During World War 2, the Bristol Aero Engine part of the Bristol Aeroplane Company was pre-occupied with developing and manufacturing radial

piston engines A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...

, such as the

Bristol Hercules The Bristol Hercules is a 14-cylinder two-row radial aircraft engine designed by Sir Roy Fedden and produced by the Bristol Engine Company starting in 1939. It was the most numerous of their single sleeve valve ( Burt-McCollum, or Argyll, typ ...

and the more powerful

Bristol Centaurus The Centaurus was the final development of the Bristol Engine Company's series of sleeve valve radial aircraft engines. The Centaurus is an 18-cylinder, two-row design that eventually delivered over . The engine was introduced into service lat ...

. However, in 1944 the Company decided to form a Project Department to investigate the design of gas turbines. Initially the department was based at Tockington Manor, a large

country house An English country house is a large house or mansion in the English countryside. Such houses were often owned by individuals who also owned a town house. This allowed them to spend time in the country and in the city—hence, for these peopl ...

close to the main factory at Patchway, Bristol. A predominantly young team was formed and was initially tasked with studying turboprop engines. The Ministry of Supply asked BAE for design studies for a 1000 hp turboprop engine. An early decision taken was to go for a centrifugal compressor configuration, because the engine would be so small that an axial unit would be challenging. Sufficient overall pressure ratio was obtained by mounting two centrifugal compressors in series on the HP shaft. These were driven by a single stage turbine. Another important decision taken was to opt for a free power turbine. This delivered power to the forward mounted propeller reduction gearbox. The two centrifugal compressors were mounted back-to-back, the outlet of the first unit being connected to the inlet of the second by four curved pipes. Four highly skewed combustion chambers were located between these pipes and discharged combustion gases into the turbine system located aft. The exhaust pipe was angled downwards. This reference shows an external view of the engine. At some point the design became known as the Bristol Janus. BAE considered it to be a very compact and light engine Later the

Ministry of Supply The Ministry of Supply (MoS) was a department of the UK government formed in 1939 to co-ordinate the supply of equipment to all three British armed forces, headed by the Minister of Supply. A separate ministry, however, was responsible for aircr ...

asked for the design to be scaled down to an output of 500 hp, to avoid conflict with the projects of other

manufacturers Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a range ...

. In the event, the Bristol Janus was never manufactured. However, the Project Department went on to design the

Bristol Theseus The Theseus was the Bristol Aeroplane Company's first attempt at a gas-turbine engine design. A turboprop delivering just over 2,000 hp (1,500 kW) was chosen rather than compete with companies that were already developing turbojets. ...

, which became the first Bristol gas turbine to be actually manufactured and developed. It passed a Type Test and was also flight tested.

Applications

Some version of the Bristol Janus was offered as the powerplant for the twin engined

Bristol Type 173 The Bristol Type 173 was a British twin-engine, tandem rotor transport helicopter built by the Bristol Aeroplane Company.Jackson 1973, pp. 260–263 It was designed by Raoul Hafner as a civil transport helicopter but evoked interest from the ...

,"discussion on Bristol Janus"
/ref> but the prototypes of this helicopter were eventually powered by 550 hp Alvis Leonides 73 air-cooled 9-cylinder radial engines.

Applications

Variants

Specifications (Janus 1)

See also

References

Notes

Bibliography