Buzz From United States of America, joined Nov 1999, 697 posts, RR: 24 Reply 1, posted (12 years 1 month 1 week 2 days 10 hours ago) and read 485 times:
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.