CONVERTING AN EX-TORNADO GAS TURBINE INTO A HOVERCRAFT ENGINE
Traditionally, two-stroke engines provided high power-to-weight power plants for portable applications and lightweight vehicles, such as hovercraft. However, increasingly stringent exhaust emission regulations are forcing these out of production.
In recent years, components from Tornado fighter aircraft, such as their T312 Auxiliary Power Units are turning up on the used equipment market at very reasonable prices.
The T312 APU, manufactured jointly by Rolls Royce and BMW, has a very high Power-to-Weight ratio. It weighs only 40Kg, but it can produce over 140 BHP. Another unexpected benefit is that the compressor stage is fitted with an air vent that can produce a high volume of compressed air. This can be used to drive ancillaries.
One disadvantage is that the output is at a fixed speed of 8,000 – 8,560RPM, meaning that the APU has to be used with a variable pitch fan or continuously variable transmission. A technique has been found to slow the turbine down, but the efficiency drops and the exhaust temperature rises. This would worsen its fuel consumption and possibly reduce the turbine’s service life.
Other disadvantages are that the APU is flange mounted, at the drive end with a non-standard mounting and it has a splined socket instead of an output shaft.
We have therefore designed and machined a special adapter shaft that is splined at one end and tapered at the other. The taper is designed to take a timing pulley to drive a belt to the hovercraft fan.
We have completed the design of the bearing housing to support the shaft and we are currently designing the support frame. This will allow the turbine to be foot mounted in the hovercraft.
Apart from powering a hovercraft, you can use an APU in other applications including:
- Field water pump
- Portable electrical generator
- Combined heat and power unit
- Propelling a Light Aircraft or small Airship