لخّصلي

Concerning the fan system with the long pipelines connected on the inlet and outlet, the structural vibration is the main component of the external radiated noise and is caused by the volute vibration which is excited by the unsteady aerodynamic force on the volute casing. The main conclusions obtained are as follows:

1. In this paper, a method of numerical calculation of air-inlet-sound is to be implemented, and the rationality of this method is to be verified by dynamic pressure measurement and vibration measurement of the volute casing as well as fan bearings including temperature
2. The normal vibration of the volute was the decisive factor that determined the volute surface vibration.

Concerning the fan system with the long pipelines connected on the inlet and outlet, the structural vibration is the main component of the external radiated noise and is caused by the volute vibration which is excited by the unsteady aerodynamic force on the volute casing. The volute vibrational noise radiation was reduced based on vibro-acoustic optimization. The parametric analysis presented in this paper is fundamental research for volute vibrational noise optimization, providing a basic database and scope of variables for optimization. The main conclusions obtained are as follows:

1. In this paper, a method of numerical calculation of air-inlet-sound is to be implemented, and the rationality of this method is to be verified by dynamic pressure measurement and vibration measurement of the volute casing as well as fan bearings including temperature


2. The normal vibration of the volute was the decisive factor that determined the volute surface vibration. The mechanism of the generated volute vibration noise can be summarized as “ the unsteady aerodynamic force induced by unsteady flow at the outlet of the impeller of the fan excites the volute vibration, which results in the high temperature of the volute casing surface, which then excites the vibration & sound of the volute casing surface.


3. Based on air path design, unsteady aerodynamic force will result in high vibration(mostly axial) eventually leading to premature bearing failure.