What does compressor surge mean?

Surge, as the name implies, is similar to asthma in humans; it involves periodic exhaust and backflow in the compressor. Surge is a type of abnormal vibration that occurs in turbine compressors (also known as vane compressors) when the flow rate decreases to a certain level. A centrifugal compressor is a type of turbine compressor, and surge poses a serious threat to centrifugal compressors. When the compressor flow rate drops to its minimum, the outlet pressure drops suddenly; the pressure in the downstream pipeline then becomes higher than the outlet pressure, causing the fluid being transported to flow back into the compressor, until the outlet pressure rises again and the fluid is sent back through the pipeline ； When the pressure in the pipe returns to its original level, the flow rate decreases again, causing the fluid in the pipe to flow backward. This process repeats over and over again, resulting in mechanical vibrations induced by the periodic absorption and discharge of the fluid. 1. Internal causes of surge The internal reasons for surge are closely related to the impeller structure and the gas present in the flow channels. When the flow rate of the incoming gas decreases suddenly and falls below the allowable minimum level, there is a significant deviation in the direction of airflow within the compressor as well as in the installation angle of the blades at their inlets. This results in severe \"rotational separation\" of the airflow within the blade channels, causing the gas to stagnate there and leading to a sudden drop in compressor pressure. However, the pressure in the outlet system does not drop instantly; as a result, the high-pressure gas in the exhaust pipe flows back into the compressor, replenishing the flow rate within the blade channels and allowing normal operation to resume. When the flow rate inside the compressor decreases again, gas flow reverses in the system, and this process repeats itself. Consequently, periodic oscillations of the airflow occur within the system, accompanied by intense noise – this is what constitutes compressor surge. 2. External causes of surge By analyzing the performance curve of centrifugal compressors, it can be seen that when surge occurs, the operating point must have entered the surge condition region. Therefore, compressor surge is closely related to the pipeline network characteristics. The so-called \"pipeline system\" refers to the piping network used by centrifugal compressors to transport gaseous media; the pipeline located before the compressor inlet is called the suction pipe, while the one located after the compressor outlet is called the discharge pipe. Piping systems generally consist of four main elements: pipes, fittings, valves, and equipment. Practice has shown that the greater the capacity of the centrifugal compressor’s piping network, the larger the amplitude of surge and the lower its frequency; whereas the smaller the capacity of the piping network, the smaller the amplitude of surge and the higher its frequency.

Surge is a type of abnormal vibration that occurs in turbine compressors when the flow rate decreases to a certain level. A centrifugal compressor is a type of turbine compressor, and surge poses a serious threat to centrifugal compressors. During surge, typical phenomena include: the compressor’s outlet pressure first rising, then dropping sharply, with periodic large fluctuations ； The compressor’s flow rate drops sharply and experiences significant fluctuations; in severe cases, air even flows back into the intake pipeline ； The current and power meter readings of the motor driving the compressor are unstable, showing significant fluctuations ； The machine generates intense vibrations and abnormal airflow noise at the same time.