Patent GB-696555-A (GB)
Title: Improvements in and relating to gas turbine plant
Inventor: MILLINGEN REVEL DUNCAN VAD
IPC: F02C9/28
Filed: 1950-11-17
Abstract: 696,555. Gas turbine plant; axial-flow compressors. ENGLISH ELECTRIC CO., Ltd. Nov. 19, 1951 [Nov. 17, 1950], No. 28118/50. Classes 110(i) and 110(iii) [Also in Group XXIX] In a gas turbine plant comprising a useful output turbine and a compressor-driving turbine, a slow-acting control means is responsive to small deviations of the speed of the useful output turbine from its set value, and a quick-acting control means is responsive to large deviations. Air from a compressor 1 is supplied by way of a heat exchanger 12 to the combustion chamber 14 of a turbine 2, and by way of a venturi 19 and heat exchanger 22 to the combustion chamber 24 of the useful output turbine 3. The speed of turbine 3 is regulated by a governor 5, the setting of which is adjustable by means of a hand lever 7 which adjusts the force of a spring 6. The governor 5 controls the valve 73 of a servomotor 72 which actuates-a spill control valve 62, whereby the rate of fuel supply to the combustion chamber 14 is varied. This means of control is comparatively slow. A much more rapid adjustment occurs when the speed of turbine 3 exceeds the set speed by, say, 2 per cent. A valve 75 is then opened, causing the pressure in a line 77 to drop sufficiently below that in a pressure fluid supply pipe 71 to allow a spring-loaded piston 50 to move against the pressure and move a throttle 20 from the fully open position shown. The throttle fully closes at, say, 7 per cent above the set speed. The fluid displaced from the cylinder 51 by the movement of piston 50 is prevented by a non-return valve 52 from returning through pipe 77 and instead passes through a pipe 53 and after opening a valve 54 by pushing it to the left, passes through a pipe 55 into the right hand side of a cylinder 41. The resultant displacement of piston 40 opens blow-off valves 34 and 36, and the fluid displaced from the left hand side of the cylinder 41 is drained off through pipes 56 and 57. To avoid the possibility of surging of the compressor 1, valves 34 open more than is necessary to compensate for the reduction of flow through the throttle 20, and are then re-adjusted by the comparatively slow action of a blow-off regulator 80. which is sensitive, through a pitot head 81 and a static head 82, to variations of the relation between the pressure and the rate of flow in the venturi 19. In the case of an underspeed condition, the throttle 20 remains open, and the blow-off valves are subjected only to the slow action of the regulator 80. To avoid overheating of the turbine 3 and the heat exchanger 22 under low load conditions, blow-off valve 36 is connected to the downstream end of the heat exchanger so as to reduce the efficiency of the latter when the valve is open. A by-pass valve 30 across the throttle 20 maintains a minimum pressure of 2 lb. per sq. inch on the downstream side of the throttle when the latter is fully-closed, so that sufficient air flows through the combustion chamber 24 to keep it alight. The fuel supply to the combustion chamber 24 is controlled by a spill valve 63 actuated as by a capsule 65 sensitive to the inlet pressure of the turbine 3. The servomotor 72 can be put out of action by a hand-operated valve 74, the fuel supply to the turbine 2 then being controlled by manual operation of a lever 9. Specification 696,566 is referred to.