ACOUSTICAL EFFECT OF THE NONLINEAR PROPERTY OF POROUS WOVEN HOSES IN ENGINE INTAKE SYSTEMS

The porous tube of coated woven fabric is recently used as an effective component of intake systems of many internal combustion engines to reduce the intake noise. The acoustic characteristics of porous woven hoses have been specified by the so-called 'porous frequency', which is experimentally determined from the ambient pressure, the internal volume of the hose, and the ratio between the specific volume flow rate through the hose wall and the effective pressure drop at this specific volume flow rate. The latter ratio is determined by the wall property according to the weaving condition and the coating condition of porous hose. In addition, it is noted that the physical meaning of the company- specified 'porous frequency' is very similar to the flow resistance through a porous material in general. Because of the aforementioned nonlinear property of the porous woven hose, the porous frequencies measured at different radius and/or different length are different even if the hoses possess the same wall property. In this paper, the nonlinear factor of the porous woven hose is investigated experimentally. It is shown that the porous frequency of the porous hose having other radius or length is predicted, based on this nonlinear factor. Developed method can be used to specify the acoustic characteristics of porous woven hoses more precisely than before and thus the transmission or insertion loss of the hose can be predicted with precision. (A) For the covering abstract see ITRD E113232.