Improvements in or relating to automatic controls for gas turbines

摘要

601,137. Automatic control systems for speed control of gas turbines. BRISTOL AEROPLANE CO., Ltd., and FORTESCUE, P. Oct. 16, 1945, No. 27044. [Class 38 (iv)] In an automatic control system for gas turbines, the change of a variable, e.g. speed, from a datum produces an outof-balance voltage in a bridge network which is detected by a sensitive relay which selectively energizes a control relay and increases the state of unbalance by applying the control relay current to the bridge network until the control relay is actuated, thus to regulate the automatic control and to restore the initial state of unbalance. In the embodiment alternator 5, driven by the turbine (not shown), energizes polarizing relay 6, the armature 9 of which vibrates between contacts 7 and 8. The network 11 is connected to battery 17 at points a, b and the condenser 10 is charged and discharged thereby as armature 9 moves from contact 8 to 9. For given values of condenser 10 and resistor 12, 13, 14, 15, 16, the network zero balance potential, measured between points c and d, occurs at one turbine speed, this datum speed being alterable by variation of the value of resistor 12. At turbine speeds other than the datum, the voltage developed between c and d energizes and operates the sensitive relay 18 of which the armature 19 moves either to contact 20 or 21 depending upon the sense of the network out-of-balance potential. If the circuit through contact 20 is made, current passes through coil 22 of control relay 23, to the junction of resistors 13 and 14, to amplify the existing balance. The resulting increase of pressure between armature 19 and contact 20 raises the current through coil 23 sufficiently to move contactors 24 and 39 simultaneously in a direction opposite to the arrow 25, against spring action. A circuit is then made through contactors 24 and 28 of control relays 23, 31 and the armature 17 of motor 27 with battery 17, the motor 27 thereupon rotates the valve 33 to control the flow of gas along pipe 35 to the turbine, the speed of which is restored to the datum. The contactor 39 when energized contacts coil 22 with the junction of resistors 15 and 16 and restores the initial state of unbalance of the bridge and consequently the sensitivity. If the change from the speed datum is such as to cause the armature 19 to move to contact 21, the control relay 31 operates to move the valve 33 in the reverse direction and to restore the sensitivity as before.