[Q&A Question 229] 2016.12.05
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【Q&A Question 229】December 05, 2016: Why can’t the compression ratios of different stages in a high-pressure reciprocating compressor differ too much? A reference ** will be shown after responding; scoring is achieved by answering the key points. An excessively high compression ratio can lead to: 1. a large temperature difference between the media and the equipment components at the two stages, which reduces the equipment’s service life. 2. The exhaust temperature is too high. 3. It may cause the lower levels to become overloaded with compression, resulting in large differences in vibration levels across various levels. Summary post of Q&A from 2016 (updated up to December~~~~) http://bbs.hcbbs.com/thread-1597792-1-1.html Seeking sponsors for the “2016 Haichuan Top 10 Members Selection Contest” http://bbs.hcbbs.com/thread-1628108-1-1.html (Source: Haichuan Chemicals Forum)
With a constant piston stroke, the work done by the cylinder can remain consistent
1. The large temperature difference between the media and equipment components in the two stages reduces the service life of the equipment. 2. The exhaust temperature is too high. 3. It may cause the lower levels to become overloaded with compression, resulting in large differences in vibration levels across various levels.
The compression ratios of each stage are roughly equal, and the compression power consumption per stage is approximately the same; as a result, the compressor has the lowest total shaft power and is thus the most energy-efficient.
Mainly, the heat generated by compression cannot be dissipated, which affects the service life of the piston rings and cylinder liners.
If the pressure ratio is too high, the exhaust temperature of the compressor rises, which can easily lead to damage to the gas valves or packing
Increased heat generation raises the demand for cooling water; the strength of components such as the crankshaft and connecting rods increases, leading to an increase in power
Theoretically, the more stages a compressor has, the better, but in practice the number of stages should not be too high. As each additional stage is added, more components such as cylinder valves are required, which complicates the compressor’s structure. The higher the compression ratio, the higher the outlet temperature, and the more power is consumed; the outlet temperature may also exceed the flash point of the lubricating oil, causing it to burn down into carbon residue. Under normal circumstances, the compression ratio per stage of the compressor should not exceed 3 to 5
A large difference in compression ratio results in a significant difference in outlet temperature. The imbalance in the work done by the piston rod is eventually transmitted to the crankshaft, causing uneven stress on it; over time, this can lead to uneven wear.
1. Increase in piston force； 2. Increased motor power ； 3. The strength of the crankshaft, piston rod, connecting rod, piston, cylinder, bearings, etc., all needs to be increased ； 4. The increased temperature resulting from an excessive compression ratio reduces the air volume, thereby increasing the requirements for cooling water and heat exchangers.
With each increase in stage, an additional set of components such as cylinder valves is added, thereby complicating the compressor’s structure. The higher the compression ratio, the higher the outlet temperature, and the more power is consumed; moreover, the outlet temperature may exceed the flash point of the lubricating oil, causing it to burn down into carbon residue