【摘要】：在閥門(mén)生產(chǎn)和運(yùn)行中,泄漏檢測(cè)是其最重要的工作環(huán)節(jié)之一。針對(duì)目前國(guó)內(nèi)很多廠家普遍采用效率低下的氣泡檢漏法的現(xiàn)狀,本文旨在研究能快速測(cè)試閥門(mén)泄漏率的聲發(fā)射檢測(cè)方法。通過(guò)理論和實(shí)驗(yàn)分析,得出聲發(fā)射泄漏檢測(cè)方法是可行的,能對(duì)閥門(mén)微小泄漏進(jìn)行定性分析,為實(shí)現(xiàn)閥門(mén)自動(dòng)化泄漏檢測(cè)提供了理論基礎(chǔ)。 首先,在本文中分析和對(duì)比了各種常用的泄漏檢測(cè)方法的原理和特點(diǎn),得出了在閥門(mén)泄漏率高于10~(-4) Pa·m~3/s下,聲發(fā)射檢測(cè)方法更易實(shí)現(xiàn)其自動(dòng)化泄漏檢測(cè);并從理論上分析了閥門(mén)泄漏射流的速度場(chǎng)和聲場(chǎng),以及通過(guò)FLUENT仿真分析,得出了閥門(mén)輸入壓力和泄漏孔大小均對(duì)射流速度場(chǎng)分布產(chǎn)生很大的影響,并進(jìn)而影響射流聲場(chǎng)的分布。 其次,基于閥門(mén)泄漏產(chǎn)生聲發(fā)射信號(hào)的原理,建立了可用于測(cè)試閥門(mén)泄漏率高于10~(-3) Pa·m~3/s的微小泄漏狀態(tài)的聲發(fā)射檢測(cè)系統(tǒng),并采用了均勻氣泡法對(duì)這一微小泄漏進(jìn)行標(biāo)定。大量實(shí)驗(yàn)的結(jié)果顯示,該標(biāo)定方法能準(zhǔn)確地測(cè)試出閥門(mén)的泄漏率。針對(duì)閥門(mén)泄漏產(chǎn)生的聲發(fā)射信號(hào)在檢測(cè)中易受環(huán)境噪聲和電氣噪聲干擾的問(wèn)題,設(shè)計(jì)了信號(hào)調(diào)理電路,以及采用了非抽樣小波變換信號(hào)處理等手段來(lái)降低各種噪聲的影響。 再次,通過(guò)編制LABVIEW程序,對(duì)采集到的聲發(fā)射信號(hào)分別進(jìn)行了時(shí)域分析、譜分析以及小波包分析,得出了均方根、FFT功率譜、FFT功率譜密度以及各頻段的能量經(jīng)歸一化處理后的大小等特征量都與閥門(mén)泄漏率有很大的關(guān)系,可以用它們來(lái)表征閥門(mén)泄漏的狀態(tài)。 最后,經(jīng)過(guò)大量實(shí)驗(yàn)統(tǒng)計(jì),得出了閥門(mén)泄漏率與輸入壓力成指數(shù)函數(shù)關(guān)系,但輸入壓力只是影響閥門(mén)泄漏率的因素之一,并不能利用同一指數(shù)函數(shù)來(lái)表示它們之間的關(guān)系;以及得出了泄漏檢測(cè)位置和輸入壓力都會(huì)對(duì)聲發(fā)射信號(hào)的強(qiáng)度、頻譜分布產(chǎn)生影響等結(jié)論。
[Abstract]:Leakage detection is one of the most important work links in valve production and operation. In view of the present situation of low efficiency bubble leak detection method adopted by many domestic manufacturers, this paper aims to study the acoustic emission detection method which can quickly test the leakage rate of valves. Through theoretical and experimental analysis, it is concluded that the method of acoustic emission leakage detection is feasible and can qualitatively analyze the micro leakage of valves, which provides a theoretical basis for realizing automatic leakage detection of valves. Firstly, the principle and characteristics of various leakage detection methods are analyzed and compared in this paper. It is concluded that when the leakage rate of valve is higher than 10 ~ (- 4) Pa 路m ~ 3 s, the acoustic emission detection method is easier to realize automatic leakage detection. The velocity field and sound field of valve leakage jet are analyzed theoretically, and through FLUENT simulation analysis, it is concluded that the valve input pressure and the size of leakage hole have a great influence on the distribution of jet velocity field, and then affect the distribution of jet sound field. Secondly, based on the principle of acoustic emission signal produced by valve leakage, an acoustic emission detection system which can be used to test the micro leakage state of valve with leakage rate higher than 10 ~ (- 3) Pa 路m ~ 3 is established. The uniform bubble method was used to calibrate the small leakage. A large number of experimental results show that the calibration method can accurately test the leakage rate of the valve. In order to solve the problem that acoustic emission signal produced by valve leakage is easily disturbed by environmental noise and electrical noise, the signal conditioning circuit is designed, and the non-sampling wavelet transform signal processing method is used to reduce the influence of all kinds of noise. Thirdly, through the programming of LABVIEW program, the time domain analysis, spectrum analysis and wavelet packet analysis of the acquired acoustic emission signals are carried out, and the root-mean-square and FFT power spectrum are obtained. The power spectral density of FFT and the normalized energy of each frequency band have a great relationship with the leakage rate of the valve. They can be used to characterize the leakage state of the valve. Finally, through a large number of experimental statistics, the relationship between valve leakage rate and input pressure is obtained as an exponential function, but the input pressure is only one of the factors affecting valve leakage rate, and the relationship between them can not be expressed by the same exponential function. It is concluded that the location of leakage detection and the input pressure will affect the intensity and spectrum distribution of AE signal.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2011
【分類(lèi)號(hào)】：TH134

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