Research on the Bionic Design and Performance of Engine Cooling Fan with Blade Tip Serrated 2022-01-0173

Turbulence caused by the blade tip of engine cooling fan is one of important noise generating factors. Existing theoretical researches show that the bionic serrated designs applied at the front and rear edges of fan blades can effectively improve the airflow characteristics and reduce the aerodynamic noise. However, the effect of its application at the blade tip needs to be explored and verified. In this research, vehicle engine fans whose tips are designed and remodeled with different size of triangular serrated edge have been tested on airduct, to explore the fan static pressure and noise that caused by changing of period and amplitude size. The large eddy simulation (LES) and FW-H acoustic analogy method are adopted to calculate the transient noise of each designed fan. Both experimentation and calculation results show that the application of serrated edge can improve the static pressure efficiency to a certain extent, and have a direct influence on the formation and development of tip vortexes, then result in the variation of noise. When the amplitude height and period length are within a certain numerical range, the sound pressure level can be reduced by 1-2dB. In addition, the noise reduction effect of the structure is also limited by the rotating speed of the fan itself. The noise reduction is more significant at a speed range from low to medium. But at the high speed, the serrated structure tends to bring about the increase of noise. To verify the validity and applicability of the conclusion, the noise-reducing serrated structure is designed on a different type cooling fan, and then tested in anechoic chamber, which shows that the noise performance gain a promotion ideally.