GB848560A - Gas turbine fuel system - Google Patents

Abstract

848,560. Gas turbine plant. GARRETT CORPORATION. April 23, 1957 [April 26, 1956], No. 12886/57]. Class 110 (3). The fuel supply system for a substantially constant speed gas turbine plant having a compressor, a combustion chamber and a turbine comprises a fuel pump, speed responsive means acting on a by-pass for governing the speed of the turbine and a second by-pass conduit around the pump including a by-pass valve controlled by means responsive to a pressure differential in the fuel line between the fuel pump and the combustion chamber and to means responsive to compressor pressure. The invention is described with reference to a gas turbine plant comprising a centrifugal compressor discharging into a chamber surrounding the compressor containing a combustion chamber the combustion products from which pass through an inward radial flow turbine mounted on the compressor shaft. Fuel is supplied to the burners by a positive displacement pump around which are arranged two by-pass pipes. One of these pipes is controlled by a valve opened by flyweights where the speed of the turbine shaft exceeds a predetermined maximum value. The second by-pass pipe is controlled by a valve 19, Fig. 2, which is responsive to the rate of fuel flow to the combustion chamber, the compressor discharge pressure and the turbine exhaust temperature. Fuel from the pump passes through pipe 20, the adjustable orifice 49, chamber 46 and the pipe 21 to the engine. The pressure at the upstream side of the orifice 49 is communicated to the chamber 47 by the conduit 50. The pressure drop across the orifice acts on the diaphragm 44 which is urged thereby and the loading on the spring 45 to the left so that the push rod 43 engages the valve element 39. The valve element 39 controls the flow through the by-pass pipes 20, 23 and is mounted in a freed bushing 41. A head 40 of the element 39 engages the bushing 41. The valve element 39 is urged to the right by the pressure difference across a diaphragm 54. The chamber 53 is connected to the compressor discharge and the chamber 60 to atmosphere. The chamber 53 is partially defined by another diaphragm 51 which has a larger area than the diaphragm 54. The chamber 52 of the other side of diaphragm 51 is also connected to compressor discharge pressure through a restricted passage 57. Normally the pressures on each side of the diaphragm 51 are equal and the diaphragm is ineffective. The chamber 52 is connected by a passage 52a with a vent valve which is opened when the turbine exhaust temperature exceeds a predetermined value. This causes the pressure in the chamber 52 to drop and the diaphragm 51 will move the bolt 56 away from the valve 39. The pressure drop across the diaphragm 44 will then cause the valve 39 to move into an open position and so bypass more fuel and thus reduce the temperature. An adjustable spring 58 acting on the diaphragm 51 maintains the valve 39 closed during starting.