贯流风机气动噪声机理及降噪机理研究

从气动声学理论出发，探讨了贯流式风机气动噪声机理及不等节距叶片调制降噪的机理。     

相似理论在风机噪声方面的应用研究

本文应用相似理论研究风机噪声特性,探讨了同类风机的噪声特性曲线;分析了风机的噪声相似准数——比噪声;讨论了风机噪声的相似定律;并给出了风机转速、外径与噪声功率的关系式。     

多翼离心风机噪声分析的试验及数值研究

通过传声器搭建的压力脉动测试系统,测量了某多翼离心风机蜗壳壁面一周的压力脉动值及风机进口的噪声频谱,并结合FLUENT计算分析风机内部的流场,分析得出所研究多翼风机的噪声主要以涡流噪声为主,同时旋转噪声也是不容忽视的一部分,最后为该多翼风机提出了降噪的改进方案。     

雷达天线系统离心风机气动噪声研究

基于FW-H方程,对离心风机进行气动声学理论分析,结合噪声测试方法,对某雷达天线系统进行噪声试验研究分析。测试数据表明,噪声和振动加速度频谱图分布较为接近,噪声振动能量峰值频率均为离心风机叶片基频的倍频,即雷达天线系统噪声主要来源于离心风机的气动噪声。通过改变均热板上翅片与风机叶片边缘的间距和调节风机转速,对单个离心风机开展噪声试验研究。由实验结果可知,随着间距增大,其噪声值降低,且噪声能量逐渐集中分布在低频区域;离心风机噪声值随着其转速增大而增加,不同工况下离心风机噪声能量均在其叶片基频的二倍频处最大。噪声试验获得的不同工况下离心风机噪声云图可为雷达天线系统均热板的结构优化设计提供试验和理论依据。     

离心风机气动噪声研究方法的分析与建议

对目前离心风机气动噪声的研究方法进行了分析,总结出数值模拟及其计算方法还不完善.提出了离心风机蜗壳简化成一个具有硬边界的理想壳体模型的思路来研究风机气动噪声.     

风机噪声的防治研究

本文作者在美国宾州大学噪声控制研究所和该所科研人员一起对一些典型的风机进行了测试研究。文中分析了风机的噪声特性、风机噪声频谱,介绍了声功率计算的实验公式和曲线,提出了降低噪声的技术措施。     

叶片进口安装角对多翼离心风机噪声的影响

应用数值模拟的方法,分别对多翼离心风机进行了稳态、非稳态及声学计算,并进一步研究了叶片进口安装角对多翼离心风机性能和噪声的影响,获得了风机在设计流量下的性能、蜗舌处压力脉动及风机进口噪声随叶片进口安装角的变化规律。最后,在对数值结果分析的基础上,获得了提高风机性能及降低风机噪声的最佳叶片进口安装角。     

如何选择消声器的类型降低离心式风机噪声的研究

本文对阻性和抗性消声器对离心式风机噪声的影响进行了声电类比理论分析和试验验证,就某型号离心风机旋转噪声和涡流噪声占的比重进行了试验研究,提出了合理地选择消声器的类型,有效地降低离心风机噪声的几个观点。     

风机叶片噪声模型研究

风机叶片的形状制约其效率的高低、噪声的大小。通过分析风机叶片噪声的类型,研究风机叶片产生空气动力性噪声的机理。结合风机叶片的具体结构形状,运用运动声源产生声场的特点,建立风机叶片噪声数学模型。对噪声数学模型采用精度高的高斯—勒让得(Gauss—Legendre)法进行计算。模拟在噪声模型参数(叶片数、风机转速、攻角、叶片展向半径和叶片截面等)变化的情况下叶片噪声的变化情况,结合试验进行分析,得出影响风机噪声的主要因素。模型可为风机低噪声设计、预测提供理论依据。     

空间站用离心风机降噪技术研究与验证

空间站需长期驻人,安静的环境对航天员的健康和安全尤为重要。因此有必要对离心风机的降噪技术开展研究。通过对离心风机气动噪声的产生及传播机理的研究,明确了离心风机的主要气动噪声源在蜗壳上。基于上述理论,针对空间站内某型号风机进行降噪设计,在其蜗壳内壁增加穿孔板和消音棉,并在进风口增加消声器,最终经过试验验证了风机噪声满足舱内稳态噪声医学要求。     

空调用贯流风机气动噪声预测的研究

基于N-S方程和雷诺输运应力方程(RSM),对空调用贯流风机进行了非稳态内流计算,并应用基于Lighthill声学类比理论的FW-H方程时域解法,预测了由叶轮表面压力波动和蜗舌表面压力波动所产生的远场气动噪声,同时还比较了不同蜗舌间隙对气动噪声的影响.     

Mean streamline analysis for performance prediction of cross-flow fans

This paper presents the mean streamline analysis using the empirical loss correlations for performance prediction of cross-flow fans. Comparison of overall performance predictions with test data of a cross-flow fan system with a simplified vortex wall scroll casing and with the published experimental characteristics for a cross-flow fan has been carried out to demonstrate the accuracy of the proposed method. Predicted performance curves by the present mean streamline analysis agree well with experimental data for two different cross-flow fans over the normal operating conditions. The prediction method presented herein can be used efficiently as a tool for the preliminary design and performance analysis of general-purpose cross-flow fans.     

横流风机内部流动试验研究

利用激光多普勒测速（LDV）技术,测量并分析在不同叶轮直径和结构尺寸时,横流风机在稳定工况和失速工况下,风机内部流场的相似与差异,通过对几组试验数据的比较,对横流风机特有的偏心涡的成因进行了理论分析,并对偏心涡的主要参数特点作了深入的探讨,同时总结了偏心涡的位置随流量变化的规律。     

电子器件散热串联轴流风扇短管降噪试验

对两台电子器件散热轴流风扇采用不同方式串联时的气动噪声特性开展试验研究。首先利用风扇等高平面内环形布置的传声器阵列对单风扇和串联风扇的远场噪声进行测量,发现串联风扇相比单风扇具有更高的宽频噪声和更复杂的单音噪声特性。然后对比加装方框、蜂窝和短管中间连接件的串联风扇在不同转速下的噪声声压级指向性分布,发现短管连接件对串联风扇的单音和宽频噪声均具有良好的降噪效果,其中设计转速下单音相比方框连接的串联风扇下降1.2dB(A),宽频下降0.5dB(A)。最后,提出串联风扇的两段短管降噪方法并验证了其在多转速运行工况下的降噪效果。论文对串联电子器件散热风扇气动噪声的研究可为工程应用中的降噪措施提供参考。     

贯流风机性能参数实验与扭曲角优化

介绍了一种自行研制的电壁炉用贯流风机性能参数检测台,详细描述了检测台中关键部件的实验测试原理,并对直叶片和扭曲叶片贯流风机在热风状态下的性能参数(出风口风速、风量和风机转速等)进行了对比实验研究,得出了扭曲角为60°的扭曲叶片贯流风机的性能明显优于直叶片贯流风机。同时对扭曲叶片贯流风机流场进行了数值模拟,并对扭曲角进行了优化。结果表明:数值计算和实验结果基本吻合,这两者的结合是研究贯流风机结构和改进其性能的有效手段。     

气垫带式输送机专用风机的试验研究

依据 GB 12 36 - 85“通风机空气动力性能试验”、 GB/T 2 888- 91“风机和罗茨鼓风机噪声测量方法”和GB 10 178- 88“通风机现场试验”,结合气垫带式输送机供风系统的性能要求和使用特点 ,介绍了气垫带式输送机专用风机的空气动力性能试验、噪声试验和现场试验的方法。     

热交换器布置方式对家用空调器噪声影响的理论分析

从理论上分析了热交换器布置方式对家用分体式空调器室内机所用横流风机系统的流场和声场的影响，说明了圆弧形为理想的布置方式；并对三种具有不同热交换器布置方式的横流风机系统的流场进行了二维数值模拟，结果与理论分析相吻合，较好的预测了家用分体式空调的内部流场。     

An investigation on the effects of irregular airfoils on the aerodynamic performance of small axial flow fans

In this paper, the effects of airfoils on the aerodynamic performance of small axial flow fans were investigated to reduce airflow turbulence on the blade surface and to improve the aerodynamic performance of small axial flow fans. Irregular airfoils where several convex grooves are bound in the blade pressure surface of the fans have two kinds. The wave-shaped edge is bound to the blade trailing edge of the fans and is designed from the smooth airfoil of the fans. The filtered N-S equations with the finite volume method and the standard k-? turbulence model were adopted to carry out the steady simulation calculation. The large eddy simulation and the FH-W noise models were adopted to carry out the unsteady numerical calculation and aerodynamic noise prediction. The results of simulation calculation are in good agreement with the tests, which proves that the numerical calculation method is feasible. The spectrum characteristics of aerodynamic noise of the smooth airfoil and the two kinds of irregular airfoils were analyzed. Although the fans of the three airfoils are regarded as noise sources, the vortex distribution features in the unsteady flow field are also described. Noise reduction mechanisms of the irregular designs of the airfoils were also discussed. The results of this research may provide proof of the parameter optimization and the structural design of small axial flow fans with low noise.     

Characteristics of unsteady flow field and flow-induced noise for an axial cooling fan used in a rack mount server computer

The recent development of small and lightweight rack mount servers and computers has resulted in the decrease of the size of cooling fans. However, internal fans still need to achieve a high performance to release the heat generated from interior parts, and they should emit low noise. On the contrary, measurement data, such as flow properties and flow visualizations, cannot be obtained easily when cooling fans are small. Thus, a numerical analysis approach is necessary for the performance evaluation and noise reduction of small cooling fans. In this study, the noise of a small cooling fan used for computers or servers was measured and then compared with the aeroacoustic noise result based on a numerical analysis. Three-dimensional Navier-Stokes equations were solved to predict the unsteady flow field and surface pressure fluctuation according to the blades and casing surface used. The simplified Ffowcs Williams and Hawkings equation was used to predict aeroacoustic noise by assuming that a dipole is the major cause of fan noise. Results of the aeroacoustic noise analysis agreed well with that of the experiment, and a tonal noise whose frequency was lower than the first blade passing frequency could be identified in the noise spectrum. This phenomenon is caused by the shape of the bell mouth. A coherence analysis was performed to examine the correlation between the shape of the cooling fan and the noise.

     

Development of low-noise axial cooling fans in a household refrigerator

Experimental and numerical investigation on the aerodynamic noise of axial fans is carried out to develop a low-noise fan, which is used to cool a compressor and a condenser in the mechanical room in a household refrigerator. First, the noise performance of the target fan is experimentally investigated and, then, computational aeroacoustic techniques based on the hybrid method are applied to predict the radiated sound pressure levels. The validity of the computational aeroacoustic techniques is confirmed by comparing the predictions with the measurements. To develop a low-noise fan, we came up with two design concepts: one is that the uneven grooves are made on the surface of the suction side of blade along the rotational direction, and the other is that two different blades are combined into one blade. We have set systematic numerical analysis to evaluate the effects of these design factors on the noise generation of axial cooling fans. On the basis of the prediction results showing the possible reduction of noise levels by applying the proposed design factors to the existing fan, experiments using a full refrigerator with two prototype fans are made, which show that the sound power levels from the newly developed fans are less than those of noise from existing fans. Finally, an additional experiment performed by using a grooved/double-bladed fan installed in a household refrigerator shows that the overall noise from the new fan is reduced by approximately 1 dB to 2.2 dB in comparison with that from the existing fan in the refrigerator over the rotating speeds from 1090 rpm to 1210 rpm.