【摘要】 窄矩形通道以其独特的尺寸及换热性能广泛应用于各种工业系统，但两相流动不稳定性限制了其进一步的发展。本文以50 mm×3 mm×1 000 mm的窄矩形通道为研究对象，构建了窄矩形通道自然循环系统，并基于已有实验数据结果进行了模型验证。研究低压下系统流动不稳定性，发现了带有冷段逆流的大幅度流量振荡现象。分析结果表明，此类流动不稳定性存在4个阶段：回路阻塞、稳压器回流、逆流冲击以及恢复阶段。流动不稳定性产生机理与系统特殊尺寸以及运行工况有关。窄矩形通道在低压低流量高加热功率下极易产生阻塞流动的大量气泡；位于加热段上游的稳压器为流量波动提供充足空间与驱动力；上升段内逆流冲击发生后系统流量处于较低状态，进而极易从短暂稳态过渡到流量振荡状态。将稳压器连接至加热段下游，以及增大冷段逆流节流系数，都对此类流动不稳定性具有抑制作用。更多还原

【Abstract】 Narrow rectangular channels are widely used in various industrial systems for their unique dimensions and heat transfer performance, but the two-phase flow instability limits their further development. In this paper, a narrow rectangular channel of 50 mm×3 mm×1 000 mm is taken as the research object. Based on the existing experimental data, the accuracy of the model is verified. And a natural circulation system of the narrow rectangular channel is constructed to study the flow instability of the system under low pressure. A phenomenon of large-scale flow oscillations with the backflow of the cold leg is observed. The analysis results show that there are four stages of this type of flow instability: loop blockage, regulator return, countercurrent shock, and recovery stage. The mechanism of flow instability is related to the special dimensions of the system and the operating conditions. Narrow rectangular channel in the low pressure, low flow rate and high heating power conditions, is easy to produce a large number of bubbles blocking the flow. The pressurizer provides system flow is in a lower state after countercurrent impact occurs in the rising section, and then very easy to sufficient space and driving force for flow fluctuations, which located in the heating section upstream. During the rising section, after the occurrence of reverse flow impact, the system flow remains at a low level, which makes it highly prone to transitioning from a short-term steady state to the flow oscillation state. Connecting the pressurizer downstream of the heating section and increasing the countercurrent throttling coefficient in the cold section have a dampening effect on such flow instabilities.更多还原