Patent GB-648798-A (GB)
Title: Improvements in or relating to control systems for gas-turbine plants
Inventor: HAWORTH LIONEL
IPC: F02C9/28
Filed: 1948-05-13
Abstract: 648.798. Gas turbine plant. ROLLSROYCE, Ltd. May 13, 1948, No. 13200. Addition to 640,958. [Class 110(iii)] [Also in Groups XIII, XX, XXIX, XXXIII and XXXV] In a gas-turbine power plant as claimed in the parent Specification, the temperature responsive means comprises a fluid container immersed in the gas flow connected to pressure responsive means movement of which adjusts the torque loading on the output shaft. In the arrangement shown, Fig. 2, the pitch of a variable pitch airscrew driven by the gas turbine plant is controlled by a valve 38, the piston valve 38c of which is responsive to the movements of an expansible capsule 42 and a lever 40 connected to it through a floating lever 39. The capsule 42 is connected through a capillary tube 43 to a tubular ring 44. The ring 44 is wholly or partially filled with a suitable liquid such as mercury or iodine so that as the temperature of the exhaust gases changes so the capsule 42 expands or contracts. The ring 44 is placed so as to sense the mean temperature in the exhaust pipe of the turbine and is supported by radial arms 45 having spade-like ends 45a which slide in slots formed in the exhaust pipe attachment flange 20a. An increase in exhaust temperature causes the capsule 42 to expand and move the piston valve 38c to the left which allows servo fluid to pass into pipe 38a and fine-off the pitch of the airscrew. The turbine then speeds up and increases the air supply and thus reduces the temperature. The lever 40 allows the position in which the valve 38c is in the neutral position for a given extension of the capsule 42 to be adjusted and so allows the controlled temperature to be preset. The lever 40 may be connected to the control arm of a constant speed governor varying the fuel supply to the plant. In a modification, the capsule 42 is connected directly to the valve 38c and the lever 40 is connected to a sliding sleeve forming the ported cylinder for the valve 38c. An override to permit the airscrew blades to be moved into reverse pitch for braking comprises a rod 47 operated by a piston 48. In a further modification, Fig. 6. the rod 52 is attached to the capsule 42, which rod carries a slidable contact carrier 54 biassed into a central position by springs 55. The carrier 54 carries electrical contacts 56 which co-operate with a pair of contacts 57 carried bv the forked end of a rod 58 the position of which may be adjusted by the lever 40. Expansion of contraction of the capsule 42 causes one or other of the contacts 56 to engage a contact 57 which completes a circuit and causes the airscrew to be moved to fine or coarse pitch. Since the control arrangements described will automatically move the airscrew blades to the coarse position on shutting down of the plant an additional control will be needed to decrease the pitch on starting. This control may consist of a solenoid plunger loading the control valve 38 which solenoid is energized during starting and de-energized when the temperature control described becomes operative. The torque may be varied by other means e.g. by regulating a variable speed transmission or torque convertor or by adjusting the load itself. According to the Provisional Specification the preset temperature may be varied by altering the resilient load against which the capsule 42 acts.