Patent GB-1044731-A (GB)
Title: Improvements in or relating to power management control for power plants
IPC: B64C27/12
Filed: 1964-01-28
Abstract: 1,044,731. Power plant control system. UNITED AIRCRAFT CORPORATION. Jan. 28, 1964 [Feb. 19, 1963], No. 3522/64. Heading F1Q. [Also in Division G1] In a power management control for a plurality of gas turbine engines supplying power to a common load each of which has a fuel control for regulating the flow of fuel thereto comprising first means for generating a signal commensurate with the power output of each of the gas turbine engines, second means for generating a signal commensurate with the speed of the common load, a first comparison system generating first error signals indicative of the load unbalance between the gas turbine engines, a second comparison system generating a second error signal indicative of the difference between the actual and the desired speed of the load, signal combining means responsive to the speed and load unbalance error signals for producing a plurality of control signals and adjustment means respectively responsive to individual ones of the control signals for adjusting respective ones of the fuel controls, each fuel control is adjusted and speed governing of and load sharing between the gas turbines is effected. The invention is thought to have particular utility when employed on a helicopter utilizing a pair of free turbine engines 10, 12, to drive a single main rotor 14. Fuel controls 18, 20 may be of the type disclosed in Specification 837,558. In order to provide the fuel flow corrections the output signals generated by power management control 22 are applied to actuators 40, and 42, which are respectively connected through appropriate mechanical means to fuel controls 18 and 20. Actuators 40 and 42 convert the electrical output signal from control 22 into mechanical shaft or linkage movements. The mechanical output signals from the actuators may be utilized to reposition the Nf setting of the fuel controls. This might be accomplished by causing rotation of the cam of the fuel control of Specification 837,558. Alternatively the outputs of the actuators 40 and 42 may be utilised through appropriate means to change the compressor discharge pressure signal to the sensing bellows on each of the hydromechanical fuel controls 18 and 20. Since fuel controls 18, 20 are responsive to compressor discharge pressue ultimately fuel flow is changed in dependence upon the output of the actuators. Indicator 44 computes and displays the power remaining in each engine and thereby gives the pilot a visual presentation of the conditions being managed. A power remaining indicator of this type is disclosed in Specification 997,698. Fig. 2 shows a block diagram of the power management control 22. The free turbine speed signals Nf and Nf<SP>1</SP> from tachometers 32 and 34 are respectively applied to speed sensing circuits 50 and 52. Circuits 50 and 52 sense a change in tachometer frequency and put out a DC voltage proportional to frequency which in turn is proportional to speed. The output signals from the speed circuits 50 and 52 are respectively applied to a pair of error circuits 54 and 56 which may be comparison circuits of a type well known in the art. Temperature limiting is accomplished by comparing a signal proportional to the T5 temperature from the engine mounted thermocouples 28 and 30 with a signal proportional to the limiting value of T5. The T5 signal from number 1 engine 10 is applied to a comparator circuit 95. Two independent units may be used one for each engine. In this case there obviously must be provision for cross feed of load information signals between the engines.