撞击流混合器速度信号的Hilbert-Huang变换分析

应用激光多普勒测速系统,对撞击流混合器的流场瞬时速度进行了测量。将Hilbert-Huang变换（HHT）应用于瞬时速度信号的分析,提取出各阶内禀模态函数（IMF）并通过经验模态分解（EMD）对速度信号进行滤波降噪。通过希尔伯特谱分析（HSA）确定了撞击流混合器速度信号的能量分布状况,信号能量集中于低频区,即存在于尺度较大的流体涡旋中。分析速度信号各阶内禀模态函数在不同频段的能量分布与转换,发现不同频段IMF的能量分布与流型转变之间的对应关系。通过能量特征值的提取表明,提高螺旋桨转速有助于强化系统的混合效果。最后将撞击流混合器的流场由内而外划分为中心区、涡旋区和回流区3个部分。

Hilbert-Huang transform of velocity signal in impinging stream mixer

The instantaneous velocity of flow field in impinging stream mixer（ISM） was measured with laser doppler anemometry（LDA）.By using hilbert-huang transform（HHT）,the intrinsic mode function（IMF） was extracted from the instantaneous velocity signal and the signal was de-noised using the empirical mode decomposition（EMD） method.The energy distribution of the velocity signal in ISM was determined through the hilbert spectral analysis（HSA）.The energy concentrated in low-frequency areas,i.e.concentrated in large-scale vortexes.Analyzing the energy distribution of different frequency segment and its transfer within different IMF,the relationship between the flow pattern in ISM and the energy distribution of the different frequency segment was found.The extraction of energy eigenvalues showed that increasing the propeller speed could help strengthen the mixed results.At last,the flow field in ISM was divided into three zones of central zone,scroll zone and recirculation zone.