This paper documents the design, manufacture and successful operation of a very small turbojet engine for particular use in radio controlled model jet aircraft and other small and unmanned drones.
This work commenced 6 years ago and basically this engine evolved around one off-the-shelf item: a radial low pressure compressor-turbine rotor from a modern automobile turbocharger system. All other major components such as the single stage compressor diffuser, reverse flow combustor, turbine first stage nozzles and inlet and exhaust ducts are newly manufactured items.
With an overall length of 310 mm, a diameter of 110 mm and a weight of 2.2 kg, this engine formed a great challenge upon both authors with respect to the development of each component. It was both a mixture of art and science. The three challenges were:
a. The reverse flow combustor with a length of 110 mm.
b. The rotor bearing module and vibration damping (balancing).
c. The single stage compressor diffuser.
The design point performance data at ISO conditions is:
Gross Thrust: 40 Newtons
Specific Fuel Consumption: 0.225 kg/N.h
Compressor Air Flow: 0.150 kg/s
Compressor Pressure Ratio: 1.90
Turbine Inlet Temperature: 680 °C
Rotational Speed: 100000 rpm
Turbine Fuel: JP3/JP4 kerosene+gas fuel
Maximum Sound Pressure Level: 90 dBA at 1 mtr
This paper will discuss the manufacturing and design techniques used and the performance and handling characteristics of the engine.