Patent GB-750408-A (GB)
Title: Improvements in or relating to prime movers and control arrangements therefor
Inventor: HERBSTRITT KARL
IPC: F02C9/28
Filed: 1952-11-26
Abstract: 750,408. Gas turbine plant. ROLLS-ROYCE, Ltd. Nov. 5, 1953 [Nov. 26, 1952], No. 30002/52. Class 110(3) [Also in Group XXIX] A gas turbine plant in which an additional fluid is injected under pressure into the combustion chamber or compressor or directly into the turbine for cooling the working fluid has governor means to control a rotational speed condition of the turbine and means responsive to the cooling fluid pressure to adjust the governor means to increase the rotational speed condition during injection of the cooling fluid. The term "governor means" is stated to include not only governors directly responsive to a rotational speed and governors responsive to a pressure drop in the fuel system representative of rotational speed but also apparatus sensitive to an engine operating variable; e.g. atmospheric pressure which acts to maintain a rotational speed at a given setting irrespective of variations in the operating variable. Fuel is supplied 'to the injectors 15, Fig. 4, by a multi-plunger pump through a throttle valve 17. The pump is of the type described in Specification 577,016 in which the stroke of the plungers 19 is determined by a swashplate 21 the angle of inclination of which is controlled by a piston and and cylinder device 32. The position of the piston 34 in the cylinder is controlled by the amount of leak-off from the spring-loaded side of the piston. This leak-off is controlled in accordance with the instantaneous atmospheric pressure and engine speed. The atmospheric pressure control 31 comprises an evacuated capsule 43a and a tappet member 39 which act on a pivoted lever 40 to control the flow through the orifice 41. The tappet 39 has a piston-like head which is loaded by the pressure drop across the throttle 17. Thus for any setting of the throttle 17, the rate of fuel supply is maintained at a selected value which is varied in accordance with the pressure in the chamber 43. The speed control comprises a bleed duct 45 the flow from which is controlled by a valve 46 carried by a lever 48 which is normally held in the closed position by a spring 48a. A spring-loaded flexible diaphragm 47 loaded by a pressure proportional to engine speed has a nib which also engages the lever 48. The pressure is generated in radial bores 51 formed in the pump rotor 18. When the engine speed reaches a predetermined value the diaphragm 47 rocks the lever 48 to open the valve 46 and the piston 34 then reduces the stroke of the plunger 19. Water from a tank 60 is supplied by an air-driven turbine pump 61 to a manifold 65 located in the combustion equipment 11. A relief valve 67 maintains the delivery pressure of the water constant. The air-driven turbine pump is supplied with air from the discharge of the compressor 10 through a conduit 68 having a shut off cock 69. The cock 69 is operated by a solenoid energized through relay contacts 75a. The coil 75 of the relay is energized through a switch 70 closed when the throttle lever 71 is moved to the full throttle position, a manually operated switch 72, a speed override switch 73, and a time controlled switch 74. The switch 73 is connected to a diaphragm 76 subject to the compressor delivery pressure. When the cock 69 is opened, the pressure of the water supplied to the manifold 65 acting through a pipeline 83 on a piston 80 increases the tension on the spring 50 and so increases the rotational speed at which the overspeed governor operates. Abutments 85, 86 limit the travel of the piston. At the same time the flow controlled by the control 31 is increased by the valve 91. The valve 91 comprises a casing divided into two .chambers 92, 93 by a spring-loaded flexible diaphragm 94 carrying a valve element 95. When the coolant supply is shut off, the spring 94a lifts the valve 95 off the outlet 96 and the chamber 43 is then open to atmosphere. When coolant is supplied to the engine, the pressure of the coolant closes the valve 95 on to the outlet. The pressure in the chamber 92, which is connected to the compressor discharge through conduits 68, 98 and orifice 97 will then increase. This increased pressure acting through conduit 90 will then increase the pressure in chamber 43 and so increase the controlled fuel supply. In this arrangement the pressure in the chamber 92 will be determined by the water pressure, the load of the spring 94a and the diaphragm area. In a modification the chamber 92 is vented to atmosphere through a restricted orifice. In this arrangement, the pressure in chamber 92 is determined as a proportion of the compressor delivery pressure by the relative size of this orifice and the orifice 97. In a modification of the arrangement shown in Fig. 4, the speed at which the overspeed mechanism operates is varied by varying the pressure in the chamber 53. The chamber 53 is provided with a port leading to a restricted orifice controlled by a valve. The valve is controlled by a spring-loaded piston which is moved against the action of the spring by the pressure of the coolant to open the valve and so reduce the pressure in the chamber 53 for a given speed. A higher speed will then be necessary to open the bleed valve 46. In another modification the tension spring 50 is replaced by a compression spring the loading of which is varied in accordance with the setting of the pilots engine control lever. The valve of the speed setting is increased when coolant injected by reducing the pressure in the chamber 53. In a further modification, the valve 46 may be used to control the pressure drop across the valve 17 and thus indirectly control the delivery of fuel to the engine. Two or more engines may be controlled and supplied with coolant from a common supply line. In this case the air for the air-driven turbine pump may be taken' jointly from the two compressors and the engines controlled by a common adjusting means for the speed governor and, when necessary, for the atmospheric pressure control. Two switches 70 arranged in series for each throttle lever 71 will be necessary to control the operation of the cock 69. In a modification of this arrangement, the control of the coolant supply to each engine from a common supply and the adjustment of the governor is made individual to each engine.