自然循环闪蒸不稳定诱发的水击现象实验研究

Experimental Investigation of Flashing Instability Induced Water Hammer in Open Natural Circulation System

针对开式自然循环闪蒸不稳定诱发的水击现象进行了实验研究。结果表明,在部分闪蒸不稳定工况下,上升段内闪蒸起始点快速周期性地上下移动,导致系统下部水平段内饱和温度周期性变化,进而诱发该处流体周期性快速汽化和冷凝,其中急速冷凝过程导致气相体积急剧收缩和环绕的水体猛烈撞击,进而诱发水击现象。同时通过实验绘制了此类水击现象区域,并分析得到了相应的边界条件。另外分析了加热段出口温度、上升段高度、入口过冷度和加热功率以及不凝气体等因素对水击现象的影响,为开式自然循环系统的设计提供了依据。

An experimental study on flashing instability induced water hammer in open natural circulation system was performed.The result shows that on some flashing instability conditions,flashing start position moves periodically along the rising channel,which leads periodical change of saturation temperature in the horizontal tube at the underpart of loop,and periodical sudden flashing and condensation in horizontal tube finally.Violent condensation results in drastic shrinkage of vapor and violent strike of the surrounding water,and induces water hammer.The water hammer region and the corresponding boundary were founded by experiment.In addition,the influence factors,such as the heating tube outlet temperature,the inlet sub-cooling and the heating power,the length of upward channel and existence of non-condensable gas on water hammerwere examined,which can provide design considerations of open natural circulation system.