The working principle of the cooling fan is implemented according to the energy conversion,namely: the electrical energy to ele ctromagnetic energy,mechanical energy to kinetic energy.The circuit principle generally divided into a variety of forms,the circuit is different,the performance of the cooliing fan will have difference.
A cooling fan to prevent accidental failure cause unnecessary loss,will be modified by design.Thus get rid of the criticism to fundamentally to changes in the nature.
The formation of a cooling fan rotating stall,a cooling fan impeller structure and size are designed according to the rated air colume,when acooling fan when he worked in a normal air volume,the direction of the gas into the impller and blade air import installation.Angle is consistent,gas can smoothly enter the impeller,when the gas flow in the impeller is less than the rated flow,the radial velocity of gas into the impeller is reduced,the direction of the relative velocity of gas flow into the impeller Angel is reduced,and therefore is not consistent with blade inlet installation Angle.Cooling fan blade in the process of machining and installation,for various reasons make the blade can’t be exactly the same shape and installation Angle.therefore,when the operation condition change and make the direction of flow deviation occurs,in each blade inlet Angle of attack is impossible to exactly the same.If aleaf of inlet Angle of attack reaches the critical value.Cooling fan into the unstable running condition area,within the impeller will produce one to a number of rotating stall area.Leaves each after a stall zone is an exciting force,which can make the blade to produce resonance.At this time,the dynamic stress of blade increase.may cause of blade fracture,so from the perspective of the absolute reference frame of impeller outside,stall area or along the impeller rotation direction,causing mechanism of rotating stall,rotating stall in impeller pressure fluctuation of the excitation rotor abnormal vibration exciting force,the size of the exciting force related to the size of the gas molecular weght,they are proportional to the relationship,the larger the molecular weight,the greater the exciting force.
Frequency of rotor rotating stall:when a colling fan running,is the direction of the impeller with the direction of the rotor is consistent,the direction of flow when the exception occurs,the abnormal vibration of the rotor.So this is also the cause of a cooling fan rotating stall.
