【Q&A Question 055】June 14, 2016

Answer: 1 When a reciprocating compressor needs to compress gas to very high pressures, thereby achieving a certain compression ratio, single-stage compression often results in the temperature of the compressed gas rising too high. The higher the single-stage compression ratio, the greater the rise in the temperature of the compressed gas. The gas inside the cylinder and the injected lubricating oil coking due to excessive temperature. It affects the proper operation of the valve and accelerates the wear of the piston rings. Moreover, the high-temperature, high-pressure gas remaining in the clearance expands and occupies a large portion of the cylinder volume; the higher the single-stage compression ratio, the higher the temperature and pressure of the gas remaining in the clearance. The greater the volume occupied by the gas after expansion within the cylinder, the lower the volumetric efficiency becomes. The gas temperature in a single-stage compression is too high, which results in increased power consumption by the compressor. The higher the single-stage compression ratio, the higher the compression temperature, and thus the greater the power consumption of the compressor. In summary, reciprocating compressors with a high compression ratio must be equipped with multi-stage compression.

Single-stage compression requires more work, and the exhaust temperature of the gas valve is higher

When a reciprocating compressor needs to compress gas to very high pressures and achieve a certain compression ratio, single-stage compression often results in the gas temperature rising too rapidly; the higher the single-stage compression ratio, the greater the rise in the temperature of the compressed gas. The gas inside the cylinder and the lubricating oil injected there undergo coking due to the high temperature, which affects the proper functioning of the gas valves and exacerbates the wear of the piston rings. The higher the temperature and pressure of the gas remaining in the clearance, the more volume the gas occupies after expansion, resulting in a decrease in volumetric efficiency. The power consumption is too high

Single-unit compression, with an oversized cooling system, prone to liquid in the compressed gas

1) When a reciprocating compressor is required to compress gas to very high pressures and achieve a certain compression ratio, single-stage compression often results in the temperature of the compressed gas rising too high; the higher the single-stage compression ratio, the greater the rise in the temperature of the compressed gas. The gas inside the cylinder and the injected lubricating oil coking due to excessive temperature. It affected the proper operation of the valve and exacerbated the wear of the piston rings. 2) The high-temperature, high-pressure gas remaining in the clearance expands and occupies a large portion of the cylinder volume; the greater the single-stage compression ratio, the higher the temperature and pressure of the gas remaining in the clearance. The greater the volume occupied by the gas after expansion within the cylinder, the lower the volumetric efficiency becomes. 3) The gas temperature after single-stage compression is too high, which results in increased power consumption by the compressor. The greater the single-stage compression ratio, the higher the compression temperature and the greater the compressor’s power consumption. Therefore, reciprocating compressors with a high compression ratio must be equipped with multi-stage compression.

The gas temperature is too high; water cooling is used to reduce the temperature between the various compression stages

(1) When a reciprocating compressor is required to compress gas to very high pressures and achieve a certain compression ratio, single-stage compression often results in the temperature of the compressed gas rising too high; the higher the single-stage compression ratio, the greater the rise in the temperature of the compressed gas. The gas inside the cylinder and the injected lubricating oil coking due to excessive temperature. It affected the proper operation of the valve and exacerbated the wear of the piston rings. (0.4) (2) The high-temperature, high-pressure gas remaining in the clearance expands and occupies a large portion of the cylinder volume; the greater the single-stage compression ratio, the higher the temperature and pressure of the gas remaining in the clearance. The greater the volume occupied by the gas after expansion within the cylinder, the lower the volumetric efficiency becomes. (0.3) (3) The gas temperature after single-stage compression is too high, which results in increased power consumption by the compressor; the greater the single-stage compression ratio, the higher the compression temperature and the greater the compressor’s power consumption. (0.2) In summary, reciprocating compressors with a high compression ratio must be equipped with multi-stage compression. (0.1)

A single-stage compressor compresses gas to very high pressures; as a result, the compression ratio increases and the temperature of the compressed gas rises. When the compression ratio exceeds a certain value, the temperature of the compressed gas surpasses the flash point of the lubricating oil used in such compressors, causing the oil to emulsify and burn