Quote:
Originally posted by fridgetech
To predict volumetric effeciency:
But compression is isentropic rather than adiabatic, as the prof explains in the fundamentals section, so residual gas in the clearance pocket doesn't necessarily add to isentropic losses, it mostly helps to drive the piston back and in so doing it helps the other pistons with their compression.
Isentropic efficiency is somewhat proportional to volumetric efficiency, especially where non unloading comps are concerned. It is proportional in the way that we could hold compressor efficiency losses fairly constant while effective displaced volume drops with increased clearance pocket and so the constant efficiency losses just become relatively large in comparison to a changing displaced volume.
I used to drill holes into over sized compressor pistons and/or valve plates to derate them by a calculated amount, obviously did this when they were over sized. Cheaper than EPR's where I came from :)
If I may restate your wonderful observation (and expect me to restate it wrong): A change in volumetric efficiency, is not so much a change in compressor efficiency, but definitely impacts the capacity of the compressor? In an almost linear fashion with a given compression ratio?