穿孔管消声器声学性能三维时域计算及分析

将三维时域计算流体动力学(Computational fluid dynamics,CFD)法应用于计算有流情况下穿孔管消声器的声学性能。在消声器进口处施加脉冲信号与不施加任何信号的两种情况下,通过非定常计算分别得到消声器上下游监视点的时域压力值。同一监视点两次计算结果之差就是脉冲信号及其反射信号。使用快速傅里叶变换将时域声压信号转换到频域,计算出消声器的传递损失。对于直通穿孔管消声器和横流穿孔管消声器,使用三维时域CFD法计算传递损失,并与试验测量结果和频域法计算结果进行比较,以验证三维时域CFD法预测穿孔管消声器声衰减性能的准确性。分析气流速度和温度对横流穿孔管消声器传递损失的影响。结果表明,随着气流速度的增加,传递损失曲线向低频方向移动,多数频率处的传递损失有所增加;随着介质温度的升高,传递损失曲线向高频方向移动。

Three-dimensional Time-domain Computation and Analysis of Acoustic Attenuation Performance of Perforated Tube Silencers

The three-dimensional time-domain computational fluid dynamics(CFD) approach is employed to compute the acoustic attenuation performance of perforated tube silencers with flow.For both cases with and without impulse signal imposed at the inlet of silencer,the time histories of the pressures at the upstream and downstream monitors of the silencer can be obtained through the unsteady calculations.The differences between two computational results at the same monitor are the impulse signal and corresponding reflective signal.The acoustic pressures in time domain are then transformed to the frequency domain by using the Fast Fourier Transform,and the transmission loss of silencer may be determined.The transmission loss of the straight-through perforated tube silencers and cross-flow perforated tube silencer is calculated using this method.The numerical predictions are compared with the experimental measurements and the calculated results from the frequency domain approach,which show that the three-dimensional time-domain CFD approach could predict accurately the acoustic attenuation performance of perforated tube silencers.Finally,the effects of gas flow velocity and temperature on the transmission loss of cross-flow perforated tube silencer are analyzed.The mean flow shifts the transmission loss curve to the lower frequency and increases the transmission loss in many frequencies.The transmission loss curve is moved to the higher frequency as the temperature increases.