Control systems for variable speed gas turbine power units

811,563. Gas turbine plant. NAPIER & SON Ltd., D. May 3, 1957 [May 14, 1956], No. 15013/56. Class 110 (3). [Also in Group XXIX] A control system for a variable-speed gas turbine power plant has a device for sensing the turbine inlet temperature and operable to adjust the fuel supply in response to any difference between the sensed temperature and a datum temperature to which the device is set, the datum setting means being actuated by the speed selecting device, and a delay device being interposed between the latter and the datum setting means whereby the delay in adjustment of the datum in response to a change in selected speed is comparable with the thermal inertia of the temperature sensing device. Alternatively the delay may be greater to provide an acceleration control. As shown, turbine inlet temperature is sensed by a mercury-filled bulb 27 connected to a Bourdon tube 29 which, through a lever 31 with an adjustable pivot 32, operates a valve 33 controlling a bleed 54 from the fuel supply conduit on the downstream side of a metering unit (not shown) which meters the fuel in accordance with the selected speed setting and embodies means for compensating for variations of temperature and pressure of air entering the compressor of the plant. The position of the pivot 32 is moved to adjust the datum temperature by a servo-piston 39 acting through a lever 48 with an adjustable fulcrum and under the control of a valve 38 which is movable relative to a restricted orifice 46 in the piston by a lever 37 which has a connection through a cam 35 and shaft 34 with the speed selector 25. Pressure fluid is continuously supplied to the lower side of the piston 39 through a pipe 42 and to the upper side of the piston through a restriction 44, the valve 38 controlling an outlet from the space above the piston so that the latter follows-up the movement of the valve. The delay in the setting of the datum is caused by the restrictions 44, 46. Anti-clockwise movement of the cam 35 at a greater rate than is allowed by the rate of movement of the piston 39 is provided for by a spring-loaded follower 47. The system may be employed in a helicopter with twin rotors driven by separate power plants wherein failure of one plant would necessitate the running of the other at emergency high power output. In this case each power plant has a torque meter on its output shaft with a pressure connection 55 to a piston 56 in the control system of the other plant whereby the temperature sen