Compressors liquid piston

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. 

Figure 1 -9. A sectional and end view of a liquid piston compressor. (Courtesy of Nash Engineering Co.)...

End view showing male and female rotors and slide valve on an 85-ton intermediate compressor. The robust design of the Series R compressor can ingest amounts of liquid refrigerant that would severely damage reciprocating compressor valves, piston rods, and cylinders. (Used by permission Cat. RLC-DS-2, Aug. 1995. The Trane Company.)... 

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. 

The liquid-ring or liquid-piston compressor is shown in Figure 36.8. It has a rotor with multiple forward-turned blades that rotate about a central cone that contains inlet and discharge ports. Liquid is trapped between adjacent blades, which drive the liquid around the inside of an elliptical casing. As the rotor turns, the liquid face moves in and out of this space due to the casing shape, creating a liquid piston. Porting in the central cone is built-in and fixed and there are no valves. 

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... 

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]. 

In contrast to other displacement compressors, liquid ring machines have a fluid piston . This is subject to a constant motion and deformation depending on effective forces. Potential differences are rapidly equalised by the motion of the fluid inside the piston. If the ring liquid plunges into the blade area, then the pressure of the enclosed medium is increased. 

The liquid-ring, or liquid-piston, compressor is shown in Figure 8.8. It has a rotor with multiple forward-turned blades that rotate about a central cone that contains inlet and discharge ports. Liquid is trapped between adjacent... 

The most used mechanical vacuum pumps or compressors are reciprocating, liquid-ring, rotary-vane, rotary blower, rotary piston, and diaphragm. 

The Nash vacuum pump or compressor has only one moving part—a balanced rotor that runs without any internal lubrication. Such simplicity is possible because all functions of mechanical pistons or vanes are performed by a rotating band of liquid compressant. 

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