旁路阀调节对高温气冷堆闭式布雷顿循环瞬态特性影响研究

闭式布雷顿循环是第4代高温堆核能系统的关键技术之一，其典型的动态过程是旁路阀调节。为分析这一过程，建立了循环中关键部件的动态模型，其中压气机在径向平衡模型基础上耦合了对附面层发展的预测，兼顾了计算效率与准确性；换热部件模型基于双曲型守恒律方程，对工质的热物性和参数的快速变化有较好的适应性。在此基础上根据回路的质量守恒和压力平衡原则将各部件的模型耦合，建立了系统的动态模型。由于旁路阀调节是氦气透平发电系统主要的功率快速调节手段，瞬态效应较为显著，以模块式高温气冷堆（HTR-10GT）旁路阀开启后的过渡过程作为算例，分析了主要循环参数的响应特性，并通过分析，给出了降低输出功率的机制。计算结果表明：系统的容积惯性对旁路阀调节的响应速度影响较大，而阀门的开度则决定了系统在末态的输出功率；回热器的温度冲击现象可能发生在调节过程中，但可通过两旁路阀联动的方式缓解；反应堆出口温度变化幅度很小，因此反应堆模型的准确程度对结果基本无影响。

Influence of Bypass Valve Regulation on Transient Characteristics of Closed Brayton Cycle Coupled with HTR

The closed Brayton cycle is one of the key techniques of the Generation Ⅳ nuclear power system with high temperature gas-cooled reactor (HTR). In order to analyze its dynamic processes, the dynamic models of key components in the system were built. For the compressor, the radial equilibrium model coupled with the prediction of end-wall boundary layer development was used with combined consideration of efficiency and accuracy. The heat exchanger dynamic model was based on hyperbolic conservation law equations considering the temperature-dependency of helium’s thermal physical properties and the fast changes of thermal parameters in the cycle. The components’ models were coupled as the system dynamic model based on the mass conservation and pressure balance. The bypass valve regulation is the major method for quick adjustment of output power in the helium turbine system, and the transient effects are prominent, so that the transients after bypass valve opened in HTR-10GT system were analyzed as examples. With the system dynamic model, the dynamic responses of thermal parameters were calculated and the mechanism of power output decrease was analyzed. It is shown that the system volume affects the speed of dynamic responses, and the bypass valve opening degree determines the power output at the end of the transients. Moreover, the thermal shock phenomenon is likely to occur in the regulation process but it can be relieved with combined operation of two bypass valves at different locations. Finally, it is proved that the core outlet temperature is almost constant, and the accuracy of the reactor model is of almost no effects to the calculation results.