本文選題：調節(jié)閥　切入點：流致振動噪聲　出處：《華東理工大學》2017年碩士論文　論文類型：學位論文

【摘要】：調節(jié)閥在工業(yè)管路系統(tǒng)中應用十分廣泛,是管路系統(tǒng)的主要噪聲源之一。內部湍流流動產生的流體動力學噪聲(流致噪聲)是調節(jié)閥噪聲的主要成分。相關研究表明,在大型管道系統(tǒng)的調節(jié)閥附近,其噪聲可高達100多分貝,導致至少兩個方面的潛在危害：一方面是在此工作環(huán)境下的工作人員的身心健康；另一方面,噪聲的產生必然伴隨著劇烈的振動,這加劇了調節(jié)閥及其鄰近管路的損壞,使工業(yè)生產及人員安全面臨巨大的風險。隨著1997年我國《中華人民共和國環(huán)境噪聲污染防治法》的頒布,環(huán)境噪聲污染的防治和生活環(huán)境改善要求的提高,對調節(jié)閥產生的噪聲進行深入研究以有效地對其進行控制,是十分重要而有意義的課題。本文以熱力發(fā)電機組中的一種最小流量調節(jié)閥為研究對象,由內而外地計算了其在內部湍流作用下使得閥門壁面結構振動進而產生的外部噪聲。閥門外部噪聲的計算考慮了流致振動噪聲產生的兩重機理,即聲壁面壓力脈動AWPF及湍流壁面壓力脈動TWPF,并分析了二者在不同頻率段的作用效果。首先采用LES/Lighthill聲類比混合計算方法計算得到調節(jié)閥內部聲場,并提取內壁面處的聲壓即聲壁面壓力脈動作為流致振動噪聲的第一種激勵,再從調節(jié)閥內部非穩(wěn)態(tài)流場中直接提取內壁面處的湍流脈動壓力即湍流壁面壓力脈動作為流致振動噪聲的第二種激勵。然后將兩種激勵加載到調節(jié)閥外部流致振動噪聲計算的聲振模型中,計算得到其外部聲場,并分析外部監(jiān)測點的聲壓級頻譜曲線。分析結果表明：調節(jié)閥外部某位置的聲壓級是兩種噪聲產生機理共同作用的結果,在800Hz以下的低頻段,湍流壁面壓力脈動單獨作用下的聲壓級較大,而在800Hz以上的頻率段,聲流壁面壓力脈動單獨作用下的聲壓級較大,且二者共同作用下的聲壓級均與較大者接近。通過比較調節(jié)閥內、外聲場的監(jiān)測點聲壓級頻譜曲線,得出結論：調節(jié)閥外部聲場產生的主要原因是其下閥腔部位湍流流場中存在的大尺度漩渦。所以,若要有效降低此調節(jié)閥的外部噪聲,可以通過破壞該位置湍流流場中存在的大尺度漩渦實現(xiàn)。結合國家自然科學基金項目中多孔結構的降噪方法,通過對閥座進行結構改造,在調節(jié)閥下閥腔位置加入多孔結構來破壞此位置存在的大尺度漩渦,以此來降低調節(jié)閥產生的噪聲。最終通過計算對比結構改造前后的調節(jié)閥內部流場、內部聲源、內部聲場、外部聲場,證實了此降噪方案的可行性。
[Abstract]:The control valve is widely used in the industrial pipeline system and is one of the main noise sources in the pipeline system. The hydrodynamic noise (fluid-induced noise) generated by the internal turbulent flow is the main component of the regulating valve noise. In the vicinity of a control valve in a large pipeline system, the noise can be as high as more than 100 decibels, resulting in at least two potential hazards: on the one hand, the physical and mental health of the staff working in this environment; on the other hand, The noise must be accompanied by violent vibration, which exacerbates the damage to the regulating valve and its adjacent pipes. With the promulgation of the Law of the people's Republic of China on Prevention and Control of Environmental noise pollution in 1997, the prevention and control of environmental noise pollution and the improvement of living environment are required. It is very important and meaningful to study the noise produced by the regulating valve in order to control it effectively. In this paper, a kind of minimum flow regulating valve in the thermal generator set is taken as the research object. The external noise caused by the vibration of the valve wall structure under the action of internal turbulence is calculated from the inside out. The calculation of the external noise of the valve takes into account the double mechanism of the fluid-induced vibration noise. That is, acoustic wall pressure pulsation (AWPF) and turbulent wall pressure pulsation (TWPF), and their effects at different frequencies are analyzed. Firstly, the internal sound field of the control valve is calculated by using LES/Lighthill acoustic analogy mixing calculation method. The sound pressure at the inner wall is extracted as the first excitation of the fluid-induced vibration noise. The turbulent pulsation pressure at the inner wall is extracted directly from the unsteady flow field of the regulating valve, that is, the turbulent wall pressure pulsation as the second excitation of the flow-induced vibration noise. Then the two kinds of excitation are loaded into the external flow-induced vibration of the regulating valve. In the acousto-vibration model of dynamic noise calculation, The external sound field is calculated and the spectrum curve of sound pressure level is analyzed. The results show that the sound pressure level at a certain position outside the control valve is the result of the interaction of two kinds of noise generation mechanisms, and the frequency range below 800 Hz is low frequency. The sound pressure level of turbulent wall pressure pulsation is larger than that of the acoustic flow wall pressure pulsation in the frequency range above 800 Hz, and the sound pressure level is larger under the single action of the wall pressure pulsation on the turbulent wall. And the sound pressure levels under the combined action of both are close to those of the larger ones. By comparing the spectrum curves of the sound pressure levels at the monitoring points inside and outside the regulating valves, It is concluded that the main cause of the external sound field of the regulating valve is the large scale swirl in the turbulent flow field in the lower valve cavity. Therefore, if the external noise of the regulating valve is to be effectively reduced, It can be realized by destroying the large scale vortex existing in the turbulent flow field in this position. Combining with the noise reduction method of the porous structure in the project of National Natural Science Foundation of China, the valve seat can be reconstructed by means of structural modification. In order to reduce the noise produced by the control valve, the porous structure is added to the position of the valve cavity under the control valve to destroy the large scale vortex in this position. Finally, the internal flow field, the internal sound source and the internal sound field of the control valve before and after the structural modification are calculated and compared. The external sound field proves the feasibility of the noise reduction scheme.
【學位授予單位】：華東理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TH134

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本文編號：1575731