Adjustment of the compression ratio in reciprocating compressors
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The outlet pressure of a reciprocating compressor is generally determined by the process specifications and remains relatively constant. If I want to reduce the compression ratio, in the case of a compressor with two compression stages, I can close the return valve between the first and second compression stages; this will lower the compression ratio. However, as the inlet pressure increases, the outlet pressure will also increase, thereby exceeding the process specifications. I’m not sure how to address this issue
Close the intake valve slightly. Open the outlet valve wide.
Reduce the air intake volume and keep the second-stage valves of the compressor fully open to avoid pressure buildup.
Generally, the compression ratio of a compressor is fixed, with the absolute pressure of the exhaust gas at the outlet being higher than the absolute pressure of the intake air at the inlet. This is a fixed value; in my opinion, it’s impossible to change the compression ratio of the compressor without affecting the manufacturing process. If there is a specific requirement regarding the pressure at the compressor’s outlet, then the only option is to adjust the pressure at the compressor’s inlet. The configurations such as ‘one-stage one’ and ‘two-stage two’ are simply used to ensure the appropriate pressure (flow rate) at the compressor’s inlet. Whenever the inlet and outlet pressures of the compressor change, the operating conditions of that compressor also change. If the requirements in terms of process are not high, then after deciding to change the compression ratio of the compressor, factors such as the load on the compressor itself need to be taken into consideration.
When one valve is closed, how can the compression ratio be reduced? What is reduced is only the compression ratio of the second stage. In fact, the inflation volume increases.
Can the suction volume of the reciprocating machine be adjusted via the inlet valve? That’s not reasonable, is it?
Can’t we use the one-time on/off control at the first-stage outlet to increase the pressure at the first-stage outlet, which is also the second-stage inlet?
Since, during the design of the compressor, the cylinder volume for each stage is determined based on the compression ratio,