Page 109 - Air and gas Drilling Field Guide 3rd Edition

100 CHAPTER 5 Compressors and Nitrogen Generators

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Axial-flow compressors have a volumetric flow rate range of approximately 10 to
6
5
10 actual cfm (4.7 to 4.7 10 actual liters/sec). Their compression ratios are
typically around 10 to 20. Because of their small diameter, these machines are
the principal compressor design for jet engine applications. There are also appli-
cations for axial-flow compressors in large process plant operations where very
large constant volumetric flow rates at low compression ratios are needed.
More detail regarding axial-flow compressors can be found elsewhere [2, 7–9].

5.4 INTERMITTENT (POSITIVE DISPLACEMENT)
COMPRESSORS
In general, only the reciprocating compressor allows for rather complete reliable
flexibility in applications requiring variable volumetric flow rates and variable
pressure ratios. The rotary compressor (which has a fixed pressure ratio built into
the compressor design) does not allow for much variation in either.

5.4.1 Reciprocating Compressors
The reciprocating compressor is the simplest example of the positive displace-
ment class of compressors. This type of compressor was also the earliest
designed. Like reciprocating incompressible fluid pumps, reciprocating compres-
sors can also be either single acting or double acting. Single-acting compressors
are usually of the trunk type (see Figure 5-7)[1]. Double-acting compressors are
usually of the crosshead type (see Figure 5-8)[1].
Reciprocating compressors are available in both lubricated and nonlubricated
versions. Lubricated versions provide lubrication for the moving pistons (in the

Vertical V-type W-type Horizontal Opposed
(Boxer type)

Engine
Engine

Compressor Compressor
Vertical with Stepped Piston Integral L-type Integral W-type
(Two-stage)

FIGURE 5-7. Single-acting (trunk type) reciprocating piston compressor [1].