Nozzle for motor-driven fan or fixed collar in motor vehicle e.g. hybrid vehicle, has rotation face whose fractal dimension is higher than specific value permitting localization of acoustic modes near of raised and/or hollow elements

摘要

The nozzle has a rotation face placed radially with respect to a free end of blades or a rotation collar of an impeller. The rotation face is arranged with a raised and/or hollow element (F1) and other raised and/or hollow elements, where fractal dimension of the rotation face is higher than 1.1 permitting localization of an acoustic modes near of the raised and/or hollow elements. The raised and/or hollow elements are made of phonic absorbent material, and define a reference pattern, where the one of the raised and/or hollow elements is truncated cone or truncated pyramid.