Experimental study of the accuracy of balancing an axial fan by adjusting the masses and by passive auto-balancers

The paper reports determining and comparison of the quality of dynamic balancing of rotating parts in the assembly (impeller) by correction mass and applying passive auto-balancers using the axial fan VO 06-300-4 as an example. The impeller is balanced in two planes of correction – from the side of a fairing and from the side of an electric motor’s shank. It was established that prior to balancing the magnitudes of root-mean-square values (RMS) of vibration speed at the casing of the fan correspond with a margin to the balance quality grade: 1x vibration components (1x) ‒ G2.5; total – G6.3. The main source of vibrations is the dynamic residual imbalance of the impeller. The basic component of vibration speeds is the 1x one (at a frequency of 25 Hz), that is, it can be reduced by balancing. The non-1x vibration components occur at subharmonic frequencies, 25/2 and 25/3 Hz, and are smaller by the order of magnitude. When the impeller is balanced by correction mass, the initial imbalances from the side of a fairing and a shank are, respectively, 81.4 and 115.2 g∙mm, and the residual ones are 7.4 and 7.2 g∙mm. The magnitudes of RMS of vibration speed can be reduced at the fan’s casing to the magnitudes corresponding to the balance quality grade (with a margin): 1x – G0.4; total – G2.5. The main contribution to the residual vibrations is made by the non-1x vibration components occurring at subharmonic frequencies. At dynamic balancing of the impeller by two ball auto-balancers, in the presence of any imbalances (in two planes of correction) that can balance the auto-balancers, the RMS of vibration speed at the fan’s casing correspond to the balance quality grade: 1x – G1; total – G2.5. Ball auto-balancers react to imbalances constituting not less than 3 % of their balancing capacity. The residual imbalances are not stable, but are not larger from the side of a fairing and a shank than, respectively, 22.2 g∙mm and 21.6 g∙mm. Research results are applicable for low-pressure axial fans, specifically VO 06-300/VO-12-300; VOG/VO-15-320; VO 2,3-130/VO 46-130. They make it possible to decide on the expediency of balancing fans by passive auto-balancers