Experimental Study on Flow Instability in Parallel Channels with Supercritical Carbon Dioxide
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摘要: 二氧化碳在拟临界点附近具有独特的理化性质，采用超临界二氧化碳（S-CO2）作为换热工质的布雷顿循环系统拥有可观的系统热效率，但物性的剧烈变化可能导致流动不稳定性问题。本文开展了S-CO2双通道流动不稳定性实验研究，获得了流动不稳定性实验数据。实验结果表明：在自然循环的功率-流量曲线的正斜率区和负斜率区均出现流动不稳定性现象，第1个区间的流动不稳定性为系统性振荡，振荡周期较长，分析为压力降流动不稳定性，第2个区间的流动不稳定性为通道间高频振荡；不稳定起始功率随着系统压力和进口质量流量的增大而线性增大，提高系统压力和进口质量流量可以增强稳定性。
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关键词:
- 超临界二氧化碳（S-CO2） /
- 并联通道 /
- 流动不稳定性
Abstract: Carbon dioxide has unique physical and chemical properties near the quasi-critical point. The Bretton cycle system using supercritical carbon dioxide (S-CO2) as heat exchange medium has considerable system thermal efficiency, but the drastic change of physical properties may lead to the problem of flow instability. In this work, the experimental study of S-CO2 flow instability in two-channel is carried out, and the experimental data of flow instability are obtained. The results show that the flow instability occurs in both the positive and negative slope regions of the natural cycle power-flow curve. The flow instability in the first section is systemic oscillation with a long period, and it is concluded as pressure drop oscillation, while the flow instability in the second section is inter-channel high-frequency oscillation. The onset power of the instability increases linearly with the increasing of system pressure and inlet mass flow rate. Therefore, increasing the system pressure and inlet mass flow rate will enhance the stability. -
图 1 S-CO2双通道实验系统示意图 mm
Figure 1. Schematic Diagram of Experimental System for Two-channel with S-CO2
图 5 自然循环工况下并联通道振荡的演变过程
Figure 5. Evolution of Oscillation in Parallel Channels with Natural Circulation
图 7 第2个振荡区域的流量振荡和温度振荡
Figure 7. Flow and Temperature Oscillations of the Second Region
图 9 质量流量对不稳定起始功率的影响
系统压力：8.41~8.56 MPa；进口温度：26.5~27.6℃
Figure 9. Influence of Mass Flow Rate on Instability Onset Power
图 10 系统压力对不稳定起始功率的影响
质量流量：171.13~173.67 kg/h；进口温度：25.2~27℃
Figure 10. Influence of System Pressure on Instability Onset Power
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