GB834868A - An emergency fuel control unit and a fuel system including such a unit - Google Patents

Abstract

834,868. Gas turbine plant. MURASZEW, A. March 4, 1958 [Nov. 4, 1957], No. 6939/58. Class 110 (3). A gas turbine fuel system has an emergency fuel control unit comprising valve means which in a first position connects a controlling pressure conduit to a servomotor controlling the output of variable flow fuel pump and allows fuel to pass through the emergency fuel control unit to a first fuel outlet conduit leading to the engine and which in a second position isolates the controlling pressure conduit from the servomotor and allows fuel to pass through the emergency fuel control, an adjustable throttle and a second fuel outlet conduit to the engine. Fuel is supplied to the gas turbine engine 10, Fig. 1, by two fuel pumps 11, 12 arranged in parallel and controlled by servomotors 25, 27. The pumps discharge through a conduit 15 to an emergency fuel control unit 16. A first fuel outlet conduit 17 leads from the control unit 16 through a proportional flow control 18 an acceleration control unit 19, a first non-return valve 20, a conduit 21 and distributer 22 to the engine. A second fuel outlet 23 delivers fuel from the emergency control unit 16 to a second non-return valve 24 and conduit 21 and distributer 22 to the engine. The servomotors 25, 27 are controlled by the pressure in a conduit 29 which pressure is determined by an altitude sensing unit 31, an acceleration control unit 19 and a temperature control solenoid valve 32. A rotary actuator 33 is operable by the pilot to change the emergency control unit 16 from a first or normal position to second or emergency condition. A rod 35 connected to the pilot's throttle lever connects the arm 34 of the emergency throttle to the arm 36 of the proportional flow control. In the first or normal position of the emergency control unit 16, Fig. 2, the fuel flows from the inlet conduit 15 into the chamber 60 and then passes between the seat 54 and land 52 and ports 50 to the first outlet conduit 17 and thence to the engine. In this position also the control pressure conduit 29 is connected to the servomotors 25, 27 so that the output of the pumps is controlled by the acceleration control unit 19, the altitude sensing unit 31 and the temperature-control solenoid valve 32. If an emergency should arise, e.g. should the conduit 17 become fractured, the pilot operates the rotary actuator 33. This causes the land 52 to engage the seat 54 and the land 53 to lift off the seat 55. The fuel then passes between the land 53 and seat 55 and ports 45 to the outlet conduit 101. The fuel then passes through the throttle 77 the position of which is determined by the pilot's throttle lever acting through the arm 34, to the second outlet conduit 23. In this position of the unit 16 the land 64 blocks the ports 102, 103 and isolates them from the control conduit 29. Under these conditions the servo pump controls 25, 27 adjust the pumps 11, 12 for maximum flow. When the fuel delivered is more than that required by the engine, a pressure relief valve formed by the piston 89 and spring 95 rises and allows fuel to pass to the suction side of the pumps through a conduit 37. The pumps may be controlled by varying the length of stroke or by varying the speed of the pumps.