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Why are all APUs turbines?

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Old 27th July 2009 | 09:52
  #21 (permalink)  
 
Joined: Apr 2008
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From: London, UK
When I stick it in my '02 BMW I don't go above a 25% A1/ 75% diesel mix and it runs fine!
I'm sure you pay the excicse man the extra duty as well

Anyway, I was going to clairify my original statement by saying that you could add the extra lubricity enchancers which modern ULSD has, or you can modify the engine like the Thielert or Austro engines.
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Old 27th July 2009 | 12:39
  #22 (permalink)  
 
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From: USA
I didn't think modern diesels would run on Jet A1, as it doesn't meet the lubricity requirements of the higher pressure pumps?
They surely will run on Jet A1, lubricity isn't a problem. The beauty of diesel engines is that they are very tolerant of a wide range of fuel formulations.
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Old 27th July 2009 | 13:32
  #23 (permalink)  
 
Joined: Mar 2001
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From: I wouldn't know.
To modify a modern automobile diesel engine into an aviation one cost thielert (and austro engines) quite a high amount of money. I think the amount cited for thielert was a high dual figure amount of millions Euro. Most of that went into fixing the lubricity problem and aviation grade engine management.

Modern diesel engines reach pressures up to 29.000 psi in their injection systems and the pumps to reach that do react to changed lubricity of course.

Old-Fashioned low tech diesel engine as you might find still in high number in undeveloped areas of this earth were indeed very tolerant to a wide range of differing diesel fuels.
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Old 27th July 2009 | 14:36
  #24 (permalink)  
 
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From: London, UK
You beat me to it Denti, I was going to say that the problem is in the pumps/injectors.

The engine itself can indeed run on pretty much anything. I believe there have been some tests in the past running diesel engines on coal dust!!

Now that it has come up, how did Thielert solve the lubricity problem?
Did they go for one of the new ultra-low friction coatings, or did they go for a multi-stage pump with lower differential pressure to allow for looser tolerances?
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