Investigation of a supercritical closed cycle with independent power turbine

In this study, thermodynamic analysis of the supercritical closed Brayton cycle with independent power turbine operating with carbon dioxide (CO2), which stands out with its thermophysical properties, was performed. For this purpose, an independent power turbine was added to the cycle based on the basic principles of the Brayton power cycle and the cycle parameters were examined. The effects of turbine inlet temperature and pressure, compressor pressure ratio, compressor efficiency, high and low (independent) pressure turbine efficiency and compressor inlet temperatures on the energy-exergy efficiency of the cycle and the cycle net power were examined in different cycle parameters. In addition, the effects of the low-pressure (independent) turbine in the cycle on the cycle were evaluated. The cycle analysis was performed using the computer program called Engineering Equation Solver (EES). When the cycle parameters were examined, it was determined that when the turbine inlet pressure was increased at a constant turbine inlet temperature, the energy-exergy efficiency of the cycle and the net power of the cycle increased. It was determined that when the turbine inlet temperature was increased at a constant turbine inlet pressure, the energy-exergy efficiency decreased while the net power of the cycle increased. It has been found that when compressor efficiency is increased at constant turbine inlet temperature, energy-exergy efficiency and cycle net power increase. When turbine parameters are examined, it is found that low-pressure (independent) turbine has a direct effect on cycle efficiency by 2.64%. In cycle parameters, maximum energy efficiency is calculated as 20.07%, exergy efficiency is 39.22% and cycle net power is 306.4 kW. In power cycles, the benefits of using CO2 turbines and the effects of low-pressure (independent) turbine on the cycle are evaluated. The gains that can be obtained with CO2 turbines are discussed. There is no study in the literature examining the performance of supercritical CO2 cycles specifically for independent power turbines.