Rolls Royce Derwent-The Classic Turbo-Jet

Rolls-Royce Derwent MK8 Turbo-Jet Engine
This page is devoted to the Rolls-Royce Derwent turbo-jet engine. The Derwent is probably the classic gas turbine engine and was inspired by the Whittle W2B engine when Rolls-Royce took over the project in 1943. Sr Stanley Hocker designed the 5000LB thrust Nene engine using his knowledge of super-chargers. The Derwent engine is a scaled down version of the Nene producing 3500LBs of thrust, at the time of its inception there was no airframe available to take the larger Nene.

The Derwent was built in Derby and two were fitted to the Gloster Meteor aircraft. This engine was also used as a snow clearing device, effectively as a very big fan-heater. A contraption consisting of two Derwent engines was pushed backwards by a tractor to de-ice runways and blow away snow-quite a novel application for a jet engine.

The Derwent is a big docile easy to run engine with simple controls and electric start. The big centrifugal compressor ensures simple and predicable handling characteristics.

Movie Time May 2007! Derwent 1 Derwent 2 Derwent 3 Derwent 4 Derwent 5

The Derwent is a very simple gas turbine engine, it uses a single stage double sided centrifugal compressor. The compressor feeds nine individual combustion chambers through a diffuser ring (Static Vanes) and nine right angle elbows. The combustion chambers are through flow devices unlike the original Whittle engine which used reverse flow combustors. Early engines used special small burners called "Torch Igniters" to "Light up" two combustion chambers, the fire would then quickly spread to the other seven through interconnecting tubes. Later engines employed "High Energy" igniters which are used today on most engines. A single stage turbine wheel is used to drive the compressor. A feature of the Derwent engine is that it uses a small mini compressor wheel to supply air to the turbine disc and nozzle assembly for cooling.

The fuel system consists of a single pump feeding the nine combustion chambers. Early engines employed "Simplex" burners (Simple spray nozzles) and later engines where fitted with "Duplex" units which gave better slow running characteristics. The throttle consists of a simple needle valve, there is no temperature or acceleration limiting on this engine. The pilot when flying the Meteor had to obey quite strict procedures if the engine was not to "Flame out", surge or overheat.

The oil system consists of two scavenge pumps and a pressure pump to feed the engine's three bearings. A gearbox at the front of the engine drives the fuel and oil pumps and attached to it is a big oil tank.

I have been lucky enough to acquire one of these fine British engines which I rescued from a scrap yard. The engine was stored inside and displayed evidence of having been protected against corrosion, it was in quite good condition considering it's age. The Derwent engine consists of many black enamel painted parts and so looks rather nice when cleaned and polished
up. All the painted pumps and drives are grouped around the front where the engine doesn't get hot, even the inlets to the combustion chambers are painted.

The engine was purchased with the intention of running it so some basic instrumentation was added and the engine was wired up with some electrics.

I added a small instrument panel to the engine to display RPM and exhaust temperature, an oil pressure gauge was also fitted.
A pump, two booster coils and two solenoid valves for starting were all wired two a small control panel. Two aircraft starter relays were used to form a start panel for the engine. Initial rotation would be achieved with a resistance in series with the starter motor and then it would be switched out. Starting power was supplied either by batteries or by another running gas turbine driving a generator. Fuel to the engine was supplied under gravity feed from a 30 gallon truck fuel tank.


Engine shut down after brief light up test.

Engine Running (Zoom Lens)

Starting and running the Derwent was quite straight forward and very similar to other gas turbine engines. The starter switch
is pressed and the engine begins to wind up, the above mentioned start panel ensures the starter engages gently at first to
reduce mechanical shock. The torch igniter feed pump is activated, as is the booster coils and the torch solenoids are opened.
With the torch igniters operating the High Pressure Cock (On/Off valve) is opened and the engine should light up. Light up
is accompanied by combustion roar and the engine accelerates towards idle speed, the torch igniters can now be canceled.
At around two thirds idle speed the starter can be cut off. The Derwent engine by virtue of it's large centrifugal compressor
idles at just 3500 rpm, so this helps to make the operation of it a bit safer.

The Derwent produces very little thrust at low to medium rpm so our stationary example remained rooted to the spot at
all times. Our engine did not have the Meteor propelling nozzle fitted to the exhaust so the maximum thrust was reduced
and also the temperatures were kept down.


Hand Starting the Gas Turbine Generator (6012)

A Petter Handyman

The venue for our engine run was a field owned by stationary engine collector Derek Hardwick. Derek provided
a little light relief from wailing compressors with a beautiful "Petter Handyman" stationary oil engine circa 1905.
As little as fourty years could separate the Rolls from the Petter.

Since this page was created, I have run the Derwent again in 1999, it is hoped that one day I can build a road trailer for it so that it can be transported more easily.

 

Derwent MK8 Specification
Power Output....................................3500 Lbs Static Thrust
RPM.................................................14,700 rpm
Compressor.......................................Dual Sided Centrifugal Impeller with Radial Inducer Vanes
Combustion Chamber........................9 thru-flow can type combustion chambers, Duplex Burners
Compressor Turbine..........................1 Stage Axial
Layout...............................................Single Spool Turbo-Jet with accessory gearbox at front.
Starting..............................................Rotax Electric Starter
Ignition..............................................High Tension Torch Ignitors with electric feed pump.
Fuel System...................................... Piston Pump with Hydromechanical Governor, Barometric (Altitude) Control Unit
Oil System.........................................Return System with Pressure and Scavenge pumps, Intergral Oil Tank.
Oil Spec............................................OX38, Aeroshell 750
Accessories.......................................Cooling Fan Mounted on centre shaft, External Airframe Mounted A/Gearbox
Weight..............................................1300 Lbs
Applications......................................Gloster Meteor Aircraft, Runway De-icer

Click Here for Diagrams Derwent Cutaway + Derwent Exploded + Thermodynamic Diagram

 

Rolls Royce Derwent engine in 2007

Derwent Manual

Derwent Model -Amazing Scale Model of Derwent MK8!

Derwent Mpeg Movie This one is owned by Karl McManus from down under!

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