Surge in centrifugal compressors

The phenomenon is that of a relatively low-pitched sound vibration; as it progresses, periodic sounds appear, growing in intensity from weak to strong and then back again. This is hearing. Vision means large fluctuations in traffic and current, or even a drop to zero. The main reasons are too low an intake pressure (too little air intake at startup) and too high a pressure. The principle relies on the compressible elasticity of air: when the pressure becomes equal to or exceeds the centrifugal force (pressure) generated by the impeller, this pressure continues to build up and flows back through the impeller’s channels (resulting in the loudest sound). When the pressure inside the cylinder decreases, the centrifugal force (pressure) generated by the impeller decreases as well, after which the centrifugal force starts to generate work once again. This process repeats itself cyclically. In daily operations, it is important to note that changes in sound are the most straightforward way to detect something. Additionally, there are issues with electricity and steam power; increased pressure and insufficient intake during startup are all things that need to be taken into account. Additionally, in the case of single-axis multi-stage centrifugal compressors, this phenomenon can also occur when there is significant leakage between certain stages or when the intermediate cooler leaks heavily.

The sound during surge is similar to the growl of a lion, accompanied by vibrations in the pipes, with a few seconds of interval between the occurrence of these phenomena.

It is generally related to the rotational speed; just control it well to quickly pass through the surge point

There is no flow at the compressor outlet; in the absence of flow, the check valve closes immediately, and pressure even reverses, causing the compressor to emit a low-frequency humming sound. There are many possible reasons for this: high inlet pressure, large variations in the composition of the medium, too low suction volume at the inlet, and flow rates and rotation speeds falling within the surge range of the compressor

Is the fundamental cause of surge in centrifugal compressors due to a decrease in suction flow or an increase in discharge pressure?

Although both phenomena are referred to as surge, one type of surge occurs under negative pressure conditions, while the other occurs under conditions of excessively high pressure. It is recommended to understand the principle of turbo compressors clearly, as this will make it easier to explain this phenomenon.

When the flow rate of a centrifugal compressor is lower than the design flow rate, flow separation occurs on the working surface of the blades； The smaller the gas volume, the more severe the separation phenomenon, and the larger the separation region ； The gas volume is reduced to its minimum value; no gas flows out of the blade flow channels, resulting in vortex backflow and a decrease in outlet pressure ； When it drops below the pipeline pressure, the gas in the pipeline flows back into the impeller inlet ； As more flow is added, the outlet pressure rises; once this pressure exceeds that of the pipeline, gas is discharged back into the system. This in turn results in a decrease in flow rate within the compressor; the same process repeats, with the gas flowing back and forth inside the compressor, causing severe fluctuations in flow rate and outlet pressure – a phenomenon known as surge.

Is the decrease in the exhaust pressure of a centrifugal compressor caused by a reduction in the exhaust volume? Therefore, the reduction in exhaust volume is the fundamental cause of surge in centrifugal compressors

Related to changes in operation and medium