Article On New Diesel Technology

[nimblemotors]

Originally Posted by Pete7

Thread drift but that sounds interesting, are you intending to use the jet drive too or via propellors? If your using the jet drives then is there the opportunity to pipe the jet up to the bow as a bow thruster? some interesting possibilities. Only downside is petrol vapour, but the jet sky manufactuferes must have solved the problem, unlike my little Suzuki trials bike which leaks fuel overnight without the fuel tap being turned off.

Pete

yeah, maybe should start another thread.. I won't use the jet drives, they are designed for high speed. I will need a gear reduction though to turn the props slow, these motors can run 7000rpm. I'm still thinking and planning the drivetrain. Why bowthrusters? I have a cat, it can maneuver quite well with two props.

I like diesel mostly because one can run biodiesel so if the modern world ends, there is the possibility of making fuel. However, I plan to depend on wind solar instead.

[mcarling]

Originally Posted by mcarling

The key to making a very small alternator at 5KW is to spin it very fast. That's one reason why I think microturbines are more promising for small light gensets than OPOC engines.

This 4.5" microturbine can produce 100 lbs of thrust, which means it can generate at least 100KW on a shaft. Getting 70KW of electricity out of this should be easy. Spinning above 50,000 rpm, the alternator would be small and light:

I found some more information about these Bladon microturbine generators which have been prototyped for Jaguar:
- 60cm (2 feet) overall length (including the generator)
- 36kg (80 lbs) total weight (including the generator)
- 80,000 rpm
- 70 kilowatt output
- burns diesel (and similar fuels)

[Cotemar]

The problem with micro turbines is:
1) They are like small blow torches, making incredible amounts of heat.
2) At 50,000 rpms the wining sounds they make are intense and you need hearing protection
3) They are made very accurate and therefore are expensive

[mcarling]

Originally Posted by Cotemar

The problem with micro turbines is:
1) They are like small blow torches, making incredible amounts of heat.

The heat produced per liter of fuel consumed must necessarily be the same -- except for the trivial effect of incomplete combustion. The apparent difference is due to the heat produced by a reciprocating engine being divided between the coolant and the exhaust, whereas in a turbine, all the heat exits through the exhaust.

Originally Posted by Cotemar

2) At 50,000 rpms the wining sounds they make are intense and you need hearing protection

Turbines are much quieter than reciprocating engines, at a given size. A diesel producing 70KW of DC would be a lot louder than this microturbine.

Originally Posted by Cotemar

3) They are made very accurate and therefore are expensive

Yes, microturbines are expensive, but that has more to do with low production volumes than with anything else. Hobbyists use microturbines in RC models, so the prices are not as high as some might think.

Turbines are also much simpler (the one shown has exactly one moving part), require little maintenance, last the full life of a sailboat (e.g. 20,000 hour lifetimes), and are much more reliable.

The disadvantages are that they are fuel efficient at only one fixed speed (not a big problem with electric propulsion), not very fuel efficient in very small sizes (the one shown consumes almost 50% more fuel per KWh than a reciprocating engine) and, as already discussed, are expensive.