受限通道内孤立汽团形成和溃灭机理及凝结水锤效应研究

The steam-water direct-contact condensation induced water hammer inside pipe widely exists in the steam systems of different industry applications, such as energy, chemical engineering, nuclear power and military. The condensation induced water hammer (CIWH) is generally accompanied with strong pressure oscillation, which induces violent pipe vibration and even severe safety accident. The generation and propagation of pressure wave due to CIWH are related with the isolated steam bubble formation and bubble collapse during steam-water condensation and flow processes in confined channels. Therefore, the present project aims to carry out the mechanism investigations on the isolated steam bubble formation and bubble collapse in confined channels and the characteristics of pressure waves due to CIWH, based on experiments, theoretical analysis and numerical simulations. Firstly, the criteria of isolated steam bubbles in confined channel will be obtained, and the interface characteristic parameters of the isolated bubbles will also be investigated. Then the mechanism of the isolated steam bubble formation in confined channels will be revealed. Secondly, the variations of the interface characteristic parameters, steam condensed rate and condensation heat transfer of the isolated steam bubble during bubble collapses will be investigated, and the coupling relations between pressure wave and bubble interface will be studied. Then the mechanism of the isolated steam bubble collapse in confined channels will be revealed. Finally, the quantitative evaluation system of CIWH and the models of performance prediction of CIWH in confined channels will be established based on the above investigations. In brief, this project aims to reveal the sophisticated mechanism of CIWH and establish the prediction model of CIWH in confined channels, which theoretically benefits for the designs and safe operations of the related steam transportation and utilization systems.

管内汽液直接接触凝结水锤广泛存在于能源、化工、核能及军事等领域的蒸汽系统中。管内凝结水锤发生时会产生强烈的压力振荡，引起管道剧烈振动乃至严重的安全事故。管内凝结水锤的产生和传播与管内汽液两相弹状流的形成及对应孤立汽团的溃灭过程密切相关。为此本项目拟采用实验、理论和数值模拟相结合的方法，对受限通道内弹状流对应孤立汽团的形成和溃灭机理及凝结水锤压力波特性展开研究。获得受限通道内孤立汽团形成的判据及其界面特征参数的变化规律，揭示受限通道内孤立汽团的形成机理；研究受限通道内孤立汽团溃灭瞬态过程中界面特征参数、蒸汽凝结速率和换热系数的变化规律，分析凝结水锤压力波与界面特征参数的耦合关系，揭示受限通道内孤立汽团的溃灭机理；据此建立管内凝结水锤的定量评价体系和性能预测模型。预期通过本项目揭示管内汽液直接接触凝结水锤的产生机理，获得凝结水锤的预测方法，为相关蒸汽输运及利用系统的设计和安全运行提供理论指导。

管内汽液直接接触凝结水锤广泛存在于能源、化工、核能及军事等领域的蒸汽系统中。管内凝结水锤发生时会产生强烈的压力振荡，引起管道剧烈振动乃至严重的安全事故。管内凝结水锤的产生和传播与管内汽液两相弹状流的形成及对应孤立汽团的溃灭过程密切相关。本项目采用实验、理论和数值模拟相结合的方法，对受限通道内汽液直接接触凝结水锤特性开展了系统研究。设计搭建了水平和倾斜管内汽液直接接触凝结水锤实验系统，开展了不同管路结构参数和汽水参数下的凝结水锤实验研究，获得了管内孤立汽团的演变、凝结水锤的产生条件、位置、强度和频次等参数，发现了周期性和非周期性水锤两种现象。建立了管内汽液两相流动的一维两流体六方程模型，综合考虑汽液两相状态方程、虚质量项、界面压力项、壁面摩擦阻力、两相之间的传热传质和动量交换等模型，形成了管内凝结水锤数学模型，据此开发了内凝结水锤性能一维计算程序，并开展了不同影响因素下管内凝结水锤数值模拟研究；获得了凝结水锤整体性能及管内含气率、两相流动和传热特性等局部参数及其变化规律。结合实验和数值模拟研究结果，查清了管内凝结水锤与孤立汽团溃灭过程的耦合关系，揭示了管内凝结水锤的产生机理；建立了管内产生凝结水锤的判定准则以及周期性和非周期性凝结水锤的转变准则，形成了管内不同凝结水锤的流型，；建立了凝结水锤特性的评价指标，开发了周期性凝结水锤频率和位置的预测模型以及两类凝结水锤压力振荡强度的理论预测模型。.相关研究工作发表SCI论文5篇，作国际会议主旨/特邀报告3次，授权发明专利7项，为管内凝结水锤的性能预测和抑制提供了理论基础。基于研究结果开发了管内汽液直接接触凝结振荡预测方法及凝结水锤抑制系列产品及装置，并应用于核反应堆安全泄压系统、舰船动力装置余热排出系统、供热管网等多种工业场景，有效抑制了汽液直接接触凝结振荡和凝结水锤现象，取得了显著的社会和经济效益，以第一完成人获2020年陕西省科技进步一等奖，同时入选2021年长江学者特聘教授。

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