Noise reduction on axial fan - involves by transferring fraction of flow from upstream of rotor to circumference of blades

摘要

Method to improve the efficiency of an axial fan ventilator involves extending the stable operating area and reduction of the noise produced by removal of through ports and rejoins the main flow in line with the tops of the fan blades. The supply of the flow medium to the circumference of the fan rotor is made with a pulsing flow at a frequency proportional to both the revolutions of the fan rotor and the number of its blades. Pulsations caused by the blades are thus neutralised.