Patent GB-1035230-A (GB)
Title: A fuel control system for a gas turbine engine
Inventor: CLARK NEIL MILLIGAN
IPC: F02C9/16
Filed: 1963-07-16
Abstract: 1,035,230. Gas turbine engine fuel systems. POWER JETS (RESEARCH & DEVELOPMENT) Ltd. July 14, 1964. [July 16, 1963], No. 28047/63. Heading F1G. [Also in Division G3] A fuel control system for a gas turbine engine comprises means to compare over a period of time sufficient to allow the effects of transient variables to average out, a parameter dependent upon fuel flow to the engine and another parameter dependent upon engine operation, there being means responsive to any change in the relationship between these parameters and the relationship determined from the same parameters for a pre-determined calorific value of the fuel and ambient conditions, to vary the upper limit of the rate of supply of fuel in a sense substantially to eliminate the change. In the gas turbine engine indicated in Fig. 1 (not shown) a device A integrates with respect to time the rotational speed of the compressor 1 and a second device B integrates with respect to time the rate of supply of fuel represented by the position of the fuel valve F, the valve F being controlled by a speed governor G which rotates at a speed proportional to that of the power turbine output shaft 7. The integrals determined by the devices A and B are fed to a comparator C where the relationship between the integrals is compared with the relationship between the integrals determined for a pre-determined calorific value of the fuel and ambient conditions. The output from the comparator is fed to an acceleration control D through a timing device E. In the arrangement shown in Fig. 2 the cam 8 is driven from the compressor 1 through reduction gearing so that the rotation of the cam in unit time is the integral of compressor speed in that same unit of time. The cam carries a contact 12 which engages momentarily the contact 13 once every revolution of the cam, the closing of the contacts setting into operation a timing device 14 and also actuating a switch 14a which starts the synchronous electric motor 15. The motor drives a cam 16 through an infinitely variable speed gear 17 and reduction gearings. The speed ratio of the gear 17 is controlled by the setting of the fuel valve F which in turn is controlled by the power turbine speed governor G so that the speed of the cam 16 is proportional to fuel flow. The rotation of the cam 16 in unit time is therefore the integral of the fuel valve settings in the same unit of time. The cam 16 carries a contact 19 which engages a fixed contact 20 once every revolution of the cam, closing of the contacts cutting off supply to the motor 15 and re-setting the timing device 14. Rollers 21 and 22 carried at the end of a lever 23 engage the cams 8 and 16 respectively, the lever being loaded by a spring so as to keep the rollers in contact with the cams. A rod 25 is connected to the lever 23 and through a spring 27 to a further rod 26 which carries at its other end a needle valve 33, the rod 26 being held by a clamp device 28, 29 which is released periodically by means of the solenoid which withdraws clamp member 29 from the rod, the solenoid being actuated by the timing device 14. The needle valve 33 controls leak-off of air under pressure from a chamber 35, air being supplied to the chamber from the engine compressor. The chamber 35 contains a bellows 36 which is connected through linkage 37 to an acceleration control device D which limits opening of the fuel valve F.