A hybrid time-frequency domain method to predict insertion loss of intake system.

Abstract

A hybrid time-frequency domain method for predicting insertion loss (IL) of intake systems is investigated with detailed evaluation and optimization in terms of acoustic performance and intake efficiency for an automotive engine intake system. Instead of progressively coupling of both domain variables, as in the existing hybrid methods, the proposed method uses frequency-domain source impedance to characterize the acoustic source, and a time-domain method to analyze the acoustic transmission. A simplified equation is derived to predict IL using noise reduction (NR) and acoustic impedance Zl rather than four-pole transfer matrices as used in the traditional frequency-domain method and hybrid-domain method. The NR and Zl of intake systems calculated by the time-domain method are used to predict IL for the first time. This hybrid method has advantages of requiring no numerical engine model while considering the convective and dissipative effect of intake flow on a complex intake system. The predicted ILs of a quarter-wavelength tube and an optimized air cleaner were validated with the measured results. The proposed method and results are applicable and useful to the design of an intake system at an early stage of engine development.