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Unstady Flow within Centrifugal Fan Casing and the Mechanism of Noise Generation

离心风机机壳内非稳态流动及噪声产生机理

基本信息

批准号：
59460088
负责人：
YOSHIOKA Eisuke
金额：
$ 4.16万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1984
资助国家：
日本
起止时间：
1984 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-59460088/
关键词：
Fluid Machinery Centrifugal Fan Fan Noise Unsteady Internal Flow 3-Dimensional Numerical Analysis Surge Similation Similarity Rule of Noise Prediction サージ

项目摘要

A fundamental study approaching a similarity rule of the centrifugal fan noise and flow mechanism related to the low frequency system oscillation is made by the following investigations;(1) The blade passing frequency noise, say BPF noise, is expressed in terms of a machine dependent factor, a rotational-speed dependent factor, an attenuation factor between the 1st and the 2nd mode of the BPF noise, and a frequency response function expressing the acoustic propagation characteristics. Each level and the geometrical parameters of the factors are determined by experiments. The frequency response function is estimated by a plane acoustic model analysis.(2) Three dimensional flow field within the fan casing is discussed by measurements of pressure fluctuation, and by inviscid numerical analysis applying the FLIC method and the DENTON technique. The levels and the spetial distributions of fluctuation components due to the impeller discharge and secondary flow related to the casing geometry … More are to be distinguished.(3) A numerical method to simulate the low frequency system oscillation is concerned by introducing the pressure-flow rate characteristic of the fan and one dimensional expressions of the system passages.The results and the future prospects of the research are obtained as follows;(a) The noise prediction rule is found very satisfactory, and the frequency response function is described by the length and the cross-sectional area of the blade-to-blade passage and the fan inlet duct. Without reduction of the fluid machinery efficiency, a noise suppression of 25 dB is found possible by a suitable selection of the fan geometry.(b) Within the casing, fluctuation due to the secondary flow is not significant in compared to the turbulent mixing. The major fluctuation distributes only on the side wall area very close to the cut-off of the scroll, and this is due to the impeller discharge.(c) The three dimensional numerical analysis and the one dimensional simulation method are found to lead satisfactory results. These method will be applied to a further analysis about the unsteady blade passage flow during the system oscillation at a low discharge operation. Less

通过以下研究，初步探讨了离心风机噪声与低频系统振荡相关流动机理的相似规律：(1)叶片通过频率噪声，即BPF噪声，用机器相关因子、转速相关因子、BPF噪声的第一、第二模之间的衰减因子和声学传播特性的频率响应函数来表示。通过实验确定了各因素的水平和几何参数。采用平面声学模型分析计算了风机机壳内的频率响应函数。(2)通过压力脉动测量，并采用FLIC方法和Denton技术进行无粘性数值分析，对风机机壳内的三维流场进行了分析。与套管几何…有关的叶轮流量和二次流引起的波动分量的水平和空间分布(3)通过引入风机的压力-流量特性和系统通道的一维表达式，提出了一种模拟低频系统振荡的数值方法，得到了如下结果和未来的研究展望：(A)噪声预测规律非常令人满意，频率响应函数由叶片到叶片通道和风机进口通道的长度和截面积来描述。在不降低流体机械效率的情况下，通过选择合适的风扇几何形状，可以抑制25分贝的噪音。(B)在机壳内，二次流动引起的波动与湍流混合相比并不显著。主要的脉动只分布在离涡旋截止点很近的侧壁区域，这是由于叶轮的排放。(C)三维数值分析和一维模拟方法得到了令人满意的结果。这些方法将被用于进一步分析小流量工况下系统振荡过程中叶片流道的非定常流动。较少