Abstract: The noise problem of the double bypass fans is analyzed in depth, and the source of the noise is diagnosed by modal analysis theory, it is found that the third mode resonance of the motor mounting plate causes the fan abnormal sound, the optimized design of the fan mounting plate structure is carried out by combining with modal simulation analysis. Finally, the optimized fan system is tested, which shows that the vibration noise of the optimized double bypass fans is eliminated, and the sound quality of the cascade fan is greatly improved. The method of noise source diagnosis and noise elimination based on modal theory can provide some guidance for the noise problems of the same type of products.

Key words: Abnormal noise, Double bypass fans, Vibration, Optimization