Reciprocating compressors use crankshaft-driven pistons to compress gases used in various processes. They fall into the category ofpositive-displacementcompressors. Positive displacementcompressorsdeal with a specific quantity of air or gas is contained in a compression chamber and its volume is mechanically reduced, thus increasing its pressure.
Figure 1 - Typical compressors classification table
Similar to internalcombustion engines, the rotary motion of the crankshaft is transformed into linear motion of the piston. As the piston moves, it sucks in low pressure gas and increases its pressure.
Structure of reciprocating compressors
Compression cylinders, also known asstages, confine the process gas during compression. Arrangements may be ofsingle-or dual-acting design: in the dual-acting design, compression occurs on both sides of the piston.
Unlike internal combustion engines, there is no ignition involved: the gas just leaves the compressor cylinder at a highet pressure than the suction pressure.
Reciprocating compressors are typically used where highcompression ratio(ratio of discharge to suction pressures) is required at relevantly small flow rates, and the process fluid is relatively dry. Axial flow compressors are mostly suitable for high flow, low compression ratio processes. Reciprocating compressors intended for higher compression ratio are designed as multistage compressors, that is with several working cylinders working in sequence.
These cylinders are driven by the same shaft, connected to a driver motor. Reciprocating compressors are typically low-speed devices and are most often direct- or belt-driven by an electric motor. Some times the motor is integral to the compressor, thus the motor shaft and compressor crankshaft are one piece, therefore eliminating the need for interconnecting coupling. At constant speed, the air flow remains almost constant with variations in discharge pressure.
往复式压缩机的应用essors
Figure 2 - Motor-driven six-cylinder reciprocating compressor
