锥阀振荡流场流动噪声增强机制研究

发布时间：2018-03-19 04:22

本文选题：锥阀　切入点：稳定性　出处：《浙江大学》2015年博士论文　论文类型：学位论文

【摘要】：液压传动具有功率密度高、传输功率大等优点,被广泛应用于工业领域,对科技发展产生重要推动作用。随着现代电力技术迅猛发展以及人们对设备操作舒适性、环保性要求日益提高,给液压传动带来严峻挑战,液压技术要取得生存与发展必须朝高能量利用效率、高压力、大流量、低噪声等方向发展。为提高能量利用效率,闭式系统是液压技术发展的方向。锥阀具有响应快、成本低、抗污染能力强等特点,被大规模应用于闭式系统中,但锥阀液动力大,液动力突变易引起锥阀失稳,产生严重的振动与噪声问题。此前关于锥阀的研究主要基于开式系统,锥阀应用于闭式系统时先前被忽略的问题可能变得非常突出。因此,为更好地设计闭式系统,需对锥阀固有问题重新进行仔细研究。本课题主要针对锥阀振荡流场流动噪声展开研究,希望通过本课题研究,深化人们对液压阀噪声的认识,为低噪声液压系统设计提供理论依据。本课题结合实验测量、理论分析以及数值仿真等手段,对锥阀振荡流场流动噪声增强机制展开了系统而深入地研究,得到了有、无空化下锥阀振动特性随无量纲参数阀座比变化的规律,分析了空化噪声增强的机制,提出空泡溃灭事件增加是锥阀振动后空化噪声加剧的主要原因。针对锥阀啸叫噪声,提出了锥阀啸叫噪声是射流激励阀腔产生流体共振的假设,并对假设进行了论证,结果表明锥阀中流体与声学耦合产生亥姆霍兹共振是导致锥阀只对特定频率噪声信号进行选择性放大的原因。论文的主要研究工作如下：1.验证了锥阀振动的机理,利用实验研究和理论分析相结合的方法分析了锥阀空化对振动特性的影响,观测到有、无空化两种工况下锥阀振动特性差异随阀座比R*的变化规律,结合锥阀中空化流流态阐述了导致有、无空化两种工况下的锥阀振动特性差异的原因。2.观测到锥阀振动后空化噪声增强的现象,提出锥阀振动后空化噪声急剧增强主要由空泡溃灭事件增加所导致的观点,利用实验与仿真等手段揭示了振荡流场中空泡溃灭事件增加的机制,指出锥阀振动破坏了回流低压区中固定型空化结构,使气核通过回流低压区时发展成空泡的事件增加,加剧了空化程度,基于锥阀中空化现象产生机理给出了低空化噪声锥阀的优化方案。3.采用频谱分析的方法研究了锥阀啸叫噪声频谱特征,利用实验与仿真相结合的方法分析了啸叫噪声的噪声源,通过大量的实验,观测到多相流、变开度及变阀腔体积下啸叫噪声基频漂移规律,提出锥阀啸叫噪声是由流-声耦合作用引起流体共振产生的假设,利用阀腔声学共振频率公式对假设进行了验证,揭示了高频啸叫噪声对特定噪声信号的选择性放大机理,为锥阀啸叫噪声的抑制提供了理论依据。
[Abstract]:Hydraulic transmission has the advantages of high power density and high transmission power. It is widely used in industrial fields and plays an important role in the development of science and technology. With the rapid development of modern power technology and the comfort of equipment operation, The requirement of environmental protection is increasing day by day, which brings severe challenge to hydraulic transmission. In order to survive and develop hydraulic technology, it is necessary to develop in the direction of high energy utilization efficiency, high pressure, large flow rate, low noise and so on. Closed system is the development direction of hydraulic technology. Conical valve has the characteristics of fast response, low cost and strong anti-pollution ability. It is widely used in closed system, but the fluid power of conical valve is large, and the sudden change of hydraulic force can easily lead to the instability of cone valve. Causing serious vibration and noise problems. Previous studies on conical valves were mainly based on open systems, and previously neglected problems with conical valves when applied to closed systems may become very prominent. Therefore, for better design of closed systems, It is necessary to re-study the inherent problems of conical valve. This subject mainly focuses on the flow noise of conical valve oscillating flow field, hoping to deepen people's understanding of hydraulic valve noise through this research. This paper provides a theoretical basis for the design of low noise hydraulic system. By means of experimental measurement, theoretical analysis and numerical simulation, the mechanism of flow noise enhancement in conical valve oscillating flow field is studied systematically and deeply. In this paper, the mechanism of cavitation noise enhancement is analyzed and the mechanism of cavitation noise enhancement is analyzed. It is pointed out that the increase of cavitation collapse event is the main reason for the increase of cavitation noise after cone valve vibration. The hypothesis that the screeching noise of the cone valve is the fluid resonance of the jet excited valve cavity is proposed, and the hypothesis is proved. The results show that the Helmholtz resonance caused by the fluid and acoustic coupling in the cone valve is the cause of selective amplification of the noise signal of the cone valve only at certain frequencies. The main research work in this paper is as follows: 1. The mechanism of the vibration of the cone valve is verified. The effect of cone valve cavitation on vibration characteristics is analyzed by means of experimental study and theoretical analysis. The variation of vibration characteristics of cone valve with seat ratio R * is observed under two conditions without cavitation. Combined with the hollow flow pattern of cone valve, the causes of the difference in vibration characteristics of cone valve under two conditions, I. e., cavitation and non-cavitation, are expounded. 2. The phenomenon of cavitation noise enhancement after cone valve vibration is observed. It is pointed out that the sharp increase of cavitation noise after conical valve vibration is mainly caused by the increase of cavitation collapse events. The mechanism of cavitation collapse events in oscillating flow field is revealed by means of experiment and simulation. It is pointed out that the vibration of conical valve destroys the fixed cavitation structure in the reflux low pressure region, increases the number of cavitation events when the gas core passes through the reflux low pressure region, and intensifies the cavitation degree. Based on the hollowing mechanism of cone valve, the optimization scheme of low altitude noise cone valve is given. The spectrum characteristics of cone valve howling noise are studied by spectrum analysis method, and the noise source of screech noise is analyzed by combining experiment and simulation. Through a large number of experiments, we observed the fundamental frequency drift law of roar noise in multiphase flow, variable opening and variable valve cavity volume, and proposed the hypothesis that cone valve roar noise is caused by fluid-acoustic coupling. The hypothesis is verified by the acoustic resonance frequency formula of the valve cavity, and the selective amplification mechanism of the high frequency whistling noise to the specific noise signal is revealed, which provides a theoretical basis for the suppression of the cone valve howling noise.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TH137

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