缩放喷嘴监界流量计算的改进模型研究

Research of Modified Critical Mass Flux Model Flowing in Convergent-Divergent Nozzle

研究了压水堆安全分析程序ＴＲＡＣ－ＰＦ１中滞止状态为饱和及欠热水流过缩放喷嘴时临界流量计算模型，发现现有模型项测的临界流量偏高，因而使计算的时间进程往往快于实测的时间进程．研究表明，减压速率Σ对临界流量预测值影响很大，而Σ是喷嘴收缩段轴向位置Ｚ的函数．将按不同轴向位置ｚ计算的减压速率及临界流量与实验数据比较，发现当取喉口上游１．０ｍｍ处计算减压速率、取排放系数ＣＤ为０．９４时，改进的临界流量模型预测值与实验数据符合良好．

The critical mass flux model of initially saturated or subcooled water flowing in convergent-divergent nozzles which is included in pressurized-water reactor thermalhydraulic analysiscede of TRAC-PF1 was investigated. It was found that such medel overpredicts the criticalmass flux, thus the predicted time of event sequence may be earlier than the expermiental result. The investigation showed that the pressure decompression rate Σ strongly affects the critical mass nux, while Σ is a function of axial coordinate z in convergent region of the nozzle.The pressure decompression rate and critical mass flux predicted at different axial positions werecompared with the experimental results [5], it was found that when Σ is evaluated at 1. 0mmupstream of throat, and the discharge coefficient CD of 0. 94 is introduced, good agreementhas been achieved between the modified model prediction and the experimental data [5].