内部湍流作用下调节阀外部噪声的耦合计算研究

发布时间：2018-03-06 17:11

本文选题：调节阀　切入点：流致振动噪声　出处：《华东理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：调节阀在工业管路系统中应用十分广泛,是管路系统的主要噪声源之一。内部湍流流动产生的流体动力学噪声(流致噪声)是调节阀噪声的主要成分。相关研究表明,在大型管道系统的调节阀附近,其噪声可高达100多分贝,导致至少两个方面的潜在危害：一方面是在此工作环境下的工作人员的身心健康；另一方面,噪声的产生必然伴随着剧烈的振动,这加剧了调节阀及其邻近管路的损坏,使工业生产及人员安全面临巨大的风险。随着1997年我国《中华人民共和国环境噪声污染防治法》的颁布,环境噪声污染的防治和生活环境改善要求的提高,对调节阀产生的噪声进行深入研究以有效地对其进行控制,是十分重要而有意义的课题。本文以热力发电机组中的一种最小流量调节阀为研究对象,由内而外地计算了其在内部湍流作用下使得阀门壁面结构振动进而产生的外部噪声。阀门外部噪声的计算考虑了流致振动噪声产生的两重机理,即声壁面压力脉动AWPF及湍流壁面压力脉动TWPF,并分析了二者在不同频率段的作用效果。首先采用LES/Lighthill声类比混合计算方法计算得到调节阀内部声场,并提取内壁面处的声压即声壁面压力脉动作为流致振动噪声的第一种激励,再从调节阀内部非稳态流场中直接提取内壁面处的湍流脉动压力即湍流壁面压力脉动作为流致振动噪声的第二种激励。然后将两种激励加载到调节阀外部流致振动噪声计算的声振模型中,计算得到其外部声场,并分析外部监测点的声压级频谱曲线。分析结果表明：调节阀外部某位置的声压级是两种噪声产生机理共同作用的结果,在800Hz以下的低频段,湍流壁面压力脉动单独作用下的声压级较大,而在800Hz以上的频率段,声流壁面压力脉动单独作用下的声压级较大,且二者共同作用下的声压级均与较大者接近。通过比较调节阀内、外声场的监测点声压级频谱曲线,得出结论：调节阀外部声场产生的主要原因是其下阀腔部位湍流流场中存在的大尺度漩涡。所以,若要有效降低此调节阀的外部噪声,可以通过破坏该位置湍流流场中存在的大尺度漩涡实现。结合国家自然科学基金项目中多孔结构的降噪方法,通过对阀座进行结构改造,在调节阀下阀腔位置加入多孔结构来破坏此位置存在的大尺度漩涡,以此来降低调节阀产生的噪声。最终通过计算对比结构改造前后的调节阀内部流场、内部声源、内部声场、外部声场,证实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.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH134

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