Patent GB-783531-A (GB)
Title: Improvements in or relating to gas turbine engines
Inventor: JOHNSON CHRISTOPHER LINLEY
IPC: F02C9/16
Filed: 1954-07-19
Abstract: 783,531. Gas-turbine plant. ROLLS-ROYCE, Ltd. July 19, 1955 [July 19, 1954], No. 21046/54. Class 110(3). [Also in Group XXIX] In a gas-turbine engine comprising means, such as the liquid pressure in a cylinder 22, Fig. 1, responsive to a torque developed by the engine and arranged on attainment of a given value of torque to open a bleed valve, for example, closure 36, in the engine fuel system to reduce the supply of fuel to the combustion equipment whereby the given value of torque is not exceeded. The gas turbine 12 drives the compressor rotor 10a and a variable-pitch propeller 13, the latter being driven via planetary reduction-gearing the torque reaction of which is transmitted to the ring gear 19 and opposed by means of a piston, connected to the gear 19, which is slidable in the fixed cylinder 22. Oil is continuously fed to the cylinder 22 from a pump 25 and as the torque increases a drain port is closed somewhat by the piston and the pressure rises in the cylinder 22 until the torque is balanced. Fuel from a tank 31 is supplied by way of a booster pump 30, pipe 29, pump 28, control 33, pipe 32 and manifold 34 to the burners 27. The propeller speed-selecting mechanism, not shown, may be interconnected with the fuel control 33 and in order to deal with the development of a torque in excess of that for which the engine is designed a by-pass pipe 35 interconnects pipes 29 and 32; in the pipe 35 is the bleed valve which is opened when the pressure in the cylinder 22 rises to a given value. The valve casing 37 is divided into two chambers 38 and 39 by a diaphragm 40, the chamber 38 being connected to the cylinder 22 by a pipe 41 whilst chamber 39 is connected either to atmosphere or, as shown, to pipe 29, the latter chamber also housing a spring 42 which loads the diaphragm in opposition to the pressure in chamber 38. The closure member 36 is attached to the diaphragm 40 and comprises two discs 43, the opposite sides of which are subjected to the pressure in a chamber 45 connected to the upstream part of pipe 35 whilst the space between the discs 43 is exposed to the pressure in a chamber 46 open to the downstream part of pipe 35. If the engine torque exceeds a preselected value the pressure acting on the diaphragm 40 overcomes the spring 42 and opens the member 36 so that fuel flows from pipe 32 into pipe 29. In a modification, the fuel is supplied by a swash-plate pump 28, Fig. 3, the angle of the swash-plate 53 and hence the stroke of the plungers 51 being controlled - by a piston 54 one side of which is open directly to the delivery pipe 32 via a port 56 whilst the other side is both connected to the latter through a restriction 59, and to two pipes 61, each controlled by a half-ball vent valve 62, only one pipe and valve being shown.' The valve 62 is carried by a lever 63 loaded by a spring 65 to close the valve and by pressure on a piston 66 to open the valve. Should the engine torque exceed a predetermined value the pressure from the cylinder 22, Fig. 1, acts on the piston 66 to open the bleed valve 62 and interconnects the by-pass pipes 61; 69 so reducing the pressure to the right of piston 54 and decreasing the delivery of the pump 28.