超临界CO_2及其混合工质布雷顿循环热力学分析

Thermodynamic Analysis of Brayton Cycles Using Supercritical Carbon Dioxide and its Mixture as Working Fluid

本文运用热力学第一、第二定律对分流、预压缩再热、改进再压缩超临界CO_2布雷顿循环进行了热力学分析,重点讨论了压缩机和透平入口工况(温度、压力)对循环热力学性能的影响。以改进再压缩循环为基础,进一步提出以CO_2为基底的混合工质布雷顿循环,分析了气体种类及加入量对混合工质布雷顿循环热力学性能的影响。结果表明:提高透平入口工况能够提高不同形式循环的效率;与压缩机入口温度对循环效率的影响相比,压缩机入口压力对循环效率的作用更大;在CO_2质量分数大于50%的情况下,加入氙气与氪气均可提高循环热效率,增幅最大分别为1.44%和3.04%,氙气与氪气对应质量分数分别为50%和26%;加入氮气反而使循环效率降低。

In this paper,the first and the second laws of thermodynamics are applied to analyze the thermodynamic performance of the split flow,pre-compression and modified recompression Brayton cycles.Firstly,the influences of the compressor and turbine inlet conditions（temperature,pressure）on the cycles performance are discussed.Furthermore,the Brayton cycles using mixture working fluid based on carbon dioxide（CO2） are proposed,and the typical modified recompression cycle is taken as an example to show the performance.The effects of different adding gases and the proportion of a gas in CO2 are analyzed.The results indicate that higher turbine inlet conditions can improve the efficiency of different cycles;the influence of the comperssoer inlet pressure on the cycle efficiency is greater than that of the compressor inlet temperature;adding krypton gas and xenon gas can improve the cycle thermal efficiency;the largest improvements of the modified recompression cycel thermal efficiency are 1.44%and 3.04%when adding 50%krypton gas and 26%xenon gas,respectively;however,adding nitrogen gas decreases the cycle efficiency.