An experimental study on the reduction of motor-fan noise by modification of the blade and shroud configuration

Abstract The noise reduction (NR) of fans used for cooling electric motors is one of the key parameters in the design of a motor fan. In the authors’ previous paper, aeroacoustic analysis (which is based on unsteady computational fluid dynamics results) was performed for the baseline fan to know its sound level. To further find a better blade shape from an NR point of view, aeroacoustic analysis on various blade profiles from the NACA-63 and NACA-65 series was conducted. In this work, an experimental study on the baseline fan and three redesigned composite material fans for the low-noise fan is performed. The experimental parameters under investigation are better aerofoil-shape blade cross-section, using inlet bell-mouth entry, using composite materials, reducing the number of blades, using uneven blade spacing, making it a mixed flow fan, using backward-skewed blade design and reducing tip clearance. From the noise measurements in a semi-anechoic chamber for Fan-2, it is observed that the overall NR was 12.8 dB(A) compared with the baseline fan. It is observed that a mixed flow fan consisting of seven evenly spaced blades of NACA 65-010 aerofoil cross-section with backward swept shape and fabricated with glass and jute fibre produced the low-noise fan design at the fan operating point.