Patent GB-730571-A (GB)
Title: Improvements in and relating to combustion apparatus and especially to such systems as are applicable to control of combustion in gas turbine plant, industrial furnaces and the like
Inventor: GRAY THOMAS
IPC: F02C7/264
Filed: 1952-03-25
Abstract: 730,571. Gas turbine plant. PARSONS & CO., Ltd., C. A. March 25 1952, No. 7664/52. Class 110 (3). [Also in Groups XI, XIII and XXIX] Combustion control apparatus applicable to gas turbines, industrial furnaces, &c, comprises a hydraulically governed timing device for admitting fuel and air to a torch igniter and an electric current to a sparking plug therefor, a servo device associated with the torch igniter and operable to close a valve in the fuel supply to,a main burner or burners in 'the event of failure to ignite, a temperature indicator controlling a fuel throttle valve to restrict flow of fuel to the burner or burners in the event of excessive combustion chamber outlet temperature occurring or in the event of excessive rate of increase of such temperature, and controlling also means for, cutting off the fuel supply when the temperature rise across the combustion chamber falls below a preset level, thereby affording protection against flame extinction. The apparatus may also have means for indicating and correcting differing combustion chamber outlet temperatures in cases where more than one combustion chamber is employed. The apparatus described is applied to a combustion system having two combustion chambers 1, 2, .Fig. 1, fitted with main fuel sprayers 3, 4 and'with torch igniters 11, 12. The sprayers 3, 4 are fed by a fuel pump 6 discharging through hand control, speed control and other fuel valves denoted by 7, a temperature-limiting fuel throttle 8, a fuel shut-off valve 9, and a flow-dividing device 10. Fuel is fed to the nozzles 55, Fig. 4, of the torch igniters through a conduit 13, timing device 14, and conduits 15, 16 whilst high pressure air is supplied by a pump 18 and passed through the timing device and conduits 20, 21, 22 to the torch igniters. The timing device consists of a spring-loaded piston 40, Fig. 2, connected to a plunger 39 which has reduced parts 43, 46 for permitting the passage of air and fuel when the spring 41 is compressed by operation of a handle 37 which incorporates an electric switch 42 for the sparking plugs 62. The piston 40 has an orificed, not-return valve 50 to allow free flow of oil from one side of the piston to the other when the lever 37 is operated but providing for return of the piston at a preset rate. In a modified timing device the cylinder in which the piston 40 is housed has inlet and outlet non- return valves whereby fuel is drawn in when the handle is operated and discharged to the torch igniters when the handle is released, the reduced part 46 being omitted. A connection from the combustion chamber inlet to the side of the piston 40 which is subject to the spring loading maintains the fuel pressure at a constant differential above combustion chamber air pressure. When the torch igniters are functioning their nozzles 58 expand and cause pistons 64 to uncover ports 67 to permit the passage of oil from a pump 30, through the ports 67 in series and thence through a restriction 35 to a drain tank 36. A piston actuating the cut-off valve 9 is subject to the pressure before the restriction 35 so that the valve 9 is opened to supply the main burners when both torch igniters are ignited. Temperature indicators 32, 33 in the outlets from the combustion chambers each comprises outer and inner tubes 68, 69, Fig. 5, of material resistant to high temperature and of high coefficient of thermal expansion, and an intermediate tube 70 having a relatively low coefficient of expansion and low thermal conductivity. The tubes are connected together at their ends 71. Consequently, pistons 77, 81, interconnected by an adjustable rod 79, are operated by a lever 82 connected to the intermediate tube 70 in response to variations of combustion chamber outlet temperature, and, due to the low thermal conductivity of the tube 70, the pistons 81, 77 are also operated according to the rate of change of temperature. Oil inlets 88 to the pistons 81 are connected in parallel with each other and the outlets 89 in series with a restriction 34 leading to the drain tank. An actuating piston of the fuel throttle 8 is subject to the pressure before the restriction 34 so that the throttle 8 reduces the fuel flow when, at a predetermined combustion chamber outlet temperature, either of the pistons 81 uncovers its outlet port 89. The ports controlled by the pistons 77 are connected in series with each other so that when the two combustion chambers are at equal temperatures a piston 94 operating an indicator 93 is in balance but divergence of the temperatures causes movement of the piston. The piston may be coupled to the valve 10 to restore equal temperatures. The inner tube 69 of the temperature indicators has a pipe connection 72 with a point upstream of the corresponding combustion chamber so that a piston 83, which is connected by a lever 85 with the inner tube 69, moves in response to the temperature rise across the combustion chamber. The ports controlled by the pistons 83 are connected in series with each other and with the restriction 35 so that in the event of extinction of the flame in either combustion chamber, pressure on the piston of the cut-off valve 9 is relieved to interrupt the flow of fuel to the main burners.