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Aviation History
1952
1952 - 1587.PDF
FLIGHT, 6 June 1952 691 (Left) Diffuser casing of compressor, showing tangential nozzles giving into transfer ducts, across the "elbows" of which are fitted cascades of guide vanes. (Centre) Main air entry casing. The inlet passages are between the shroud ducts through which pass the combustion tracts. (Right) Turbine entry casing, showing the translation of cross section from the combustion tracts to the entry nozzles. (Above) 1st and 2nd stage rotors (for the compressor turbine) with output shaft, front bearing and toothed-coupling bell-sleeve. (Right) Detail of turbine assembly, showing labyrinth seals, rotor and stator construction, blade forms and inter-disc and discjshaft couplings. PROTEUS 705 . . . diaphragm and the skirt of a cone ring which forms the inner wall of the turbine entry casing. The turbine front diaphragm is an integrally swaged ring of heat-resisting sheet steel, bolted to a hub in which are formed air passages for cooling the com pensated labyrinth housed within the bore of the hub and serving the turbine front support bearing. This bearing is housed at the head of a conical steel ring through-bolted at its skirt to the air entry casing. Both discs of the compressor two-stage turbine are forgings in Jessops G.18B, united by a Hirth coupling and, indeed, giving torque to the output shaft by means of a similar coupling. Both discs are drawn up to the output shaft by a sleeve-type retaining bolt threaded in the rear mouth of the shaft. The compressor turbine rotor blades are machined from Nimonic 80 bar (as are the entry nozzle blades) and the inter-stage row of stator blades. The stator blades are carried on twin-walled diaphragm assemblies of heat-resisting steel, the bores of which accommodate labyrinth seals. Although, strictly, it would be correct to speak of the first and second stages of the compressor turbine, and the first and second stages of the power turbine, it is perhaps easier (and not altogether unjustifiable) to refer to the first, second, third and fourth stages of the turbine assembly as a whole : that is to say, the airscrew turbine first and second stages are referred to as the third and fourth turbine stages. On this basis, then, the stator blades between the second and third and between the third and fourth turbine stages are precision castings in HR Crown One—in general, an unusual procedure, although not contrary to previous Bristol practice. Although the third and fourth stage rotor blades are Nimonic 80, the turbine discs are forgings of Jessops H.46 or, alternatively, Rex 448, and they, too, are united through a Hirth coupling. Torque is given to the output shaft through splines in the bore of the fourth-stage disc. In all four turbine stages the blades are diagonally fir-tree anchored in the disc peripheries. Rear support for the turbine assembly is provided by a tungsten steel deep-groove ball-bearing carried on the hub of the fourth- stage disc. The bearing is enclosed within a light-alloy housing which also serves as a distributor for oil feeds to the front and rear bearing assemblies. The housing is studded commonly to the labyrinth seal assembly guarding the rear bearing, and to a dished ring of heat-resisting steel flange-bolted to the i/d of the turbine exit duct. This last is fabricated in sheet stainless steel, the turbine discharge area being divided by seven aerofoil-section spokes spanning the inner and outer drums of the duct. To the
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