【作者】 李希川；

【导师】 孙中宁；

【作者基本信息】 哈尔滨工程大学 ， 核能科学与工程， 2013， 博士

【摘要】 液泛现象广泛存在于降膜蒸发器、回流冷凝器和热管等工业设备中。反应堆内可能出现的两相流逆向流动，特别是事故状态下蒸汽发生器内的回流冷凝极限对反应堆安全性具有重要影响。随着科技的发展和反应堆设计的不断改进，相应的堆芯换热通道由传统的较大口径变为窄小乃至微小尺寸，深入研究窄小通道内的液泛问题为开发新型反应堆提供理论基础和实验依据，具有重要实际意义。本文对竖直窄矩形流道液泛进行了理论分析和实验研究，通过流道内液泛试验现象与压差变化规律分析了气体入口条件、流道长度和流道间隙等因素与液泛起始点、完全携带点、流向反转点和液泛消失点的内在联系，阐述了竖直窄矩形流道内的液泛机理；分析了竖直窄矩形流道液泛产生的原因，深入研究了完全携带点、流向反转点和液泛消失点的影响因素；最后将竖直窄矩形流道液泛和传统流道液泛进行了对比。主要成果如下：1.与传统流道以压差突变判断液泛起始点不同，竖直窄矩形流道液泛发生时需要具备四点特征：流道内压差有明显的变化；有液体被携带出注水口；流道内液体下泄流量明显降低；流道内出现强烈扰动的液膜。2.在相同的液体流量下，发生液泛时，流道间隙越小所需要的气体流量越少。流道长度越长，流道内压力越大，发生液泛时所需要的气体流量越小。气体入口条件是影响液泛起始点的重要因素。平切口气体入口条件发生液泛时所需气体流速最低，喇叭口气体入口条件发生液泛时所需气体流速最高，斜切口介于喇叭口与平切口之间。三种气体入口条件的液泛产生位置不同，平切形入口和斜切形入口液泛在流道气体入口产生，而喇叭形入口液泛则在液体入口处产生。3.完全携带点与气体流量大小、气体入口条件和流道注水量无关。流向反转点与气体流量大小、气体入口条件和流道注水量无关，而与流道干燥程度有关；相同水流量条件下，流道湿润时发生流向反转所需的气体流量要比流道干燥时所需要的气体流量大的多。4.在不同的流道长度、流道间隙、气体入口条件下液泛消失现象均存在一定的滞后。水流量较小时，液泛起始点和消失点差别不太大，随液体流量的不断增大，液泛消失滞后现象越明显。流道间隙越小，滞后现象越明显；流道长度越长，液泛消失时需要的气体流量越低。5.窄矩形流道与传统流道液泛过程中压差变化趋势存在较大差异：传统流道发生液泛时，流道内压差发生突变，且为极大值，而在窄矩形流道内，发生液泛时，虽然流道内压差增大，但并没有发生突变，液泛发生时流道内压差并没有达到极大值，窄矩形流道内压差极大值发生在完全携带点。更多还原

【Abstract】 The phenomenon of flooding widely exists in many industrial equipments, such as thefalling film evaporator, reflux condenser, heat pipes and so on. The possible counter currentflow of gas-liquid two-phase flow occurring within reactor, especially reflux condensing limitwithin the steam generator under the accident will generate critical impact toward the reactorsecurity. With the technolgy development and the continuous improvement of reactor design,the channel used for core heat removal changes from a traditional larger diameter to narrowand even small one. In further study of the flooding problem in the narrow channel to providetheoretical and experimental basis for the development of new reactors, has importantpractical significance. In this paper, the theoretical analysis and experimental study of verticalnarrow rectangular channel flooding were investigated. Firstly, the internal relation of the gasentrance conditions, channel length and the gap of flow etc. with the flooding starting point,completely carrying point, flow reverse and liquid the vanishing point were studied by theresearch of experimental phenomenon and pressure drop of relationship. And floodingmechanism in vertical narrow rectangular channel was described. Moreover, the reason ofvertical narrow rectangular channel flooding and the influencing factors of completelycarrying point, flow reverse and flooding disappear were analyzed respectivly. Finally, theflooding of the narrow rectangular channel was compared with traditional channel. The mainresults are as follows：1. As differenting from jadging onset of flooding by pressure mutation in traditionalchannel, four characters should be had on flooding in vertical narrow rectangular channels:sudden rise in the pressure gradient in the test section; appearance of a sustained liquid flowabove the liquid inlet; reduction in the down flow rate of the liquid; appearance of a highlydisturbed film flow.2. At the same liquid flow rate, the gap size of channel is smaller, the gas flow rate islower on flooding. Flooding gas velocities decrease as the pipe length increases. Gas entrancecondition is the important factor effecting on onset of flooding. The gas flow rate is lowest onflooding at plane entrance, highest at bell-mouthed entrance and intermediate at obliqueentrance. Onset of flooding of plane entrance and oblique entrance are produced in the gasentrance but bell-mouthed entrance is produced in the liquid entrance. 3. Carryover of flooding is no related with liquid flow rate, entrance conditions andliquid flow rate. Reversal point related to channel dryness, but no correlation with gas flowrate, entrance conditions and liquid flow rate; with the same water flow rate, gas flow ishigher in a dry channel than in a dry channel at reversal point.4. In different channel length, gap size and gas entrance conditions, flooding disappearedthere are some hysteresis. At the low water flow rate,, onset of flooding and the vanishingpoint are similarly, with the liquid flow increasing, flooding disappeared hysteresisphenomenon more obvious.The hysteresis of flooding becomes more apparently with the gapsize decreasing. At the same liquid flow rate, the length of channel is smaller, the gas flow rateis lower on vanish.5. The results show that the flow characteristics and the tendency of pressure drop invertical narrow rectangular channels were similarly with the conventional channels. However,the maximum of pressure drop appeared at the completed carrying up of flooding in verticalnarrow rectangular channels, and it appeared at the onset of flooding in conventionalchannels.更多还原