Why does centrifuge surge occur

During operation of the compressor, a decrease in the inlet volumetric flow rate causes boundary layer separation on the non-working surfaces of the impeller or the blades of the vane compressor, which in turn leads to rotational separation. If the flow continues to decrease, the rotational separation will further increase, and several clusters will combine to form a larger cluster. When almost the entire flow channel of the compressor is in a separation zone, the flow conditions deteriorate severely, the gas pressure cannot be increased, resulting in a sudden drop in the compressor outlet pressure. Since the compressor always operates in conjunction with the piping system, the pressure in the piping system has not yet had time to drop; as a result, the pressure in the piping system is higher than the pressure at the compressor’s outlet, causing the gas in the piping system to flow back into the compressor. Backflow increased the flow rate, separation disappeared, normal operation was restored, and air was supplied to the piping network. After the air is released, the volumetric flow rate at the compressor inlet drops again, causing the gas in the pipeline network to flow back once more. The repeated occurrence of such forward and reverse flows causes periodic axial airflow oscillations with low frequency and large amplitude throughout the entire system, resulting in severe noise and vibration. This phenomenon is called surge, and the flow rate at which surge occurs is known as the “surge flow rate”.

The prelude to surge: rotational separation. When the operating flow rate of the compressor is below the minimum value, the airflow impacts the compressor blades at their inlets, causing severe separation of the airflow boundary layer on one side of the blades and the formation of vortex regions, which leads to rotational separation or rotational stall.