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Aviation History
1946
1946 - 2024.PDF
386 FLIGHT OCTOBER IOTH, 1946 THESEUS I Further Details of the Bristol Turbine/Airscrew Unit Part-section cut-away drawing illus- trating the disposition of main units and affording an insight into the air and gas flow through the unique heat exchanger. THE first announcement of the Bristol Theseus Iturbine / airscrew power unit was given in theDecember 6th,. 1945, issue of Flight, and since that date several references to the engine have been made. As our readers will be aware, the Theseus is a turbine/ airscrew power unit employing an axial main compressor and a heat exchanger through which the jet gases are discharged. It is the only engine of its kind to employ heat energy recuperation, and reference to the cut-away drawing will clarify details of the internal design and the arrangement of main components. Inducted air enters the compressor through an annular intake surrounding the reduction gear immediately rear- ward of the airscrew. The compressor itself comprises nine stages of axial blading and a final stage centrifugal impeller, giving an overall compression ratio of about 5: 1 at 300 m.p.h. at 20,000ft. At full throttle the com- pressor runs at 8,200 r.p.m. and delivers 30 lb of air per sec at sea level static conditions; this is equivalent to a power input of approximately 3,500 h.p. Air delivery from the compressor discharge manifold is taken by eight equi-spaced transfer ducts to the heat exchanger, a matrix type unit the tubes of which are arranged in 16 sets, 8 inlet and 8 outlet, separated by suitable headers. Air flow is radially inward, then radially outward to the headers serving the eight combustion chambers. During its passage through the heat exchanger the air abstracts heat from the hot jet gases and so is given a further measure of compression before entering the combustion chambers. In order to mitigate differential expansion effects the heat exchanger itself is carried on the main engine mount ing structure and is located at the forward end only. Gases from the combustion process are delivered by a tangential manifold to a ring of 48 nozzles, whence they pass through the two-stage first turbine, which powers the compressor and auxiliaries, and the single-stage second ASSUMING AIRSCREW EFFICIENCY IS 80% REDUCTION GEAR 400M.P.H.350M.P.H. 300 M.P.H. 250 M.P.H. 200M.P.H. I 400M.P.H.350 M.P.H. 25OM.P.H.200M.P.H. - STATIC(JET THRUST TO BE ADDED) 10.000 2QP00 30000 ALTITUDE-FEET 4Q0OO TOTAL EFFECTIVE POWER = 1 (AIRSCREW SHAFT POWER JET POWER \ so ,) ASSUMING 1 j! AIRSCREW EFFICIENCY IS 80% " REDUCTION GEAR » -97-596CALORIFIC VALUE OF FUEL IS 200M.P.H\ 300 M.P.H. 400 M.P.H. STATIC SPECIFIC CONSUMPTION07 LBS/SHAFT B.H.P/HR. Curves of power variation with altitude for range of representative flight speeds. 200 403 600 800 IpOO £00 1400 £00 1/300 2000 2200 2400 2600 TOTAL EFFECTIVE B.H.R Typical curves of specific fuel consumption for various powers at different altitudes and speeds.
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