Patent GB-1232318-A (GB)
IPC: F02K3/10
Filed: 1969-11-19
Abstract: 1,232,318. Gas turbine jet engine fuel systems. ROLLS-ROYCE Ltd. Nov. 19, 1969, No. 56677/69. Heading F1J . The invention relates to a gas turbine engine fuel system and is described with reference to an engine which has exhaust reheat equipment comprising pilot and main reheat burners, also burners disposed in the by-pass duct. In Fig. 2 fuel is supplied by pump 11 to duct 13 thence to duct 14, 15, 16, the duct 14 supplying pilot reheat burners, the duct 15 supplying main reheat burners and the duct 16 supplying by-pass duct burners. A restrictor 20 is provided in the duct 14, also a flow control valve 21, the valve being dependent on the value of at least one engine variable such as engine rotational speed. A restrictor 25 is provided in the duct 15 and a restrictor 26 in the duct 16. A valve 33 is provided in the duct 15 downstream of the restrictor 25 and a valve 37 in the duct 16 downstream of the restrictor 26. The valve 33 comprises a piston member 40 which controls flow between the portions 30, 31 of the duct 15, the valve being controlled by the difference between the pressure in the pilot supply duct 14 downstream of the restrictor 20 and upstream of the flow control valve 21 and that in the duct 15 downstream of the restrictor 25. The valve 37 is similar to the valve 33 and is controlled in the same way. The restrictor 25 is of variable area comprising an axially movable needle valve 27 controlled by link 56. The restrictor 26 is similar to restrictor 25 and is controlled by a link 57. The links 56, 57 are controlled by the assembly shown in Fig.1. The pressure difference across the flow control valve 21 is sensed at lines 23, 24 and is utilized to control the pump 11. A bleed duct 103 downstream of the flow control valve 21 is controlled by a valve 101, 102 which is controlled by a link 100 from the assembly shown in Fig. 1. In a second embodiment Fig.3, fuel supplied by pump 104 passes to lines 110, 111, 112 leading respectively to pilot reheat burners, main reheat burners and by-pass duct burners. A fixed restriction 113 is provided in the duct 110 and downstream of the restriction between the ducts 114, 115 is a flow control valve comprising a valve member 125. In the line 111 is a restrictor 180 and downstream thereof a valve assembly 164. Similarly in the line 112 is a restrictor 181 and downstream thereof a valve assembly 165. The valve member 125 is mounted for axial and rotational movement in a casing 117 which is divided by an internal wall 122 into chambers 120, 121, the line 110 and duct 114 leading through ducts 123, 124, into the chamber 120, 121. An outlet chamber 140 is formed in the internal wall 122 and connects with outlet duct 115 leading to the pilot reheat burners. The valve member 125 carries a piston 126 at its left hand end, the chambers 128, 129 at each side of the piston being connected through lines 130, 131 to compressor discharge pressure P 3  and jet pipe pressure P 6  respectively. The valve member is loaded at its right-hand end by spring 132. The valve member 125 is formed with an internal chamber 108 and with two sets of triangular shaped orifices 133, 134 and a set of elongated orifices 107. The orifices 134 co-operate with a fixed sleeve 135 and the orifices 133 co-operate with a sleeve 118 the position of which is pre-set by adjuster 139 acting through lever 137. Thus fuel passes from the chambers 120, 121, through the orifices 134, 133 into the chamber 108 then through orifices 107 to chamber 140 and then to outlet 115 to the pilot burners, the flow being controlled by the axial position of the valve member 125 which in turn is controlled by the pressure difference P 3  -P 6  acting on the piston 126. The valve member 125 is rotated in operation from shaft 143 through pinion 142 and gear 141. The valve assembly 164 comprises a piston member 162 which controls fuel-flow between portions 172, 173 of main reheat fuel line 111, the piston member being acted on at its right hand side by the pressure of fuel in chamber 120 i. e. by pressure of fuel in the pilot supply duct 110 downstream of the restriction 113 and upstream of the flow control valve 125; the piston member 162 is acted on at its left-hand side by pressure of fuel in the main reheat supply duct 111 downstream of the restriction 180. The valve assembly 165 in the by-pass duct fuel supply line 112 is controlled similarly to the valve assembly 164. A valve member 144 is driven from the shaft 143 through pinion 142 and gear 145, the valve member being formed adjacent its right-hand end with a groove 150 which controls flow of highpressure fuel from line 151 to line 152, the line 152 passing to the control unit of the reheat fuel pump 104. The valve member 144 is acted on by centralizing springs 146, 147. The valve member 144 is acted on by the pressure difference across the metering valve assembly 125, 133, 134, the left-hand end of the member being acted on by pressure in chamber 120 i.e. pressure upstream of the metering valve, and the righthand end of the member being acted on by pressure in chamber 140 i.e. pressure downstream of the metering valve, the latter pressure being communicated to end face 153 of member 144 through duct 154. A governor 155 is also carried by the member 144 such that with increasing speed the member is urged towards the left so restricting the flow of fuel through lines 151, 152 and thus reducing the output of the reheat fuel pump 104. The valve members 176, 177 are rotated in operation by gearing 142, 156, 157. The assembly shown in Fig. 1 comprises a manually axially-movable shaft 45 which is connected to a lever 48 mounted on a vertically adjustable pivot 50, the opposite end of the lever 48 being connected to levers 52, 53 mounted at fixed points 54, 55, the opposite ends of the levers 52, 53 being connected to links 56, 57 which in turn are connected to the needle valves 27, 28, Fig. 2, or 182, 183 Fig.3. As the pivot point 50 is moved upwardly or downwardly so the manual movement of the rod 45 produces differential movements of the needle valves. The pivot point 50 is controlled by a servo-device 10 which comprises a spool 73 and piston 67, compressor discharge pressure P 3  being applied to chamber 69 and jet pipe pressure P e  being applied to chamber 68. The spool is mounted within axially movable sleeve 64 which carries a slave piston 65, high-pressure engine fuel being supplied to chambers 86, 87 at each side of the piston, the arrangement being such that as the piston 67 moves axially to the left or right in dependence on pressure difference P 3 -P 6  so does the piston 65 and sleeve 64. Such movement of the sleeve results in upward or downward movement of the pivot point 50 and thus differential movement of the needle valves 27, 28. Axial movement of the member 45 also results in axial movement of the link 100 and thus of the needle valve 101 controlling the bleed 103 from the line 14.