Posted for George Braly <gwbraly@gami.com>:
I believe it was the Navy, in the 1920s, that issued a famous statement:
  
"Cooling an aircraft engine with water makes about as much sense as cooling
a submarine with air."
  
That said,  I think there is a role for a clean sheet design of a liquid
cooled engine/airframe combination.
  
Regards,  George