Compressors liquid-piston type

The liquid-piston type of compressor has been of particular advantage when hazardous gases are being handled. Because of the gas-liquid contact and because of the much greater liquid specific heat, the gas-temperature rise is veiy small. 

Rotary compressors are generally classified as of the straight-lobe type, screw type, sliding-vane type, and liquid-piston type. 

Liquid-Piston Type This type is illustrated in Fig. 10-97. These compressors are offered as single-stage units for pressure differentials up to about 0.52 MPa (75 Ibf/in ) in the smaller sizes and capacities up to 6.8 X 10 mVh (4000 fF/min) when used with a lower pressure differential. Staging is employed for higher pressure differentials. These units have found wide application as vacuum pumps on wet-vacuum service. Inlet and discharge ports are located in the impeller hub. As the vaned impeller rotates, centrifugal force drives the sealing liquid... 

Another important positive displacement compressor is the rotary compressor. This type of compressor is usually of rather simple construction, having no valves and being lightweight. These compressors are constructed to handle volumetric flowrates up to around 2,000 actual cfm and pressure ratios up to around 15 (see Figure 3-69). Rotary compressors are available in a variety of designs. The most widely used rotary compressors are sliding vane, rotary screw, rotary lobe, and liquid-piston. 

The liquid compressor has rather low efficiency, about 50%. The liquid piston compressor may be staged. The main advantage to this type of compressor is that it can be used to compress gases with significant liquid content in the stream. 

Several types of compressor have characteristics intermediate between those of PD compressors and centrifugal or axial-flow compressors. These include the lobe type, sliding vane, and liquid piston. For all these, the discussion of compressor work and compressor efficiency applies just as well as the above-mentioned types. Descriptions of the mechanical arrangements of these can be found in texts on pumps and compressors [2]. 

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