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Old Oct 01, 2009, 06:22 PM
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Inside a turbine

I have a question about the mini jet engines that are used for RC jets. Do they really have thousands of little turbine blades like a real jet engine or have they been simplified? I have never seen inside a model jet engine before so I do not know. I am more familiar with the internal workings of a full size jet engine.
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Old Oct 01, 2009, 06:29 PM
The reviewer
XJet's Avatar
Tokoroa
Joined Mar 2004
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Model turbines are far simpler than the kind of engine yu'd find in a fighter-jet or airliner.

Instead of having many stages of axial-flow compressor blades, the model engines have a single centrifugal compressor stage (just like a car turbocharger).

This makes for a much simpler, lighter and cheaper engine than would be the case if a mult-stage axial-flow compressor system was used.

Likewise there's only a single turbine wheel (except in the case of turboprop engines).
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Old Oct 01, 2009, 08:55 PM
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Cool! So basically they are kind of like a turbocharger jet engine? I have some plans for a turbocharger jet engine and it sounds like these are basically the same thing but scalled down and they look better.
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Old Oct 01, 2009, 09:53 PM
The wheels touch down FIRST??
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Australia, VIC, Melbourne
Joined Jun 2009
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Yah... but your average everyday basic 'turbocharger' jet engine is usually a 'radial' jet rather than an 'axial' jet - i.e. the first turbocharger fires air into a remotely mounted combustion chamber, where the fuel is injected and ignited, and the exhaust drives the second turbocharger whose shaft is connected to the first turbocharger - the more exhaust you feed into the second turbocharger the faster it spins, and because it's hooked up to the first turbocharger on a common shaft, the faster the first turbocharger spins and so provides more air to burn more fuel to feed the the second turbocharger more gas to make it go faster still, and the cycle repeats.

The main difference here between a radial jet engine and an axial jet engine is that in the radial design, the comubstion chamber is not directly part of and in the air-fuel-exhaust train. The air flow to the combustion chamber and gas flow from it are not along the same axis (hence 'axial' jet when they are).

The mini Turbines still work on along the same principals as their bigger military and commercial jet cousins in that they have a compressor wheel up the front, a burner can along the same axis, and a turbine wheel and the other end of the common shaft.

The compressor stage, as was stated in an earlier post, is a lot more simpler than in the big jet engines. There's no multiple stages separated by stators, multiple burner cans, or multiple turbine wheels up the other end. Or any fancy diminishing diameters to compress the inlet airflow. I don't think you've ever be able to get a single stage mini turbine to go supersonic, for example, as you just can't get the gases to flow fast enough with such a simple design. Having said that, they still provide a fair amount of poke!

Here's a pic of the compressor/shaft/turbine assembly. Wrap a casing around the outside and place a burner can beween the compressor and turbine, inject the fuel into the burner, and you've more or less got your 'mini turibine'
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Last edited by BJ64; Oct 01, 2009 at 10:01 PM.
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