物性变化对超临界CO_(2)光热系统动态特性影响

The Effect of Property Changes on the Dynamic Characteristics of Supercritical CO_(2) Solar Thermal Power System

超临界CO_(2)布雷顿循环是太阳能光热利用最具潜力的技术之一,清晰认识系统性能的动态变化特性是机组高效平稳运行的必要条件,超临界CO_(2)在临界点附近的物性变化对系统动态特性分析提出了新要求。本文搭建了系统的动态模型,并对不同输入扰动下系统的动态响应特性进行分析,重点讨论了物性剧烈变化对系统动态性能的影响。结果表明,热源输入增加和冷却水质量流量减少会使系统整体运行温度升高,但低压侧参数对动态扰动的敏感性较低,有利于机组维持稳定;反之,系统整体温度下降,压缩机入口工质处于两相区,影响系统性能。透平转速对系统性能影响较小,相比于主压缩机转速的影响可以忽略。本文所获得的动态响应分析结果可为控制策略建立提供基础。

Supercritical CO_(2) Brayton cycle has become one of the most promising technologies for solar thermal utilization,a clear understanding of system’s dynamic performance is necessary to the efficiency and smooth operation of the unit,while the property changes of CO_(2) near the critical point put forward higher requirements.In this article,a dynamic system model is proposed to analyze the responses of the system under different input perturbations,which emphasizes the effect of drastic changes in the properties of supercritical CO_(2) on system’s dynamic performance.The results show that an increase in heat source input and a decrease in cooling water mass flow rate will increase the overall system operating temperature,but the parameters in lower pressure side are less sensitive to the perturbations,which is conducive to the unit stability;Conversely,the overall system temperature drop,resulting in the compressor inlet fluid being in the two-phase region and thus affecting system performance.Meanwhile,the impact of turbine rotational speed on system performance is negligible compared to the impact of main compressor rotational speed.The analysis of the dynamic response developed in this paper lay the foundation for the control strategies.