共查询到19条相似文献,搜索用时 265 毫秒
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本文用声电类比方法分析了声学共振器降低与放大声音的分界点,并用该方法对声学共振器固有频率共振对离心式风机噪声的影响进行了系统的理论和试验研究,提出了用λ1/4共振器降低离心风机噪声时必须注意共振器固有频率的选择这个极其重要的问题。 相似文献
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本文从理论上与试验上论证了与声学共振器深度有关的声驻波理论,并根据该理论提出了用腔深各等于离心式风机基频和二阶谐频旋转噪声波长的1/4倍的双腔共振器降低离心式风机噪声的问题,试验证明以双腔深均为基频旋转噪声波长的1/4倍时降噪效果最好,并分析了风机蜗壳区域噪声源的特性。 相似文献
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《制冷与空调(北京)》2016,(5)
针对应用于空调系统的无蜗壳离心式风机和有蜗壳离心式风机,利用Ansys Fluent软件模拟分析水平进出风方式下的空气流场,并结合实测数据,对相同叶轮直径、风量和静压的无蜗壳离心式风机与有蜗壳离心式风机性能进行对比分析。结果表明:在满足效率要求的情况下,无蜗壳离心式风机具有低噪声等优势,气流流场更加均匀,但压损较大,导致全压效率低于有蜗壳离心式风机。 相似文献
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《振动工程学报》2016,(2)
对风机激励下钢-混凝土结构的振动响应开展了模型试验和有限元对比计算分析,系统研究了结构的自振性能、共振形态、受迫振动特性、动位移和动应变等力学行为。研究表明:试验数据与计算结果吻合较好。前两阶振型接近,振型在A形架处有回收趋势,说明该处质量和刚度发生突变。同一测点东西向和南北向反应峰值不同时出现,角部测点的振动反应比中间测点大。悬挑部位测点振动响应较大,说明风机激振力导致了局部杆件振动。结构振动响应随着风机开启数量的增加而增大。风机全部开启时结构最大振动位移约0.1 mm,最大动应变为256.5×10-6。结构低阶共振响应大于高阶共振响应,风机高频运转时出现局部杆件强迫振动。建议避开结构前三阶频率,同时应采用合理构造措施防止构件疲劳破坏。 相似文献
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与大房间声学设计不同,小房间声学设计中还需要妥善处理房间的长、宽、高尺寸比例,这对于降低声染色对音质的不利影响至关重要。通过对矩形刚性墙面封闭房间的谐振(驻波)频率计算公式的讨论,就如何降低房间简正模式简并现象提出了解决方案,即采用房间尺寸优化软件,在给定的房间尺寸范围内自动寻找最佳的房间的长、宽、高尺寸比例;也给出房间尺寸比例不当,出现房间简正模式简并现象时的应对措施。最后,小房间还要考虑低频下限频率以上(即进入声学大房间)的声学处理。 相似文献
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试验分析普通离心风机、无蜗壳离心风机和箱式无蜗壳离心风机的性能差异,总结不同测试方法对无蜗壳离心风机性能测试结果的影响。 相似文献
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陈玉良 《制冷与空调(北京)》2010,10(3):38-40
针对组合式空调机组研制一种新结构的风机段——风机墙,其由无蜗壳风机单元按照一定的规则并联排列组成,可通过关闭风机数量及采用变频技术2种途径实现节能,与其他组合式空调机组的风机段相比具有很大优势。 相似文献
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Abstract An innovative cooling fan with distinguishing features such as ultra thinness, high performance, and quietness is proposed for notebook computers. In particular, the configuration of the proposed fan allows it to suck the largest volume of hot air from surfaces along the vertical direction and expel exhaust air onto the side surface along the horizontal direction, therefore, thinner notebook PCs can be designed. In order to achieve these characteristics, unique designs are required; a 13‐blade impeller is designed for the centrifugal fan in stead of the common conventional design for axial fans, which is a complicated centrifugal blade shape design. A flat rectangular casing for the fan is designed with external dimensions of 89 mm × 76 mm × 13 mm. The casing contains a rotor impeller and a volute; the design of curved throat of the volute is complicated. The top and bottom surfaces, each, have one circular inlet hole. The side surfaces each have a long rectangular outlet hole. In this study, we focus on the P‐Q performance curves of this centrifugal cooling fan designed for notebook PCs, the P‐Q curves are obtained by numerical analysis and tests based on the AMCA standard 210–85. When this fan is subject to real operating conditions, with regard to the maximum flow rate to the near cut‐off point, the pressure P gradually increases from the fan inlet to the fan outlet. The average percentage (%) error in the flow rate Q was determined by both numerical analysis and AMCA test. Additionally, from the result of the standard CNS‐8753 noise test, the fan noise level is 30~33 dBA and the flow field around the inlet, the outlet and the flow passage can be visualized by Particle Interference Visualization (PIV). Finally, according to the P‐Q curve, it can be inferred that this cooling fan outperforms other comparable regular products available. The noise level is satisfactory, and the heat removal is good; hence this design is proposed for application in industry. 相似文献
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J. B. JONKER T. G. VAN ESSEN 《International journal for numerical methods in engineering》1997,40(2):269-294
A finite element based method has been developed for computing time-averaged fluid-induced radial excitation forces and rotor dynamic forces on a two-dimensional centrifugal impeller rotating and whirling in a volute casing. In this method potential flow theory is used, which implies the assumption of irrotational inviscid flow. In comparison with other analyses of fluid-induced impeller forces, two main features have been included. Firstly, the hydrodynamic interaction between impeller and volute isproperly modelled. Secondly, the variation of the width of the volute has been adequately included in the two-dimensional analysis by a modification of the equation of continuity. A regular perturbation method is used to deal with the effects of the whirling motion of the impeller. The excitation forces are calculated from the zeroth-order problem in which the impeller axis is placed at the volute origin. The rotor dynamic forces associated with the whirling motion of the impeller are derived from the first-order solution. The force components, tangential and normal to the whirl orbit, are predicted as functions of the impeller--volute geometry, the flow conditions and the whirl speed ratio. The method is applied to a centrifugal pump experimentally tested at the California Institute of Technology. Comparisons between predictions and experimental data show the capabilities of the proposed method to reproduce the main features of fluid-induced impeller forces in centrifugal pumps. © 1997 by John Wiley & Sons, Ltd. 相似文献
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当风机进出口连接长管道时,其外部辐射噪声主要是内部非定常流动诱发蜗壳振动产生的振动噪声。风机壳体的振动噪声是典型的流固干涉噪声,通常基于非定常流场获得振动激励源。为了控制此类噪声,通过振动噪声数值计算方法,并结合试验设计方法(Design of Experiment, DOE),给出了一种以壳体各板块厚度(前板TF,侧板TS,后板TB)为设计变量、以壳体振动辐射声功率为目标函数的单目标优化方法。研究表明,当保持壳体质量不变时,优化后,壳体表面辐射声功率均有不同程度降低,壳体表面基频辐射声功率降幅最大,达到6.23 dB。 相似文献
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利用FLUENT软件结合有限元体积法和Navier—Stokes方程,通过数值模拟方法研究离心泵蜗壳内的二维流场情况。根据分析结果表明离心泵的蜗壳壁面随着与叶轮距离的增大,受到的冲击越小。蜗壳出口处的壁面位置会存在低压区,对离心泵的内部流场造成能量损耗。利用数值模拟的方法,对离心泵蜗壳的设计优化提供了理论依据。 相似文献
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离心泵流体激励力的研究:蜗壳部分 总被引:4,自引:3,他引:1
研究了叶轮转动过程中离心泵蜗壳所受流体激励力。基于CFD计算了离心泵叶轮转动过程中的瞬态内流场,而后积分得出蜗壳内表面三个方向上流体激励合力并进行频谱分析,最后运用九次多项式拟合、傅立叶级数与分段多项式拟合分别建立叶轮单周转动各向流体合力数学模型。结果表明:蜗壳所受出口方向、进口方向与垂直于进出口方向的流体激励力以叶片通过频率为基频波动,且波动幅值依次减小,波谷均出现于叶片通过蜗舌时;采用三段多项式拟合所建的数学模型与原始波形有最小的偏差,并且具有较低阶次 相似文献