Airliners.net

What is a air scroll on a APU,What does it do,And what is it used for?Thanks 



-BryanBecker 

Hi Bryan, Buzz here. It's one of those funny names for the inlet area of a centrifugal compressor. If you got close enough to kiss one (got to be a mechanic sometimes) you'll notice that it's kind of rolled up (like a scroll), sea-shell shaped so the air is inhaled , spun around by the impeller, and slung out to edges to the diffuser (another word with the same basic meaning). The diffuser uses Bernoulli's law in reverse: turns high velocity into pressure with a divergent (spread apart) area to slow down the air.
g'day