Reduction of motor fan noise using CFD and CAA simulations

Motor fans used for cooling electric motors have long been recognized as one of the major noise sources. Current paper focuses on design of motor fan for electric motors that are used in submarines for pumping sea water. Noise reduction at source is very important and the critical task, for under water applications. An attempt has been made for reduction of motor fan noise by modification of noise sources. For this purpose computational fluid dynamics and computational aeroacoustics code FLUENT package is used to identify the noise sources and to know the overall sound pressure level of motor fan. From these results it is observed that aerodynamic noise is the dominate fan noise source. Aerodynamic noise of motor fan can be reduced by modifying fan geometry. The aerodynamic noise level of motor fan has been reduced by replacing the straight blades with various digits of NACA (National Advisory Committee for Aeronautics) 65 series airfoil sections. From the numerical results it is observed that the minimum sound pressure level for NACA 65-010 is 65.4 dB(A). These numerical results are compared with measurements in a semi-anechoic chamber. It is found that there is good agreement between numerical and experimental results.