离心泵内部非稳态流动激励特性研究

发布时间：2018-03-08 21:14

本文选题：离心泵　切入点：流场结构　出处：《江苏大学》2016年博士论文　论文类型：学位论文

【摘要】：振动噪声性能是离心泵重要的考核参数,在某些特殊领域(船舶、核电、潜艇)振动噪声等级甚至是离心泵必须满足的首要指标。离心泵内部湍流场结构复杂,存在多重尺度的涡结构及宏观的分离流动、尾迹、动／静干涉等现象,多种非稳态流场结构的耦合作用导致流激机理极为复杂,流激响应特性尚不明确。离心泵内部复杂流动结构是诱发水力激励力的直接驱动源,构建非稳态流动结构和水力激励力之间的映射关系对初步完善低噪声离心泵设计理论及发展振动噪声能量的主动控制技术至关重要。本文在国家自然科学基金“泵内受迫湍流的涡动力学特征及其激励机制”(51576090)、军工委托项目及江苏省研究生科研创新计划(KYLX-1036)的资助下对离心泵内部非稳态流动结构的激励特性展开研究,主要工作及创新性研究成果如下：采用高精度数值计算手段对泵内精细流场结构进行捕捉,全面获得了不同工况下模型泵内部流动结构分布特性,提取了模型泵蜗壳壁面上的压力脉动信号。从叶片尾迹涡演变机制角度出发剖析动静干涉作用的形成机理,重点研究了泵内非稳态涡结构的分布、演变过程。详细刻画了叶片尾缘脱落涡及其和隔舌产生的撞击、干涉、运动、变形、耗散的发展过程,构建压力脉动能量和涡结构特性的内在关联,提出泵内涡结构的分布特性直接决定相应位置处的压力脉动频谱能量。系统地总结了离心泵过流部件参数对压力脉动特性的影响,基于涡激响应特性,从主动抑制叶片出口尾迹涡强度角度出发,通过数值计算手段探索了叶片出口形状对离心泵性能、涡结构强度及压力脉动能量的影响规律,提出叶片工作面修整可以达到7%左右叶频幅值降的效果。结合空化可视化、空化激励振动特性,首次提出将离心泵内部空化发展过程划分为4个主要阶段,分别为稳定、附着的片状空化；周期性脱落的云状空化；可压缩的泡状空化；具有明显汽／液分界面的空化形态。界定了各阶段的空化数区间,并详细分析了各个阶段空化形态特征及其非稳态发展、演变过程。建立压力脉动、振动试验系统,全面分析了模型泵工况、测点位置对压力脉动、振动频谱特性的影响规律,构建了频谱中主要峰值信号及不同频段内的RMS能量随流量的响应特性。结合离心泵内部复杂流场结构,初步形成离心泵工况-流场结构-水力激励力的关联特性。分析空化对压力脉动、振动频谱的影响规律,描述压力脉动、振动频谱能量随空化数降低的变化趋势,提出该演变过程与离心泵内部的空化形态直接相关。基于空化激励振动特性,本文定义扬程下降1%点为振动临界空化点,低频段振动能量在该点附近达到极大值。由振动能量的变化特性可知：常规3%扬程临界汽蚀点的空化判据略显不足。从空化诱导振动角度出发可以提前判断空化的产生,避免离心泵工作在空化状态,因此可以有效地预防空化对泵系统安全稳定性和叶轮的破坏。通过本文的研究工作初步掌握了离心泵内部非稳态流动结构及其激励特性,可以为低噪声离心泵设计理论及其主动控制技术的发展提供参考。
[Abstract]:Vibration and noise performance of centrifugal pump is an important parameter for assessment, in some special fields (ships, nuclear submarines, vibration and noise level) or even the primary index of centrifugal pump must be satisfied. The internal turbulence field of centrifugal pump with complex structure, the existence of multiple scale vortex structure and the flow from the macro, dynamic / static wake interference phenomenon a variety of non steady flow, coupling structure leads to flow induced mechanism is very complex, the flow induced response is not clear. The internal complex flow structure of centrifugal pump is directly driven by hydraulic power source excitation, mapping between unsteady flow structure and hydraulic exciting force on the active control technology is initially improved low noise centrifugal pump design theory and the development of vibration and noise energy. Based on the National Natural Science Foundation of China "by the pump vortex dynamics characteristics and incentive mechanism of forced turbulence" (51576090), military Research commissioned by the project in Jiangsu province and student research and Innovation Program (KYLX-1036) under the auspices of the excitation characteristics of centrifugal pump internal unsteady flow structure is studied, the main work and achievements are summarized as follows: using high precision numerical calculation method of the pump flow structure to capture fine, full access to the interior of the pump model under different conditions the flow structure distribution, extraction pressure fluctuation signal model of pump volute wall. The formation mechanism of mechanism from the angle of blade vortex evolution analysis of rotor stator interaction, focusing on the distribution of pump, unsteady vortex structure evolution. A detailed characterization of the trailing edge vortex shedding and tongue impact. Interference, movement, deformation, development of dissipation, internal connection construction of pressure fluctuation energy and vortex structure characteristics, put forward the distribution characteristics of the pump vortex structure directly decides Should the pressure fluctuation spectrum energy position. Systematically summed up the influence of parameters on the pressure fluctuation of flow parts of centrifugal pump, vortex induced response based on the characteristics, starting from the active suppression of blade vortex intensity angle, explores on the performance of centrifugal pump blade shape through numerical calculation, influence of vortex intensity and pressure the pulse energy, the trimming blade can reach about 7% leaf drop frequency amplitude. The effect of combination of cavitation visualization, the vibration characteristics of cavitation excitation, is proposed for the first time on cavitation of centrifugal pump development process is divided into 4 main stages, respectively, the attached sheet cavitation cloud cavitation; periodic shedding; compression bubble cavitation; cavitation pattern has obvious steam / liquid interface. The definition of the cavitation number interval of each stage, and a detailed analysis of the morphological characteristics of each stage and its cavitation Unsteady development, evolution. Establishment of pressure pulsation, vibration test system, a comprehensive analysis of the model of pump working condition, measuring position of pressure pulsation, influence of vibration spectrum characteristics, construction of the main peak signal spectrum in different frequency bands and RMS energy with the flow response characteristics. Combined with the internal complex flow structure of centrifugal pump the initial formation of the correlation, the flow structure of centrifugal pump working - - hydraulic excitation force. Analysis of cavitation on the pressure fluctuation, influence of vibration spectrum, describe the pressure pulsation, vibration energy spectrum changes with the cavitation number reduction trend, this is directly related to the process of evolution and the internal form of cavitation of centrifugal pump cavitation characteristics based on vibration. In this paper, the definition of head drop 1% points for the critical cavitation vibration, vibration frequency reaches the maximum value near the point. By the change characteristics of vibration energy: conventional lift 3% A critical point of the cavitation cavitation induced vibration. Lack of perspective can determine in advance of cavitation from cavitation, avoid centrifugal pump in cavitation, thus can effectively prevent cavitation damage to the pump system safety and stability. The impeller centrifugal pump unsteady flow structure and characteristics of internal incentive through research in this paper and can provide a reference for the development of low noise centrifugal pump design theory and active control technology.

【学位授予单位】：江苏大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH311

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