GB930148A - Improvements in and relating to fuel feed systems for gas turbines and applications thereof - Google Patents

Abstract

930,148. Gas-turbine plant. J. SZYDLOWSKI. Nov. 9, 1959 [Feb. 5, 1959], No. 37958/59. Class 110 (3). [Also in Groups XXIX and XXXIII] A fuel-feed unit for a gas-turbine engine driving a helicopter rotor, the absorbing power of which can be varied manually or automatically by a rotor collective pitch control member is characterized by the fact that said unit comprises, between the fuel feeding pump and the gas-turbine fuel nozzles or burners, a flow-metering unit having a flow passage which is adjustable in relation to the engine speed and, upstream of said flow metering unit on the fuel feeding line, a pre-regulator for adjusting the pressure difference between the upstream and downstream sides of said passage in relation to the position of the rotor collective-pitch control member. In the embodiment a gas-turbine engine 48 drives through gearing and shafting 70 a helicopter rotor 36 and the fuel control unit is regulated by the collective pitchadjusting mechanism 27 to supply fuel to the engine burners 47 so as to maintain the speed of the engine at its rated value. A fuel pump 5 delivers fuel from a conduit 6 past a by-pass pressure-regulating valve 8 to a fuel-flow regulating device comprising co-operating components 4, 2 and 3, component 4 being responsive to variations in the collective pitch of the rotor blades and component 2 being a fuel-flow metering element operatively connected to a governor in component 3, driven by the engine. Component 4 comprises a pressure modifier 10 having a hollow slide valve 11 urged by a spring 13 into contact with a flexible diaphragm 12 which separates two cavities 14 and 15. Cavity 14 is supplied with fuel through a port 18 in valve 11 and cavity 15 contains an axially slidable plunger 17 which loads a spring 16, connected to the diaphragm, the plunger being acted upon by a cam 24 pivoted at 23 and connected by a rod 26 to the collective-pitch adjusting plate 27. The upper face of plunger 17 is formed with a metering orifice 21 which connects cavity 15 with a chamber 22 in turn connected by a conduit 40 to the fuel supply through a port 19 in valve 11, a conduit 20 and a port 42 in a body 41, the flow through port 42 being regulated by a slidable plunger 43. Conduit 40 also connects through conduit 49 and a hollow drive shaft 46 with the rotary fuel burners 47 which supply an annular combustion chamber 48. The plunger 43 is adjusted by a centrifugal governor driven through gearing 44 and 45 from shaft 46. Under steady working conditions with the engine running at a rated speed for an optimum setting of the collective pitch of the rotor blades the area of aperture 42 will be maintained constant by plunger 43 under the action of the centrifugal governor, and the fuel pressure in chamber 22 and cavity 15 will be the same as in conduit 49. Under transient working conditions, an instantaneous increase, say, of collective pitch of the rotor blades will cause rod 26 to operate cam 24 to move plunger 17 down and, through spring 16, operate valve 11 in a sense to increase the flow of fuel from conduit 7 to conduit 20. A decrease of collective pitch, by a reverse process, will produce a reduction in fuel flow. Another embodiment is described (see Group XXIX), utilizing a fluid pressure servo system for effecting fuel control. Specifications 693,217 and 860,283 are referred to.