With a large number of large-capacity thermal generator set to put into production, Axial Fan axial fan with its large flow, small start-up torque, Axial Fan the advantages of the wind duct system change adaptability to gradually replace the centrifugal fan become mainstream. Axial-flow fans have 2 kinds of regulating modes of movable leaves and static leaves. The movable vane adjustable axial fan can change working condition by changing the angle of work blade. No interception loss, high efficiency, but also to avoid the small flow under the conditions of instability, but its complex structure, the stability and reliability of the regulator requirements are higher, Axial Fan the manufacturing accuracy is also higher, easy to malfunction, so generally only for the fan and a fan. Axial Fan The static vane adjustable axial flow fan can change the working condition by changing the flow area and the inlet airflow direction, but its structure is simple and the failure rate of the regulating mechanism is very low, so it is generally used in the bad working environment.
With the wide application of axial-flow fan, Axial Fan the vibration problem corresponding to its structural characteristics is gradually exposed, which is not present or uncommon on centrifugal fan. In this paper, some characteristics of vibration and its causes are summarized and analyzed by summarizing the cases of abnormal vibration of various axial-flow fans.
The movable vane adjustable axial flow fan can change the operating condition of the fan by adjusting the opening degree of the moving vane on line. This is mainly dependent on the hydraulic control mechanism in the hub to achieve, the adjustment of each blade angle involves a series of adjustment parts, Axial Fan so the installation of the components, fit and parts of the deformation, wear requirements are higher, Axial Fan hydraulic dynamic vane regulation system structure as shown in Fig. 1. Influence of dynamic vane regulating structure on vibration the main part of the single stage impeller blade opening different steps, two-stage impeller of the blade opening is not synchronized and adjust the parts themselves eccentric 3 aspects.
Single-stage impeller partial blade opening is mainly due to sliding block wear, adjusting rod and crank with loosening, petiole guide bearings and thrust bearings caused by rotation. Axial Fan These components are the driving mating parts between the hydraulic cylinders to the moving blades, will cause some of the fan blade opening is not in place, and the fan blade weight and installation radius are large, Axial Fan some of the fan blade opening inconsistent will produce a serious imbalance in quality, resulting in a high speed fan vibration.
Vibration spectrum and ordinary mass are unbalanced, the vibration fault spectrum is mainly the power frequency components, at the same time, some of the blades are not synchronized will produce a certain flow pulsation, the vibration spectrum of the blade through the frequency and its harmonics, Axial Fan some parts of the wear and loosening will have a certain non-linear impact, so that the vibration spectrum of the high-frequency higher harmonic components, which in the vibration velocity spectrum is relatively obvious, Axial Fan in the displacement spectrum is almost not observed.
The amplitude of the fan is unstable, the amplitude change mainly occurs in the dynamic leaf opening adjustment process, when the dynamic leaf opening is stable, Axial Fan the amplitude basically remains stable, and sometimes changes gradually with the dynamic leaf opening degree.
The amplitude of the fan is generally smaller when the speed of the engine is not open or the opening degree is small.
The adjustment part eccentricity mainly refers to the high quality adjustment part installment eccentric, the loosening, because of the high quality, when its revolving center and the rotor center occurs the deflection, will produce the big mass unbalance, but by the looseness causes the eccentricity also to produce the mass imbalance. For the movable vane adjustable axial flow fan, the main point is the installation eccentricity and looseness of the hydraulic cylinder. If only the hydraulic cylinder is mounted with eccentricity, Axial Fan and tight enough, it will only lead to a change in the distribution of mass, the fan rotor will appear pure quality imbalance fault, the fault spectrum is mainly a stable frequency components, each time the starting speed after the vibration values are relatively stable, will not vary with the load conditions. If it is due to the lack of tightness caused by the hydraulic cylinder installation, will produce unstable quality imbalance, Axial Fan every time after the shutdown, due to the change of centrifugal force, the position of the hydraulic cylinder will change, resulting in the vibration data each time is inconsistent,Axial Fan vibration mainly in the main frequency, in the same speed when the vibration is relatively stable. For this kind of fault, because the vibration is very stable after the Tanjiti speed, Axial Fan it is easy to confuse with the original mass unbalance, resulting in unnecessary repetitive dynamic balance.