Centrifugal compressor performance curve
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I’m seeking help from everyone – I have some questions I can’t figure out regarding the curves related to the flow rate, compression ratio, or outlet pressure of centrifugal compressors. 1 If the inlet valve of the centrifuge is closed or the pipeline is blocked, how does the operating point change? Does it move along the performance curve, or does a new performance curve appear? (Will a new curve appear if the rotation speed remains unchanged?) 2 If it is not moved according to the performance curve, then during the manufacturer’s tests, it should be a curve obtained by keeping the rotation speed constant and changing the flow rate. 3 means reducing the size of the inlet valve; it’s a bit confusing to understand how the flow rates at the inlet and outlet, as well as the pressures and pipe resistance, change in such a situation. :P
This post was last edited by upc-ljb on 2017-6-9 at 10:53. First of all, performance curves are generally obtained through software simulation or calculation, and are not actual operating condition curves. Under actual operating conditions, changes in gas composition, molecular weight, inlet pressure, and so on can all cause changes in the performance curve. If you’re not in design, you think about too many things; these very complex issues cannot be resolved through simple calculations. Now many manufacturers have compressor simulation software that can simulate the scenarios you imagine. It is important to note that during operation, it is necessary to consider the control requirements of the entire process system. If the goal is to control the pressure at the compressor outlet, then the ITCC system (or other systems) adjusts itself based on the various parameters collected; for example, by increasing or decreasing the rotation speed, supplying additional air at the inlet, or adjusting the opening degree of anti-surge valves, in order to maintain a stable outlet pressure.
Thank you. I’m not in the design field; I’ve just been reading books about methods for adjusting the flow rate of centrifuges recently. By closing the inlet valve, I understand that the flow rate and pressure after the inlet, as well as those at the outlet, should decrease. But according to the performance curve relating flow rate to compression ratio, when the flow rate is low, the compression ratio or the outlet pressure increases – it’s a bit confusing, haha
Through the inlet throttle valve, the performance curve of the centrifugal compressor:
Compressor performance curve regulated by the inlet guide vane IGV:
This post was last edited by w1d3d55 on 2017-6-10 10:02; the performance curve remains unchanged.
Thank you, I have a question: does this range of 0.5 to 1 refer to different opening degrees of the inlet valve? Is the horizontal axis the flow rate? So for my inlet valve, for example, during the process from full open to half open, how does the operating point roughly change?
Thank you; I know this process might not be something that can be described so simply. I just want to know roughly: for example, if the inlet valve is closed partially, I know that both the inlet and outlet flow rates will decrease. As for pressure, if the curve remains unchanged as you said, then with a decrease in flow rate, the curve will shift upward to the left, resulting in an increased compression ratio? How do import and export pressures change?
0.5~1 is the valve opening degree, and the abscissa is the flow rate. If the outlet pressure remains constant, from full open to half closed, the operating point moves along a horizontal line from right to left, meaning the flow rate decreases.