低压轴流风机的内部涡流特性及气动噪声

以中央空调中带导风圈的低压轴流风机为研究对象，对其内部涡流特性和气动噪声展开研究。采用大涡模拟计算了均匀进气情况下半管道式低压轴流风机的三维瞬态流场。计算结果表明叶尖涡是其内流场主要特征，叶尖涡的形成、发展和破碎对气动噪声源的分布有重要影响。提取了主要噪声源处的非定常压力脉动进行频谱分析，显示其叶片尾缘处脱落涡频率特征明显。风机的远场噪声采用LES/FW H声类比方法进行预测，结果表明低压轴流风机的气动噪声以宽频成分的紊流噪声为主，预测的声压级频谱与实验吻合得较好。

Inner Vortical Flow and Aerodynamic Noise in a Low Pressure Axial Flow Fan

The inner vortical flow and aerodynamic noise in a semi open axial fan with a shroud in a central air conditioning is studied. Three dimensional unsteady flow field under the condition of uniform inflow is calculated using a large eddy numerical simulation. The results show that the tip vortex is the main feature of inner flows. The formation, development and breakdown of the tip vortex have a great effect on the aerodynamic noise. A spectral analysis is carried out by extracting the unsteady pressure fluctuation at main sound source region. There are three characteristic frequencies corresponding to the blade passing frequency, the harmonic frequency, and the vortex shedding frequency. Far field aerodynamic noise of the fan is predicted using LES/FW H acoustic analogy method. It is indicated that the aerodynamic noise radiated from the semi open low pressure axial fan is mainly the broad band turbulent noise. The predicted sound pressure level spectrum agrees well with the experimental results.