加热双通道密度波流动不稳定性数值研究

Numerical Investigation on Density Wave Oscillation of Two Heated Parallel Channels

密度波流动不稳定性是影响换热设备安全性和可靠性的重要因素之一,其发生机理十分复杂。本工作基于RELAP5程序对加热通道密度波脉动进行了动态计算分析,揭示了脉动期间流体密度、流量及压降等参数的变化规律,并与两种经典机理进行比较分析。结果表明:密度波脉动期间,通道内流量、密度(空泡)及压降呈周期性脉动,加热通道内轴向不同位置流量不同,进出口流量反相脉动,单向段压降和两相段压降基本反相;加热通道密度波脉动的发生与两相段流量波动传播的延迟性有着密切的关系。

Density wave two-phase flow instability plays an important role in operation safety and reliability of heat exchange equipments. The mechanism of density wave oscillation was complicated. RELAP5 was adopted to simulate the flow instability and analyze the density, flow rate and pressure drop characteristics when the density wave oscillation occurred, and the two types of classical mechanisms were compared. The results show that flow rate, density and pressure drop oscillate periodically; the flow rates are different along the heated flow channel and the inlet and outlet flow rates oscillate almost out of phase. The single phase section pressure drop oscillates almost out of phase with two-phase section pressure drop; the density wave oscillation is mostly governed by time delay of flow perturbation propagation along the two-phase section of heated channel.