Patent GB-777960-A (GB)
Title: Improvements in or relating to gas-turbine engine fuel systems
Inventor: COLLEY ROWAN HERBERT
IPC: F02C7/22
Filed: 1954-06-28
Abstract: 777,960. Gas turbine plant; centrifugal pumps. ROLLS-ROYCE, Ltd. May 24, 1955 [June 28, 1954], No. 18939/54. Addition to 684,244. Classes 110 (1) and 110 (3). [Also in Groups XI and XXIX] A reheat fuel system as claimed in the parent Specification which comprises a plurality of main burners and a pilot burner to which fuel is supplied continuously while fuel is supplied to the main burners and in which means are provided to supply fuel to the pilot burner so as to maintain substantially constant the fuel to air ratio at the pilot burner has means responsive to the fuel flows to the pilot and main burners and adapted to maintain these flows in a predetermined relationship. Fuel is supplied to the reheat combustion equipment in the jet pipe 15 by two sets of injectors, namely, primary injectors 23 and secondary injectors 24. Fuel from the tank 27 is supplied by a booster pump 28 and an air turbine driven centrifugal pump 30 to a delivery line 31 leading to a control unit 32, which is as described in Specification 776,672, which is connected in turn to the injectors 23, 24 by pipe-lines 25, 26. The air turbine 34 is supplied with air from the discharge of the gas turbine compressor 10 and the rate of air flow is controlled by the servomotoroperated throttle valve 36. The valve 36 is connected to a piston 37 working in a cylinder 38. Fuel from the discharge of the main pump 20 is supplied direct to one side 38a of the piston and through an orifice 41 to the other side 38b which also has a vent pipe 42, the outlet of which is controlled by the unit 32. The rate of fuel flow to secondary injectors 24 is controlled by valve mechanism 133 and that to the primary injectors 23 by the unit 32, part of which consists of a valve element 50 which co-operates with an orifice 49 so that the pressure drop across the orifice is directly proportional to the fuel flow through it. This pressure drop is applied to a diaphragm contained in the unit 32 by ducts 52, 53. The mechanism 133 controls the fuel supply to the secondary injectors 24 so that it is a predetermined proportion of the fuel supply to the primary injectors 23. A conduit 86 containing a fixed area flow restrictor 87 and a variable area flow restrictor 88 is connected to the pipeline 25 upstream and downstream of the orifice 49 so that the pressure drop across the fixed area flow restrictor 87 is a proportion of the pressure drop across the orifice 49, the proportion depending upon the selected effective area of the restrictor 88. The flow to the secondary injectors 24 is passed through a linear flow valve 91, 92 similar to the valve 49, 50 and a control valve 94. The control valve 94 is connected by a stem 95 to a pair of diaphragms 96, 98. The pressure drop across the linear flow valve 91, 92 is applied to the diaphragm 98 in the sense of closing of the valve 94 and the pressure drop across the linear flow valve 49, 50 is applied to the diaphragm 96 in the sense of opening the valve 94. Since the diaphragms 96, 98 are equal in area, the valve 94 will take up a position in which the pressure drop across the orifice 92 is equal to that across the restrictor 87 so that the fuel flow to the secondary injectors 24 will be in a constant proportion to the fuel flow to the primary injectors 23. The valve member 50 may be used as a shut-off cock for the injectors 23 as described in Specification 776,672. The control valve 94 may be used as a shut-off cock for the injectors 24. The valve stem 95 is provided with a bore 105 containing a restrictor 106 which leads from a chamber 103 to a chamber 104. The chamber 104 has a vent pipe 107 controlled by a valve 108. When the valve 108 is opened, the pressure in the chamber 104 falls and the valve 94 closed. The valve 108 may be connected to the valve 84 controlling the closing of valve member 50 and a valve 110 in the conduit 86 so that when valve 110 is open, valves 84 and 108 are shut, and vice versa. Cooling fuel may be passed through the valve mechanism 133 when the reheat system is shut off by way of orifice 92, chamber 103, bore 105, chamber 104, vent pipe 107 and pipe 82. Specification 667,394 also is referred to.