【文章內(nèi)容簡介】 optimization of the design by implementing appropriate modifications to its constituent elements. The BEM widely used in the design of intake and exhaust system can be used to pute the interior, exterior, or both fields simultaneously and only requires that the perimeter of the air cleaner be divided into elements。and the ease in imposing the boundary condition is another attraction. In this paper BEM is used to predict the air cleaner39。s transmission loss and noise emission. The redesign of the original intake system arises in connection with a high passby noise with level above the legislative target at full throttle with engine speed around 5200 r/min. The spectral characteristics of the noise signal are normally dominated by an extensive sequence of discrete tones that are harmonically related to the engine firing frequency which is 173 Hz corresponding to 5200 r/min and the inline 4cylinder 4stroke engine. In many instances the bulk of the acoustic energy from the primary source is distributed among the lower frequency ponents that may be difficult to control. Thus frequency range this paper referred to is from 0 to 1 kHz. In this frequency range, as the influence of filter paper on acoustic performance of integrated system is trivial, so filter paper is disregarded. The noise is emitted from the inlet of the air cleaner, and the outlet of the air cleaner system connects to the inlet of the engine. So the pressure at the inlet of the engine or the outlet of the air cleaner is the boundary condition for the BEM. Traditional intake system with a function of noise reduction normally has two parts: air cleaner and silencer. Due to the constraint of space in the engine partment, the redesigned air cleaner bines the effect of cleaning and silencing. In this work, a socalled silencing air cleaner was redesigned, with geometrical structure determined by predicted TL and sound power emission by BEM. Also, in order to minimize the sound power of the intake system at low frequency, a bypass pipe was added to the airchanneling pipe. Analysis of the resulting acoustic performance showed that the method is feasible for the goal of reducing the overall engine noise by minimizing the intake system noise. 一個用于內(nèi)燃發(fā)動機進氣系統(tǒng)的無聲空氣濾清器的虛擬設(shè)計及性能預(yù)測 9 DESIGN OF THE SILENCING AIR CLEANER Original air cleaner evaluation This original air cleaner of mainly cleaning design paying little attention to minimizing noise emission is its BEM mesh. During calculation of TL, the outlet section of the air cleaner is given a unit velocity amplitude to model a sound source, all other surfaces are modeled as acoustically hard by default . The sound power of the outlet section can be calculated from the formula. All the subsequent TL predictions have the same boundary condition. The predicted air cleaner performance is shown The sound power level at the engine intake port is shown . The peaks of the noise source signal are harmonically related to the engine firing frequency of 173 Hz. As the bulk of the acoustic energy from the engine bustion distributed among the low frequencies from 100 Hz to 800 Hz is too high, the transmission loss at the frequency range of 220 Hz to 1 kHz is so low that the noise emission cannot be minimized, so a silencing air cleaner with a higher TL at 200 Hz to 1 kHz is required. Initial design of the silencing air cleaner If there is sufficient space, a plex structure can be assigned to minimize the intake noise emission. So we must make good use of the limited space. In this work CAD software Pro/E was used to envelop the rest of the space of the other automotive ponents in the engine partment. Then the total air cleaner volume required is obtained from the enveloped space. The next step is to choose appropriate silencer units