GB826508A - Rotor thrust reducing means for a gas turbine power plant - Google Patents

Abstract

826,508. Gas turbine power plant. ARMSTRONG SIDDELEY MOTORS Ltd. Dec. 23, 1957 [Dec. 28, 1956], No. 39397/56. Class 110(3). In an axial-flow gas turbine power plant having a compressor and turbine rotor assembly associated with a thrust bearing which is subjected to the difference between the oppositelyacting thrusts of the turbine and compressor rotors during operation, a plurality of coaxial thrust pistons is provided, each secured to and axially-spaced along the rotor assembly and coacting with an associated stationary reaction piston so as to form a pressure chamber to which the compressor outlet pressure is communicated in parallel, the sides of the pistons opposite to the pressure chambers communicating with the atmosphere. A hollow shaft extension is provided at the side of the turbine remote from the compressor, the shaft being supported in a balltype combined journal and thrust-bearing 12. The end of the shaft is of reduced diameter and three thrust pistons 29 are mounted thereon, being secured by a nut 38. The axiallyextended hub portions 36 of the pistons are formed with openings 32a which are aligned with openings 32 in the shaft extension. Stationary reaction pistons 30 are disposed adjacent the thrust pistons 29 to define chambers 33 therewith, air under pressure tapped from the compressor outlet being supplied to the chambers through the hollow shaft 11 and openings 32 and 32a. The sides of the thrust pistons 29 opposite the pressure chambers 33 communicate with atmosphere through openings 35 in the axially-extending flanges 39 of the reaction pistons, the side of the outermost thrust piston 29 being open directly to atmosphere. The flanges 39 of the reaction pistons are connected together, the innermost reaction piston being secured to stator structure 31. The pressure acting on the thrust pistons 29 counteracts the axial thrust in the direction 28 towards the compressor rotor. When the compressor outlet pressure rises, the piston-type valve 46 opens against the loading of spring 48 whereby air under pressure passes through openings 32b, 32a to the outermost pressure chamber 33a, thereby providing an additional axial thrust in the direction opposed to direction 28. In Fig. 2 the assembly of thrust pistons 29 and reaction pistons 30 is enclosed within a casing 49, the spaces on the sides of the two innermost thrust pistons 29 opposite the pressure chambers 33 communicating therewith through openings 35. The chamber within casing 49 communicates with atmosphere through duct 50 and a valve device which comprises a piston 54 in a cylinder 55. Air under pressure from the compressor outlet acts on the piston 54 against the loading of spring 58 and when the air pressure reaches a certain value the piston 54 and rod 53 move to the position shown in which the duct 50 communicates with atmosphere through ports 57 and 51 when the axial counter-thrust on the pistons 29 is a maximum.