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Aviation History
1946
1946 - 2025.PDF
o OCTOBER IOTJI, 1946 FLIGHT (Left) The nine- stage axial com- pressor rotor with its double- shrouded centri- fugal impeller final stage. (Right) Com- pressor turbine wheel showing both banks of blading for the two stages, and internally splined hub for driving com- pressor drum. Below i One of the three identical sections which go to make up the compressor rotor drum. The " fir-tree " anchoring slots for the blades can clearly be Half compressor casing showing the stages of stator blading and the flange against which the centri- • fugal impeller rotates. Epicyclic reduc- tion gear showing cage for com- pound planet gears, bell-coupling for. input drive, and air- turbine by which the airscrew is driven; this turbinerotates at 9,000 r.p.m. as against the compressor turbine's 8,200 r.p.m. The gases then flow through a diffuser intothe heat exchanger, and are finally discharged through a variable nozzle to atmosphere. The absence of any mechanical coupling between thecompressor and airscrew turbines renders the speed control aspects of the engine performance somewhat less critical,but as the speeds of the two turbines must be kept in reasonably constant ratio to or, 2 another, an ingeniousgovernor mechanism is incorporated whereby the airscrew blade pitch is automatically controlled to ensure the main-tenance of the fixed ratio as between the two turbines. Airscrew Gearing * The reduction gear is of epicyclic type incorporating foursets of compound planet wheels, and gives a reduction ratio of approximately 8.4: 1. Thus for the airscrew tur-' bine speed of 9,000 r.p.m. the rotational speed of the air- screw itself is about 1,070 r.p.m. The fixed annulus gear is mounted on torque dynamometerpistons, and this provides the additional advantage of equalising the tooth loads on all the planet wheels. Single-lever control will be provided, and this will nor-mally operate the fuel delivery only to obtain the appro- priate airscrew speed for any given flight condition. Ifdesrred, however, this lever may also be arranged to con- trol feathering and reversing. The airscrew shaft is aNo. 5 standard and the direction of rotation left-hand tractor. The original and main application of the Theseus is screw shaft. for long-range medium-speed aircraft, and Handley Page,Ltd., have announced their intention to iit these units in a prototype Hermes aircraft. The heat exchanger, which v 3ighs 500 lb, requiresseveral hours' flying in order to save its own weight in fuel, and this factor makes this particular version of theTheseus essentially a long-range power unit. However, for short ranges the heat exchanger can be omitted, with theresult that although fuel consumption is slightly increased, the weight is considerably reduced. It is claimed thateven without heat-energy recuperation the fuel consump- tion is very much lower than that of contemporary jetengines and, in fact, is still of the same order as for piston engines of comparable power. Initial flight trials will be conducted with an Avro Lin-coln, the normal two outboard Merlins of which will be replaced by Theseus. It is further planned eventually tofly the aircraft with four Theseus. An extensive amount of bench testing has already been accomplished, including100 hours' endurance at operating conditions, with satis- factory results.
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