How is the discharge volume of a centrifugal compressor calculated?
Thread Content
For reciprocating compressors, the displacement is calculated as volume = pi multiplied by the square of the cylinder radius, multiplied by the piston stroke, multiplied by the rotational speed; for double-acting compressors, this value must be multiplied by 2. The actual value needs to have the clearance factor taken out of it. So, what determines the discharge volume of a centrifugal compressor?
According to my understanding, the displacement of reciprocating compressors and the displacement of centrifugal compressors (as indicated on the nameplate) are both actual flow rates under the conditions of the intake state – that is, at the pressure and temperature levels specified for the intake port – converted to flow rates under standard conditions, expressed in Nm3/min. Generally, the unit “N” is omitted. For positive-displacement reciprocating compressors (with constant volume and variable pressure), their displacement is 8.5 m3/min; this displacement remains unchanged whether under standard conditions or under the actual operating conditions at the intake stage. Note that one unit is Nm3 while the other is m3. In contrast, for centrifugal, velocity-type compressors (with variable volume and constant pressure), the displacement is a value converted from the actual intake conditions to standard conditions, and its volumetric flow rate changes depending on the conditions of the incoming air. . . .