Centrifugal fan often encounter what is the cause of the failure occurs

　　Rotating stall is a typical fault of centrifugal induced draft fan, if not, could lead to further surge. Will destroy the internal flow field of impeller rotating stall inhomogeneity, generate additional aerodynamic load, serious when may induce blade high stress points of fatigue, fracture, decreased the efficiency of the fan, on the ontology and the connection of the pipe vibration and cause accidents.

　　When the gas flow in the impeller is lower than the rated flow, the radial velocity of gas into the impeller is reduced, vortex near the blade trailing edge points, thus causing air separation from the blade back, the flow of air flow in the blade back, lift decreases, and the resistance increases sharply, eventually leading to stall. At this point, from the perspective of the relative coordinates of fixed on the impeller, rotating out of the regiment in angular frequency of the rotating angular frequency omega 1, and from the perspective of the absolute coordinates of impeller outside, rotating out of the regiment is angular frequency (omega - omega 1) rotating, direction and the rotation of the rotor in the same direction, which is suitable for the rotation of the rotor frequency omega. As a result, the fan rotating stall failure occurs, will occur at the same time the abnormal vibration of rotor 1 and omega (omega - omega 1) two characteristic frequency. By its calculation formula, the impeller speed loss frequency (omega - omega. 1) probably in the range of 0.5 ~ 0.8 speed frequency omega.

　　In addition equipment vibration caused by rotating stall is different from other mechanical fault vibration, rotor imbalance and may make the rotor amplitude is higher in wrong, but doesn't necessarily feel obvious on chassis and pipeline vibration; Into the category of air vibration of rotating stall is different, sometimes in the amplitude of the rotor area although not too high, but it showed severe vibration in casing and pipeline. Additional vibration caused by rotating stall along with the change of load and the pressure and flow rate changes.