离心泵内非定常流动及其激励信号分析

发布时间：2018-05-07 15:09

本文选题：离心泵 + 非定常流动　；参考：《江苏大学》2017年硕士论文

【摘要】：离心泵内非定常流动诱发的压力脉动是引起泵振动噪声的主要因素之一。由于泵内部流动结构的多样性和复杂性,水力因素诱发的激励信号也极为丰富,难以直接对其展开研究。压力脉动、振动实则为水力激励的具体表现,可以通过数值计算及试验手段精确提取相应信号。因此,探寻合理、有效地信号处理与分析方法,对于认清内流激励本质、揭示泵内流诱发振动激励机制至关重要。同时也可为离心泵内非定常流动诱导振动机理的研究提供新方法,为泵的低振动噪声水力设计提供参考。本文以一台单级单吸离心泵为研究对象,综合运用CFD和压力脉动、振动测量等手段对其内部非定常流场及激励信号进行提取,并采用多种信号处理方法对激励信号展开多角度剖析和总结。论文主要工作及成果如下:1.归纳了离心泵内非定常激励信号的处理方法,在传统时、频域分析的基础上,引入了时频分析、相关分析、相干分析,探寻适合泵内流激励信号的处理与分析方法,以期能揭示更为丰富的流场及激励信息,并建立不同激励信号之间的关联关系。2.基于RNG k-ε湍流模型开展了模型泵内部三维非定常流场数值模拟,获得了不同工况下的压力场和速度场分布信息,并提取了蜗壳内壁面周向的非定常压力脉动和速度脉动信号;从稳态和非稳态两个角度分析了离心泵的压力分布特性和速度分布特性,揭示了离心泵内部非定常流场基本特征。3.搭建了模型泵闭式试验系统和LMS多通道振动噪声测量平台。采用微型高频动态压力传感器,对不同工况下蜗壳内壁面周向的压力脉动信号进行了测量与提取;同时采用三向振动加速度传感器对模型泵外壁面、基脚、轴承等位置的振动信号进行了测量与提取。4.基于快速傅里叶变换(FFT),研究了采样频率对离心泵压力脉动信号的影响;考察了不同测点位置、运行工况、变转速下的压力脉动频谱特性;基于短时傅里叶变换(STFT)获得了压力脉动信号的时频特性,发现小流量工况下的流动随时间表现出明显的不稳定性;利用互相关函数研究了隔舌附近压力脉动信号与蜗壳周向压力脉动信号的相关性,证实了压力脉动在蜗壳流道的周向传播路径;利用相干函数研究了隔舌附近压力脉动信号与蜗壳周向压力脉动信号在频域上的相干性,发现二者在叶频及其高次谐频波处的相干程度较高。5.基于FFT研究了测点位置、空间方向、运行工况对泵振动频谱特性的影响,揭示了不同测点各个方向在0-1000Hz频段振动能量的均方根值RMS及振动总能量E随运行工况的变化规律;利用相干函数,初步建立了压力脉动信号与振动信号之间的关联,分析了二者的相干性,结果验证了由叶轮-隔舌动静干涉作用诱发的压力脉动是导致泵体在叶频及其高次谐频处具有较高振动能量的主要原因。
[Abstract]:Pressure pulsation induced by unsteady flow in centrifugal pump is one of the main factors causing pump vibration and noise. Because of the diversity and complexity of the flow structure in the pump, the excitation signals induced by hydraulic factors are very rich, so it is difficult to study them directly. The pressure pulsation and vibration are the concrete manifestation of hydraulic excitation, and the corresponding signals can be accurately extracted by numerical calculation and test. Therefore, it is very important to find a reasonable and effective method of signal processing and analysis for recognizing the essence of internal flow excitation and revealing the mechanism of pump inner flow induced vibration excitation. It can also provide a new method for the study of the mechanism of unsteady flow induced vibration in centrifugal pumps and a reference for the hydraulic design of pumps with low vibration noise. In this paper, a single stage single suction centrifugal pump is used as a research object, and the unsteady flow field and excitation signal are extracted by means of CFD, pressure pulsation, vibration measurement and so on. Various signal processing methods are used to analyze and summarize the excitation signal from different angles. The main work and results are as follows: 1. The processing method of unsteady excitation signal in centrifugal pump is summarized. On the basis of traditional time and frequency domain analysis, time-frequency analysis, correlation analysis and coherence analysis are introduced to explore the processing and analysis methods suitable for pump inner flow excitation signal. In order to reveal more abundant flow field and excitation information, and to establish the correlation relationship between different excitation signals. 2. Based on the RNG k- 蔚 turbulence model, the three-dimensional unsteady flow field in the model pump is numerically simulated. The distribution information of pressure field and velocity field under different working conditions are obtained, and the unsteady pressure pulsation and velocity pulsation signal in the circumferential direction of the inner wall of the volute are extracted. The characteristics of pressure distribution and velocity distribution of centrifugal pump are analyzed from the point of view of steady and unsteady state, and the basic characteristics of unsteady flow field in centrifugal pump are revealed. The model pump closed test system and LMS multi-channel vibration and noise measurement platform are built. The pressure pulsation signals of the inner wall of the volute are measured and extracted under different working conditions by using the micro high frequency dynamic pressure sensor, and the external wall and the base of the model pump are also measured and extracted by using the three direction vibration acceleration sensor. The vibration signal of bearing at equal position was measured and extracted. 4. 4. Based on fast Fourier transform (FFT), the influence of sampling frequency on pressure pulsation signal of centrifugal pump is studied, and the spectrum characteristics of pressure pulsation under different measuring points, operating conditions and variable rotational speeds are investigated. Based on short time Fourier transform (STFT), the time-frequency characteristic of pressure pulsation signal is obtained, and it is found that the flow shows obvious instability with time under the condition of small flow rate. The correlation between the pressure pulsation signal near the tongue and the circumferential pressure pulsation signal of the volute is studied by using the cross-correlation function, and the circumferential propagation path of the pressure pulsation in the volute passage is confirmed. The coherence between the pressure pulsation signal near the tongue and the circumferential pressure fluctuation signal of the volute in frequency domain is studied by means of coherence function. It is found that the coherence degree between the two signals is higher than that at the blade frequency and its high order harmonic frequency wave. Based on FFT, the effects of measuring point position, space direction and operating conditions on the vibration spectrum characteristics of pump are studied. The RMS root mean square value (RMS) of vibration energy of different measuring points in 0-1000Hz frequency band and the variation rule of total vibration energy E with operating conditions are revealed. By using the coherence function, the correlation between the pressure pulsation signal and the vibration signal is preliminarily established, and the coherence between the two signals is analyzed. The results show that the pressure pulsation induced by the impeller-tongue dynamic and static interference is the main reason for the higher vibration energy of the pump body at the blade frequency and its high order harmonic frequency.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH311

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