發(fā)布時(shí)間：2018-05-07 15:09

  本文選題：離心泵 + 非定常流動(dòng)��； 參考：《江蘇大學(xué)》2017年碩士論文

【摘要】：離心泵內(nèi)非定常流動(dòng)誘發(fā)的壓力脈動(dòng)是引起泵振動(dòng)噪聲的主要因素之一。由于泵內(nèi)部流動(dòng)結(jié)構(gòu)的多樣性和復(fù)雜性,水力因素誘發(fā)的激勵(lì)信號(hào)也極為豐富,難以直接對(duì)其展開研究。壓力脈動(dòng)、振動(dòng)實(shí)則為水力激勵(lì)的具體表現(xiàn),可以通過數(shù)值計(jì)算及試驗(yàn)手段精確提取相應(yīng)信號(hào)。因此,探尋合理、有效地信號(hào)處理與分析方法,對(duì)于認(rèn)清內(nèi)流激勵(lì)本質(zhì)、揭示泵內(nèi)流誘發(fā)振動(dòng)激勵(lì)機(jī)制至關(guān)重要。同時(shí)也可為離心泵內(nèi)非定常流動(dòng)誘導(dǎo)振動(dòng)機(jī)理的研究提供新方法,為泵的低振動(dòng)噪聲水力設(shè)計(jì)提供參考。本文以一臺(tái)單級(jí)單吸離心泵為研究對(duì)象,綜合運(yùn)用CFD和壓力脈動(dòng)、振動(dòng)測(cè)量等手段對(duì)其內(nèi)部非定常流場(chǎng)及激勵(lì)信號(hào)進(jìn)行提取,并采用多種信號(hào)處理方法對(duì)激勵(lì)信號(hào)展開多角度剖析和總結(jié)。論文主要工作及成果如下:1.歸納了離心泵內(nèi)非定常激勵(lì)信號(hào)的處理方法,在傳統(tǒng)時(shí)、頻域分析的基礎(chǔ)上,引入了時(shí)頻分析、相關(guān)分析、相干分析,探尋適合泵內(nèi)流激勵(lì)信號(hào)的處理與分析方法,以期能揭示更為豐富的流場(chǎng)及激勵(lì)信息,并建立不同激勵(lì)信號(hào)之間的關(guān)聯(lián)關(guān)系。2.基于RNG k-ε湍流模型開展了模型泵內(nèi)部三維非定常流場(chǎng)數(shù)值模擬,獲得了不同工況下的壓力場(chǎng)和速度場(chǎng)分布信息,并提取了蝸殼內(nèi)壁面周向的非定常壓力脈動(dòng)和速度脈動(dòng)信號(hào);從穩(wěn)態(tài)和非穩(wěn)態(tài)兩個(gè)角度分析了離心泵的壓力分布特性和速度分布特性,揭示了離心泵內(nèi)部非定常流場(chǎng)基本特征。3.搭建了模型泵閉式試驗(yàn)系統(tǒng)和LMS多通道振動(dòng)噪聲測(cè)量平臺(tái)。采用微型高頻動(dòng)態(tài)壓力傳感器,對(duì)不同工況下蝸殼內(nèi)壁面周向的壓力脈動(dòng)信號(hào)進(jìn)行了測(cè)量與提取;同時(shí)采用三向振動(dòng)加速度傳感器對(duì)模型泵外壁面、基腳、軸承等位置的振動(dòng)信號(hào)進(jìn)行了測(cè)量與提取。4.基于快速傅里葉變換(FFT),研究了采樣頻率對(duì)離心泵壓力脈動(dòng)信號(hào)的影響;考察了不同測(cè)點(diǎn)位置、運(yùn)行工況、變轉(zhuǎn)速下的壓力脈動(dòng)頻譜特性;基于短時(shí)傅里葉變換(STFT)獲得了壓力脈動(dòng)信號(hào)的時(shí)頻特性,發(fā)現(xiàn)小流量工況下的流動(dòng)隨時(shí)間表現(xiàn)出明顯的不穩(wěn)定性;利用互相關(guān)函數(shù)研究了隔舌附近壓力脈動(dòng)信號(hào)與蝸殼周向壓力脈動(dòng)信號(hào)的相關(guān)性,證實(shí)了壓力脈動(dòng)在蝸殼流道的周向傳播路徑;利用相干函數(shù)研究了隔舌附近壓力脈動(dòng)信號(hào)與蝸殼周向壓力脈動(dòng)信號(hào)在頻域上的相干性,發(fā)現(xiàn)二者在葉頻及其高次諧頻波處的相干程度較高。5.基于FFT研究了測(cè)點(diǎn)位置、空間方向、運(yùn)行工況對(duì)泵振動(dòng)頻譜特性的影響,揭示了不同測(cè)點(diǎn)各個(gè)方向在0-1000Hz頻段振動(dòng)能量的均方根值RMS及振動(dòng)總能量E隨運(yùn)行工況的變化規(guī)律;利用相干函數(shù),初步建立了壓力脈動(dòng)信號(hào)與振動(dòng)信號(hào)之間的關(guān)聯(lián),分析了二者的相干性,結(jié)果驗(yàn)證了由葉輪-隔舌動(dòng)靜干涉作用誘發(fā)的壓力脈動(dòng)是導(dǎo)致泵體在葉頻及其高次諧頻處具有較高振動(dòng)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.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TH311

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