Power Jets WU

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WU
Type Turbojet
Manufacturer Power Jets
First run 12 April 1937
Major applications none
Number built 3
Developed from concept patented by Whittle in 1930
Developed into Power Jets W.1

The Power Jets WU (i.e. Whittle Unit) was actually a series of three very different experimental jet engines produced and tested by Frank Whittle and his small team in the late 30's.

Design and development[edit]

WU First Model was the very first jet engine to be built and run in the UK and possibly the world. Purely an experimental engine, the WU was not intended for flight so little attempt was made to save on weight. The straight through engine had four basic components: a single stage, double-sided, centrifugal compressor, a combustor with a single straight through chamber, a single stage, axial flow turbine and a convergent propelling nozzle attached to a jet pipe. The shaft connecting the turbine to the compressor was made as short as possible to avoid whirling. The combustion chamber was connected to the compressor outlet by a very large single spiral duct. Consequently, the engine had a very asymmetric appearance. Whittle designed the centrifugal compressor to develop about 4:1 pressure ratio, when as far as he was aware, the best previously demonstrated performance of such a unit was about 2.5:1. He specified a double sided impeller, not only to minimise the engine diameter, but also to increase the shaft speed. This reduced the loading on the single stage turbine, thereby improving its efficiency. The turbine, of 16.5 in (419 mm) outside diameter, was designed to develop 3,000 horsepower (2,237 kW), all absorbed by the compressor.

Testing continued with the W.U. Edition 1. The 31st and final run was on 24 August 1937. The B.T.-H. Chief Engineer placed a maximum speed of 12,000 r.p.m. on testing at the Rugby factory for safety reasons after a run on 23 August at up to 13,600 r.p.m..[1] Testing was to recommence with the same, but greatly modified unit (W.U. Edition 2) at the premises of the B.T.-H.'s redundant Ladywood foundry at nearby Lutterworth in Leicestershire in March, 1938 until this the turbine of this unit was damaged on 6 May 1938.

A significantly different symmetric trombone-style design was adopted for the second model. Ten spiral ducts connecting the compressor outlet to a large reverse-flow combustor, the outlet of which discharged forward through the turbine before turning rearwards to exhaust through multiple jet pipes.

Significant changes were also introduced in the third model, which featured multiple reverse-flow combustors and had a similar configuration to that of the later Power Jets W.1 and Power Jets W.2 turbojet engines. This configuration was also adopted for the Rolls-Royce Welland and General Electric J31 jet engines. One advantage of the multiple combustors was that a single unit could easily be tested in isolation.

Owing to a shortage of funds, many of the components would have been recycled through the later models.

Whittle and his team experienced many problems developing these units, including poor compressor performance, combustion instability and turbine blade failures. The team did, however, demonstrate that the turbojet had the potential to compete with the large reciprocating aero-engines then being mass-produced for the UK Re-armament Programme.

Variants[edit]

WU First Model Experimental Engine
Initial straight through design with asymmetric spiral duct connecting compressor outlet to annular combustor. First run 12 April 1937
WU Second Model Experimental Engine
Trombone-style configuration with single reverse-flow combustor. First run 16 April 1938
WU Third Model Experimental Engine
Trombone-style configuration with multiple reverse-flow combustors. First run 26 October 1938

Applications[edit]

None.

Specifications (WU First Model Design Assumptions, performance not actually achieved)[edit]

General characteristics

  • Type: Centrifugal flow turbojet
  • Length: ~67.2 in (~1707 mm) excluding jet pipe
  • Diameter: ~45 in (~1143 mm) across compressor
  • Dry weight:

Components

  • Compressor: Single stage double sided centrifugal flow, with no diffuser vanes
  • Combustors: single straight through design, located immediately downstream of elbow in spiral pipe
  • Turbine: Single stage axial flow, with no nozzle guide vanes
  • Fuel type: Kerosene

Performance

See also[edit]

References[edit]

  1. ^ The National Archive, AIR62/15

Notes[edit]

Bibliography[edit]

External links[edit]