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Bristol Siddeley Olympus Mk 301


At the end of World War II, the Bristol Engine Company’s major effort was the development of the Hercules and Centaurus radial piston engines. By the end of 1946, the company had only 10 hours of turbojet experience with a small experimental engine called the Phoebus which was the gas generator or core of the Proteus turboprop then in development. In early 1947, the parent Bristol Aeroplane Company submitted a proposal for a medium-range bomber to the same specification B.35/46 which led to the Avro Vulcan and Handley Page Victor. The Bristol design was the Type 172 and was to be powered by four or six Bristol engines of 9,000 lbf (40 kN) thrust.

The thrust required of the new engine, then designated B.E.10 (later Olympus), would initially be 9,000 lbf (40 kN) with growth potential to 12,000 lbf (53 kN). The pressure ratio would be an unheard of 9:1. To achieve this, the initial design used a low pressure (LP) axial compressor and a high pressure (HP) centrifugal compressor, each being driven by its own single-stage turbine. This two-spool design made the compression more manageable, enabled faster engine acceleration ("spool up"), and reduced surge. The design was progressively modified and the centrifugal HP compressor was replaced by an axial HP compressor. This reduced the diameter of the new engine to the design specification of 40 in (100 cm). The Bristol Type 172 was cancelled though development continued for the Avro Vulcan and other projects.

Gas-flow diagram of Olympus Mk 101.The first engine, its development designation being BOl.1 (Bristol Olympus 1), had six LP compressor stages and eight HP stages, each driven by a single-stage turbine. The combustion system was novel in that ten connected flame tubes were housed within a cannular system: a hybrid of separate flame cans and a true annular system. Separate combustion cans would have exceeded the diameter beyond the design limit and a true annular system was considered too advanced.

In 1950, Dr (later Sir) Stanley Hooker was appointed as Chief Engineer of Bristol Aero Engines.

The BOl.1 first ran in May 1950 and produced 9,140 lbf (40.7 kN) thrust. The next development was the BOl.1/2 which produced 9,500 lbf (42 kN) thrust in December 1950. Examples of the similar BOl.1/2A were constructed for US manufacturer Curtiss-Wright which had bought a licence for developing the engine as the TJ-32 or J67. The somewhat revised BOl.1/2B, ran in December 1951 producing 9,750 lbf (43.4 kN) thrust. The engine was by now ready for air testing and the first flight engines, designated Olympus Mk 99, were fitted into a Canberra WD952 which first flew with these engines derated to 8,000 lbf (36 kN) thrust in August 1952. In May 1953, this aircraft reached a world record altitude of 63,668 ft (19,406 m). (Fitted with more powerful Mk 102 engines, the Canberra increased the record to 65,876 ft (20,079 m) in August 1955.)

 

Brist-Olymp-02

 

The Olympus 551 'Zephyr' was a derated and lightened version of the BOl.6 and rated at 13,500 lbf (60 kN) thrust. The engine was the subject of a licence agreement between Bristol Aero Engines and the Curtiss-Wright Corporation - the engine being marketed in the USA as the Curtiss-Wright TJ-38 Zephyr. There were hopes to fit the Olympus 551 to the Avro Type 740 and Bristol Type 200 trijet airliners which did not progress beyond the project stage. Curtiss-Wright also failed to market the engine.

Bristol Aero Engines (formerly Bristol Engine Company) merged with Armstrong Siddeley Motors in 1959 to form Bristol Siddeley Engines Limited (BSEL) which in turn was taken over by Rolls-Royce in 1966.

The performance specification for TSR2 was issued in 1962. It was to be powered by two BSEL Olympus Mk 320 (BOl.22R) engines rated at 30,610 lbf (136.2 kN) with reheat at take-off. The engine was a cutting edge derivative of the Olympus Mk 301 with a Solar-type afterburner.[32] The engine first ran in March 1961 and was test flown in February 1962 underslung Vulcan B1 XA894 and was demonstrated at the Farnborough Air Show in September. In December 1962 during a full power ground run at Filton, the engine blew up after an LP turbine failure, completely destroying its host Vulcan in the subsequent fire.

On its first flight in September 1964 the engines of the TSR-2 were scarcely flightworthy being derated and cleared for one flight. Nevertheless, the risk was deemed acceptable in the political climate of the time. With new engines, the TSR-2 XR219 flew another 23 times before the project was cancelled in 1965.

Plans to civilianise the Olympus go back as far as 1953 with the unveiling of the Avro Atlantic airliner based upon the Vulcan. However, most of the civilian derivatives, except for supersonic airliners, were developed from the BOl.6.

One project that got beyond the drawing board was a supersonic development of the Gloster Javelin, the P370, powered by two BOl.6, 7, or 7SR engines. The design evolved into the P376 with two BOl.21R engines rated at 28,500 lbf (127 kN) with reheat. Eighteen aircraft were ordered in 1955. The project was abandoned the following year.

As early as 1952, Bristols had considered the use of reheat, or afterburning, to augment the thrust of the Olympus. Initially, a system called Bristol Simplifed Reheat was devised which was tested on a Rolls-Royce Derwent V mounted in an Avro Lincoln. Later it was tested on an Orenda engine in Canada and on an Olympus Mk 100 in the Avro Ashton test bed. Fully variable reheat became possible after an agreement with the Solar Aircraft Company of San Diego which manufactured bench units for the Olympus Mks 101 and 102.

As of 2012, the Olympus remains in service as both a marine and industrial gas turbine. It also powered a restored Avro Vulcan XH558.

Variants:

BOl.1/2A

BOl.1/2B

BOl.1/2C

BOl.2

BOl.3
Of all the early initial developments, BOl.2 to BOl.5 (the BOl.5 was never built), perhaps the most significant was the BOl.3. Even before the Vulcan first flew, the Olympus 3 was being suggested as the definitive powerplant for the aircraft. In the event, the 'original' Olympus was continuously developed for the Vulcan B1. The BOl.3 was described in 1957 as "a high-ended product intermediate between the Olympus 100 and 200 series."

BOl.4

BOl.5
not built

BOl.6
(Mk.200)

BOl.7
(Mk.201)

BOl.7SR

BOl.11
(Mk.102)

BOl.12
(Mk.104)

BOl.21
(Mk.301)

BOl.21R

BOl.22R
(Mk.320)

Olympus Mk 100
(BOl.1/2B) Similar to Olympus Mk 99 rated at 9,250 lbf (41.1 kN) thrust for second Vulcan prototype VX777. First flew September 1953.

Olympus Mk 101
(BOl.1/2C) Larger turbine, 11,000 lbf (49 kN) thrust for initial production Vulcan B1 aircraft. First flew (XA889) February 1955.

Olympus Mk 102
(BOl.11) Additional zero stage on LP compressor, 12,000 lbf (53 kN) thrust for later production Vulcan B1 aircraft.

Olympus Mk 104
(BOl.12) Designation for Olympus Mk 102 modified on overhaul with new turbine and burners, 13,000 lbf (58 kN) thrust initially, 13,500 lbf (60 kN) thrust on uprating, standard on Vulcan B1A.

'Olympus 106'
Used to describe the development engine for the Olympus 200 (BOl.6). Possibly a corruption of BOl.6 (Olympus 6).

The initial design of the second generation 'Olympus 6' began in 1952. This was a major redesign with five LP and seven HP compressor stages and a canullar combustor with eight interconected flame tubes. In spite of a much greater mass flow, the size and weight of the BOl.6 was little different to earlier models.

Rival manufacturers Rolls-Royce lobbied very hard to have its Conway engine installed in the Vulcan B2 to achieve commonality with the Victor B2. As a consequence, Bristols undertook to complete development using company funds and peg the price to that of its fully government-funded rival.

Olympus Mk 97
This early engine tested an early annular combustion chamber. It was test flown on Bristol's Avro Ashton test bed WB493.

Olympus Mk 200
(BOl.6) 16,000 lbf (71 kN) thrust. First B2 (XH533) only.

Olympus Mk 201
(BOl.7) Uprated Olympus Mk 200. 17,000 lbf (76 kN) thrust. Initial Vulcan B2 aircraft.

Olympus Mk 202
Disputed. Either Olympus Mk 201 modified with rapid air starter, or Olympus Mk 201 with redesigned oil separator breathing system. This was the definitive '200 series' engine fitted to Vulcans not fitted with the Mk 301. The restored Vulcan XH558 is fitted with Olympus Mk 202 engines.

'Olympus Mk 203'
Very occasional reference to this elusive mark of engine can be found in some official Air Publications relating to the Vulcan B2. It is also noted in a manufacturer's archived document dated circa 1960.

Olympus Mk 301
(BOl.21) Additional zero stage on LP compressor. 20,000 lbf (89 kN) thrust. Later Vulcan B2 aircraft plus nine earlier aircraft retrofitted. Later derated to 18,000 lbf (80 kN) thrust. Restored to original rating for Operation Black Buck.

Olympus 510 series
With a thrust in the region of 15,000 lbf (67 kN) to 19,000 lbf (85 kN), the 510 series were civilianised versions of the BOl.6. A team was sent to Boeing at Seattle to promote the engine in 1956 but without success.

Olympus 551

Specifications:

Olympus 101

Type: Axial flow two-spool turbojet
Length: 152.2 in (387 cm)
Diameter: 40 in (100 cm)
Dry weight: 3,615 lb (1,640 kg)
Compressor: Axial 6 LP pressure stages, 8 HP stages
Combustors: Cannular 10 flame tubes
Turbine: HP single stage, LP single stage
Fuel type: AVTUR or AVTAG
Maximum thrust: 11,000 lbf (49 kN)
Specific fuel consumption: .817
Power-to-weight ratio: 3.04:1

 

 


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