The characteristic of the cross-flow fan is that the fluid flows through the fan impeller twice, the fluid flows in radially first, and then flows out radially, and the inlet and exhaust directions are in the same plane. The exhaust gas is evenly distributed along the width of the fan. Due to its simple structure, small size and high dynamic pressure coefficient, it can reach long distances and is widely used in laser instruments, air conditioners, air curtain equipment, dryers, hair dryers, household appliances and grain combine harvesters and other fields.
The internal structure of the cross-flow fan is very complex. Although the impeller is symmetrical in the circumferential direction, the airflow is asymmetrical, and its velocity field is unstable. There is a vortex on the inner side of one side of the impeller circumference, which can control the flow of the entire airflow, that is, the eccentric vortex of the so-called cross-flow fan. The center of the vortex is somewhere in the inner circumference of the impeller, and it moves in the circumferential direction under different throttling conditions. Under certain working conditions, due to the enhanced eccentric eddy current control of the cross-flow fan during high-speed operation, the gas in the cross-flow fan cannot be discharged or inhaled normally, and an abnormal situation occurs in the test system, which is the so-called surge phenomenon.
If the area of the vent is small, the resistance of the resistance layer is large, the flow in the pipeline is small, the working requirements of the cross-flow fan are low, the influence of the eccentric eddy current is small, and the flow is not obvious. However, when the rotation speed is high and the vent area is large, the eccentric eddy current control force is enhanced, the gas in the cross-flow fan cannot be discharged or inhaled normally, the test system is abnormal, and the cross-flow fan has a surge phenomenon and a surge period. Specifically:
(1) Noise increases.
When the cross-flow fan is working normally, the noise is relatively small. However, when the surge phenomenon occurs, there will be a dull humming sound inside the cross-flow fan, and a sharp roaring sound will be emitted from time to time, and the sound is relatively loud;
(2) Vibration intensifies.
When the cross-flow fan is surging, the drive belt of the power trolley vibrates obviously, and the whole test device vibrates obviously;
(3) Difficulty in reading.
When the cross-flow fan is surging, the values displayed by the micromanometer and the tachometer change rapidly, and the magnitude and magnitude of the change are large, which is a periodic change. In this case, it is difficult for testers to read. Under normal circumstances, the displayed value is the normal working value of the cross-flow fan, and the surge phenomenon almost disappears, but within a cycle, it is short-lived and very unstable, and the displayed value is the reading that occurs when the surge phenomenon is serious.
Post time: Jul-20-2022