Why does an increase in the inlet flow rate of a centrifugal compressor lead to a decrease in the outlet pressure? ...
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This post was last edited by wlf1234 on 2020-3-3 09:56. With the rotational speed of the centrifugal compressor, inlet pressure, and temperature remaining constant, why does an increase in inlet flow lead to a decrease in outlet pressure?
It is the increase in user usage that reduces pressure, thereby leading to an increase in traffic. In the production process, the centrifugal compressor acts as a power device that increases gas pressure to supply pressurized gas to users. The products of this equipment are required to meet standards regarding pressure, temperature, and flow rate. The device that meets this standard is a centrifugal compressor.
Flow rate is inversely proportional to outlet pressure, which is understandable
The inlet of the centrifugal compressor is designed for mass flow rate
Check whether the outlet backpressure has decreased or there is no resistance anymore (for example, if you have a recycle hydrogen compressor, when the feed is stopped the outlet pressure of this compressor will decrease, but the flow rate will increase significantly)
The design institute reminds you: it’s not the work done by the compressor that remains constant, but rather the speed of the compressor that stays unchanged. According to the curve of the compressor speed (which can be found easily online), when the speed remains constant and the inlet pressure stays the same, an increase in flow rate leads to a decrease in the outlet pressure. The root cause is that the blades are backward-curved, which is caused by the exit triangle and friction.
This post was last edited by Zhuge Sima Linghu Chong on 2020-3-2 at 16:56. Hehe, this issue should be understood as follows: under the premise that all conditions remain unchanged, when the outlet pressure decreases, the inflow rate increases. Instead, the inlet flow increases while the outlet pressure decreases! If the outlet pressure does not decrease, under the premise that the above conditions remain unchanged, the inlet flow rate cannot be increased! Everything has a cause and effect; you’ve got the cause and effect backwards. It’s like when you’re hungry and you go to eat; you have to understand it in terms of being hungry, otherwise you surely won’t be able to figure it out. Hahahahaha
Although I didn’t understand the last sentence, it seemed very professional.
For example, what if we add a valve at the compressor inlet and adjust it to increase the inlet flow rate? What will the outlet pressure be if the rotational speed remains constant?
It can be easily determined based on the inlet flow–exit pressure performance curve of the centrifugal compressor
I know the performance curve. Looking at the performance curve, when the rotation speed remains constant and the temperature and pressure are fixed, it is clear that the higher the flow rate, the lower the pressure. I just don’t understand why it’s like this. My understanding is that when the flow rate is high, the output pressure should also increase accordingly. It’s like blowing up a balloon; the more you blow, the more it expands. The higher the pressure inside the balloon.