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Aviation History
1946
1946 - 1803.PDF
SEPTEMBER 12TH, 1946 F LiG HT 275 TURBINES AT THE SHOW Synoptic Survey of Current British Jet and Turbine/Airscrew Power Units on Exhibition THE activity of most of the British gas turbinemanufacturers is demonstrated by their exhibitsat the S.B.A.C. show, at Radlett today, and for the benefit of foreign buyers and others who may be particu- larly interested in this section of British aeronautical pro- ess, a broad survey of the current and projected models libited is here given so that the present state and future aspects are conveniently collated under one head. Armstrong Siddeley Motors Limited entered the gas tur- bine sphere with the production of the A.S.X. axial-flow unit, but during the development of this engine alterna- tive designs were studied with a view to increasing thrust and producing a power plant suitable for moderate-speed aircraft. As a result the decision was taken to develop a turbine /airscrew unit based on the A.S.X. The new engine, named the A.S.P. or Python, first ran in March, 1945, since when it has passed its acceptance test and has done some hundreds of hours of development running. Air for combustion in both the A.S.X. and A.S.P. engines is taken in either through an annulus (for existing installations) or through two forward-facing ducts ; it is then divided airscrew unit. This engine is of particular interest since it is the only British unit so far produced which employs a heat exchanger to recuperate energy which would other- wise be lost. Novel Compressor Arrangement The Theseus has a nine-stage axial-flow compressor, the final stage of which is arranged as a centrifugal impeller so that inspirated air, after passage through the axial stages, arrives at the final centrifugal stage where it is further compressed and at the same time thrust radially outward into an annular manifold. From the manifold, nine ducts feed the air to the heat exchanger, the tube arrangement of which takes the induction air radially in- ward toward the centre, then radiallyoutward to the ducts ARMSTRONG SIDDELEY A.S.P. T-0 and Combat rating : (a) 3,670 s.h.p. + 1,150 Ib jet thrust at 8,000 r.p.m. static, and (b) 5,520 s.h.p. + 280 Ib j-t at 8,000 r.p.m. at 500 m.p.h. Cont. cruise rating : (c) 2,720 s.h.p. + 950 Ib j-t at 7,600 r.p.m. static, and (d) 4,250 s.h.p. + 60 Ib j-t at 7,600 r.p.m. at 500 m.p'.h. Fuel cons. : (a) 359 g.p.h. ; (b) 425 g.p.h. ; (c) 290 g.p.h.; (d) 341 g.p.h. Max. dia., A.S.P. l-l : 54.5in ; A.S.P. 1-2: 48in. Length: I Ift 4/n. Estimated installed weight with airscrew : A.S.P. l-l, 4,100/b; A.S.P. 1-2, 3,950 Ib. between 11 throats where it is reversed in direction of flow. Next it is passed forward through a 14-stage (five low-pressure, nine high-pressure) axial-flow com- jor, then radially outward through a diffuser into induction elbows and so back on itself again into the 11 combustion chambers. This double reverse-flow system allows the combustion chambers to be grouped around the compressor and coaxially with it, and by so doing ensures the extreme compactness of both these power units. The latest Armstrong Siddeley gas turbine unit is the Mamba, a small airscrew/turbine engine of light weight whose take-off power output is roughly equivalent to that of a 1,120 h.p. piston engine. Six combustion chambers are used and the frontal area and weight of the unit are but respectively about ^o and 75 per cent of those of an equivalent piston engine. The Bristol Aeroplane Company's contribution to gas turbine power plants is embodied in the Theseus I turbine / ARMSTRONG SIDDELEY A.S.X. Take-off rating : 2,6001b at 8,000 r.p.m. Max. dia.: 42in. Length to nozzle : 14ft. Weight: 1,900 (b. Fuel con- sumption : 1.03 lb!hrilb. •" fftg. ARMSTRONG SIDDELEY MAM&A. T-0 rating : 1,000 s.h.p. + 320 Ib j-t. Max. dia. : 27in.. Weight : 750 Ib. feeding the nine combustion chambers. From these latter the gas-flow undergoes a 180-deg. change of direc- tion to impinge successfully en the twin turbines, the first of which powers the compressor whilst the second, through an extension shaft, provides power for driving the airscrew, the drive being taken through a compound epi- cyclic reduction gear forward of the compressor. After passage through the turbines, the gas is exhausted rearward through the heat exchanger, so giving up some heat which is passed on to the inflowing air on its way to the combustion chambers. On leaving the heat ex- changer the gas is discharged through a controllable nozzle to atmosphere so providing a proportion of residual jet thrust to supplement the main thrust from the airscrew. The de Havilland Engine Company hold a position in the van of gas turbine manufacturers, since they were the first established British aero-engine concern to enter the
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