Compression ratio issue
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This post was last edited by WQC on 2011-8-23 23:01. What determines the compression ratio of a compressor? For example, it is a five-stage compression process with an inlet pressure of 60 KPa and an outlet pressure of 200 KPa. What is the compression ratio for stage 1 and stage 2? What is the compression ratio between stage 2 and stage 3? What kind of relationship exists among the compression ratios for the inlet and outlet air in each stage?
As I recall, it is generally required that the compression ratio for each segment be below 8
The pressure ratio should not be too high, as a high ratio requires high-grade materials for the impeller; if the ratio is too low, it fails to achieve the purpose of pressurization. The pressure ratio is equal to the ratio of the absolute exit pressure to the absolute inlet pressure
The suction flow rate and rotational speed of each stage of the compressor determine the compression ratio for that stage. The suction flow rate is related to the suction temperature and pressure, while the rotational speed remains the same across all stages; generally, it is ensured that the suction flow rate in each stage is consistent, which in turn means that the compression ratios for each stage are consistent. Since the overall compression ratio remains the same, it is necessary to distribute the compression ratios among different sections. If the compression ratio for a particular section is not properly assigned, a high compression ratio will lead to higher exhaust temperatures, which in turn increases the risk of scaling. Furthermore, an unreasonable distribution of the compression ratios most easily leads to uneven flow rates in different sections, increasing the risk of surge; therefore, return lines are generally installed between sections with different compression ratios to prevent surge.
Reply to 3# lizhenpeng: Must absolute pressure be used to calculate the pressure ratio? Can gauge pressure not be used?
Reply to 5# yuchen1980_04: It doesn’t work
The more stages there are, the relatively smaller the pressure ratio for each stage. Generally, random data provides the pressures at the inlet and outlet of each stage, and the pressure ratio can be calculated using those values. If the differences are too large, there may be problems