Complex compression trains may be supplied in series and parallel arrangements to achieve the total flow and head requirements of a specific application. The most fundamental configuration of a centrifugal compressor is the straight-through design.
This layout is composed of one or more impellers, aligned in the same direction, contained within a single casing fitted with a single inlet nozzle and a single discharge nozzle to accommodate the gas flow. The number of stages contained within the section is a function of the produced head requirements. However, there are practical limitations to the number of stages that can be included.
One of these limitations is connected with the resulting discharge temperature which is a function of the overall pressure ratio, compression efficiency, and thermophysical properties of the gas. This temperature limitation may be due to material temperature limits of components within the compressor, or gas temperature limits imposed by other equipment or the process in which the compressor is operating.
An important limitation in the number of stages allowed in a single, straight-through configuration is associated with lateral rotordynamic considerations. Current beam-style designs restrict the number of stages in a single casing to 10 or less. However, this may also be impacted by the magnitude of the flow coefficients of the individual stages.
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