先进超临界二氧化碳(supercritical carbon dioxide,S-CO2)布雷顿循环系统因具有紧凑、高效灵活的特点,在第三代光热系统和第四代核电系统中具有良好的应用前景,而布雷顿循环系统中的流动不稳定性威胁着机组的安全运行.为研究竖直上升并联管内 CO2 的流动不稳定性,该文建立CO2流动不稳定性系统进行实验研究,获得热工参数对流动不稳定性的影响规律;引入无量纲节流系数,构建 CO2 流动不稳定性预测模型;模型预测效果良好,预测值与实验值吻合良好(误差±20%).研究发现,增加系统压力、增加质量流量及过冷度范围在 5～20℃时,减小过冷度均有利于提高并联管间流动的稳定性;随着出口节流增加,并联管间流动稳定性降低,且发生不稳定性的界限热负荷逐渐减小.
An Experimental Study on Flow Instability of Carbon Dioxide Between Two Parallel Vertical Upward Channels
Due to its compactness,high efficiency and flexibility,the potential applications of advanced supercritical carbon dioxide(S-CO2)Brayton cycle in Generation III of Solar-thermal systems and Generation IV nuclear reactors are fantastic.The flow instability in the Brayton cycle system threatens the safe operation of the unit.To study the flow instability of CO2 in parallel vertical upward channels,an experimental system is established,and the effect of operational parameters on the flow instability is obtained.A prediction model on CO2 flow instability is established by introducing a dimensionless throttling coefficient.The predicted value is in good agreement with the experimental value(±20%).It is found that increasing the system pressure and the mass flow,and reducing the subcooling(ΔTsub=5～20℃)can increase the flow stability between parallel tubes.With the increase of outlet throttling,the flow stability between parallel tubes decreases,and the stability boundary of heat load gradually decreases.
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