Patent GB-947335-A (GB)
Title: Improved gas turbine engine
Inventor: JUBB ALBERT
IPC: F02C7/22
Filed: 1961-05-05
Abstract: 947,335. Gas turbine engine fuel systems. ROLLS-ROYCE Ltd. May 1, 1962 [May 5, 1961], No. 16494/61. Addition to 850,477. Heading F1G. A gas turbine engine fuel system for controlling the supply of pressurised fuel from a source thereof to a burner of a gas turbine engine comprises a cylindrical metering device which is provided with a metering orifice, there being means for varying the size of the metering orifice in accordance with engine rotational speed and independently in functional relationship with the ratio of the outlet and intake pressures of the engine compressor; also a throttle valve mounted concentrically within the cylindrical metering device, for controlling the fuel flow to the burner in accordance with the pressure drop across the metering orifice. The invention is an improvement in or a modification of the invention disclosed in the parent Specification. The control unit comprises a casing 10 to which fuel under pressure is supplied through line 82, fuel being discharged through passages 39 and 39<SP>1</SP> to the main and pilot burners of the engine respectively. A shaft 11 is driven from the engine and drives through gearing 13, 14 a sleeve 15 which in turn is drivingly connected to a cylindrical cage 16. The cage 16 carries governor weights 27 pivotally mounted at 28, the governor arms 29 acting to adjust the axial position of a sun gear 23. The governor 28 constitutes an acceleration control governor. The cylindrical cage 16 also carries three planet gear shafts 17, only one of which is shown, a compound gear pinion 19, 20 being mounted on each shaft. The gears 19 engage with an axially movable and rotatable sun gear 21 which is secured to a cylindrical sleeve 22, while the gears 20 engage with the axially movable but non-rotatable sun gear 23, the gear 23 being formed integrally with a shaft 24 which is adapted to be moved axially by the governor arms 29. The sleeve 22 is formed with triangular shaped orifices 77 also with a series of orifices 38, and is connected at its left-hand end by a bearing 40 and housing 41 to a pair of acceleration control capsules 42 disposed on diametrically opposite sides of the sleeve 22 and mounted within a common chamber 43. Each capsule 42 is divided into two compartments 42<SP>1</SP>, 42<SP>11</SP>, the compartments 42<SP>1</SP> being evacuated and the compartments 42<SP>11</SP> being connected to a pressure which is proportional to the intake pressure P 1  of the engine compressor. The chamber 43 is connected to a pressure which is functionally related to P 1  and P 2 , P 2  being the outlet pressure of the engine compressor. The capsules 42 therefore act to position the cylindrical sleeve 22 in dependence on P 1 F (P 2 /P 1 ). The sleeve 22 is disposed within a pair of sleeves 46, 47, the sleeve 46 being an integral part of the casing 10 and the sleeve 47 being axially movable by a top speed governor device 50.'The sleeves 46, 47 together define an annular orifice 48 of axially adjustable width which co-operates with the triangular orifice 77 to define a variable area metering orifice through which fuel passes from the space within the casing 10 into the space within the sleeve 22. The governor 50 controlling the axial position of the sleeve 47 comprises flyweights 49 pivotally mounted within the cylindrical cage 16, the governor arms 51 bearing against a flange 52 of the sleeve 47. The sleeve 47 is formed with an extension 471 having axial abutment faces 53 each of which is engaged by a roller 59 carried by a forked lever 57 which is pivotally mounted at 58, movement of the lever being limited by a pair of stops 75, 76. The lever carries an arm 61 at its lower end, the arm bearing against a tubular member 60 against which acts one end of a spring 62. A rod 65 extends through a guide sleeve 64 and is secured thereto at its lower end, and the lower end of the rod bears against a lever 67 which is pivotally mounted at 68, a cam 71 which is carried by the pilot's throttle lever bearing against a roller 70 disposed centrally of the lever 67. The cam 71 also bears against one end of a lever 73 which is pivotally mounted at 73<SP>1</SP>, the other end of the lever 73 being engaged by a spring 74. The pilot's control lever thus acts to adjust the loading of the spring 62 which is the control spring of the governor 50. Flow of fuel from within the sleeve 22 through the orifices 38 to the outlet passages 39, 39<SP>1</SP> is controlled by a throttle valve 31 which is formed with a skirt portion 35 having openings 37 therein. The throttle valve is formed at its right-hand end with a piston 34, the right-hand side of the piston being acted on by pressure of fuel upstream of the metering orifice 48, 77 and the left-hand side of the piston being acted on by pressure of fuel downstream of the metering orifice. The throttle valve thus takes up a position dependent on the pressure drop across the metering orifice. The axial position of the throttle valve 31 is also controlled in dependence on engine rotational speed. For this purpose, the throttle valve is connected to the shaft 24 of the axially-movable but non- rotatable sun gear 23 by a guide-shaft 30 which is splined to both members; the throttle valve is also connected to the shaft 24 by a tension member 32 such as a piano wire. The throttle valve may thus move axially within the sleeve 22 but is prevented from rotation therein.