Formulas for calculating the compressor surge point and margin internally
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As the title suggests, I am having difficulty understanding a compressor control program. The manufacturer has implemented surge control as a functional block; the internal logic of this block is not visible. All that can be seen are the X and Y coordinates of six points on the critical surge curve, along with five variables: the inlet and outlet pressures, the inlet flow rate, and the inlet and outlet temperatures. There is also a safety margin factor, etc. Finally, this surge control functional block outputs an AO signal for the surge valve, as well as a DO signal for interlock purposes (presumably to ensure that the surge valve remains fully open). Therefore, I would appreciate it if experts could explain how these five variables are used to determine the operating point I heard that the standard approach is to calculate the pressure ratio and the mass flow rate at the inlet after compensation using five variables, then to refer to a surge curve to find the critical flow rate corresponding to that pressure ratio. Finally, by comparing the mass flow rate with the critical flow rate, it can be determined whether surge is occurring and what the degree of margin is, as well as whether it is necessary to adjust the opening degree of the vent valve. Is that correct? Please, experts and seasoned users, explain it to me. Thank you~
My SHENGU unit works as follows: when it approaches the anti-stall line, the AO signal is used to adjust the valve; when it approaches the full-open line, the DO signal directly drives the solenoid valve to open the valve fully. I am also monitoring this situation.
X= (X2-X1)/(Y2-Y1) *(Y-Y1) +X1
The second floor unit is probably controlled by Triconex’ ITCC; the anti-surge function blocks within it are also not accessible. The third floor unit seems to be based not on anti-surge calculations at all, but rather on range conversion formulas! There seems to be an expert on the 4th floor; thank you! ~