When I first started doing research on model jet engines several years ago, I was at first amazed a jet turbine engine could be made so small and even though they were several thousand dollars, I actually thought they would have cost much more.
Model jet engines are actually very simple in design, after all they really only have one moving part… the main rotating shaft that is attached to the compressor blades at the front of the engine and the turbine blades at the back end.
The most complicated part of the engine is actually the combustion chamber where the fuel is vaporized and evenly distributed to ensure proper and complete combustion. The materials of course are very important and have to be of the highest quality to be able to withstand the high temperatures and the extremely high centrifugal forces produced.
After all, the compressor and turbine blades are spinning upwards of 200,000 RPM. I still can’t get my head around this number - that’s over 3000 rotations per second! Even at idle, these little engines are spinning at around 50,000 RPM (almost 1000 revolutions per second).
As you can imagine, machining tolerances are absolutely critical as is balancing. If you end up getting a model jet engine, there is little doubt it will probably be the most precise and balanced piece of equipment that you own. It is the high quality materials and precision you are paying for.
Here's a video that shows the components and manufacturing process of a typical model jet engine.
Of course the other component that has made small turbine engines a reality and easy to operate is the
(Full Authority Digital Engine Control computer)also called the engine control unit or ECU for short.
The fuel used in these little jet engines is the same as the big ones – kerosene or Jet-A fuel. You must also add a little bit of jet oil such as Mobil Jet Oil II, to your kerosene/Jet-A. Typical mix ratios range from as low as 40:1 (about 2.5% oil) up to as much as 20:1 (about 5% oil) depending on the engine manufacturer. Kerosene can be purchased anywhere; you can purchase the jet oil from any aviation facility that services turbine engines/turbine aircraft and Jet-A fuel from most airports or heliports.
Heliports seem to be more accommodating for this Jet-A fuel service since they are used to refueling in smaller amounts and have the proper equipment for it. I just take a couple 20L Jerrycans and large funnel to our local heliport and they have no problems with pumping out small quantities like that. Not to mention it's a great excuse to see the big birds and talk helis with the the chief operations pilot. The guys/gals there (pilots, technicians, and even the office staff) are also usually rather interested in seeing the model jet engine and heli/airplane - they get a kick out of it all... It doesn't hurt to take your model the first time you befriend your local heliport or airport to explain exactly why you want a smaller quantity of Jet-A (they will ask and want to know what it's being used for). Chances are they will be very interested in the model and want to know more about the hobby in general. It's a great opportunity to meet some like minded individuals and promote our hobby in a fun and positive way.