Plessey Dynamics “Solent” Gas Turbine Starter

The Solent engine, cleaned and repainted. Exhaust left, ignition coil top right, acceleration control unit lower center.

Oh, no! Seems like this turbine wheel has seen better times. Notice the crimped cupwasher to secure the turbine nut.

Gas generator NGV. The 1 o’clock position vane is burned through completely. Bearing retaining part sitting in front.

Gas generator rotating assembly. Must have been a nimonic-rat nibbling on the blades.

Compressor side of rotor. Some evidence of rubbing can be seen on the vanes. After balancing it might be still usable.

Some wheels, the main shaft and the failed bearings in front.

This is my most powerful engine (well, at least at the time of this writing), capable of supplying about 70hp at a weight of 35kg.

It is a Solent Gas Turbine Starter, built in UK by Plessey Dynamics.

I haven’t run the engine yet, for I will first need to build a test fixture to mount the engine and dissipate the power it generates. If the engine is started without a proper load, the free power turbine will probably explode.

And now the story of this engine:

After getting infected with the “Turbine Virus”, I figured out how to get hold of a “real thing”. At this time I also planned to use the engine as the powerplant for an ultralight aircraft, but by now I think a little different about this...

At James Engineering Ltd, UK, David James offered me a Solent  at a very competetive price. He pointed out though, that the rotor of the gas generator was stuck, but blamed this to the debris that had settled down in the compressor intake during storage.

So I agreed, and arranged shipping, which was quite difficult at reasonable cost.

Finally the engine arrived, and after having modified some tools to separate the power-turbine and gearbox from the gas generator assembly, the view I had to encounter was rather disappointing. The turbine wheel had thrown all of its blade tips. Further disassembly of the engine revealed even more severe damage.

Both main bearings were destroyed, the rear one ran about 2 mm off of center, causing the main shaft to wobble badly. The compressor rubbed slightly on the intake, the rear bearing retainer was broken, and two of the NGV blades were burnt. The failure sequence must have been somewhat like this:
First, the main shaft rear bearing must have degraded, resulting in increasing friction. The governor increased fuel pressure to maintain rpm, resulting in increased EGT. This must have worked a while, until the bearing was damaged so badly that the blades of the turbine disk touched the shroud. This caused a further increase of friction, and still the governor supplied more fuel to the injectors, so that the combustion flames leaped down to the NGV and the turbine wheel, causing the metal to soften and break.

Though David James stated prior to purchase of the engine that he cannot grant any warranty, he supplied another Solent engine to me for free, which was otherwise in quite bad shape, but revealed still very nice looking gas generator components. Thanks, David!

So next was disassembly of both engines, a lot of cleaning, some repainting, and reassembly of one engine out of the best condition parts of both.

I already tested all the electric components of the engine and I can tell, this little thing is hot. Just motoring on starter produces almost as much noise as my turbocharger engine at idle. I believe running this beast must be a real blast!

The gas generator assembly of the second Solent, power turbine wheel and NGV in front, and the rotor of a Garrett turbocharger (60mm wheel diameter, just to scale). In the background half of my fine new inkjet printer ;-)

This turbine wheel looks much better. The eight metal plates cover the fuel injector nozzles in the burner ring.

Gas generator section with the burner ring removed. On the lower right, partly covered with tape, the starter motor (24V, 400A, oh yeah). On the left the fuel pump with governor, orifices covered. The gas generator is governed at approx. 60000rpm. The eight fuel injector nozzles are set to open at different fuel pressures, the two adjacent to the spark plugs first, then in sequence. This ensures smooth ignition.

The engine core, the combustion chamber with the big dilution air holes of the secondary zone. The primary air holes (rear row) are tweaked as to induce swirl into the atomized fuel jets.

The engine core, gas generator turbine wheel in front. The NGV is mounted in place. The fuel injector nozzles stick through the big holes in the rear of the combustion chamber (reverse flow design). The whole combustion chamber is welded out of large pipe segments and formed sheet metal. The material is probably nimonic 90 or 105, which is really nasty to work with. Almost all of the tool materials used for cutting will weaken with the developing heat faster than the nimonic part. I have tried turning a turbine wheel to shape, and it wrecked a widia steel almost without cutting at all. So I’ll have to look out for someone with a grinding machine.

The free power turbine wheel and the rotating components of the two stage epicyclic reduction gear. The output shaft is connected via a sprag clutch to allow the main engine to run freely without having to turn the power turbine.

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