Unbalanced identification method of counter rotating propeller fan considering harmonic coupling
In the double propeller rotor system of the counter rotating propeller fan,the vibration signals are transmitted between the inner and outer rotors through the intermediate bearings to generate complex coupling vibration,which usually takes the form of beat vibration of basic frequency and multiple frequency,resulting in difficult identification of vibration signals and low efficiency of dynamic balance.The conventional least square identification method only considered the basic frequency signal,but neglected the interference of harmonics and noise,resulting in low identification accuracy.In order to solve this problem,a harmonic least square method(HLSM)signal was proposed.Through simulation experiments,the identification effects of various identification methods and HLSM were compared,verifying that the identification accuracy of HLSM was higher.The results of HLSM identification were applied to double rotor dynamic balancing on the built coaxial counter rotating double rotor test-bed.The results showed that the unbalanced vibration of inner and outer rotors was reduced by 70％and 96％,respectively.
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