New York Application October 15, 1956, Serial No. 615,952
14 Claims. (Cl. 60-39.16)
This invention relates to governing mechanism for thermal powerplants, particularly to regulating means for controlling a gas turbine prime mover adapted for marine propulsion. It relates specifically to a gas turbine of the type having a turbine-combustor-compressor unit and a second mechanically independent turbine rotor for delivering power to the propeller shaft, with a variable turbine nozzle ring interposed between the compressor turbine and the propeller turbine.
An earlier type of governing system for a gas turbine of the type to which the present invention relates is disclosed in United States Patent 2,625,789, issued January 20, 1953, in the name of N. E. Starkey and assigned to the same assignee as the present application. The present invention is an improved governing system intended particularly for the application of this type of gas turbine powerplant to marine propulsion, where a variable pitch propeller is employed.
The general advantages which led to the introduction of the two-shaftl gas turbine with a Variable intermediate turbine nozzle have been detailed in the abovementioned Patent 2,625,789. This type of gas-turbine powerplant, coordinated with a variable pitch propeller as the power absorbing load device, results in a powerplant of great flexibility having many desirable characteristics for marine service. At the same time, integrating the control of the variable pitch propeller with the fuel regulating mechanism for the powerplant introduces certain problems. In maneuvering the ship, as when in port, it is important to have quick and flexible control of the power output, automatically integrated with changes in propeller pitch; and rapid response to changing conditions is more important than optimum fuel economy. On the other hand, cruising operation, at sea, requires the best possible fuel economy. Thus maneuvering control should be quite different from cruising control, in order to obtain best overall performance of the ship. It is, of course, necessary to provide proper safeguards for preventing excessive rotor speeds and gas temperatures. Proper integration of numerous operating conditions which have to be taken into account'must be accomplished by mechanism which is suciently simple that utmost reliability can be built in, since the operator of a marine powerplant obviously cannot afford to have his ship disabled at sea or laid up for an extended period in a foreign port because of the failure of some small governor component.
Accordingly, an object of the present invention is to provide improved regulating mechanism for a gas turbine powerplant of the type having mechanically independent compressor-turbine rotor and output-turbine rotor, with a variable nozzle between, capable of operating with quick response during maneuvering and at maximum thermal efficiency during normal operation at sea, together with proper safeguards against excessive speed and temperature conditions.
Another object is to provide an improved gas turbine control system of the type described which in large part 2,912,824 Patented Nov. 17, 1959A,
the water, or where the propeller. pitch suddenly goes to 'zero pitch (minimum torque) position.
Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings in which the single gur'e a very diagrammatic representation of a gas turbine' powerplant having mechanically independent compressorturbine and output-turbine rotors, withy governing mechanism in accordance with the invention. l
Generally stated,'the invention is practiced in normal operation by regulating the supply of fuel to the combustion system of the powerplant in accordance with a temperature condition, altering the power output in a desired manner by changing the speed setting of the compressor-turbine speed governor, and regulating the variable turbine nozzle to maintain the compressor-turbine speed at the selected value. For start-up and maneuvering, the governing system is specially arranged to properly coordinate changes of propeller pitch with the operation of the powerplant, during which the speed governor maintains the compressor-turbine speed by adjusting the fuel supply, and the variable turbine nozzle is positioned by manual control, until temperature conditions come up to normal operating values, where control automatically reverts to the temperature governor. Special emergency means are provided for bypassing air from the compressor around the combustion system and l turbine in the event extremely rapid reduction in energy release is required to prevent overspeed.
Referring now more particularly to the drawing,` the).
governing system is shown as applied to a gas turbine powerplant consisting of a compressor shown generally delivers hot motive fluid to a first turbine series with a second turbine at 4.
Air from the ambient atmosphere enters compressor 1 through the inlet casing 1a and is compressed in themultiple stage axial ow compressor having a rotor 1b. YA projecting shaft end portion 1c drives various governing components as will be described more particularly hereinafter. Compressed to a pressure on the order of perhaps 65 pounds per square inch, the air passes to the combustion system 2 through the compressor discharge casing 1d.
The combustion system 2 may comprise a plurality of similar cylindrical combustion chambers or combustors each having an outer air supply casing 2a and an inner liner 2b which defines the combustion space proper. Fuel is sprayed into the liner by a suitable nozzle 2c. The combustors may, for instance, be constructed and arranged in accordance with the principles of the .Nerad combustor described in detail in United Statesr Patent 2,601,000, issued June 17, 1952 in the name of-A. I.
Nerad and assigned to the assignee of the present applicathat there is no mechanical interconnection between the rst stage turbine rotor 3b and the second stage rotor 4a, so that each is free to rotate at a speed independent of the other.
The conversion of energy in the `second stage turbine 4, and the division of the available energy of the motive fluid between the first stage turbine 3 and the second stage turbine 4, is controlled by a variable area turbine nozzle indicated generally at 5. This variable nozzle includes a. plurality of circumferentially spaced vanes 5a carried on separate radially disposed spindles 5b connected by levers 5c to a control ring member 5d adaptedV be pesi tioned circumferentially by an operating rod member Se. Further mechanical details of the variable area turbine nozzle need not be described here, since one suitable form for this mechanism is disclosed in United States Patent 2,651,496, issued September 8, i953 to O. Buckland and G. B. Warren and assigned to the same assignee as the present application. lt need only be noted here that motion of the control rod Se upwardly causes the variable vanes 5a to pivot so as to open the nozzles to increase their effective area and thereby reduce the energy available to the second stage turbine 4, while increasing the energy available to the compressor-turbine 3. Conversely, motion of rod 5e downwardly causes the variable turbine nozzles to close, increasing the energy available to the second stage turbine 4 and reducing the pressure drop across, and the energy conversion in, the first stage turbine 3.
Spent gases are discharged from the second stage turbine 4 through a suitable exhaust casing 4c. Heat remaining in the exhaust gases may be utilized in a regenerator, or in a suitable water heater or other heat recovery device.
The power output shaft 4b is connected to a suitable variable pitch propeller 6 through appropriate reduction gearing, which is not shown in the drawing since the details thereof do not form a part of the present invention. Likewise, the mechanism for altering the pitch of propeller 6 are not disclosed in detail since not a part of this invention. The pitch control mechanism is illustrated diagramatically at 7. It will be understood by those familiar with the art that this mechanism is arranged to feather the propeller, that is, move the blades to zero pitch position at zero pov/er output, and to progressively increase the blade setting to positive pitch angles up to a preselected maximum value for normal cruising operation. This pitch control mechanism is also arranged to reverse the blade pitch, to provide for a stern operation of the ship. The schedule of propeller pitch setting, as a function of the operating program of the power plant, will be noted more particularly hereinafter.
Other auxiliary control devices associated with the power output shaft 4b include a pre-emergency governor and an emergency overspeed governor. As shown diagrammatically in the drawings, the pre-emergency governor may be a pump 8 furnishing a pressure signal which varies as a function of speed of shaft 4b. The emergency overspeed governor may be of the unbalanced bolt type employed commonly in steam turbine governors, but is illustrated here as a simple centrifugal flyball governor 9 arranged at a preselected speed to close an electrical circuit 9b at switch 9a. Both governors are driven by suitable gearing from the shaft 4b.
The auxiliary governing components associated with the shaft extension ic at the inlet end of the powerplant include the following. A compressor speed signal is provided by a centrifugal ilyweight governor l0, which may be driven from the shaft llc by suitable gearing lila. Also geared to the shaft le is a suitable lubrication and hydraulic control oil pump lll receiving oil from a suitable reservoir (not shown) and delivering it at a pressure of perhaps 55 pounds per square inch past a check-valve 11a to supply conduit l2. When the speed of pump 11 is inadequate to supply hydraulic operating liquid at the pressure required, as during the starting cycle, a second pump 13 may be driven by a suitable prime mover, shown diagrammatically as an electric motor il3a energized by a switch 13b from a suitable source of auxiliary power. Pump i3 supplies hydraulic liquid past check-valve 13e to the supply conduit 12. It will be obvious to those skilled in the art that the pump 13 may either run continuously, or be arranged to automatically stop whenever the pressure delivered by the geared pump ll is above a preselected safe value. Such arrangements are wellknown in the art and the details of such a system are therefore not shown in the drawing.
For starting the gas turbine, a suitable starting motor is geared to the shaft llc. This could, of course, take the form of a small steam turbine or reciprocating internal combustion engine coupled by appropriate clutch and gearing mechanism to the shaft llc, but for simplicity is shown in the drawing as an electric motor 14 connected to shaft 1c by gears 14a and arranged to be energized by a switch 14h. The source of energy may be the ships service electrical system.
The main fuel supply for the powerplant is provided by an appropriate pump l5 coupled by gears 15a to the shaft extension lc. Pump l5 receives a suitable uid fuel from a reservoir (not shown) through inlet conduit 5.11 and delivers it to supply conduit lSb at a discharge rate which varies in accordance with the dictates of a servo-mechanism indicated diagrammatic-ally at llSc. This may, for instance, take the form of a hydraulic servo-mechanism arranged to vary the displacement of the pump l5, in accordance with an input signal communicated by pump controd rod 15d to the bell crank le. While various pumps of this general type may be employed, a suitable one is shown in United States Patent 2,709,449, issued May 3l, i955, to D. E. Garr and M. A. Edwards and assigned to the assignee of the present application. This multi-piston pump may have one or more cylinders connected by separate supply conduits to the several cornbustors 2a, instead of the single supply conduit tSb and branch conduits 15g. The details of the pump l5 and servo-mechanism 15C are not important here. It need only be noted that movement of the pump control rod iSd downwardly increases the rate of fuel supply, and movement of rod ld upwardly decreases the fuel supply rate.
The main fuel supply conduit lh contains an emergency stop valve 16, arranged to be tripped automatically, upon the occurrence of a preselected overspeed condition, by servo-mechanisrn described more particularly hereinafter. As shown in the drawing, the fuel is distributed from an annular supply main 15j' by branch conduits lg to the nozzles 2c in the respective combustors. Fuel flow is indicated by broken arrows in the drawing.
The nature and interrelation of the various components of the regulating mechanism to which the invention particularly relates will be seen from the following.
Temperature governor In normal operation, the rate of fuel supply delivered by the pump l5 is determined by the temperature governor indicated generally at 17. While this could talte many forms, it is illustrated diagrammatically as comprising a fluid-filled bellows 17a connected by a capillary tube li'i to a long fluid-filled bulb l7c arranged in the exhaust casing 4c so as to be responsive to an integrated average temperature of the hot gases discharged from the turbine. Temperature sensitive bellows l7a is contained within a housing 76! which also defines a valve housing forming a port l7e adapted to be closed by a valve disk 17]" connected to be positioned by bellows 17a. Disk l'f is biased towards its closed position by a suitable spring 17g. Hydraulic fluid from a suitable source, such as the supply conduit l2, enters by way of conduit i711, which contains an orifice 171'. The inlet chamber l7j is in communication at all times by way of conduit f/c with the weer s pressure chamber 17m of the temperature servo-motor 17u. Temperature servo 17n contains a flexible bellows 17o sealed at its upper end to the housing 17n and at its lower end to a movable abutment member 17 p. The abutment 17p is forced upwardly by the fluid pressure in chamber 17m against an abutment member 17W, which is connected to rod 17r and is downwardly biased by spring 17q. Thus it will be observed that pressure sensitive abutment 17p is not connected to, but merely bears against, the lower end abutment 17w of the temperature signal output rod 171'. The spring 17g causes rod 171' to follow movements of abutment 17p.
The operation of the temperature governor is as follows.
Upon an increase in temperature of the eXhaust'gases in casing 4c, the uid pressure in temperature sensitive tube 17e increases, which pressure is communicated by conduit 17b to the bellows 17a. When the temperature reaches a selected value, 4as determined by the design of bellows 17a and spring 17g, the resulting upward movement of valve disk 17 f opens port 17e to release the pressure in chamber 17j, the operating liquid draining freely from the housing 17d by drain 17 u. The decrease in pressure in chamber 17m causes abutment 17p to move downwardly under the influence of spring 17g. Biasing spring 17q causes the output rod 17r to descend, so as to follow the motion of abutment 17p. Conversely, a
decrease in the temperature signal pressure in bellows 17al supplied through conduit 17h causes an increase in pres-v sure in chamber 17m, moving abutment 17p upwardly so `as to raise the output rod 17r. Thus a temperature increase, above the preselected value, is accompanied by downward motion of the rod 17r, while a temperature `decrease produces an upward motion of rod 17r, as indicated by the legend in the drawing.
The temperature governor 17 is connected quite directly to the fuel pump control rod a', by means of a pump control lever 18 pivoted at its left end to the pump control rod 15d and carried on a fulcrum 18a. The connection between the temperature governor 17 and the pump control lever 18 comprises a multi-part rod indicated generally at 19 as comprising three separate portions 19a, 19h, 19e connected by two breakaway links 20, 21, respectively. The link 20 comprises a housing 20a connected to the rod portion 19a and containing a spring 20b which exerts a downward bias on an abutment member 20e connected to the second rod portion 19h. Likewise, the link 21 comprises a housing 21a connected to the rod portion 19b and containing a biasing spring 2lb which pushes downwardly on an abutment 21e carried v on the third rod portion 19e. It will be apparent from the drawing that in normal operation springs 20h, 2lb force the respective abutments 20e, 21e into lirm engagement with the bottom of the housings 20a, 21a, so that the three-piece rod 19 tends to act as a solid link connecting the temperature governor lever 17s and the pump control lever 18.
As noted more particularly in the above-mentioned Patent 2,709,449, the fuel pump mechanism includes means for biasing the control relay 15e to the minimum delivery condition. For the purpose of illustration here, this biasing means is represented by the spring 18h which exerts an upward force on an abutment 18e carried by the upper end of pump control rod portion 19e. It will be apparent from the legends in the drawing that this upward bias tends to move the fuel pump control relay 15e in the decrease fuel direction.
It will now be apparent that the normal operation of temperature governor 17 is to move the pump control rod 15d downwardly to increase the fuel supply when the turbine exhaust temperature decreases below a preselected value, and to move rod 15d upwardly to decrease the fuel supply when the exhaust temperature exceeds a preselected value. Thus the action ofthe temperature governor is to keep the fuel rate at a value consistent with a preselected desired turbine exhaust temperature level, which results in the powerplant operating at its maximum thermal eciency.
Speed governor The normal function of the speed governor 10 is to adjust the variable turbine nozzle 5 so as to hold at a set value the speed of the turbine-compressor rotor3b, 1b; but it also may assume control of the fuel supply to control the speed of the turbine-compressor rotor whenever the exhaust temperature is below the preselectedl value vat which the temperature governor 17 becomes operative, as during the starting cycle and maneuvering operation of the powerplant. The manner in which the speed governor 10 performs its function will be seen from the following.
As indicated by the legend in the drawing, theaction of the yweight governor 10 is to push rod 10b upwardly be appreciated from the drawing that clockwise rotation of speed-setting lever 10e decreases the compression of spring 10c so as to decrease the speed setting of governor 10, while counterclockwise rotation of lever 10e increases the compression of spring 10c so as to increase the speedv held by governor 10. l y
The upper end of speed control rod 10b is connected by a lever 10h fulcrumed at 10i to a link 10j connected to an intermediate portion of the main control lever 10k. The left-hand end of lever 10kl is pivoted at 10m to the pump control rod portion 19b. At its right-hand end, the main control lever 10k carries a fitting 10n which serves as an abutment in a manner described hereinafter, and also forms a pivot connection with link 5h which connects the main control lever with the turbine nozzle control lever 5f, which is supported on fulcrum 5g. This fulcrum may be rendered adjustable, as by mounting it on alead-screw 5l' with an adjusting thumbscrew Sk, so as to vary the rate of change of the nozzle 5 with motion of abutment 10u.
It will be seen that the main control lever 10k thus integrates the compressor speed control with the fuel pump control, and with the turbine nozzle control, for if the left-hand pivot point 10m be held stationary, then speed governor 10 will cause lever 10k to pivot about its left end to actuate the variable turbine nozzle 5.y On the other hand, if the tting 10n at the right-hand end of the main control lever is held lined, then the speed governor will cause the lever 10k to fulcrum about its right-hand end so as to position the control rod 19.
The operation of the speed governor 10 may be outlined in more detail as follows.
In normal operation, the temperature governor 17 will position the rod 19, determining the position of pivot 10m, and the function of the speed governor 10 will be to adjust the variable turbine nozzle 5. Upon an increase in the speed of governor 10, the speed control rod 10b descends, causing lever 10h to pivot counterclockwise, thus raising link 10j and causing lever 10k to move upwardly about pivot 10m, so that lever 5f moves clockwise about fulcrum 5g to move nozzle control rod Se in the nozzle closing direction. `Closing the turbine nozzle vanes 5a has the effect of reducing the pressure drop across the first stage turbine wheel 3b, with the result that the energy available tothe first stage turbine decreases. This fdecrease in available energy results in slowing down the turbine-compressor rotor, so that speed governor 14) returns to its set speed condition. Conversely, a decrease of turbine-compressor rotor speed causes the speed control rod 10b to rise, so that lever 10k pivots clockwise about pivot 10m causing the nozzle control rod e to rise and open the variable nozzle 5. This increases the pressure drop across the first stage turbine wheel 3b, so as to increase the energy available to the turbine-compressor rotor and bring it back up to the set speed.
Thus, in normal operation, with the temperature governor 17 controlling the rate of fuel supply by positioning the pump control lever 18, the action of the speed governor is to regulate the variable turbine nozzle 5 so as to hold the turbine-compressor rotor at a speed selected by the speed-setting lever 10e. As noted more particularly hereinafter, during certain parts of the operating cycle (specifically, start-up and maneuvering) the right-hand end of the main control lever 10k is held fixed, in which case the speed governor 10 acts directly on the control rod 19h to adjust the fuel supply rate. Specilically, upon a decrease in speed of the turbinecompressor rotor, the speed control rod 10b rises to cause lever ltllz to pivot clockwise, so that the main control lever 10k pivots counterclockwise about its righthand end 10ft, thus causing the pivot Nm to descend in the increase fuel direction. ln the event of a speed increase, the action is the opposite, so that rod 19h rises in the decrease fuel direction. This action of the speed governor 10 to decrease the fuel supply may take place irrespective of the fuel rate called for by the temperature governor 17, since the abutment 20c of the breakaway link 2t) will, if necessary, rise against the compression of spring 20h. Thus the speed governor 10 is effective, when the right-hand end of lever 10k is held fixed, to reduce the fuel supply irrespective of the condition of the temperature governor 17. But on the other hand, the speed governor cannot increase the fuel supply rate above that called for by the temperature governor 17, since in that case the abutment 20c engages the bottom of the housing 20a, and the temperature governor positively positions rod 19 upwardly to override the speed governor. The temperature governor then controls fuel rate, and the speed governor is free to position abutment 10ft downwardly, away from stop collar 33a, to control speed by adjusting turbine nozzle 5.
In addition to the normal temperature and speed control, the powerplant is provided with a number of fuel limiting and emergency shut-olf devices, as follows.
A powerplant driving a marine propeller may be subject to sudden reduction in torque, as for instance when the propeller momentarily leaves the water in a heavy sea. This sudden loss of torque on the output shaft is an extremely serious matter when the powerplant is a gas turbine witn an independent turbine stage generating the power output, since the fuel control will at least transiently tend to keep the rst stage turbine-compressor rotor at a constant speed, with the result that the rate of air flow through the plant will remain essentially constant. Thus a sudden loss of torque on the output shaft, without an instantaneous compensating reduction in the energy available to the output turbine, may cause it to run away.
Accordingly, this governing system incorporates special means for instantaneously reducing, by a substantial amount, the energy available to the output turbine in the event the speed of the output shaft 4b rises to a preselected pre-emergency speed, which may be for instance on the order of 108% of normal rated speed. This is accomplished by arranging the pre-emergency governor mechanism to first reduce the speed setting of the governor It() to its low-speed position, and at the same time to open the turbine nozzle 5, and then secondly to open a valve in a bypass conduit which takes air from the compressor discharge casing and passes it directly into the exhaust casing of the turbine, without going through the combustion system and turbines.
in the drawing, this bypass or blow-off conduit is identified at 22 as communicating between the compressor discharge casing 1d and the turbine exhaust casing 4c. This bypass is controlled by a blow-off valve 22a. The valve disk 22b is carried on an operating rod 22C and is biased to the closed position by a spring 22d. The blow-off valve is actuated in the opening direction by a linkage connected to the pre-emergency governor servomotor 23. This servo comprises a housing 23a containing a piston 23b biased upwardly by a spring 23C and adapted to be moved downwardly to actuate the blowolf valve by a hydraulic pressure signal supplied to the cylinder 23a by conduit 8a in accordance with the speed of the pre-emergency governor pump 8.
Piston 23b is connected to a piston rod 23d carrying an adjustable abutment member 23e. This abutment is adapted to engage the right-hand end of a lever 24 which is carried on a fulcrum 24a and is connected at its left-hand end with a link Zdb the lower end of which is pivoted to one arm of the lever member 24C, which is carried on fulcrum 24d and pivoted at its right-hand end to the operating rod 22C of the blow-off valve.
During normal operation of the powerplant, the adjustable stop 23e remains out of engagement with the lever 24. When the pre-emergency speed is reached, as determined by the upward biasing force of spring 23C and the adjustment of the position of adjustable stop 23e, the abutment 23e just engages the right-hand end of lever 24. Further movement of the servo piston 23b will cause the linkage 23d, 24, 24h, 24C to begin to open the blow-off valve 22a. Release of air from the compressor discharge casing 1d instantly reduces the weight flow of motive uid going through the combustion system and turbines. The pre-emergency governor will act to progressively open the blow-off valve 22a until the reduction in flow and energy available to the turbine rotors decreases sufficiently to bring the output shaft speed down. If the speed falls below the pre-emergency speed, then the servo 23 will re-close the blow-off valve 22a. On the other hand, the overspeed condition may be such that the blow-off valve 22a will perform a regulating function, closing and opening as the speed of the output shaft 4b changes. Thus in certain emergency situations, the blow-off valve mechanism may actually assume` primary control of the power output, while the speed governor 10 regulates the fuel flow to its minimum value in an attempt to hold the compressor rotor speed constant at the low speed stop setting, as described more particularly hereinafter.
Emergency overspeed governor In the event of an emergency overspeed condition which the pre-emergency governor 8 cannot handle, the emergency overspeed governor 9 comes into action. As noted above, this comprises the fiyball governor 9 arranged to close emergency stop valve 16 in the fuel inlet conduit S/z upon the occurrence of a dangerous overspeed condition. The mechanism by which this is accomplished is as follows.
The emergency fuel shut-off valve 16 has an operating rod 6a connected to the piston 16b which is slidably disposed in cylinder 16C and biased upwardly to closed position by spring 16d. Operating liquid is admitted to the chamber 16e by a conduit 12b communicating with the hydraulic supply conduit 12, which contains the orifice 12a. Liquid is drained from chamber 16e by a drain conduit 16f containing the overspeed dump valve 65; connected to be actuated by solenoid 36h. As will be apparent in the drawing, solenoid 16h is arranged in circuit 9b to be energized from a suitable source of power when flyball governor 9 closes the switch 9a.
The operation of the emergency,overspeed governor isy as follows.
In normal operation, dump valve 16g is closed and hydraulic fluid from conduit 12` holds the piston 16b downward against the bias of'spring 16d, so the fuel shut-olf valve 16 remains wide open. If by .some accident 'the supply of hydraulic actuating liquid should fail entirely, piston 1611 will promptly be biased upwardly by springld to close the fuel shut-off valve 16. In the eventf'of an emergencyl overspeed condition, which may lfor instanec be at about 120% of normal rated speed, the governor 9 closes the switch 9a to energize solenoid 16h, open drain valve 16g, so that release of the hydraulic fluid in chamber 16e permits piston 1Gb t0 rise under the influence of spring 16d and quickly close the fuel shut-off valve 16.
A second dump valve 12d is arranged to be normally open, and to be closed by solenoid 12e when energized by switch 12f, for reasonswhich will appear hereinafter.,
Thus it will be seen that the emergency stop valve 16 provides protection against the failure of the hydraulic liquid supply system and against emergency overspeed of the output shaft 2.
Fuel limit devices ing a piston rod 25d. The accelerating relay 26 includes the housing 26a containing piston 26h biased downwardly by spring 26e, and having piston rod 26d. Hydraulic Aoperating liquid is supplied from conduit 12 by branch conduit 12a` directly to the cylinder 25a, and by way of a valve 26e to the cylinder 26a. Valve 26e may, for instance, be opened by solenoid 26j when energized by switch 26g. v
The upper ends of piston rods 25d, 26d are pivoted to opposite ends of a floating lever 27, to the midpoint of which is pivoted a rod 27a carrying an adjustable stop member 27b. It will be seen in the drawing that rod 27a passes freely through an opening in the right-hand end portion 18d of pump control lever I18 so that the adjustable stop 27b denes an upper limiting position for thelever portion 18d.
The relays 25, 26 position the fuel limit stop member 27b in the following manner.
When the plant is shut down, solenoid dump valve 12d is de-energized and open, so the fuel shut-off valve 16 will be biased closed, and any hydraulic operating liquid in cylinders 25a, 26a will be drained through valve 12d. Both pistons 25h, 26h are therefore biased to the bottom of the cylinders 25a, 26a by the springs 25e, 26C. The result is that the adjustable stop 27b engages the pump control lever portion 18d and pulls it downwardly to the extreme lowermost position identified Off in the drawing. Solenoid valve 12d isenergized by closing switch 12f when the compressor rotor is up to a desired firing speed, which may be on the order of of rated speed. Hydraulic pressure then builds up in conduit 12. Piston b rises with increasing hydraulic pressure, and the stop 27b rises correspondingly, so as to permit pump control lever 118 to move counterclock- Wise about fulcrum 18a in the increase fuel direction. When piston 25h reaches its uppermost position, as shown in the drawings, the right-hand end portion 18d of the pump control lever will reach the position identified Fire. This corresponds to the fuel supply rate desired for initiating combustion in the combustors 2a. After combustion has begun, by energizing suitable spark-plugs (not shown), and the turbine-compressor rotor speed reaches a value on the order of 401% of rated speed, the switch 26g is closed, whereupon solevpressor rotor.
noid 26j opens valve 26e to admit operating liquid to cylinder 26a. The resulting upward movement of piston 26b causes the stop 27b to rise to a higher position, as shown in the drawing, and the right-hand end of pump control lever 18 follows stop 27b. This increases fuel delivery rate to accelerate the turbine-com- Actually, lever portion 18d transiently follows the stop 27b to the extreme uppermost (Max.) position Ashown in the drawing and then is caused to back off away from stop 27b to the position identied Accelerate in the drawing (under the action of the temperature and/ or speed governors).
lt will be apparent that additional servo devices likeV 25, 26 may be employed to provide intermediate steps in the firing and accelerating process.
Thus, the function of the tiring relay 25 and accelerating relay 26 is to establish definite, successively higher, stops limiting the fuel supply rate in different portions of the starting cycle, While having no influence on the governing system in normal running operation, In the event of failure of the operating liquid supply, or when oil pressure is dumped by the overspeed valve 16g or the dump valve 12d upon shut-down, pistons 2Sb, 2Gb will descend so as to cause stop 27b to pull pump control lever 18d down to the OE position.
Output and propeller pitch control The mechanism for selecting a desired operating condition for the powerplant, and for coordinating the changes in propeller pitch is as follows.
While the means actually used for varying the power output ofthe plant may assume many forms of known timing mechanism and program control devices, the means for selecting the operating condition of the powerplant is illustrated diagrammatically in the drawing by a manual contro-l lever- 28 connected to position simultaneously a main control cam 29 and the propeller pitch control device 7a.
As noted previously, the propeller control mechanism does not form apart of the present invention; but the device 7a may be considered to represent an electrical selsyn, connected by electrical circuit 7b to a selsyn motor in the pitch control boX 7, so that the pitch of the propeller 6 is adjusted in accordance with rotational position of the cam 29, as described more particularly hereinafter.
The function of cam 29 is to position the load selecting lever 30. The right-hand end of lever 30 is provided with a cam follower roller 30a, which is biased into contact with the cam 29 by a spring 30h. The left-hand end of lever 30 is supported by a link 30C, which is in turn supported by a load release lever 31. The left-hand end of lever 31 is pivoted to the piston rod 23d of the preemergency overspeed servo 23.' The right-hand end of lever 31 is pivoted to the piston rod of a low oil pressure release servo indicated generally at 32.
The low oil pressure release servo l32 vis a safety device comprising a cylinder 32a supplied with operating liquid by conduit 32b and containing a piston 32e biased downwardly by a spring 32d. The hydraulic liquid supply conduit 32b communicates with the discharge side of auxiliary pump 13 upstream from the check valve 13C, so that the pressure of oil supplied by the gear-driven pump 11 has no effect on the low oil pressure servo 32. In other words, the servo 32 senses only the discharge pressure of the auxiliary pump 13 which is motor-driven and supplies oil'to the ships lubrication system, including the main propeller drive gear (not shown).
It will be apparent that the low oil pressure release piston 32C is ordinarily maintained in the elevated condition shown in the drawing, by the normal discharge pressure of hydraulic supply pump 13. In the event the supply pressure` should fail for any reason, spring 32d will bias piston 32C downwardly to cause the load release lever 31 to pivot clockwise about its connection llil with piston rod 23d. The effect on the load selecting lever 3@ will be noted hereinafter.
An intermediate portion of the load selecting lever 30 carries a rod 33 having an adjustable stop member 33a. As will be seen in the drawing, the rod 33 projects freely through the upper end of the fitting 1011. In normal operation, the stop 33a is spaced away from the upper surface of fitting 1G11, but is adapted to engage the fitting and force it downwardly under certain conditions noted below.
Another portion of the load selecting lever 30 carries a rod 34, the function of which is to position the speedsetting lever 10e. To this end, the extreme lower end of rod 34 projects freely through an opening in the righthand end of lever 10e. The connection between rod 34 and lever 10e is resiliently established by a pair of bottled springs. The first spring 34a is disposed between the upper surface of lever 10e and an abutment member 34!) on the rod 34. Similarly, the other spring 34C is disposed between the lower surface of lever 10e and an abutment 34d carried on the extreme lower end of rod 34. It will be appreciated by those familiar with the art that springs 34a, 34C are under a preselected initial compression so that ordinarily the speed setting lever 10e will be positioned in accordance with movement of rod 34. The resilient bottled spring connection permits overtravel of the rod 34 in the downward direction after the speed setting lever engages the low speed stop 10g.
The contour of the load-selecting cam 29 is determined by the following considerations.
The Off position indicated at 29a is at about the middle of an extended dwell portion of cam 29, identified 29b, 29e. This portion of the cam represents a constant minimum position of the cam follower 30a. These cam dwell portions 29b, 29e represent the rotation of the control cam during which the pitch control selsyn 7a acts to cause the propeller 6 to be moved to maximum pitch. More specifically, the pitch of propeller 6 is zero at the Off position 29a. The pitch increases, through positive angles for ahead operation, through the cam dwell portion 29h; and the pitch increases, through negative angles for astern operation, through the cam dwell portion 29e. The rising portions of the cam identified 29C, 29f represent the upward motion of cam follower 30a required to raise the stop member 33u and the speed setting rod 34, the significance of which will be seen from the description of the operation hereinafter. The cam portion 29d and 29g represents a gradually rising position of cam follower 30a, for bringing the operation of the powerplant from maneuvering power condition to maximum power, adjacent the end stop portion 29h.
The manner in which the control cam 29 determines the operation of the plant will be seen in more detail from the following description of the integrated operation of the system.
Operation Stated generally, the operation of the governing system is as follows.
During the starting cycle, the compressor rotor is turned by the starting motor 14, and when the proper air ow is established through the combustion system, the fuel rate required to initiate combustion is set by the firing relaiv 25. When combustion is begun, the accelerating relay 26 establishes an increased fuel rate, adequate to render the gas turbine cycle self-supporting. The starting motor 14 may then be disconnected. During this firing and accelerating process, the control cam 29 remains at Off to hold the variable turbine nozzle 5 in maximum open condition, so as to furnish maximum energy to the compressor turbine 3 and minimum energy to the output turbine 4. The compressor turbine now cornes up to speed as controlled by governor and speed is held at a value set by low-speed stop 10g. The cam 29 may then be rotated through the initial dwell portion 29h to cause the propeller 6 to progressively increase to full pitch. After full pitch is attained, the first rising portion 29e of the control cam produces additional power by simultaneously closing the variable turbine nozzle 5 and increasing the fuel rate. The speed of compressor rotor 1b is still maintained at the minimum setting determined by the low speed stop 10g. The final rising portion 29d of the control cam increases the speed setting of the compressor rotor, by moving the speed setting lever 10e away from stop 10g; and at the same time the exhaust temperature increases to the value at which the temperature governor 17 assumes control. Thereafter, normal operation is accomplished by progressively resetting the speed governor 10 to call for changing air dow through the plant. increasing the air liow has the transient effect of reducing the exhaust temperature, whereupon the temperature governor 17 increases the fuel supply to hold the temperature level at the maximum safe value.
Thus, in normal operating condition the fuel rate is primarily under the control of the temperature governor 17, and power output is selected by changing the speed of the turbine-compressor rotor and hence the air iiow so that resulting changes in the exhaust temperature cause the temperature governor to increase the fuel supply. This arrangement keeps the plant operating at maximum thermal efficiency.
In the event of a sudden overspeed condition, the pre-emergency governor 8 senses the speed of the output shaft 4b and acts first to reduce the speed setting of the governor i0 and open nozzles 5, and then to open the compressor blow-off valve 22a to effect a very rapid reduction in energy available to the turbine. This action ordinarily keeps the speed of the output shaft below the emergency speed value. If emergency speed is reached, the overspeed governor 9 trips the emergency stop valve 16 to closed position, instantly shutting off the fuel supply. In the event the oil pressure in the ships lubrication system fails, the low oil pressure relay 32 acts directly to open the variable turbine nozzle 5 to bring to a minimum the conversion of energy in the output turbine 4 and to simultaneously move speed governor 10 to its minimum speed setting. This lastmentioned motion also moves the `fuel pump control rod 19 in the decrease fuel direction.
The manner in which the mechanism performs these functions is as follows.
First, it is to be noted that the drawing illustrates the governing mechanism in the normal operating condition for ahead operation, with the temperature governor 17 regulating the fuel supply and the speed governor 10 adjusting the turbine nozzle 5 to hold the compressor speed at the value determined by control cam 29.
In the Ofi condition, the various components are in the following positions. The cam 29 is at the Off position 29a, with the pitch of propeller 6 at zero. Cam follower 36a will be at its lowermost position, with stop 33a forcing lever end fitting 10ft to its lowermost position, so that the variable nozzle 5 is held in the maximum open condition. The iiyweight speed governor 10 will be in collapsed position with the speed control rod 10b in its uppermost position. The speed setting rod 34 will also be in lowermost position, with the bottled spring 34a compressed and the speed setting lever 16e held clockwise against the low speed stop 10g. This reduces to a minimum the compression force exerted by speed setting spring 10c on the speed control rod 10b. Since the right-hand end of the main control lever 10k is held fixed by the stop 33a, the upward spring bias on speed control rod 10b will tend to rotate lever 10k counterclockwise about its right-hand end fitting 1011. The result is that the pivot point 10m at the left-hand end of lever 10k is biased downwardly. Since no hydraulic actuating pressure is available, the bellows 17o of the temperature governor 17 will be in fully extended 13 position. This will cause the pump control rod 19 to be moved to its uppermost position, determined by the minimum fuel stop 19d engaging abutment 19e. This causes lever 18 to pivot clockwise and move the pump control rod 15d to its maximum elevated (minimum fuel rate) position. l
Without hydraulic pressure, the low oil pressure piston 32C will be biased to its lowermost position by spring 32d, while the pre-emergency governor piston 23b is in its uppermost position, as shown in the drawing. The result is that the link 30e will support the left-hand end ofload selecting lever 30 in its lowermost position, which will further tend to compress the bottled spring 3441, Also, the absence of hydraulic pressure means that the firing relay piston 25b and the accelerating relay piston 26b will be biased to their lowermost position by the springs'25c, 26C; and the emergency stop valve 16 will have its piston 1617 biased upwardly to close valve 16. The drain valve 16g will be closed, and dump valve 12d will bel open. Switch 26g will be open, so valve 26e is closed.
Since the relay pistons 25b, 2Gb are in their lowermost position, the stop member 27b will hold the end portion 18d of the pump control lever 18 at the lowermost Off position, with the left-hand end of lever 18 in its uppermost, zero Vfuel delivery position. This means that lever 18 will position control rod portion 19C upwardly so as to somewhat compress the spring 2lb of the breakaway link 21.
In order to furnish lubricating oil and hydraulic operating liquid prior to the time the supply pump 11 reaches its normal discharge pressure, the auxiliary motor 13a is energized by closing switch 13b and pump 13 provides operating liquid past the check valve 13C. Also it supplies oil through conduit 3217 to raise the low oil pressure piston 32a. Reverse flow through the pump 11 is prevented by the check valve 11a. The operating liquid supplied past the restricted orifice 12a now passes out throu-gh the open solenoid dump valve 12d, so pressure in servos 25, 16e remains essentially zero. The starting motor14 may now be energized by closing switch 14b, and the compressor rotor 1b begins to turn. This drives fuel pump 1S and hydraulic pressure pump 11. No fuel is delivered since inlet valve 16 is still closed. When the appropriate compressor speed is reached, furnishing the proper air liow for initiating combustion, switch 12f in closed, so that solenoid valve 12d closes and p ressure builds up in chamber 16e, moving piston 16b downwardly to open the fuel stop valve 16, and the pump 15 now` begins to supply fuel to the nozzles 2c. The ignition system (not shown) is simultaneously energized to ignite the fuel spray. Meanwhile, oil pressure has built up in servo cylinder A25a to elevate piston 25h. This brings stop 27b to a position where it will allow lever 18d to move to the Fire position, but not higher.
The hydraulic operating liquid has also been supplied through conduit 17h to the valve chamber 17g of the temperature governor 17, and the resulting increase in pressure in chamber 17m causes the abutment 17p and rod 17r to be moved to their uppermost position. This has the effect of compressing spring 2Gb of the breakaway link 20, abutment 20c moving upwardly, away from contact with the bottom of housing 20a. The additional downward force thus imposed by spring 2Gb on rod portion 19b is added to the downward bias at pivot 10m produced by the speed setting spring c, which causes the rod 19b to descend, carrying with it the housing 21a, so as to compress spring 21b of the breakaway link 21, overcoming the upward bias of spring 18b and rotating .pump control lever 18 counterclockwise to the Fire position determined by stop 27b. The displacement control relay c of the fuel pump 15 now calls for the rate of fuel delivery required for firing the combustion system. The accelerating relay piston 26b is still in lowermost position since the valve 26e remains closed.
Since. the gas turbine cycle is not self-supporting at tiring speed, the starting motor 14 is accelerated, todrive the compressor rotor 1b to a higher speed. After a preselected time delay, determined by experience asl that required to permit theturbine to warm up and combastion to become stable, or by an appropriate Speed-responsive relay (not shown), the accelerating relay switch 26g is closed and valve 26e opens to admit operating liquid to raise the accelerating relay piston 26h; This has the effect of elevating stop 27b still further so that pump control lever 18 is free to move upwardly to the accelerate position. Since the speed of governor 10 is not yet at the value corresponding to the minimum speed stop 10g, the speed setting spring 10c will continue to bias rod 10b upwardly so that pivot 10m moves down, to cause pump control lever 18 to rotate counterclockwise to the extent now permitted by stop 27b. Now the fuel pump increases the fuel supply rate to cause the power-plant to accelerate until the gas turbine cycledoes become self-supporting. The starting motor 14 mayno'w be disconnected, l
It will be noted that the stop 33a is still holding the abutment llln in its lowermost position, sovthe variable nozzles 5 are still wide open, with maximum power being developed in the rst stage compressor turbine 3b and minimum energy supplied to the output turbine 4a. With the increased fuel supply effected with the stop 27b in the accelerate position, the compressor rotor speed will rise so that speed governor 10 reaches a speed corresponding to the minimum speed setting of stop 10g.
The speed governor 1 0 will now control the fuel supply rate directly so as to keep compressor rotor speed constant at the minimum speed determined by stop 10g. Any increase in speed above that corresponding to the minimum speed setting will cause speed control rod 10b to move downwardly, pivoting 'lever 10h counterclockwise and moving lever10k clockwise about its right-4 hand end. This causes the pump control rod 19b to move upwardly in the decreased fuel direction. Conversely, a decrease in speed below the set value will cause speed control rod 10b to move upwardly, main control lever 10k to rotate counterclockwise about its right-hand end and move the pump control rod 19b ldownwardly in the increase fuel direction. Thus thel speed governor 10 elects primary control of the fuel rate during initial operation to maintain the speed of the compressor rotor prior to the time the exhaust temperature reaches the' preset .operating value.
The speed of the compressor rotor may now be at about 60% of its normal ratedspeed, and the plant is selfsupporting with minimum energy being delivered to the output rotor 4a. The propeller shaft 4b may be provided with a suitable brake (not shown) to hold the propeller stationary until the powerplant reaches operating conditions at which power may be supplied to the output turbine ta. When this brake is released, the propeller 6 (still at zero pitch) may begin to turn slowly, depending on whether the small amount of power developed by vturbine 4a with the nozzles 5 wide open is enoughto overcome the friction in propeller shaft bearings and reduction gear.
The vessel is now ready to move. The manual lever 28 now positions cam 29 away from the Off position through the Ahead dwell portion 295, which motion causes the propeller control selsyn 7a -to adjust the pitch control mechanism 7 to increase the pitch of propeller' 6 through positive angles of attack. As noted above, this portion of the motion of cam 29 produces no change in the position of the cam follower 30a therefore the governing system essentially tends to remain in the idling condition described above. The propeller pitch reaches its maximum condition at the end of the cam dwell portion 29h, whereupon the rising cam portion 29e moves follower 36a upwardly to cause stop 33a topermit lever end fitting 1011 to rise so that leverSf pivotsk clockwise about fulcrum 5g to move the nozzle control rod ySe.
in the downward direction and move the pivoted nozzle blades a in the decreasing area direction. As noted above, this has the effect of increasing the back pressure on the first stage turbine wheel 3b (decreasing the pressure drop across the first stage turbine) and increasing the energy made available to the second stage turbine 4a. The main control lever end fitting 10ft will tend to follow the stop 33a upwardly, since as noted previously the temperature governor 17 is in the low temperature position and the spring 2Gb of the breakaway link 2f? is compressed, biasing pump control rod por 10b downwardly. It will also be recalled that the speed governor is determining the position of the link 10j, as determined bythe speed setting lever 10e, which is still against the low speed stop 10g. In this connection it will be recalled that the spring 34a was put under a substantial initial compression so that a certain upward travel of load selecting lever 30 must occur before the spring 34a will be unloaded sufficiently that the speed setting lever 10e will be moved away from the low speed stop 10g.
Thus it will be seen that rotation of the main control lever 10k counterclockwise about the link i0j, in accordance with upward movement of stop 33a, has the joint effect of increasing the fuel rate of the pump and closing the variabile turbine nozzles 5 toward their minimum effective area position. Both of these factors tend to increase the power output of the second stage turbine 4a. Thus the propeller shaft begins to turn, with the propeller at maximum pitch, to absorb the increasing power output.
Increasing the fuel supply of course has a tendency to raise the temperature in the combustion chambers and thereby increase the energy available to the first stage turbine wheel 3b, but the increasing back pressure, caused by closing the variable turbine nozzles 5, tends to offset this increase in available energy. The speed governor 10 will of course act as described above to re-position the link 10j and change the fuel supply, so as to keep the compressor rotor speed constant at the minimum value determined by stop 10g. Stop 33a has not yet moved up and away from end fitting 10u; but has merely risen, with fitting 1011 following.
Thus it will be seen that the rise portion 29C of the cam 29 represents a range of operation in which the load selecting lever 30 acts directly to position the variable turbine nozzles 5 and to increase the fuel supply rate to provide the increased power required to turn the propeller shaft, while the speed governor 10 also acts on the main control lever 10k to maintain the compressor speed constant by adjustment of the fuel rate. Further rotation of the control cam into the gradually increasing portion 29d, brings the powerplant into its normal operating range. Progressive rise of cam follower 30a increases the fuel supply as described above, until eventually the temperature of the gases in the exhaust casing 4c reaches the desired limiting value. The temperature detector 17C now produces a fluid pressure in the bellows 17a of temperature governor 17 such that valve 17f begins to open and drain liquid from chambers 17g and 17m faster than it can enter past orifice 17z'. This permits the bellows 170 to extend under the bias of spring 17g so that rod 171' descends. Downward motion of rod 17r causes breakaway link housing a to rise and eventually the piston 20c reaches the bottom of housing 20a, so the link 20 thereafter acts as a solid connection between the pump lever control rod portions 19a, and 19b.
The design of the various springs and links in the temperature governor 17 and pump control rod 19 are such that when the temperature governor comes into action it overruns all other devices and positions the pump control rod 19, in the decrease fuel direction, as if it were a solid rod. The main control lever 10k is now positioned jointly by the control rod 19 and the speed governor 10, with the result that the right-hand end fitting i6 10x1 floats free of the stop 33a, which latter has no further effect during normal operation of the plant.
It will be apparent that the temperature governor 17 is now in primary control of the fuel pump 15, and performs its function in such a manner that the exhaust temperature seen by detector 17C remains at the maximum safe value for best thermal efficiency of the plant. The function of the speed governor fr0 is now to position the main control lever 10k, about its pivot 10m as a ful- Crum, so as to adjust the variable turbine nozzle y5 in order to keep the compressor speed constant.
Further increase in power is obtained in the following manner. Continued rise of cam follower 30a, in accordance with further rotation of cam 29 towards the maximum stop 29h, will cause the load selecting lever 30 to pivot counterclockwise about the link 30C so as to raise the speed setting rod 34. This eventually relieves the initial compression of spring 34a so that the bottled spring connection between rod 34 and speed setting lever 10e causes the lever to rotate counterclockwise about its fulcrum 10]", away from the low speed stop 10g. Further rotation of cam 29 causes a further rise of speed control rod 34 to move the speed setting lever 10e counterclockwise in the increase speed direction, the action of which is to further compress the speed-setting spring 10c, causing the governor 10 to maintain a higher compressor rotor speed.
More specifically, the action is as follows. It will be recalled that the fuel supply rate is determined by the setting of the fuel pump control relay 15e, while the air fiow to the combustion system is a function of the speed of compressor 1b. When the speed setting lever 10e moves counterclockwise to call for increased compressor speed, speed control rod 10b moves upward, lever 10h causes the main control lever 10k to move downward about pivot film, and link 5h rotates nozzle control lever 5f counterclockwise about fulcrum 5g to move the nozzle control rod Se in the opening direction. Opening of nozzle 5 transiently decreases the energy made available to the output turbine 4, but increases the energy available to the compressor turbine 3b, with the result that it speeds up. The exhaust temperature now decreases because of the increased air fiow accompanying the increased compressor speed. The temperature governor 17 then reacts to increase the fuel rate, to a value corresponding to the increased call for power output by the control cam 29.
This process repeats until the maximum limiting stop 29h on cam 29 engages the roller 30a, or until the pump control lever 18 engages the stop 27b. Thus it will be seen that stop 27b also forms the maximum fuel limit in normal operation.
Operation in the Astern direction is a described above, except that motion of the cam 29 in the range identified 29e causes the propeller to change pitch through negative angles of attack.
In the event of overspeed conditions, the action of the pre-emergency governor S and emergency overspeed governor 9 is as follows.
When the speed of the output shaft 4b rises to a value on the order of 108% of normal rated speed, the pressure signal generated by pre-emergency governor pump 8 causes the piston 23h of the pre-emergency overspeed servo 23 to begin to descend against the bias of spring 23C. Since the stop 23e is adjusted to define a clearance space with the right-hand end of lever 2.4, the first effect of downward movement of piston rod 23d is to lower the left-hand end of the load release lever 31. Since the right-hand end of lever 31 is fulcrumed on the piston rod 32e, the lever 31 rotates counterclockwise about its right-hand end to lower the link 30e. Downward motion of the link 30C causes the lever 30 to drop sufficiently to cause the stop 33a to engage the lever end fitting 10u and push it downwardly so as to cause the turbine nozzles 5 to open. This motion causes the main control lever k to pivot about the link 10j and move pivot 10m upwardly against the bias of spring h in the breakaway link 20 (irrespective of what fuel setting the temperature governor 17 may at the moment be calling for) with the result that pump control rod 15d is moved upwardly to reduce the fuel rate. This simultaneous reduction in the fuel supply rate and reduction of the energy available to the output turbine 4a, will of course tend to reduce the output shaftl speed. lf, however, propeller shaft speed continues to rise, the overspeed relay piston 23h continues to move downwardly and the adjustable stop 23e engages the righthand end of the blow-off control lever 24. Rotation of lever 24 clockwise about fulcrum 24a causes the link 24b to rise, lever 24C to pivot clockwise about fulcrum 24d to open the blow-off valve 22a. As described above, bypassing air from the compressor discharge casing 1d through the bypass conduit 22 into the exhaust hood greatly reduces the weight ilow of motive fluid through the turbine, so as to quickly reduce the energy conversion in both `the first and second stage turbine wheels. The resulting loss of power in the first stage turbine causes the compressor speed to drop, so as to reduce still further the flow of motive fluid through the system. The net result is that the energy available to the output turbine 4a is very substantially reduced.
If the blow-off valve is not capable of controlling the overspeed condition, a further rise in speed (to perhaps 120% of rated speed) will cause the emergency overspeed governor 9 to open the overspeed dump valve 16g by closing switch 9a to energize solenoid 16h. This shuts down the plant by closing the fuel stop valve 16. Opening the dump valve 16g also has the effect of draining the ring relay and accelerating relay 26, so the maximum fuel stop 27b moves down and lever 1S is returned to its Off position. Thus the fuel rate setting of pump 15 is quickly returned to its zero condition. The inertia of the compressor rotor 1b will cause cause it to continue to pump air through the plant, thus scavenging unburned fuel from the combustors and serving to blow out residual heat in the hot turbine parts, so the temperature detector 17C land temperature governor 17 return to the low temperature condition. With the output shaft 4b at rest, the pre-emergency governor 8 no longer provides a pressure signal to the servo 23, and piston 23b rises under the influence of spring 23e.
The powerplant can now be made ready to re-start by closing the accelerating relay valve 26e by opening switch 26g, opening dump valve 12d by opening switch 12j, and returning the control cam 29 to the Off position. This has the effect of lowering the stop 33a to open the variable nozzles 5, at the same time moving rod 34 downwardly to bring the speed setting lever 10e against the low speed stop 10g.
This improved governing system provides means especially adapted for regulating a gas turbine powerplant for marine propulsion having separate turbines driving the compressor rotor and the power output shaft. The control of the fuel supply by the temperature governor, for maximum thermal efficiency, is integrated in an effective ma-nner with the action of the speed governor controlling the compressor speed by varying the turbine nozzles. Special means are provided for establishing desired fuel supply rates during the starting cycle, during which the speed governor is in primary control of the fuel supply, and means are provided for rapidly reducing the power output of the plant in the event of pre-emergency and emergency overspeed condi-tions.
While only one embodiment of the invention has been described completely herein, it will be obvious to those acquainted with thermal powerplant regulators that the actual mechanism may take many alternate forms. Many conventional devices have been omitted from this description for purposes of clarity. For instance, the turbine nozzle control rod 5e may position `a hydraulic pilot `18 valve which in turn controls a servomotor which effects positioning of the nozzle ring 5d. Also, there may be an appropriate device associated with the control rod 15d of fuel pump 15 for limiting to a preselected rate the motion of the control rod in the increase fuel direction, in order to limit to a preselected value the rate of increase of temperature in the plant, as shown for instance in Patent 2,528,252, issued October 3l, 1950 and assigned to the assignee of the present invention. Such devices are well known in the art andneed not be detailed here. The mechanical details of the break-away links 20, 21, of the emergency fuel shut-off valve 16, and of the accelerating and firing relays 25, 26 may obviously take many forms. Also, the operation of the switches 12j, 13b, 14h, 26g, etc. may be effected automatically in proper sequence by a suitable master controller, the details of which are not a part of this invention. These components may, of course, be controlled manually by the operator, by the means represented diagrammatically in the drawing. Other suitable sources of thermal energy may, of course, be substituted for the fluid-fuel burning combustion system disclosed herein. Other types of compressor could be used instead of the axial` ow compressor 1; and each of the turbines 3, 4 could be replaced by multi-stage turbines.
It is, of course, intended to cover by the appended claims all such alternatives and equivalents as fall within the true spirit and .scope of the invention.
What we claim as new and desire to secure by Letters Patent in the United States is:
l. In a regulating system for a gas turbine power plant having a compressor-combustor-turbine unit and a load output turbine unit, the compressor-turbine 'rotor discharging the motive Huid through variable area nozzle means to the load output turbine rotor, said rotors being mechanically independent, the combination of first means responsive to a tempertaure condition in the powerplant which varies as a function of the motive uid temperature and connected to exercise primary control of the supply of fuel to the combustion system, and second means responsive to the speed of the compressor-turbine rotor and connected to adjust the variable turbine nozzle means.
2. A gas turbine regulating system in accordance with claim l and including third means interconnecting the speed responsive means with the temperature responsive means, and fourth means for opening wide the variable turbine nozzle means to effect minimum development of power by the load output turbine rotor, independently of the action of the speed responsive means, whereupon the speed responsive means controls the fuel supply rate when said fourth means holds the variable turbine nozzle means open.
3. In a regulating system for a gas turbine thermal powerplant having a compressor-turbine unit, a load output turbine unit, heating means for the motive fiuid, and variable area nozzle means connected in series between said units to divide the available energy of the motive fluid between the compressor-turbine rotor and the load output turbine rotor, said rotors being mechanically independent, the combination of first means controlling the addition of heat to the motive fluid by the heating means to maintain substantially constant a temperature condition in the powerplant, and second means controlling said variable nozzle means Ito maintain compressor rotor speed substantially constant.
4. In a regulating system for a gas turbine thermal i powerplant having a compressor-turbine unit, a load loutput turbine unit', and heating means for the motive fluid, the compressor-turbine rotor being mechanically independent of the load output turbine rotor, the combination of first means connected to inversely alter the power developed by the compressor-turbine rotor relative to the power output of the load output turbine rotor, second means responsive to a temperature condition of the motive fluid and connected to control the heating kmeans to alter the addition of heat to the motive fluid to maintain said temperature condition substantially constant, and third means connected to adjust said first means to hold substantially constant the speed of the turbine-compressor rotor.
5. In a regulating system for a gas turbine thermal powerplant having a compressor-turbine unit, a load out put turbine unit, heating means for the motive fluid, and variable area nozzle means connected in series between the compressor-turbine rotor and the load turbine rotor for altering the development of poner the compressor-turbine rotor, the compressor-turbine rotor being mechanically independent of the load output rotor, the combination of first means controlling the addition of heat to the motive fluid in the heating means lo infrintain substantially constant a temperature condition o c motive fluid, and second means controlling the variable nozzle means to maintain substantially constant the speed of the turbine-compressor rotor. 6. In a regulating system for a gas turbine powerplant having a compressor-heater-turbine unit and a load output turbine unit, the compressor-turbine rotor discharging the motive fluid through a variable area nozzle to the load output turbine rotor, said rotors being mechanically independent, the combination of first means regulating the addition of heat to the motive fluid in the heater unit in accordance with a temperature condition of the motive fluid, second means responsive to the speed of the turbinecompressor rotor, third means adjusting the variable turbine nozzle to alter the relative amount of power developed by the compressor-turbine rotor and the output turbine rotor respectively, a main control lever member interconnecting said first heater regulating means with said second speed responsive means and said third nozzle control means, and means connected to maintain said third nozzle control means in a preselected condition corresponding to minimum power output in the output turbine rotor, whereby said second speed responsive means is rendered effective through said main lever member to control the heater regulating means while said third means maintains the nozzle control means in said mimmum power output condition.
7. ln a regulating system for a gas turbine powerplant having a compressor-heater-turbine unit and a load output turbine unit, the load output turbine rotor being mechanically independent of the compressor-turbine rotor, and variable area nozzle means directing motive fiuid from the compressor-turbine rotor to the output turbine rotor, the combination of first means for regulating the addition of heat to the motive fluid in the heater unit in accordance with a temperature condition of the motive fluid in the powerplant, main control lever means having a first portion connected to said first regulating means, second means connected to position a second portion of said main control lever means in accordance with the speed of the compressor rotor, means connected to position a third portion of said lever means to regulate said variable nozzle means, and means for positioning said third lever portion to cause the variable nozzle to move to the position corresponding to minimum power output of the output turbine, whereupon said second means is effective to position the control lever means to regulate said first means.
8. In a regulating system for a gas turbine powerplant having a compressor-turbine unit, means for heating the motive fluid, and a second turbine unit, the compressorturbine rotor being mechanically independent of the second turbine rotor with variable area nozzle means for controlling the relative amount of power developed by the respective turbine rotors, the combination of first means for varying the rate of heat addition to the motive fluid lin the heater means in accordance with a temperature condition in the powerplant which tends to vary as a function of heat supply rate, main control lever means having a first portion connected to regulate said rst heater control means, second means connected to position a second spaced portion of said control lever means in accordance with the speed of the compressor-turbine rotor, third means positioned by a third spaced portion of said lever means to regulate the variable nozzle means, and means for positioning said third lever portion to cause the variable nozzle to effect minimum development of power in the second turbine rotor whereupon said second means positions the lever means to regulate said first heater control means.
9. in a regulating system for a thermal powerplant having variable delivery means for supplying fuel to the plant, the combination of first means automatically controlling said fuel supply means in accordance With an operating condition of the plant which tends to vary as a function of fuel supply rate, positive stop means for limiting motion of said first control means in the increasefuel direction, servo means for positioning said stop means from the off position to a rst position corresponding to a first minimum fuel rate, second servo means connected to position said stop means to a second maximum fuel limit position, and third servo means responsive to an abnormal operating condition and connected to disable both said first and second servo means and return said stop means to the off position.
l0. In a regulating system for a thermal powerplant having variable fuel supply means with first control means for varying the delivery thereof, a fuel control member connected to position said first means, second means connected to position said fuel control member automatically in accordance with an operating condition of the powerplant which tends to vary as a function of fuel supply rate, fuel rate limiting means including adjustable stop means adapted to be engaged by said fuel control member to determine the limiting position thereof in the increase-fuel direction, first servo means for positioning said adjustable stop means to a position corresponding to a first minimum fuel rate, second servo means for positioning said adjustable stop means to a second position corresponding to a second limiting fuel supply rate, emergency shut-off means for stopping the delivery of fuel, third servo means for positioning said emergency shut-off means, and means responsive to an abnormal operating condition for causing said three servo means to simultaneously position the adjustable stop means to move the fuel control member to the off position and to close the fuel shut-off means.
ll. ln a regulating system for a thermal powerplant having heat generating means and regulating means for varying the rate of heat addition to a motive fluid during normal operating conditions, a load selecting lever member, first means for adjusting the regulating means and having a movable member connected to a first portion of said lever member, means connected to a position a second spaced portion of the load selecting lever member in accordance with the power output desired, load release servo means connected to support a third spaced portion of the load selecting lever member in a normal operating position, and means responsive to an abnormal operating condition for causing the load release servo means to move said third spaced portion of the lever member in a direction to cause said first means to reduce the heat generation rate.
l2. In a regulating system for a gas turbine powerplant having a compressor-combustion-turbine unit and a load output turbine unit, the load output turbine rotor being mechanically independent of the compressor-turbine rotor, variable area nozzle means dividing the available energy of the motive fiuid between the compressor-turbine rotor and the load output turbine rotor, and variable delivery means for supplying fuel to the combustion unit, the combination of first means connected to control the delivery rate of the fuel supply means in accordance with a temperature condition in the powerplant, second means responsive to the speed of the compressor rotor, third means connected to position the variable nozzle means, main control lever means having a rst portion connected to said rst fuel control means, a speed-setting member connected to alter the speed setting of said second speed responsive means to determine the speed of the compressor rotor, a load selecting member, fourth means for positionl ing said load selecting member to determine the power output of the plant, fth means connecting the load selecting member to the speed-setting member to determine the speed of the compressor rotor, and sixth abutment means connected to be positioned by the load selecting member and adapted to engage a second portion of the main control lever means, whereby, when the load selecting member is moved to its minimum power position, the fth connecting means moves the speed-setting member to its minimum speed position and the sixth abutment means engages the main control lever means to move said third variable nozzle control means to a position corresponding to minimum power of the output turbine, whereby the second speed-responsive means positions the main control lever means to determine the fuel supply rate when the load selecting lever member is in minimum power position.
13. In a regulating system for a gas turbine powerplant having a compressor-combustion-turbine unit and a load output turbine unit, the load output turbine rotor being mechanically independent of the compressor-turbine rotor, variable area nozzle means dividing the available energy of the motive fluid between the compressorturbine rotor and the load output turbine rotor, and variable delivery means for supplying fuel to the combustion unit, the combination of first means connected to control the delivery rate of the fuel supply means, second means responsive to the speed of the compressor rotor, third means connected to position the variable nozzle means, main control lever means having a rst portion connected to said lirst fuel control means, a speedsetting member connected to alter the speed setting of said second means to determine the speed of the compressor rotor, low speed stop means determining the minimum speed position of said speed-setting member, a load selecting member, fourth means for positioning said load selecting member to determine the power output of the plant, fth means connecting the load selecting member to the speed-setting member and including lost motion means to eiect overtravel of said fth means after the speed-setting member engages the low speed stop, sixth abutment means connected to be positioned by the load selecting member and adapted to engage a second portion of the main control lever means, whereby, when the load selecting member is moved to its minimum power position, said fth connecting means moves the speed-setting member to the minimum speed condition determined by the low speed stop means while the lost motion connection of said fth means effects overtravel, and said sixth abutment means engages the main control lever means to move the third variable nozzle control means to a position corresponding to minimum power of the output turbine rotor, said fourth means being connected to position the load selecting member in a iirst range of positions in which said sixth abutment means positions the third variable nozzle control means to vary the energy made available to the output turbine rotor, and in a second range of positions in which said sixth means disengages from the main control lever means and the fifth connecting means positions the speedsetting member away from the low speed stop means to alter the speed setting of the second speed responsive means.
14. In a regulating system for a gas turbine powerplant having a compressor-turbine unit, means for heating the motive fluid, and a second turbine unit, the compressorturbine rotor being mechanically independent of the second turbine rotor, and variable area nozzle means for controlling the relative amount of power developed by the respective turbine rotors, the combination of iirst means for varying the rate of addition of heat to the motive fluid in the heater means in accordance with a temperature condition in the powerplant which tends t0 vary as a function of heat supply rate, main control lever means having a iirst portion connected to regulate said irst heater control means, second means connected to position a second spacedV portion of said control lever means in accordance with the speed of the compressorturbine rotor, and third means positioned by a third spaced portion of said lever means to regulate the variable turbine nozzle means.
References Cited in the le of this patent UNITED STATES PATENTS 2,603,063 Ray July l5, 1952 2,625,789 Starkey Jan. 20, 1953 2,654,217 Rettaliata Oct. 6, 1953 FOREIGN PATENTS 960,332 France Oct. 24, 1949 256,079 Switzerland Feb. 1, 1949