Patent GB-776345-A (GB)
Title: Improvements in or relating to engine control arrangements
Inventor: HAWORTH LIONEL
IPC: F02C9/28
Filed: 1953-11-17
Abstract: 776,345. Gas turbine plant. ROLLS-ROYCE, Ltd. Oct. 28, 1954 [Nov. 17, 1953], No. 31917/53. Class 110 (3). [Also in Group XXIX] In a fuel control system for gas turbines in which the fuel supply to the engine is cut down when the temperature at a selected point in the engine exceeds a selected valve, the fuel control element is actuated by a pressure responsive means the fluid pressure acting on which is a proportion of the pressure of a source of pressure fluid the pressure of which is maintained in predetermined relation to engine intake or atmospheric pressure, the proportion being varied by valve means responsive to the temperature at the selected point. In Fig. 2, the fuel control element comprises a servo bleed valve 27 controlling a spring-loaded servopiston 23 which adjusts the inclination of the swashplate 22 of a multi-cylinder fuel pump 14 supplying fuel from a tank 16 through a throttle 18 and a shut-off cock 19 to the fuel burners of the gas turbine engine. The bleed valve 27 is carried by a lever 28 subject to three loads, namely that of a spring 29, that of a piston 31 subject to the pressure drop across the throttle 18, and that of a pair of opposed resilient capsules 34, 35 acting through a peg 37. The capsule 34 is evacuated and the interior of the capsule 35 is connected by a pipe 50 to a valve chamber 51, Fig. 3, having aligned ports 52, 53 controlled by a shuttle valve 54 urged by the high pressure in a further chamber 56 against a tappet 58. The tappet 58 is loaded by a spring 59 arranged between abutments 60, 61 one 61 of which is adjustable through a lever 62 by a manually adjustable cam 63. The spring load on the tappet is opposed by a Bourdon tube 64 connected through piping 65 to one or more bulbs 38 arranged at selected points in the engine. The tappet 58 is carried by coaxial diaphragms 66, 67 the space between which is filled with liquid and functions as a dash-pot chamber. The valve 54 varies the proportion of the pressure in the chamber 56 acting within the capsule 35. The port 52 opens into a chamber 55 at engine air intake or ambient atmospheric pressure. The pressure in the chamber 56 is derived from a source of higher pressure connected to a pipe 82 and is regulated by a pressure-reducing valve 80 carried by a stirrup 78 connected to two coaxial diaphragms 71, 72 loaded by a spring 79 and by engine air intake or ambient atmospheric pressure acting in an end chamber 73. The space 74 between the diaphragm is connected to the other end chamber 75 and acts as a dash-pot chamber. The controlled pressure in the chamber 75 which is connected to the chamber 56 by a passage 57 is thus a predetermined amount above the air intake or ambient pressure. It may be arranged that when the valve 54 restricts the ports 52, 53 equally the spring 29 balances this predetermined excess of pressure. In another arrangement, a further valve such as 80 maintains the pressure in the chamber 55 a predetermined amount above air intake or atmospheric pressure. The shuttle valve 54 may be replaced by a bleed-off valve. The reducing valve 80 in the casing 70 may be replaced by a chamber fitted with a spring-loaded relief valve and through which there is always a flow of fluid from a chamber connected to the source of higher pressure and to the chamber 56. The temperature-sensitive element may be located between the stages of a two-stage turbine, at the outlet of the combustion chamber, or at the turbine outlet. As shown, the thermal bulbs 38 are housed within the leading edges of the low-pressure nozzle-guide vanes 12d.