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Aviation History
1955
1955 - 1284.PDF
398 Abort: Rollt-Royee Avon RAJt turbojet. Axial compressor, annular combustion cham- ber and multi-stage turbine. Overall diameter, +1.5in; length, 113in: dry weight, 2.890 Ib; maximum thrust. 10,000 Ib rated, with s.f.e. of 0.86 Ib/hr/lb. Be/ow. Rolls-Royce Avon RA.7 turbojet. Twelve-stage axial compressor, eight combustion chambers and two-stage turbine. Overall diameter, 42.2in; length, 102.1in; dry weight, 2,460 Ib; maximum thrust, 7,500 Ib at 7,800 r.p.m. with s.f.c. of 0.92 Ib/hr/lb. Rolls-Royce Conway by-pass turbojet. Large-diameter low-prassure compressor, small- diameter high-pressure compressor, annular combustion system and two sets of turbine stages. Maximum type-tested thrust, 13,000 Ib, with very low specific fuel consumption. Not*: The diagram below is not intended to portray the Conway, but has been prepared by Rolls-Royce in order to clarify the operation of a by-pass engine. Below: Rolls-Royce Soar RSrJ turbojet. Single axial compressor, annular high-intensity combustion system and turbine. Overall diameter, 1S.8tn; overall length, with exhaust cone, 58.9in; dry weight, 275 Ib; maximum type-tested thrust, 1,810 Ib at high r.p.m. with s.fx. of 1.27 Ib/hr/lb. FLIGHT, 2 September 1955 Avon Under this name has been establishedthe widest range of military and civil gas turbines in the world. The first production rating was6,500 lb, and this range of Avons began to flow from Rolls-Royce—and, later from Bristol,Napier and Standard Motors, as. well as from Commonwealth Aircraft in Australia—in 1950. In 1952, the RA.7 (see drawing) went intoproduction at a rating of 7,500 lb. In these engines, full all-weather protection and triple-breech turbo-starters were introduced, and—in spite of strengthening to meet the needs of tran-sonic flight—the thrust/weight ratio was im- proved. Engines of this family have now beenbuilt in large numbers, a proportion having an afterburner to boost the maximum thrust by2,000 lb. The RA.21 is the latest production engine of this series, with a rating of 8,000 lbthrust, at slightly higher r.pjn. A considerable advance was made with theintroduction of the RA.14 (see data table, p. 407), in which higher compression, and other modifica-tions, made possible the achievement of signifi- cantly greater thrust and better specifics. Enginesof this type were actually being delivered two years ago, and a number of related units have sincebeen evolved, including the RA.28 illustrated. All these later Avons have an annular combustion sys-tem in order to accommodate the increased mass flow, while actually reducing the overall diameter. Conway Culminating many years of patienttoil is the announcement of a type test of the Conway at 13,000 lb thrust, with the lowest speci-fic fuel consumption of any type-tested turbojet. In this remarkable engine, the excess deliveryfrom an oversize low-pressure compressor is passed around the outside of the engine and re-enters the jet stream aft of the turbine section. The remainder of the compressor delivery passesthrough a smaller, high-pressure compressor, combustion system and turbines, and is expelledas a propulsive jet through the centre of trie by- pass flow. By this means, the mass flow is in-creased (compared with a simple turbojet burn- ing fuel at the same rate) and the mean jet velocityreduced, so improving the propulsive efficiency and reducing both the specific consumption andthe noise level. Installation and fire problems are also eased by the cool air flow which surroundsthe engine. The accompanying photograph, the first to bereleased of an actual Conway, shows the engine (in this particular form, at least) to be not dis-similar in appearance to a normal turbojet. Some indication of the enormous mass flow through thelow-pressure compressor is given by the length of the inlet guide vanes. Other features of interestare the duplex fuel supply to nine or ten burners and the pipe leading hot air from the high-pressurediffuser, through an electrically actuated gate- valve, to anti-ice the front of the engine. Various Conway ratings have been published,the latest being RCo.2, 3 and 5, but no details of these engines may be published. Flight trials areprogressing with a modified Ashton, and four Conways will take the Vickers 1000 transportinto the air before many months have passed. Soar When it was first revealed to the publicone year ago the RB.82 Soar had a far better thrust/weight ratio and thrust/frontal area ratiothan any other gas turbine, and there has since been no announcement of any unit to challenge it.Although it clearly has immense importance as an expendable engine it does not follow that allSoars are lifed at 10 hr only. Versions have been developed for a number of applications,and it is worth remembering Rolls-Royce work in the field of vertical take-off, which will requirea lifting jet described as "a distant cousin of the Soar.
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