【作者】 庞力平；

【导师】 孙保民；

【作者基本信息】 华北电力大学（北京） ， 热能工程， 2010， 博士

【摘要】 径向引入联箱的并联分支管两相流量分配问题广泛存在于电站锅炉、换热器和蒸汽发生器等受热部件中。两相流动的特点决定了流量分配过程中存在着严重的相分离现象,使联箱各个分支管不能保证两相均匀分配,会影响换热设备安全经济运行,因此研究联箱内的两相流量分配问题具有重要的实用价值和理论意义。搭建了空气-水两相流分配实验台,针对径向引入单入口和双入口两相流联箱开展了实验研究,主要进行了入口流型为分层流、波状流和气弹状流下联箱内并联分支管的两相流量分配研究。实验研究发现入口干度在0.006～0.244、质量流速在56-570kg/m2.s范围内时,径向引入联箱分支管中的两相流量分配极不均匀。为了定量分析联箱分支管内的两相流动分配规律,提出了径向引入多并联分支管联箱中的两相流量分配计算方法。应用分流和分支T型三通管相分离计算模型,计算得出径向引入单入口和双入口联箱并联分支管流量分配结果,计算结果和实验结果相符良好。应用计算流体力学(CFD)中自由表面模型,分析联箱内部两相流量分配规律和两相流动变化过程,数值模拟结果和高速摄影结果均显示径向入口联箱内部会出现明显的气液分层现象,形成一个波动的气水界面,影响了各分支管相分配的均匀程度。首次提出加装笛形管均流器能够改善径向引入联箱并联分支管流量分配,提高气液两相分配均匀程度。数值模拟发现笛形管均流分配器能够有效解决普通联箱内部两相分层波动造成的流量分配不均问题。首先进行了径向单引入联箱的两相流量分配的实验研究,实验结果发现加装笛形管均流器后联箱分支管的流量分配接近单相分配；其次实验比较了三种不同结构笛形管均流器的优缺点,结果证明三种笛形管均流分配器均能不同程度地改善联箱分支管两相流量分配；然后针对径向双入口联箱进行了实验研究,实验结果发现加装笛形管均流器不仅能够获得满意的两相流量分配,而且能够在一定程度上解决双入口不对称引入引起的两相流量分配不均问题；最后高速摄影发现加装笛形管均流器后与联箱形成的环形空腔内能够形成块状流动,有效改善气液分层现象,使两相流量分配均匀。试验研究了某电站锅炉水平侧包墙变形问题,现场试验测量获得了包墙区域的温度分布,分析得出包墙下联箱流量分配不佳是造成水平侧包墙变形的原因,并提出了解决办法。更多还原

【Abstract】 The two-phase flow distribution of parallel channels in the manifold under radial inlets has wide applications in conventional power plant, heat exchanger and steam generator, etc. Because of the complexity of two-phase flow fluid, there is severe phase separation during two-phase flow distribution in the manifold. Even phase distribution can’t happen during operation at parallel channels of a manifold. The deterioration of the performance and safety for heat exchanger appears. There is practical and theoretical significances for the study of two-phase flow distribution in a manifold.An air-water two-phase experimental loop is designed and installed for the two-phase flow parallel channel distribution in the manifold. The experiments are performed on manifolds under single and two radial inlets. The inlet flow pattern belongs to stratify, wavy and slug. There is severe uneven two-phase flow distribution and the air and water flow ratios keep at 0.5-1.8 and 0.25～2.0 under the inlet mass quality,0.006～0.24 and mass flow flux,56-570kg/m2.s. The air and water flow ratios distribution have the converse trend.In order to analyze the two-phase flow distribution of parallel channels of manifold with one and two radical inlets, a calculating method is present. The method is based on two T-junction phase separating models, whose of the one is used for a horizontal impacting T-junction and the others is used for a vertical dividing T-junction with a horizontal inlet and a upward outlet and a horizontal outlet. The calculating method is applied to calculate respectively the flow distribution of two experimental test sections with a single and two radial inlets. The calculating and experimental results match well.The free surface model is applied to analyze the two-phase flow inside a manifold using computational flow dynamics (CFD) software. The simulating result is compared with that from a high-speed camera. The numerical simulation finds that there is severe recirculation in the end of manifold and the recirculation will change under different inlet conditions and it will have effects on the two-phase flow distribution of parallel channels. Based on the phenomena, new geometrical test section of manifold with flute is present to overcome the influence from the wavy interface between air and water inside manifold. The simulation shows that the new geometry can make an even two-phase distribution of parallel channels inside manifold.The experiments on a single and two radical inlets with a flute distributor are performed. The experimental results show that there are almost evenly distributed air and water flow ratios among the parallel channels compared with the ordinary manifolds. The air and water flow ratios are among 0.7 and 1.3 in varied inlet conditions. The experimental results are near to the single-phase flow distribution.A practical application is present to analysis a two-radial-inlet manifold. The experiment is performed on the pendant wall superheater in two utility boilers. The deformation in pendant wall superheater happened because of the uneven flow distribution at the downward manifolds in pendant wall superheater.更多还原