两腔型双模式车用消声器流场及声学特性分析

双模式车用消声器可以有效降低压力损失，同时降低再生噪声，是一种半主动噪声控制设备。目前对双模式消声器的研究较少，需要进一步了解双模式消声器的内部气体流动情况和低频声学特性。通过流场仿真分析得出了高气体流速下双模式消声器有效降低压力损失的原因，并对结构进行改进，使湍流能量损失降低，减少了压力损失。通过声学仿真得到阀门关闭时共振腔的共振频率，符合亥姆霍兹公式计算结果，证明低频消声效果来自亥姆霍兹共振腔。同时分析了阀门打开时消声器低频消声原理，得出阀门打开后共振频率向右偏移，能够追踪不同转速下的排气噪声。

Flow and acoustic characteristics analysis of two-chamber type dual-mode mufflers

Dual-mode muffler is a semi-active noise control device which can effectively reduce pressure drop and regenerative noise. Internal flow and noise attenuation principle of dual-mode muffler require in-depth analysis. Through flow field simulation, the reason why that dual-mode muffler can effectively reduce pressure drop is found and the structure is improved accordingly, reducing turbulent energy and pressure drop further. Resonance frequency is obtained by acoustic simulation when the valve is closed, which coincides with the calculation result of Helmholtz formula, proving that the effect of low frequency muffling comes from Helmholtz resonator. The principle of noise attenuation at low frequency is analyzed when the valve is open and it is concluded that the resonance frequency of the muffler shifts to the right after the valve is opened, by which the exhaust noise at different rotating speeds can be tracked.