sCO_(2)循环部分负荷运行特性研究

Partial load operation characteristics of the sCO_(2) cycle

超临界二氧化碳(supercritical CO_(2), sCO_(2))循环发电系统结构紧凑,具有灵活高效的特点.本文以300 MW级s CO_(2)循环发电系统为研究对象,基于存储控制(inventory control)运行方式构建了耦合部件非设计(off-design)计算的系统部分负荷模型.部分负荷运行时,回热器和涡轮机械运行参数都会发生变化,且变化规律不同,为剖析系统性能损伤机理,设置了两种不同研究方案:(1)涡轮机械主要运行参数(主气压力和等熵效率)不变,研究回热器对系统热效率的影响;(2)涡轮机械和回热器参数均发生变化.不同研究方案结果表明,随负荷率减小回热器效率增加,压降减小,对系统性能产生正效应.部分负荷运行时主气压力的减小对透平做功影响较大,同时透平效率降低明显,对系统产生负效应.标准存储控制条件下,系统热效率随负荷率呈抛物线变化. 100%~75%负荷时,系统中正效应大于负效应,热效率大于设计热效率,在85%负荷时系统热效率达到最大值49.82%. 75%~30%负荷时,系统中正效应小于负效应,热效率小于设计热效率.研究结果可为sCO_(2)循环系统的变负荷运行提供指导,并可为系统动态调控过程提供目标值.

The supercritical carbon dioxide(s CO_(2)) cycle power generation system is compact, flexible, and efficient. In this paper, a 300-MW s CO_(2)cycle power generation system is taken as the research object, and a partial load model based on the inventory control operation mode is established by coupling the off-design models of components. During partial load operations, the operating parameters of the regenerators and turbomachines change according to different rules. To analyze the performance damage mechanism of the system,two research schemes are established:(1) The main operating parameters of the turbomachine(the main gas pressure and isentropic efficiency) are unchanged, and the influence of the regenerators on system thermal efficiency is studied and(2) the parameters of the turbomachines and the regenerators are varied. The results of these research schemes show that with decreasing load ratio, regenerator effectiveness increases, and the pressure drop decreases, which has a positive effect on system performance. During a partial load operation, the reduction of the main gas pressure greatly influences the turbine work, and simultaneously, the turbine efficiency decreases substantially, which has a negative effect on the system. Under standard inventory control operation, system thermal efficiency varies parabolically with the load ratio. When the load ratio is 100%–75%, the positive effect on the system is greater than the negative effect, so the thermal efficiency is greater than the design thermal efficiency. At 85% load, the system thermal efficiency reaches the maximum value of 49.82%. When the load ratio is 75%–30%, the positive effect on the system is less than the negative effect, and the thermal efficiency is less than the design thermal efficiency. The research results can guide the variable load operation of the s CO_(2)cycle system and provide target values for the dynamic control process of the system.