轴流泵流动噪声数值模拟

Numerical simulation of flow noise in axial-flow pump

为了研究轴流泵内部压力脉动和流动噪声在不同工况下的变化规律及其关系,采用数值模拟方法,应用计算流体动力学软件Fluent和声学软件LMS Virtual Lab分别模拟轴流泵流场和声场分布,并进行时域和频域分析.取叶片非定常脉动力作为声源,运用边界元法对比分析了有泵壳振动影响和无泵壳振动影响下泵壳体边界声场分布的不同.结果表明:叶轮叶片、导叶叶片和动静交界面处监测点的静压均表现出明显的离散频谱特性,叶片通过频率(BPF)是压力脉动和流动噪声的主频,这是由叶轮和导叶之间的动静干涉引起的;而流动噪声在2倍谐频(133.4 Hz)和3倍谐频(200.1 Hz)处也有明显峰值,这是由叶轮叶片和泵壳壳体振动引起的.忽略泵壳振动影响的情况下,噪声水平偏大,考虑声振耦合的噪声情况更接近于实际,所以结构振动是噪声辐射分析的重要因素.噪声指向性分布图表明了叶片噪声辐射具有明显的偶极子特性.

In order to research the rules and relationship between internal pressure pulsation and flow noise under different conditions,flow field and acoustic field of an axial-flow pump were simulated by computational fluid dynamics software Fluent and acoustic software LMS Virtual Lab numerically,and then both time and frequency domain analysis were applied.Taking the unsteady fluctuating pressure exerted by the fluid on the blade as noise source,BEM was applied to compare the difference of pump casing boundary acoustic field distributions between the condition of acoustic-only and acoustic-vibration coupling.The results show that static pressure pulsation in each checkpoint on impeller blades,guide vane blades and interfaces between rotating blades and the stationary blades show obviously discrete spectrum characteristics in spectrum diagrams,and the blade passing frequency is the dominate contents of both the pressure fluctuations and flow noise data,which manifests that the fluid-structure interaction between the rotating blades and the stationary ones may be the primary disturbance source.The flow noise frequency spectra has obvious peak at the double harmonic frequency and the triple harmonic frequency.Neglecting the pump casing vibration influence,the sound level is too high,while it is closer to practice with considering that influence.Therefore,structure vibration is very important in analyzing the noise radiation level.Noise directionality distribution chart indicates that blade noise radiation has obvious dipole characteristics.