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Rolls-Royce Engines: Derwent

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1946.
1947.

Note: This is a sub-section of Rolls-Royce

The Derwent was a 1940s British centrifugal compressor turbojet engine, the second Rolls-Royce jet engine to enter production.

Essentially an improved version of the Rolls-Royce Welland, itself a renamed version of Frank Whittle's Power Jets W.2B, Rolls inherited the design from Rover when they took over their jet engine development in 1943. The performance over the original design was somewhat improved, reliability dramatically, making the Derwent the chosen engine for the Gloster Meteor and many other post-World War II British jet designs.

When Rover was selected for production of Whittle's designs in 1941 they set up their main jet factory at Barnoldswick, staffed primarily by various Power Jets personnel. Rover felt their own engineers were better at everything, and also set up a parallel effort at Waterloo Mill, Clitheroe. Here Adrian Lombard attempted to develop the W.2 into a production quality design, angering Whittle who was left out of the team.

After a short period Lombard decided to dispense with Whittle's 'reverse flow' design, and instead lay out the engine in a 'straight-through' flow with the hot gas exiting directly onto the turbine instead of being piped forward as in Whittle's version. He may have been inspired by Frank Halford's layout of the Halford H.1 which was being built at about the same time. This layout made the engine somewhat longer and required a redesign of the nacelles on the Meteor, but also made the gas flow simpler and thereby improved reliability. While work at Barnoldswick continued on what was now known as the W.2B/23, Lombard's new design became the W.2B/26.

By 1941 it was obvious to all that the arrangement was not working; Whittle was constantly frustrated by Rover's inability to deliver production-quality parts for a test engine, and became increasingly vocal about his complaints. Likewise Rover was losing interest in the project after the delays and constant harassment from Power Jets.

Earlier, in 1940, Stanley Hooker of Rolls-Royce had met with Whittle, and later introduced him to Rolls' CEO, Ernest Hives. Rolls had a fully developed supercharger division, directed by Hooker, which was naturally suited to jet engine work. Hives agreed to supply key parts to help the project along.

Spencer Wilks of Rover met with Hives and Hooker, and decided to trade the jet factory at Barnoldswick for Rolls' Meteor tank engine factory in Nottingham. A handshake sealed the deal, turning Rolls-Royce into the powerhouse it remains to this day. Subsequent Rolls-Royce jet engines would be designated in an "RB" series, standing for Rolls Barnoldswick, the /26 Derwent becoming the RB.26.

Problems were soon ironed out, and the original /23 design was ready for flight by late 1943. This gave the team some breathing room, so they redesigned the /26's inlets for increased air flow, and thus thrust. Adding improved fuel and oil systems, the newly-named Derwent Mk.I entered production with 2,000 lbf (8.9 kN) of thrust.

Mk.II, III and IV's followed, peaking at 2,400 lbf (10.7 kN) of thrust. The Derwent was the primary engine of all the early Meteors with the exception of the small number of Welland-equipped models which were quickly removed from service. The Mk.II was also modified with an extra turbine stage driving a gearbox and, eventually, a five-bladed propeller, forming the first production turboprop engine, the Trent (RB.50).

The basic Derwent design was also used to produce a larger 5,000 lbf (22.2 kN) thrust engine known as the Rolls-Royce Nene. Development of the Nene continued in a scaled-down version specifically for use on the Meteor, and to avoid the stigma of the earlier design, this was named the Derwent Mk.V.

Several Derwents and Nenes were sold to the Soviet Union by the then Labour government, causing a major political row, as it was the most powerful production-turbojet in the world at the time. The Soviets promptly reverse engineered the Derwent V and produced their own unlicensed version, the Klimov RD-500. The Mk.V was also going to be used on the Canadian Avro Jetliner, but this was never put into production.

On 7 November 1945, a Meteor powered by the Derwent V set a world air speed record of 606 mph (975 km/h) TAS.

Variants

  • Derwent I - first production version, 2,000 lbf (8.9 kN) of thrust
  • Derwent II - thrust increased to 2,200 lbf (9.8 kN)
  • Derwent III - experimental variant providing vacuum for wing boundary layer control
  • Derwent IV - thrust increased to 2,400 lbf (10.7 kN)
  • Derwent V - scaled-down version of the Rolls-Royce Nene developing 3,500 lbf (15.6 kN) of thrust

General characteristics (Derwent I)

  • Type: Turbojet
  • Length: 84 in (2,135 mm)
  • Diameter: 41.5 in (1,055 mm)
  • Dry weight: 975 lb (443 kg)

Components

  • Compressor: Single-stage dual-entry centrifugal compressor with two-sided impeller
  • Combustors: 10 flow combustors with igniter plugs in chambers 3 and 10
  • Turbine: Single-stage axial flow with 54 blades
  • Fuel type: Aviation kerosene with 1% lubricating oil
  • Oil system: 2.75 gal (12.5 L) capacity, circulation rate 215 gal/hr (976 L/hr), maximum inverted flying time 15 s

Performance

  • Thrust: 120 lbf (0.5 kN) at 6,000 rpm at idle. 2,000 lbf (8.9 kN) at 16,500 rpm for takeoff. 1,550 lbf (6.9 kN) at 15,000 rpm for cruise
  • Overall pressure ratio: 3.9:1
  • Fuel consumption: 470 lb/hr (215 kg/hr) at idle. 1,820 lb/hr (830 kg/hr) at cruise power.

2,360 lb/hr (1,070 kg/hr) at maximum power

  • Oil consumption: 0.125 gal/hr (0.57 L/hr)
  • Thrust-to-weight ratio: 2.1:1 (20.1 N/kg)


See Also

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