Positive displacement multistage compressors

This is not the complete view of these two compressor classes. Figure 3-70 gives the general performance curves for various positive displacement and dynamic compressors. The positive displacement compressors, particularly the multistage... 

The general multistage compressor model may have several functions polytropic and isentropic compressor, positive displacement compressor, inter-cooler between stages, isentropic turbine. Single phase, as well as two- or three-phase calculations, is possible. 

Reciprocating compressors which are of the positive displacement type using pistons are available for higher pressures. Multistage machines are also available for pressures up to lOOOOkPa or more. 

Compressors and pumps share a common set of operating principles. The dynamic and positive displacement families share common categories. Therefore, the symbols for compressors may closely resemble those for pumps. In most cases, the symbol Is slightly larger In the compressor symbol file. For a multistage, centrifugal compressor, the symbol clearly describes how the gas is... 

Compressors fall into one of two fundamental types - positive displacement and turbo-machines. Positive displacement machines can be either rotary or reciprocating. They both trap the gas in a cylinder and then force it into a smaller volume and so increase its pressure. Turbo-machines impart velocity to the gas and its momentum carries it into a narrowing space and so its pressure increases. Turbo-machines can be either axial (in which the flow is parallel to the shaft) or centrifugal (in which the flow is at right angles to the shaft). Multistage turbo-machines, with intercoohng, are common. 

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