Do you seriously believe that you can improve a well designed engine like the MW54 just by fitting a fan in front of it? You will most likely waste a bucketload of cash and end up with a ruined engine, if you need more thrust just get a bigger engine.... ;-)
Extending the shaft could cause shaft oscillations at higher rpm´s and probably bend it permanently.
//Anders
adding a stage to a model turbine
Moderator: Mike Everman
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Fricke
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Re: adding a stage to a model turbine
It won´t work unless You redesign the whole engine, ie. shaft and combustionchamber and the NGV and turbine wheel...superhornet59 wrote:so would it work? would it increase power?
All that work is not worth it. As there are bigger engines with more thrus in them.
Take a look at Skyfrogs site... that´s a really big micro turbine...
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jthompso
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re: adding a stage to a model turbine
I'd say that at best you're going to lose some power by adding this second stage to a small turbine like this--at worst it simply won't run. The problem lies in the interaction of an axial "fan" compressor and the centrifugal compressor that almost every small gas turbine employs today. The flow of air in an axial compressor wheel is concentrated most highly at the ends of the individual vanes, which is the exact opposite of what is needed for the intake of a centrifugal compressor. The centrifugal compressor wheel relies on air sliding the maximum length along it's vanes to impart the maximum amount of force to the air. By putting an axial compressor in front of a centrifugal compressor you do four things that may impact performance:
1. The center-mass of the axial compressor wheel blocks direct air passage into the center intake fins of the centrifugal compressor decreasing the length of travel of air in the vanes and thus decreasing the final air pressure.
2. The axial turbine delivers air directly to the outer portion of the centrifugal turbine, if the air pressure it too high (unlikely) then the air flowing down the vanes of the centrifugal compressor will hit a wall which will decrease it's compression.
3. If the axial wheel does not deliver as much air as the centrifugal wheel at a given rpm then air will simply flow past the vanes of the axial compressor at a speed high enough that the vanes will not catch and compress it.
4. The addition of a second stage increases the amount of inertia needed to spin the compressor/turbine assembly, this could cause starting problems. In addition, it will take longer for the engine to spool up, and if the moment of inertia is too high then when you increase throttle on the engine it will take so long to increase rpm of the shaft assembly that the engine will run rich and overheat the turbine.
All in all it's not the best idea, if you really wanted to pursue this I would suggest attempting to convert a "stock" production model turbine to a double stage axial compressor turbine. There would, no doubt, be lots of interest on this forum, and potential marketability for an aftermarket upgrade kit.
1. The center-mass of the axial compressor wheel blocks direct air passage into the center intake fins of the centrifugal compressor decreasing the length of travel of air in the vanes and thus decreasing the final air pressure.
2. The axial turbine delivers air directly to the outer portion of the centrifugal turbine, if the air pressure it too high (unlikely) then the air flowing down the vanes of the centrifugal compressor will hit a wall which will decrease it's compression.
3. If the axial wheel does not deliver as much air as the centrifugal wheel at a given rpm then air will simply flow past the vanes of the axial compressor at a speed high enough that the vanes will not catch and compress it.
4. The addition of a second stage increases the amount of inertia needed to spin the compressor/turbine assembly, this could cause starting problems. In addition, it will take longer for the engine to spool up, and if the moment of inertia is too high then when you increase throttle on the engine it will take so long to increase rpm of the shaft assembly that the engine will run rich and overheat the turbine.
All in all it's not the best idea, if you really wanted to pursue this I would suggest attempting to convert a "stock" production model turbine to a double stage axial compressor turbine. There would, no doubt, be lots of interest on this forum, and potential marketability for an aftermarket upgrade kit.