Bristol Siddeley Orpheus
| Orpheus | |
|---|---|
_used_in_FIAT_G91,_at_Flugausstellung_Hermeskeil,_pic1.JPG) |
|
| Orpheus on display at the Flugausstellung Hermeskeil | |
| Type | Turbojet |
| National origin | United Kingdom |
| Manufacturer | Bristol Siddeley |
| First run | 1957 |
| Major applications |
Fiat G.91 Folland Gnat Fuji T-1 HAL HF-24 Marut |
| Developed into | Rolls-Royce Pegasus |
The Bristol Siddeley Orpheus was a single-spool turbojet developed by Bristol Siddeley for various light fighter/trainer applications such as the Folland Gnat and the Fiat G.91. Later, the Orpheus formed the core of the first Bristol Pegasus vectored thrust turbofan used in the Harrier Jump Jet family.
The engine had its genesis in a 1952 request by Teddy Petter of Folland for an engine in the 5,000 pounds (22 kN) class to power a new trainer and lightweight fighter-bomber they were developing.Stanley Hooker, relatively new to the company after an earlier career at Rolls-Royce, took the project under his wing. He delivered a relatively simple and easy to maintain engine, which was put into use in the Folland Gnat, flying in 1955.
The Orpheus incorporated a number of novel developments to give this thrust of 5,000 lbf from a lightweight engine of 800 lb. The first of these innovations was the central spindle. Rather than linking the turbine and compressor with a narrow shaft supported by multiple bearings, the Orpheus used a large diameter thin-walled tube, more than 8 inches in diameter. This was so stiff in resisting any whirling vibration that it could be supported by only two bearings, rather than the usual three. Two bearings gave a further advantage: previous engines had also needed a coupling in the shaft to allow for any misalignment between the static parts of the three bearings. With two bearings, the shaft simply followed the straight line between them. This allowed the removal of a bearing, a coupling, the engine's support structure for that bearing together with its lubrication system and cooling air supply.
A cannular combustor was used with seven flame tubes. This was a recent development in jet engines and the Orpheus also included the innovation of incorporating the turbine entry duct and its stator vanes into the flame tube outlet, each flame tube providing one seventh of the overall duct. This had two advantages, it simplified the manufacture of a complicated and unreliable component, also the segmented design allowed easier allowance for thermal expansion.
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