Dynamic modelling and transient characteristics of supercritical CO₂ recompression Brayton cycle

In the supercritical CO₂ recompression Brayton cycle, recuperators play an important role in cycle efficiency and operating performance. In this work, a dynamic model of the supercritical CO₂ recompression Brayton cycle is developed. The effects of high-temperature and low-temperature recuperators on the dynamic characteristics of the cycle are examined. It is found that cycle parameters, including temperature, power, and cycle efficiency, exhibit sinusoidal variations like the source signal provided by the hot-side inlet temperature of recuperator. The transient responses in different locations of the cycle have different amplitudes and phases. The source signal with amplitude of 12.5 K at the hot-side inlet temperature of the high-temperature recuperator causes power variations of 10, 1, and 1.3 kW, respectively, in the turbine, main compressor, and recompressor, while the maximum variance of the cycle efficiency is within 1.57%. When the amplitude at the hot-side inlet temperature of the high-temperature recuperator is changed to 25 K, variances in the cycle efficiencies, powers, and temperatures, respectively, nearly double in the turbine, compressors, and recuperators. When two source signals are added to the cycle, the phase of the cycle efficiency well matches each phase of the two individual source signals.