GB677274A - Improvements in and relating to gas turbine nozzle structures - Google Patents

Abstract

677,274. Gas turbines. BRITISH THOMSON-HOUSTON CO., Ltd. Nov. 22, 1949 [Nov. 27, 1948], No. 29914/49. Class 110(iii) A nozzle ring assembly for a high temperature gas turbine comprises two concentric radially-spaced blade support rings 77, 78 having circumferentially-spaced openings, and a plurality of nozzles blades 74 having root and tip portions 76 loosely disposed in the openings which are of substantially the same shape as the co-operating parts of the blades. The openings have projecting portions 85, 85a extending around their peripheries to close the small clearance spaces 84, 84a to prevent leakage of fluid therethrough, the size of the projecting portions being so small that thermal expansion during operation of the turbine will result in some crushing of the projecting portions without imposing excessive stresses on the blades or rings. The blade support rings are formed of segments with clearances between each to allow for expansion, and locking rings 80, 80a fit into circumferential grooves to allow a limited movement of the blades in a radial direction. The outer blade support ring 78 is located circumferentially by means of radially-disposed dowel pins 83 fitted in the main frame ring 38 which engage in notches formed in the axially-extending flange 78c of the support ring. The inner blade support ring is located by means of small dowel pins 77a. The turbine casing comprises rings 38, 42 bolted together which are cooled by water flowing through the passages 42d, 42e and which are provided with heat insulation pads 92, 99. The main frame ring 16 which carries a shaft bearing 15 is protected from heat by a cooling pad 59 having concentric grooves 59a at one side to form a radiating surface. The pad is cooled by water flowing through the passages 60, 59b, 62 and 61. The nozzle blades are cooled by air flowing from the annular passage between the combustion chamber casing 22 and the frame tube 26, through the opening 71c in the outer nozzle casing member 71, through the hollow nozzle blades whence it passes through the clearance between the inner nozzle casing member 65 and the blade support ring 77 into the flow of combustion gases. High pressure air is supplied through a pipe 33a to the annular chamber 33 from which part flows through the labyrinth seal 31 to prevent leakage of hot gases, and part flows through the labyrinth seal 30 to prevent leakage of oil from the bearing 15. The exhaust gases pass through a passage formed by walls 52, 53 in which are disposed guide vanes 53, 54a for straightening the flow of gases or for directing the gases on to further rotor blades. Specification 608,476 is referred to. Reference has been directed by the Comptroller to Specifccation 582,152.