The influence of applying turbine inlet air cooling to a small-scale parallel-flow Brayton cycle

Abstract

To improve an open air-operated parallel-flow Brayton cycle, the air entering the compressor inlet can be cooled via the concept of turbine inlet air cooling (TIAC). This work investigates whether TIAC forms a worthwhile improvement to the power output and thermal efficiency of a parallel-flow Brayton cycle. An analytical approach is followed to compare the results between a low-temperature turbine (LTT) setup and a similar setup with an added cooling loop for the TIAC concept, considering different crossflow condenser dimensions. A range of commercial turbochargers are used to model the compressor and turbines and the best turbocharger combinations are considered for further analysis. Considering the same pressure ratio, the TIAC cycle does not offer better power output nor thermal efficiency than the LTT cycle, however, it is able to lower the required gasifier turbine inlet temperature (which may not exceed 1200 K due to turbomachinery manufacturer limits). When comparing the LTT and TIAC cycles at their optimum operating points, which shifts to a higher compressor pressure ratio for the TIAC cycle due to a larger TIAC compatibility range, the TIAC layout obtains 64.9 % more power output and a 31.4 % improvement in thermal efficiency for the combination between the G25-550 (AR = 0.92) main shaft turbocharger and the GBC14-200 power turbine. It is recommended to investigate recuperated and solar cycle configurations for further cycle thermal efficiency improvements.