An investigation of axial flow fan noise

Abstract Measurements of noise from fans designed for military vehicle cooling installations have been made. Two fan rotors in particular have been run under varied test conditions. The main parameters investigated were tip speed, tip clearance, back pressure, blade stagger angle, the presence of inlet and outlet struts, and number of blades. The effect has been measured of running a fan in conjunction with a radiator matrix. The nature and magnitude of the possible noise-producing mechanisms are discussed in the light of the above tests and also of results and theories published elsewhere. The relevance to noise production of the steady and of the unsteady components of the aerodynamic forces has been studied, and the possibilities for noise minimization assessed.