GB707272A - Improvements in and relating to regulating systems for the supply of fluid fuel to gas turbines - Google Patents

Abstract

707,272. Gas-turbine plant. BRITISH THOMSON-HOUSTON, CO., Ltd. June 10, 1952 [June 15, I951], No. 14587/52. Class 110(3) [Also in Group XXIX] A fuel supply system for a gas turbine burning e.g. fuel gas, and having a fuel metering valve operated in accordance with load demand has the metering inlet pressure controlled by a valve 23, 21 placed between a fuel source and the metering valve and operated by a servomotor responsive to the metering valve inlet pressure P2 and the pressure Pc in the combustion space, or at the outlet of the compressor supplying the combustion space, so as to maintain a predetermined pressure ratio between the pressures P2 and Pc. The metering valve is operated by a hydraulic-mechanical servo mechanism responsive to, e.g. rotor speed, motive fluid temperature, ambient atmospheric temperature and pressure, air speed, and the position of an automatically or manually set control member, of the kind disclosed in Specifications 638,494 and 700,092, [Group XXXV]. The piston 36 of the servomotor is controlled by a pilot valve 51 movable in response to the pressure P2 acting on a bellows 85 and adjustable ratio lever 90, and the pressure Pc acting on an opposed bellows 73, With the plant starting from shutdown the bellows springs 79, 84 and abutments 81, 89 are so adjusted that the pilot valve allows pressure oil from conduit 61 to flow via port 59, land 53 port 65 and passages 46, 49, 50 to the lower side of the piston which is raised against its spring 44 to open first the auxiliary valve 23 and then the main valve 21. As the piston moves upward oil above the piston is forced via passage 45, port 66. land 54, port 62 to a drain chamber 64 above a follow-up piston 104 and from which the oil escapes via an adjustable orifice 64a. The piston 104 acting through the lever 90 together with the increased valve outlet pressure P2, tends to recentre the pilot valve with a force proportional to the velocity of the piston 36. A drain chamber 58 with orifice 58b allows the exhaust oil from below the piston 36 to act on the lower side of the follow-up piston. Because the pressure P2 must always be greater than Pc, the abutment 89 on the lever 90 is nearer the fulcrum 91 than the abutment 92 of the pilot valve on the lever. To vary the ratio of Pc to P2, the position of the fulcrum and therefore the ratio of the lever arms may be altered by rotating an eccentric 98 bearing on a slide 95 carrying the fulcrum. The position of the piston of valve 23, 21 is shown by a sight indicator 40. A passage 71 from the oil inlet 61 leads to a recess 72 to prevent gas leaking along the valve spindle 24 into the cylinder 29, while a scraper 33 cleans the spindle of dirt.