Does changing the medium shift the anti-surge operating point to the left? ?
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During testing, CO2 was used as per the design, and anti-stall control functioned properly; however, after switching to nitrogen, it was observed that the operating point shifted slightly to the left at the same flow rate. What could be the reason for this?
The molecular weight can change significantly; with the same pressure difference, the flow rate is not the same
The volumetric flow rate remains unchanged, but the mass flow rate has changed.
Is your horizontal axis the flow rate? Are the outlet pressures of the two media the same? If it’s the same, has the rotation speed decreased?
Yes, the volumetric flow rate remains unchanged while the mass flow rate does change. But how does this result in a shift of the operating point to the left on the anti-stall control display?
The outlet pressure is the same; if the horizontal axis isn’t flow rate, then what is it? Driven by a motor, with constant speed
The inlet flow rate is the same, and the temperature and pressure are also identical; it’s just that the operating point has shifted significantly to the left. I don’t understand why
Mainly, the molecular weight has decreased, and the pressure difference across the orifice plate is different
It was found that the operating point shifted slightly to the left at the same flow rate, due to differences in molecular weight
With the same flow rate, and the same pressure and temperature, is the pressure difference different?
It is not the pressure difference at the compressor inlet and outlet, but rather the differential pressure of the orifice plate used to measure the flow rate at the inlet.