Research of long period operation characteristics of supercritical CO₂/propane mixture brayton cycle

Abstract The use of a CO 2 -based binary mixture with high critical temperature is a potent way to enhance the supercritical CO 2 Brayton cycle performance under a high-temperature environment. The mixtures’ thermal stability at high temperatures significantly affects the Brayton cycle performance. Consequently, investigating the thermostability of CO 2 -based binary mixture is of great importance. In the paper, the thermal decomposition process and main thermal decomposition products of the CO 2 /propane mixture are studied by using ReaxFF. The component models of a 10 MW power plant are established to research the Brayton cycle performance over various operating years after the thermal decomposition of the CO 2 /propane mixture. It demonstrates the CO 2 /propane mixture decomposition rate rises upon the growth of cycle operating years, leading to changes in its critical parameters and compressor power consumption. The decrease in thermal power supplied to the intermediate heat exchanger triggers a drop in cycle thermal efficiency. The cycle performance degradation can be mitigated by optimizing the shaft speed of the cycle. Besides, with the rise in ambient temperature, the cycle performance will also decrease.