Tonal noise of voluteless centrifugal fan generated by turbulence stemming from upstream inlet gap
Tonal noise of voluteless centrifugal fan generated by turbulence stemming from upstream inlet gap
复制标题
无蜗壳离心风机上游入口间隙湍流产生的音调噪声
DOI：
10.1063/5.0055242
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发表时间：
2021
影响因子：
4.6
通讯作者：
Lars Davidson
中科院分区：
文献类型：
--
作者：
M. Ottersten;H. Yao;Lars Davidson
在这项研究中，噪声产生的一般无蜗壳离心式暖通空调风扇在非设计运行点，音调噪声增加。模拟是通过耦合IDDES与FW-H声学模拟，并在一个实验台上进行的充气室和混响室组成。与由风扇叶片引起的典型音调噪声源相比，我们发现另一个主要的噪声源是由风扇护罩和进气管道之间的差距产生的湍流。湍流沿着围带发展，并向下游扫掠，与叶片前缘的顶侧相互作用。这种相互作用导致叶片表面压力分布不均匀。此外，在围带附近的压力是显著不稳定的。噪声的功率谱密度（PSD）在273 Hz处有明显的单音，约等于叶片通过频率（BPF 0）与风机转速之差。通过粗化入口间隙和护罩附近的网格分辨率，我们在数值模拟中人为地使差距湍流失活，因此，检测到273 Hz处的音调完全消失。在该频率下，只有当差距湍流得到解决时，才能在进口间隙和叶片顶侧发现表面压力波动的PSD轮廓。这些结果表明，273 Hz的音调噪声源是差距湍流与叶片之间的相互作用。由于差距湍流存在于叶片上游的围带壁附近，旋转壁由于壁摩擦而将旋转动量引入湍流中。因此，随着风扇旋转频率的减小，相互作用的音调频率小于BPF 0。据作者所知，这是首次对无涡壳离心式通风机的差距湍流噪声进行研究。
In this study, noise generation is investigated for a generic voluteless centrifugal HVAC fan at an off-design operation point where tonal noise increases. The simulations are performed by coupling IDDES with the FW-H acoustic analogy, and the experiments are conducted in a rig consisting of a plenum chamber and a reverberation room. In contrast to typical tonal noise sources induced by the fan blades, we find out that another predominant source is the turbulence stemming from the gap between the fan shroud and the inlet duct. The turbulence evolves along with the shroud and is swept downstream to interact with the top side of the blade leading edge. The interaction accounts for uneven surface pressure distribution on the blades. Moreover, the pressure is significantly unsteady near the shroud. The power spectral density (PSD) of the noise shows obvious tones at 273Hz that is approximately equal to the difference of the blade passing frequency (BPF0) and the fan rotation frequency. By coarsening the mesh resolution near the inlet gap and shroud, we artificially deactivate the gap turbulence in the numerical simulations and, consequently, detect that the tone at 273Hz disappears completely. At this frequency, the PSD contours of surface pressure fluctuations are found potent at the inlet gap and the blade top side only if the gap turbulence is resolved. These findings indicate that the tonal noise source at 273Hz is the interaction between the gap turbulence and blades. As the gap turbulence exists near the shroud wall upstream of the blades, the rotating wall introduces rotational momentum into the turbulence due to the wall friction. Hence the tonal frequency of the interaction is smaller than BPF0 with a decrement of the fan rotation frequency. To the authors' knowledge, it is the first time that voluteless centrifugal fans are studied for the noise generation from the gap turbulence.