螺旋轴流泵内流致噪声特性的数值模拟

Numerical simulation of the characteristics of flow-induced noise in a helical-axial pump

关键词:  螺旋轴流泵  压力脉动  声学有限元法  流致噪声  涡结构  时空关联性分析

Key words:  helical-axial pump  pressure pulsation  acoustic FEM  flow-induced noise  vortex structure  spatial-temporal correlation analysis

摘要:

为识别螺旋轴流泵内流致噪声声源位置并分析非定常流场对流致噪声的影响,文中结合计算流体力学和声学有限元法对泵内流致噪声进行了数值模拟分析。首先,基于ANSYS CFX软件,采用剪切应力输运（SST）模型对泵内三维非定常流动进行模拟,获取泵内流场的压力脉动特性。其次,将固体壁面处压力脉动作为激励源,基于LMS Virtual Lab软件并采用FW-H方程对泵内声场进行数值计算,重点分析了流致噪声频域特性以及不同部件和区域对噪声的贡献,以识别声源位置。最后,结合时域信号相关性及相干性理论,对叶片表面压力脉动信号的时空关联性进行深入分析,揭示关键声源区域的流动特性及其对噪声的贡献机理。结果表明:与导叶下游相比,叶轮上游的流致噪声更大,随频率衰减更慢,噪声贡献量最高的频带位于0~3 000 Hz范围内,声压级最大峰值出现在叶片通过频率处；旋转声源在此处总声压级比静止声源高25.4 dB,其中,叶片吸力面比压力面产生更大的噪声,其前50%弦长区域对噪声贡献量更大；对叶片吸力面不同位置处压力脉动信号的时空关联性分析表明,此区域的压力脉动主要来源于此处的附面层分离。

Abstract:

To identify the flow-induced noise sources in a helical-axial pump and analyze the influence of the unsteady flow on the flow-induced noise, a numerical simulation analysis of the flow-induced noise in the pump was conducted using a combination method of computational fluid dynamics (CFD) and acoustic finite element method (FEM). Firstly, the 3D unsteady flow within the pump was simulated using the shear stress transport (SST) turbulence model in ANSYS CFX to obtain the pressure pulsation characteristics of the flow field. The pressure pulsations on the solid walls were treated as excitation sources, and the flow-induced noise field in the pump is numerically calculated using the FW-H equation with the software of LMS Virtual Lab. In order to identify the noise source location, the focus was put on the frequency domain characteristics of flow-induced noise and the contribution of different components and regions to noise. Finally, based on the temporal signal correlation and coherence theory, the spatial-temporal correlation of the pressure pulsation signal on the impeller blade surface was deeply analyzed to reveal the flow characteristics and noise contribution mechanism of the key noise source region. The results indicate that, compared with the downstream of the diffuser, the flow-induced noise at the upstream of the impeller is greater and exhibits a slower attenuation with increasing frequency, with the highest noise contribution occurring in the frequency range of 0~3 000 Hz. The maximum sound pressure peak appears at the blade passing frequency. The total sound pressure level of the rotating source at the monitoring point is 25.4 dB higher than that of the stationary source, with the suction surface of the blade generating more noise than the pressure surface, particularly in the first 50% chord length region, which contributes significantly to the overall noise. Spatial-temporal correlation analysis of pressure pulsation signals at different positions on the suction surface of impeller blades reveals that the pressure pulsation in this region primarily originates from boundary layer separation.