Suction flow enters the rotating element (impeller) axially, and is discharged radially at a higher velocity. The change in diameter through the impeller increases the gas velocity. This velocity (Dynamic Pressure) is then converted to (static pressure) throughdiffusion, which generally begins within the impeller and ends in aRadial diffuser and volute outboard of the impeller.
Suction gas generally passes through a set of adjustable inlet guide vanes or an external suction damper before entering the Impeller these devices are used for capacity control.
High-velocity gas discharging from the impeller enters the radial diffuser, which can be vaned or vaneless. Vaned diffusers are typically used in compressors designed to produce high pressure. These vanes are generally fixed but can be adjustable. Adjustable diffuser vanes can be used for capacity modulation either in lieu of or in conjunction with the inlet guide vanes.