Analysis of Bending Vibrations of Rotors in Axial Mine Fans with Two Impellers

Spotlight of the analysis is on bending vibrations of axial fan rotor of main ventilation fans in mines. Their feature is two impellers that act interchangeably as directing and guide vanes, and one impeller only rotates in an active mode. Such design allows attaining high capacity in the reverse mode which preserves 90–95% of the straight flow mode. The presence of two impellers in the rotor influences the frequency behavior of the fan, which can vary in a wide range depending on some parameters that govern the mass and geometry of the rotor. The article describes the analysis of the rotor frequency characteristics obtained from solving a system of differential equations of bend. The curves of free bending vibrations of main shafts and masses of impellers are plotted for different values of added mass of transmission shaft and for different lengths of the main shaft areas. It is shown that in the test range of the main shaft lengths, impeller masses and added masses of the transmission shaft, the operation of rotors of fans with two impellers is safe and reliable in terms of vibrations.