【作者】 王升飞；

【导师】 阎昌琪；

【作者基本信息】 哈尔滨工程大学 ， 核能科学与工程， 2010， 博士

【摘要】 密度锁是一种非能动设备,它的作用相当于阀门,但是工作原理却不同于阀门。密度锁内没有任何活动部件,从关闭状态到打开的过程中不需要任何操纵人员的干预也不需要外部动力源,仅仅依靠系统内工作介质本身特性的改变来实现流体通路的截止或连通。因此,掌握密度锁技术及其设计方法,对进一步提高我国核电站的安全性有着非常重要的意义。本文通过实验研究与理论分析相结合的方法,对密度锁技术及其设计方法进行了研究。首先根据密度锁的工作环境,遵循由简单到复杂的原则,把密度锁的工作条件分为4种：不存在外界扰动的静态条件；密度锁上方存在水平剪切流动的水平扰动条件；密度锁内分层界面存在竖直振荡运动的竖直振荡条件；以及综合考虑水平扰动和竖直振荡的综合条件。然后,依次对各条件下密度锁进行实验研究,分析各参数对密度锁的影响。最后,总结研究结果,提出密度锁设计方法,并进行样机结构设计。主要工作和结果如下：(1)根据密度锁的功能提出密度锁的工作要求,确定研究步骤；建立密度锁研究实验台,并对静态条件下密度锁特性进行研究。研究结果表明：静态条件下密度锁内可以形成非常明显的分层,并且分层稳定性好,温度梯度大；通过对密度锁内传热传质进行分析,证明了静态条件下的分层能满足隔离密度锁两侧流体的要求,并得到在设计密度锁结构时需满足的一个条件。(2)在静态条件实验台基础上进行改造,建立模拟密度锁上方存在水平剪切流动的水平扰动条件实验台；通过改变流速、温差和结构等因素,研究各因素对密度锁的影响。研究结果表明：密度锁可以分为混合区,分层区和恒温区,其中分层区又分为强分层与弱分层,分层界面位于混合区与分层区之间；在分区模型的基础上,把密度锁内温度场分为A、B、C、D和E等5类,其中B类温度场最佳,是密度锁正常工作时的最佳选择；当水平流速较小时,分层形成后的温度梯度大,温度场接近静态条件下的温度场；当水平流速较大时,分层形成的较晚且温度梯度较小；当水平流速超过某一临界值时,密度锁内无法形成分层或分层很快消失,密度锁失效；温差的增大,导致分层温度梯度增大,密度锁稳定性增强；栅格结构能增强密度锁的抗扰动能力,使分层形成位置靠上；建立水平扰动条件下密度锁内传热模型,并与实验数据对比进行验证。(3)在水平扰动条件实验台基础上进行改造,建立模拟密度锁内分层界面存在上下振荡的竖直振荡条件实验台,通过实验研究竖直振荡过程中振幅、频率、温差和结构等因素对密度锁的影响。研究结果表明：竖直振荡过程使密度锁内换热方式发生了转变,从导热变为对流换热,强化了密度锁向外界散热,从而导致在振荡速度较大,时间较长时,振荡之后密度锁内的温度场向高温热源方向发生偏移；通过理论分析,给出温度场偏移的计算公式。(4)在综合考虑水平扰动和竖直振荡的条件下,通过实验研究各因素对密度锁的影响。对综合条件中密度锁失效情况进行分析,提出3种解决方法并通过实验进行验证。对密度锁的结构参数进行分析,给出各参数的选取原则,进而提出密度锁设计流程,并设计密度锁样机结构。更多还原

【Abstract】 Density lock is a passive device, functioning as a valve. It has no moving parts and does not need outside power and any operator during the process from closure to open. It only depends on the change of the characteristics of working medium in the reactor to achieve cut-off or connected of fluid channels. Therefore, a detailed knowledge related to the technology and design of density lock is of important significance to further improve the security of nuclear power plants.With the methods of experimental study and theoretical analysis, the research on the density lock technology and design method was carried out. According to the work environment of density lock, the work condition of density lock can be divided into 4 categories:the static condition without external disturbance; horizontal disturbance condition with horizontal flow above the density lock; vertical oscillation condition with the vertical oscillations of stratification; comprehensive condition with both horizontal disturbance and vertical oscillation. The experiment study was carried out in sequence and the effect of different parameters on the density lock was analyzed as well. The method of density lock design was proposed based on the research results and a prototype was also designed. The main work and results are given as follows:First, according to the function of density lock, working requirements of density lock were given. Based on these requirements, the research steps can be determined. Then, we built the experimental loop of density lock and took the research on the characteristics of density lock at the static condition. The results show that:a very clear stratification can be formed in the static condition and it also has a well stability and large temperature gradient; through the analysis of heat and mass transfer in density lock, it is proved that density lock can separated the fluid around it by stratification in static condition, and a condition which is required at the design of density lock was obtained as well.Second, reconstructed the experimental loop for horizontal disturbance condition and studied the effect of the flow rate, temperature difference and structure on the density lock. The results show that:fluid in density lock can be divided into three zones:mixing zone, stratification zone and constant temperature zone; the stratification zone can be divided into strong stratification and weak stratification and the interface is located between the mixing zone and the stratification zone; based on zone model, the temperature field of density lock is divided into five categories in which the second class is the best for normal work; when the horizontal flow rate is small, the temperature gradient of stratification in horizontal disturbance condition is large and closes to the static condition; with the horizontal flow rate becoming larger, the stratification will form later and with a low temperature gradient; when the horizontal flow rate exceeds a critical value, the stratification can not form or will disappear soon and density lock is out of work; with the increase of temperature difference, the temperature gradient increases and the stability of density lock is enhanced; the anti-disturbance ability of density lock can be enhanced by the structure of grid and the stratification also can form at a upper place; the heat transfer model of density lock in horizontal disturbance condition is established and validated by the experimental data.Third, the vertical oscillation experimental loop was rebuilt and the effect of amplitude, frequency, temperature difference and structure on the density lock was researched through the experiment. The results show that:because of the vertical oscillations, the mode of heat transfer in density lock has been changed from heat conduction to convection, enhancing the heat transfer from the density lock to outside, so it leads to that the temperature field of density lock moving to high temperature heat source when oscillation speed is large; temperature offset distance formula is given through theoretical analysis.Fourth, the effect of different factors on the density lock was carried out through experiment at comprehensive consideration; the conditions of density lock failure were discussed and three solutions were proposed which were verified by experiment. Through the analysis of the structural parameters of density lock, the design process of density lock was proposed; based on design process, the density lock prototype structure was given at last.更多还原