夹点对超临界二氧化碳布雷顿再压缩循环性能的影响

Effect of pinch point on thermal and exergetic performance of supercritical carbon dioxide Brayton recompression cycle

研究了超临界二氧化碳(supercritical carbon dioxide,SCO2)布雷顿再压缩循环回热器的夹点问题,分析了换热器夹点对SCO2布雷顿再压缩循环热效率、净输出功、不可逆损失和?效率等性能的影响,阐述了膨胀机进口温度和循环压比对SCO2布雷顿再压缩循环的影响,并比较了再压缩循环和简单回热循环的性能。结果表明:夹点的位置随着分流比的增大,先出现在低温回热器低温侧的出口,然后出现在低温回热器内部,最后出现在低温回热器低温侧进口;在给定的初始条件下,分流比存在最小值,随着分流比的增大,循环的热效率和?效率先增大后减小;分流比对加热器、低温回热器、冷却器和高温回热器的?损失有较大影响;压比的增大和膨胀机进口温度的升高都会使再压缩循环最小分流比减小;在一定分流比下,再压缩循环的热效率比简单回热循环要高。

The pinch point problem of recuperator on supercritical carbon dioxide Brayton recompression cycle was studied.Then,the effect of the pinch point on the thermal efficiency,specific work output,irreversible exergy losses,and exergy efficiency of supercritical carbon dioxide Brayton recompression cycle was analyzed;and the effect of the inlet temperature of turbine and pressure ratio on supercritical carbon dioxide brayton recompression cycle was discussed.The simple regenerative cycle and the recompression cycle was coampared.The results showed that,with the increase of the spilt ratio,the pinch point first appeared at the outlet of low temperature side of the low temperature recuperator,then at the inside,finally at the inlet.A minimum split ratio existed for the given initial conditions.The thermal efficiency and the exergy efficiency first increased with the rise of split ratio,and then decreased.The split ratio had a great effect on the exergy losses of heater,low temperature recuperator,cooler,and high temperature recuperator.Increasing of the pressure ratio and the inlet temperature of turbine decreased the minimum split ratio of recompression cycle.Furthermore,within a certain range of split ratios,the thermal efficiency of recompression cycle was higher than that of the simple regenerative cycle.