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Aviation History
1956
1956 - 0571.PDF
11 May 1956 571 Bristol Olympus 102. Split-compressor turbojet. Multi-stage low-pressure and high-pressure compressors driven by independent turbine stages and annular combustion chamber with ten burners. Diameter, 40in; length, about 125m; dry weight, about 3,700 Ib, equipped; mass flow and pressure ratio, restricted (reported to be 165 Ib/sec and 10:1 on the earlier Mk 101); maximum thrust, 12,0001b dry (r.p.m. and s.f.c, restricted, but reported to be 6,500 l-p. and 0.79 on the Mk 101). Bristol Orpheus (BOr.3 rating). Single-shaft turbojet. Reported to be seven- stage compressor, annular combustion chamber and single-stage turbine. Overall diameter, 32.4in; length as shown (with jet pipe), 150in; dry weight, about 750 Ib; mass flow and pressure ratio, restricted; maximum thrust, 4,850 Ib, reportedly with s.f.c. of 0.99. An afterburning version of this engine is being developed. i) at 10,500 low-pressure r.p.m. maintained to 16,500ft i.s.a.; typical cruising figure, 3,080 e.h.p. at 350 kt at 36,000ft with s.f.c. of 0.385. with Solar Aircraft (in respect of afterburners, propelling nozzles andother equipment) and S.N.E.C.M.A. (in respect of turbojet reverse- thrust mechanisms). Olympus. In the design of this advanced turbojet the Bristol EngineDivision (as it then was) aimed considerably beyond anything previously attempted. Originally, the B.E.10 was a long-term project with long-range-bomber applications, and the first models established a diameter of 40in, weight of about 3,600 lb, and a rated thrust of 9,140 lb withan s.f.c. well below 0.8—world-beating figures six years ago. The first series of engines were some of the earliest to be built with a split, orcompounded, compressor (often referred to as the two-spool arrange- ment), and several examples were shipped to the Curtiss-Wright Cor-poration, who used them as a basis for an up-rated design of their own designated J67 (q.v.~). In 1954 the first service-cleared powerplant, the Olympus 101, wentinto production for the Avro Vulcan with a rating of 11,000 lb dry. Although equipped with every form of accessory and protection system,the weight is approximately the same as that of the first prototype engine. The 101 has now been superseded in production by the 102(BO1.11) with a dry rating of 12,000 lb. This engine holds the world altitude record at 65,890ft. Development of afterburning engines ispresumably with a view to fighter applications. Frequent reports have spoken of "B.S.R." (Bristol simplified reheat) in which fuel is injectedinto the tailpipe and used to provide limited thrust augmentation, the nozzle being fixed at the non-reheat area. It is known, however, thatthe co-operation with Solar Aircraft involves the development of large afterburners for Bristol turbojets. The existence has been revealed of a later series of Olympus, of whichthe first rating to be announced is BO1.6. In America it has been stated that "the Olympus 106 and all succeeding modifications aredesigned for supersonic speeds," and it may be this type of engine which will power the forthcoming Gloster twin-engined, all-weatherintercepter. This family of engines has been unofficially reported to be of the 15,000 lb-thrust class. Owing to their extremely high thrust,great efficiency and high degree of development, it is not surprising that American jet-transport manufacturers have spoken of the attraction ofan advanced civil Olympus. Orpheus. All records for rapidity of development have been brokenby this neat turbojet. The original B.E.26 design was begun as a private venture in 1953, yet the first prototype ran on December 17th, 1954, anda complete 150-hr type-test was successfully completed five months later. It is reported to be a very simple two-beanng engine with stress-bearing casings. The compressor has "button-on" stages and the com- bustion chamber is of radically new design enclosed in a wrapped andwelded Nimonic casing with the turbine stator formed from segments of blades welded to the rear of each flame-tube. As early as last September,the hot portions of the engine were lifed at 800 hr. The first type-test was at 3,285 lb (BOr.l), and, at this initial rating, the engine first flewin the prototype Gnat last July. Running time now exceeds 4,000 hr, and the engine has flown at more than Mach 1 and at above 50,000ft.Ratings published include BOr.2 (4,520 lb) and BOr.3 (4,850 lb). A recent report stated that thrusts in excess of 5,000 Ib had been recordedwith an "external fuel system" and that the engine was stall- and surge-free during accelerations from idling to maximum thrust in justunder four seconds. Even greater thrusts should be achieved with jet- pipe augmentation, either in the form of a large afterburner or by theuse of the B.S.R. arrangement mentioned in connection with the Olympus. The Orpheus has been chosen as a standard powerplant for NATO.It has been reported that the U.S. Government will pay 75 per cent of all development costs up to a total of £ 1.25m, America havingauthority to appoint licencees, but Bristol receiving a royalty on each engine licence-produced. The first Orpheus for the Fiat G-91 wasdelivered to Italy in January, and other aircraft scheduled to use the engine are the Breguet 1001 Taon, and the Dassault Mystere 26 (twin-Orpheus). It is possible that the Orpheus may be the first gas turbine to be produced in India, associated with the Gnat airframe. Therehave also been persistent reports of a Trainer Orpheus, in which reduced operating stresses are claimed to have permitted a weightsaving of over 7f> lb. Zeus. It has been unofficially reported that this is the name of anew Bristol turbojet of high thrust. Three published references speak of it as "a turbojet of 12,000 lb thrust," "reported to be of 19,000 lbthrust" and "starting near the 20,000-lb mark." No official references have been made to any engine with this name.B.E.2S. In the design of this turboprop, Bristol set out to equal, or better, the best reciprocating engines in all respects. At the con-ception of the engine in the winter of 1952-53, the underlying thoughts were also to achieve a cruising power of the order of 3,500 h.p. at30,000ft with the lowest possible specific weight, and to produce a turboprop capable of giving its full rated take-off power under all air-field conditions of altitude and temperature. The resulting engine is described in the accompanying data. Thedesign-points are exceptionally advanced, and the weight is scarcely greater than that of a Proteus. Incidentally, the low-pressure com-pressor is aerodynamically similar to that of the Orpheus, except for the employment of steel blades. Basic control is provided by twolevers, one of which is the fuel throttle controlling the speed of the h-p compressor assembly, and the other is connected to the c.s.u.and so governs the r.p.m. of the l-p (or supercharging) compressor and airscrew. The compressor work-split has been carefully chosen Bristol BE.25: complete powerplant mounted for testing.
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