非纯净超临界CO_(2)再压缩布雷顿循环的热力学分析

Thermodynamic analysis of Brayton cycle of recompression of impure supercritical CO_(2)

针对实际超临界二氧化碳(supercritical carbon dioxide,S-CO_(2))发电系统中CO_(2)为非纯净这一问题,以S-CO_(2)再压缩循环为研究对象,基于热力学第一定律建立了再压缩循环的数学模型,纯CO_(2)和非纯净CO_(2)的热物性采用NIST物性数据库,研究了CO_(2)纯度对系统热力学性能的影响。结果表明,在近临界压力区,空气质量分数对密度、焓值的影响较大,远离临界压力区影响较小。主压缩机和透平入口参数对系统热效率影响较大。空气质量分数越大,循环热效率越小。在计算工况内,非纯CO_(2)系统循环热效率较纯CO_(2)系统减小约1~6百分点。研究结果对实际S-CO_(2)循环设计提供一定的理论指导,具有重要的工程意义。

Aiming at the problem that CO_(2) in the actual S-CO_(2) power generation system is impure,a mathematical model of the SCO_(2) recompression cycle is established based on the first law of thermodynamics,the thermal properties of pure CO_(2) and non-pure CO_(2) were obtained using NIST physical properties database,and the influence of CO_(2) purity on the thermodynamic performance of the system is studied.The results show that the influence of air mass fraction on density and enthalpy is greater in the near critical pressure region,and less in the far from the critical pressure region.The main compressor and turbine inlet parameters have great influence on the thermal efficiency of the system.The greater the air mass fraction,the smaller the cycle thermal efficiency.In the calculated working conditions,the thermal efficiency of the non-pure CO_(2) system is reduced by about 1~6 percentage points compared with that of the pure CO_(2) system.The research results provide some theoretical guidance for practical S-CO_(2) cycle design and have important engineering significance.