GB741442A - Improvements in liquid fuel supply systems for gas turbine engines - Google Patents

Abstract

741,442. Supplying fuel to burners. DOWTY FUEL SYSTEMS, Ltd. May 5, 1954 [May 5, 1953], No. 12505/53. Class 75(1). [Also in Groups XXVI and XXIX] A liquid fuel supply system for a gas turbine engine in which an engine-driven fuel pump has its inlet connected by a feed line with a fuel tank and its outlet to spill type burners and in which the spill line is connected to the feed line through a throttle valve; has a valve controlled branch line between the fuel tank and a point in the spill line between the throttle and the feed line and means sensitive to the fuel temperature of the system to operate the valve so that when the fuel temperature reaches a critical value, the fuel flow in the branch line will increase or commence. In the fuel system, Fig. 1, an engine driven fuel pump 11, connected to a fuel tank 13 having the normal booster pump 14 by a feed line 12, discharges through a line 15 to spill type burners 16. A spill line 17 leads back to the feed line 12 through a servooperated spill valve 18 controlled by a servogovernor mechanism 19 which may be as described in Specification 694,318, [Group XXVI]. A filter 20 may be provided in the feed line 12. When the engine is operating at high speed at high altitude, the amount of fuel leaving the burners 16 may be only a small part of the fuel circulating through the system comprising the delivery line 15, the swirl chambers of the burners 16 and spill line 17 and as a consequence the fuel may become overheated. To prevent this, a branch line 21 is provided between the fuel tank 13 and a junction on the spill line 17 between the spill valve 18 and the feed line 12. Flow of fuel into the branch line 21 is controlled by a valve 22 actuated by temperature sensitive means 23 through a servo mechanism 24.. The servo mechanism 24, Fig. 2, comprises a spring loaded piston 26 which moves in a cylinder 25 the opposite ends of which are connected through a passage including a fixed restriction 30. Fuel is supplied to one end of this passage from the delivery line 15 through a feed line 31. The other end of the passage has a vent 32 controlled by a valve 35. The valve 35 is carried by a pivoted lever 36 and is urged to the closed position by a spring 37. The lever is also acted upon by a Bourdon tube 38. When the fuel temperature exceeds a predetermined figure the pressure in the Bourdon tube 38 overcomes the spring 37 and causes the valve 35 to open. This causes a flow through the restriction 30 and the resulting pressure drop across the piston causes it to move against the action of the spring 27 and operate valve 22 to open passage 21. In a modification, Fig. 4, the valve 22 and its operating mechanism is replaced by a unit 41, comprising a through passage 42 which opens at its opposite ends to a chamber 45 through valve seatings 46, 47. The chamber 45 is connected to the branch line 21. The double valve 48 has an extension 51 connected to a bellows device 53 containing a liquid such as liquid ether which, at the critical fuel temperature will .partially vaporize and so overcome the valve closing spring 49 to open the valve seats 46, 47. This allows some of the fuel to return to the fuel tank 13 through the branch line 21.