Page 94 - Compression Machinery for Oil and Gas

Centrifugal Compressors Chapter 3 83

P
exit

C
exit
P
cavity front
P
cavity rear

P
inlet C inlet

FIG. 3.47 Forces on the impeller.

F
Impeller

P P
discharge suction

FIG. 3.48 Balance piston.

A simple approach would assume constant swirl coefficients for front and
rear cavities. This approach is frequently used in the industry, but high-pressure
compressors require more accurate estimates. Correlations and CFD analysis
(Fig. 3.49) are typically used for these, along with subscale test measurements
for validation.