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文采用CFD与声学求解器耦合计算的方法,对一离心泵在不同叶片出口角下的内部流场及其外辐射声场进行了数值计算.通过对比不同出口角下离心泵模型的水力特性、流场内特性及压力脉动来分析叶片出口角对离心泵流场及流动诱导噪声的影响。流场计算结果表明,出口角从18°增加到39°,扬程升高6.48%而效率下降10.89%;出口角增加,导致基频处压力脉动强度降低而二阶谐频处脉动强度增加,脉动总强度增加。蜗壳外表面在二阶谐频处振速明显高于其它频率下的振速.外声场声压级的指向性曲线显示,出口角增大,声压级增大,出口角为39°时声压级比出口角为18°时声压级高出约8.6 dB. 相似文献
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叶轮产生离散噪声的原因是叶片间周向夹角均匀布置,因此降低叶轮离散噪声的有效手段就是破坏叶片周向夹角的均匀布置,通过合理布置各叶片夹角降低叶轮离散噪声。本文提出了采用叶片周向角不等距布置降低叶轮总离散噪声A声级的一种优化设计模型,模型充分考虑了A计权函数与波动力对脉动流场响应参数Sc乘积有关的综合衰减曲线的高低频段衰减较大的特性和人可听域频率范围在20-2000Hz之间的特点,通过算例验证采用该模型可以降低总离散噪声A声级。 相似文献
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离心泵内部非定常流动与流场中生成的旋涡密切相关.本文采用Omega涡识别方法研究离心泵流场涡结构及非定常流动特性,阈值选择为0.51.分析得出LES湍流模型相对比其他两种湍流模型涡识别结果更为细致,对叶片流道中的小涡结构可以很好地捕捉.设计工况下,LES模型识别出的涡面积数值是DDES模型的1.15倍,是SSTk-ω模型的1.55倍.压力脉动受流场空间位置与工况影响较大,其主要激励为叶频,并且压力脉动强度与涡面积密切相关.叶轮出口处的涡结构周期性脱落,在隔舌处会撞击隔舌而破裂.离心泵动静干涉的产生与叶轮出口处的涡结构脱落有关. 相似文献
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《工程热物理学报》2020,(7)
为研究离心泵导叶流道进口处压力脉动的分布及传播规律,深入探究导叶式离心泵内动静干涉作用机理。试验采集某核级离心泵相邻两个导叶流道进口处压力脉动信号,并对其进行分析。结果表明:模态节径模式分析方法可以用来分析预测压力脉动主要特征频率成分,导叶流道进口处压力脉动主要为叶片通过频率及其倍频,并以此形式沿叶轮旋转方向向下传播。相同导叶流道进口处流体流动具有不均匀性,各测点压力脉动主要特征频率及最大幅值对应频率不同。压力脉动在叶片通过频率及其倍频处相关性强,随着流量增大至设计工况,压力脉动能量逐渐集中到叶片通过频率及其倍频处。研究可为降低泵内压力脉动提供一定参考。 相似文献
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叶轮产生离散噪声的原因是叶片间周向夹角均匀布置,因此降低叶轮离散噪声的有效手段就是破坏叶片周向夹角的均匀布置,通过合理布置各叶片夹角降低叶轮离散噪声。本文提出了采用叶片周向角不等距布置降低叶轮总离散噪声A声级的一种优化设计模型,模型充分考虑了A计权函数与波动力对脉动流场响应参数SC乘积有关的综合衰减曲线的高低频段衰减较大的特性和人可听域频率范围在20∽20000Hz之间的特点,通过算例验证采用该模型可以降低总离散噪声A声级。 相似文献
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为了减小离心泵的压力脉动,本文提出了一种新型分半错列叶轮结构,将叶轮分半错列,错列角度分别为10°、20°与30°,以比转速为69的离心泵为研究对象,对原模型、叶轮分半错列10°、20°与30°模型进行不同工况下数值计算,获得了泵水力性能与内部压力脉动特性。通过对比分析发现:相比与原始模型,采用分半错列叶轮能有效提高离心泵水力性能;当叶轮分半错列30°时,泵性能提升最大,叶轮与蜗壳间动静干涉作用大幅下降,泵内压力脉动能量降低。研究表明,分半错列离心叶轮是低噪声泵设计可采用有效途径之一。 相似文献
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Experiments on the unsteady flow field and noise generation in a centrifugal pump impeller 总被引:4,自引:0,他引:4
Jong-Soo Choi Dennis K. McLaughlin Donald E. Thompson 《Journal of sound and vibration》2003,263(3):493-514
This paper reports on an experimental investigation of large-scale flowfield instabilities in a pump rotor and the process of noise generation by these instabilities. Measurements of the fluctuating components of velocity and surface pressure were made with hot-wire probes and surface mounted pressure transducers on a seven bladed back swept centrifugal water pump impeller operating with air as the working fluid. The impeller was operated without a volute or scroll diffuser, thereby eliminating any sound generation from pressure fluctuations on the volute cutoff. Thus the study focused on flow field and noise components other than the blade passage frequency (and its harmonics). The primary goal of the study was to provide fundamental information on the unsteady flow processes, particularly those associated with the noise generation in the device. It was further anticipated that detailed flow measurements would be useful for the validation of future computational simulations.The measured data at the discharge show a jet-wake type of flow pattern which results in a strong vorticity field. The flow with high velocity found on the pressure side of the impeller tends to move to the low-pressure region present at the suction side of the passage as a form of roll-up around the blade trailing edge. This motion causes an unsteady flow separation at the suction side of the blade and consequently disturbs the flow in the adjacent passage. By interacting with the impeller blades near the trailing edges, this instability flow causes a periodic pressure fluctuation on the blade surface and generates noise by a trailing edge generation mechanism. The spectrum of surface pressure measured at the trailing edge of each blade reveals a cluster of peaks which were identified with azimuthal mode numbers. The correlation between the acoustic farfield pressure and the surface pressure on the impeller blade has proven that the azimuthal modes synchronized with the number of impeller blades generate noise much more efficiently than the other modes. The paper also clarifies the correlation between unsteady flowfield measurements, in both impeller and laboratory co-ordinates, with the radiated noise properties. Thus some light is shed on the noise generation mechanisms of this particular device. 相似文献
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The experimental and numerical studies have been carried out to investigate the blade passage frequency (BPF) noise of a cross-flow fan (CFF) with the block-shifted impeller. Firstly, the aeroacoustic and aerodynamic features about the five different block-shifted impellers have been obtained experimentally. Secondly, the dynamic pressure sensors were put in the noise generating surfaces to investigate the pressure fluctuations generated by the shifted blocks in the near-field through the cross-correlation analysis. Thirdly, the two-dimensional (2D) unsteady flow field has been simulated by commercial CFD software and the vortex flow patterns and the unsteady force of the blade have been analyzed to detect the noise source about the CFF. Finally, the noise properties about the CFF were predicted by a hybrid method through the Farassat’s equation and the surface pressure fluctuations were provided by the CFD simulations. A simplified theory model has also been built up at the same time. The comparisons are made between the results of hybrid method and the theory model to validate the correctness of the noise prediction methods. The accuracy of these results was also evaluated by the corresponding experimental ones. The results indicate that the impellers with different block-shifted angles are the same in aerodynamic performance but different in the BPF noise. The relations between the shifted angles and the BPF noise levels have been predicted and discussed for the noise reduction. 相似文献
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Experimental and numerical investigation of the unsteady flow field and tone generation in an isolated centrifugal fan impeller 总被引:1,自引:0,他引:1
Daniel Wolfram 《Journal of sound and vibration》2010,329(21):4380-1010
In spite of a low circumferential Mach number the sound of isolated centrifugal fan impellers is sometimes dominated by distinctive tones at blade passing frequency (BPF) and integer multiples. This paper reports on an experimental and numerical investigation intended to unveil the tone generating mechanism. The sound spectra from three impellers operating at a large range of speed were measured and decomposed into Strouhal and Helmholtz number dependent functions. This led to the preliminary conclusion that the BPF related tones are exclusively flow-induced. Based on hot-wire and blade pressure fluctuation measurements and a subsequent correlation analysis, coherent flow structures different from those associated with the principal azimuthal flow pattern due to the blades were detected. Eventually a numerical three-dimensional unsteady flow simulation revealed an inlet vortex. It takes on a helical form, with the vortex core slowly varying its position with respect to the impeller center. As the blades cut through that quasi-stationary helical vortex they encounter blade force fluctuations, producing the BPF tones. Slow spin of the vortex core and slow variation of vortex strength were identified as the reasons for amplitude modulation of the BPF tone. 相似文献
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为了探讨叶型弯曲不同分布对叶轮效率的影响,本文使用三元粘性数值模拟方法,对几个具有弯曲母线的离心叶轮进行了分析比较,在减损机理、特别是设计准则方面进行了摸索和探讨。 相似文献
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W. Neise 《Journal of sound and vibration》1976,45(3):375-403
This paper summarizes the research work done by various experimenters during the last fifteen years. Only those investigations are included in which an attempt was made to reduce the generated sound by modifying the fan itself. Noise attenuation by applying any kind of silencer is not the subject of this paper. Most of the work described was aimed at reducing the blade passage sound, but in some cases a decrease of the broad band noise was also obtained. Three different centrifugal impeller designs are dealt with: multi-vane impellers with forward curved blades, impellers with backward curved blades, and impellers with radial blades. 相似文献
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大小叶片贯流风机内流特性分析与实验研究 总被引:1,自引:0,他引:1
为降低空调用贯流风机的噪声,改善音质,通过采用直叶片贯流风轮达到斜扭叶片贯流风轮的音质和低噪声特性,从而降低贯流风轮的制造成本,本文设计了大小叶片交错组合的新型非等距贯流风机,并采用滑动网格对其内流特性进行了非定常数值模拟,同时对其气动噪声特性进行了实验研究.大小叶片贯流风机的偏心涡基本稳定在叶轮中心与蜗舌相连的切线上,位于叶轮内圆周附近.风轮非定常运转时,偏心涡的涡核位置在直径为2mm的圆所围成的区域内变化.大小叶片交错组合的贯流风轮改变了叶轮与蜗舌的间距,有效地降低叶片通过频率噪声并改善了音质.采用大小叶片交错组合的贯流风轮能够达到斜扭叶片贯流风机的降噪效果. 相似文献
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离心泵叶轮参数对进口回流的影响 总被引:3,自引:0,他引:3
本文对不同叶片进口角、叶片数、不同叶顶间隙的开式和闭式离心叶轮共12种叶轮的进口流场和回流发生情况进行了探针的动态测试和可视化观察.弄清了上述叶轮参数对进口回流初始流量和进口流场的影响. 相似文献
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A numerical study of the aerodynamic and aeroacoustic behaviors of a backward curved blade centrifugal fan was conducted under two important flow conditions: BEP and 1.3 × BEP. Three-dimensional numerical simulations of the complete unsteady flow field for the whole impeller-volute configuration were used to determine the aeroacoustic sources. To locate the unsteady flow and perturbations, the near field wall pressure fluctuations at different strategic points on the volute were computed using the URANS approach. Thus the intensities and positions of the aeroacoustic sources were identified by analyzing frequency spectra. The aeroacoustic sources caused by fluctuations in the interactions of the flows leaving the impeller and volute were close to the volute tongue, and the most effective noise sources related to the flow rate were near the impeller shrouds. In addition, the unsteady flow variables provided by CFD calculations were used as inputs in the Ffowcs Williams-Hawkings equation to estimate the noise tones of the fan. The aeroacoustic calculation results showed that the volute noise was much larger than the blade noise, and the noise mainly propagated from the outlet duct of the fan. Moreover, to account for the noise propagation, three calculation methods were used by applying different solid boundaries. Compared with the other methods, the FEM method, which accounted for the complex solid boundaries, produced good agreement and showed that the complex solid boundaries cannot be neglected in aeroacoustic predictions. The calculation results showed good agreement with the experimental results. 相似文献