Research on the effectiveness of the key components in the HAT cycle

Humid Air Turbine (HAT) cycle is considered to be one of the most advanced gas turbine cycles due to its high efficiency, flexible operation, low NOX emissions, and low investment cost. The heat recovery determines the temperature field distribution of the humidification process, which is critical to the performance of the HAT cycle. However, so far, the effect of heat recovery of heat exchangers on cycle performance is still a research gap. Filling up the research gap is of great significance to the full utilization of the thermodynamic potential of the HAT cycle. This paper built a humid air turbine cycle with additional heat exchangers (aftercooler, regenerator, economizer) based on a humid air turbine test rig. A comprehensive thermodynamic analysis of the effectiveness of the heat exchanger components had been carried out. To conclude, the water-air ratio, aftercooler effectiveness and regenerator effectiveness can effectively affect the humidification performance and efficiency. The above analysis provided a theoretical reference for the actual transformation and performance enhancement of the test rig. In addition, research on the influence of the water-air ratio on the HAT cycle at different power outputs showed that the optimal water-air ratio gradually decreases with the increase of power output. The effect of the pressure ratio on the HAT cycle was clarified by comparison with a simple regenerative cycle. Finally, exergy analysis of the HAT cycle was carried out based on different optimization strategies. For the humid air turbine of 4 MW-class, increasing recuperator effectiveness is one of the effective techniques to enhance exergy recovery as well as efficiency, and improving the proportion of exergy utilized for water evaporation can augment specific work output. The maximum efficiency of 48.5% was obtained where its corresponding exergy efficiency reaches 44.4%. The maximum specific work output of 560.6 kJ/kg was achieved with an exergy efficiency of 38.0%.

Automated summary

The water-air ratio, aftercooler effectiveness and regenerator effectiveness are key factors affecting the humidification performance and efficiency of the HAT cycle.