Experiences with Flow-Induced Vibration and Low Frequency Noise Due to Rotating Stall of Centrifugal Fan

Abstract

In recently constructed electric power plants, the forced draft fan (FDF), induced draft fan (IDF) and boost up fan (BUF) centrifugal fans and duct-systems have become larger in capacity and limited in space every year. As a centrifugal fan is enlarged, the diameter of the impeller is enlarged and its rotating speed is lowered. Therefore, there is an increasing tendency to generate a low frequency noise.5 In the case of an IDF or BUF, the rotating stall of the centrifugal fan frequently causes low frequency noise, since the inlet flow is often throttled during operation. If the hydrodynamic and acoustical characteristics are insufficient, a strong flow-induced vibration with low frequency noise is generated in the fan-duct system, and not only are problems caused in terms of structural strength, but also physical and physiological problems are induced due to low frequency noise.

Noise generation by rotating stall and surge in vane-axial fans

“…⋅ BPF . The value of the coefficient ξ was similar to that obtained by Suzuki and Okada,14,15 although there are differences in place and form of rotating stall generation depending on fan configurations. Equation (3) differs from Suzuki's equation (2), derived for centrifugal fans, for the number of the rotor blades z.…”

“…Suzuki and Okada,14,15 who investigated centrifugal fans with inlet guide vanes, proposed the following equation:…”

Experimental study on the noise reduction of an industrial forward-curved blades centrifugal fan

“…This difference is not owing to the rotating stall of the impeller blades, although the performance drop is gradual when the volume flow rate is less than Q 1 . Mongeau et al [26], Suzuki et al [27] and Okada et al [28] have experimentally studied the noise generated by rotating stall in centrifugal impeller and draw a conclusion that the frequency of stall noise is usually accordance with the following formulation:…”

Triboelectrification induced self-powered microbial disinfection using nanowire-enhanced localized electric field

“…The PFA lm is a negative triboelectric material and the PFA-covered Al electrode serves as the other electrode of the TENG 32 . During operation, the TENG is placed on the ventilator of a building, the middle layer of the TENG will vibrate due to the vibration of the ventilator operating with a frequency of ~30 Hz 30,33 . The vibrating middle layer may contact and then separate from the top/bottom layers and AC power will be generated during this contact-separation process due to the coupling effect of triboelectri cation and electrostatic induction 34 .…”