GB900744A - Gas turbine power units - Google Patents

Abstract

900,744. Fluid-pressure servomotor-control systems. NAPIER & SON Ltd., D. March 4, 1960 [March 9, 1959; Aug. 26, 1959], Nos. 8086/59 and 29244/59. Class 135. [Also in Group XXVI] A gas turbine power unit having a free power turbine and equipped with a fuel metering unit which is actuated in response to pressure and temperature at the compressor air inlet, is provided with a governor which is coupled to the free power turbine and compares the actual speed of this turbine with a datum and further modifies the fuel supply to maintain the datum speed which is set by a manual speed selector. The gas turbine engine 10 has a free power turbine 22 driving a helicopter rotor 11. Fuel is supplied to the burners 19 through a metering unit 17 which is responsive to ambient air pressure and temperature at the compressor inlet through sensing devices 95, 96, respectively, the metering unit being fed by a variable-stroke pump 16. Geared to the turbine output shaft 26 is a hydro-mechanical speed signal generator 28, e.g. as disclosed in Specification 832,195, which produces a differential hydraulic pressure between two pipes 29, 30 connected to a comparator unit 31 in which the datum is set by a manual speed selector lever 34 through a lever 32. A control pressure set up by the comparator through a pipe 35 acts on a servoadjuster 47 to adjust the stroke of the pump 16. The selector lever 34 is also connected to the metering unit 17. Pipes 29, 30 lead to opposite sides of a diaphragm 36, Fig. 2, in the comparator 31, this diaphragm actuating through a lever 42 a half ball leak-off valve 45 controlling the pipe 35, in opposition to a datum loading spring 40. The compression of this spring is set through a movable abutment 50 carried by a double-acting servo piston 51 which is arranged to follow up the movement of a control-valve 54 connected through lever 32 to the manual setting lever 34. Operating pressure to this servo piston is supplied through a pipe 59 and exhausted along with the leak-off from valve 45 through a pipe 48. In a modification, an indication of the governor authority is obtained electrically through a variable induction device, Fig. 4, having'a movable armature 66 actuated by a pressure-balanced plunger 64 which contacts the half ball valve lever 42 to indicate, e.g. on a dial, the effective movement of this lever. Several forms of the inductive device are described.