Numerical Investigation of Unsteady Flow and Aerodynamic Noise Characteristics of an Automotive Axial Cooling Fan

Abstract

Low-speed axial cooling fans are frequently used to manage engine temperature by ensuring that adequate quantities of air pass through heat exchangers, even at low vehicle speeds or in the idle condition. This study aims to provide a better understanding of the unsteady flow behavior around an automotive axial cooling fan with seven blades and its impact on the aerodynamic noise generation. Large Eddy Simulation (LES) near the near-field region and the Ffowcs-Williams and Hawkinbygs (FW-H) method were performed to analyze the flow characteristics around the fan and predict the aerodynamic noise emitted from the fan under a constant rotational speed of 2100 rpm. The simulation results for the velocity distributions and aerodynamic noise were compared with the experimental data measured by single hot-wire probe and in a dead-sound room. The results showed a comparatively good agreement upstream and downstream from the fan and at two different receivers of 0.5 m and 1.0 m. When the fan was rotating, a strong tonal noise numerically existed near the leading edge of the blades at the tip and amounted to 110 dB sound pressure level (SPL) caused by the increasing angles of attack with the increasing radial velocity near the ring, which caused the entire air foil to emit a low-frequency noise. Furthermore, the different SPL decay characteristics of approximately 5 dB in the near-field region and 6 dB in the far-field region were observed each time the distance from the fan doubles. The findings of this research can provide important insights into the design of axial fans with low noise and high performance.

Design, Study, and Comparison of a New Axial Fan Using the Fibonacci Spiral and a Classic Axial Fan

“…In Figures 12(c) and 12(d), the same trend is observed; Model A has larger regions of high vorticity at 6000 RPM compared to Model B. These results could be explained by what was observed by J. O. Mo et al [15],where flow separation on the blades affects performance and increases noise. It would also support this explanation reported by Yang et al [11], who found that the noise level increases due to blade twist when they have a positive angle.…”

“…In recent times, there has been a notable increase in the utilization of axial fans for cooling electronic components or heat transfer equipment [1],both in industrial and domestic settings [2], [3], which leads designers to make improvements to them to maximize their performance [4], [5], and reduce the noise they generate [6], [7]. Most of the research is based on improving existing axial fan designs [8], with a concentration on studies involving aerodynamic profile geometry or inlet geometry [9], [10], others study the effects of blade twisting or airfoil [11]- [14],and others studied the behavior of the fluid and its influence on fan noise generation [15], [16].…”

Advances in Vibroacoustics and Aeroacustics of Marine, Aerospace and Automotive Systems

“…Low-speed axial cooling fans are frequently used to manage engine temperature by ensuring that adequate quantities of air pass through heat exchangers, even at low vehicle speeds or in idle conditions. The study in [16] aims to provide a better understanding of the unsteady flow behavior around an automotive axial cooling fan with seven blades and its impact on the aerodynamic noise generation. LES near the near-field region and the FW-H method were performed to analyze the flow characteristics around the fan and to predict the aerodynamic noise emitted from the fan at a constant speed of 2100 rpm.…”

Numerical and experimental investigation of aerodynamic noise from a cooling fan in a turbulent flow

“…The aerodynamic noise characteristics of an axial cooling fan were studied by Mo and Choi. 26 They studied the analysis of the noise sources generated by the fan using an LES and FW-H method through the commercial CFD software.…”