Observation of Noise of Fan with Obstacle for Electric Components

Noise Prediction by Analytical or Numerical Models

The recent trend in downsizing electric equipment has caused an increase in the heat generation density and an accompanying need to increase air flow to enable cooling. Therefore, the aerodynamic noise from the fan is the dominant source of noise in air-cooled electrical equipment. Fan noise is known to be influenced by the fan operating point and the fan’s surrounding structures.
This study presents the use of experimental and numerical simulations to observe the noise made by a fan used to cool electrical components when interacting with an obstacle.
A simplified experimental setup was designed consisting of three parts: a fan, a duct, and an obstacle. The one-block obstacle in the experimental model was assumed to be an aggregate electric component. The sound pressure level (SPL) was found to be influenced by the distance between the obstacle and the fan. Decreasing these distances, the SPL are increasing, particularly below a half distance of the fan diameter, SPL is drastically increased.
To conduct a numerical analysis of aerodynamics noise, either the hybrid computational aeroacoustics (CAA) method or the direct CAA method can be employed. The hybrid CAA method can be assumed to separately solve incompressible turbulent flow and the acoustic wave. The direct CAA method uses compressible Navier–Stokes equations to compute both the turbulent flow and the acoustic wave. In our study, the direct CAA method is used to consider the aero acoustic interactions between the fan and the obstacle under a low Mach number flow. A compressible Large Eddy Simulation (LES) approach was used to predict the SPL. The numerical simulation captured the sound pressure propagation toward the sound observation point. And it was found that the SPL influenced by the distance between the fan and the obstacle can also captured. This method was found to be applicable for predicting the SPL when developing low-noise products.