Coupling effect of key parameters of heat recovery components on the HAT cycle performance

Abstract

Humid Air Turbine (HAT) cycle that uses a water-air mixture as a working fluid has a significant advantage in the distributed generation technologies and combined heat and power. The feature of the HAT cycle is that air humidification is carried out at a variable temperature. This cycle is considered as one of the optimal humidified gas turbine cycles to achieve the energy cascade utilization. However, most studies typically use the method of a single variable to investigate the coupled process of humidification and heat recovery, which limits the further performance improvement of the HAT cycle. Herein, we study the interactions among air humidification, heat recovery and system performance to elaborate the effects of interactive variables on the HAT cycle performance. Considering the complexity of the interaction of water-air ratio, aftercooler effectiveness and recuperator effectiveness, a thorough numerical analysis was carried out from the following perspectives: the thermodynamic correlation between components and systems was investigated by controlling a single parameter; the interaction of multiple variables was performed with identical turbine inlet temperature (TIT) and pressure ratio (PR) conditions; and the coupling relationship between interactive variables with a variation of TIT and PR conditions. A thorough analysis revealed that the variables that significantly impact the HAT cycle efficiency are successively RE, W/A, and AE. The analysis of the coupling effects of interactive variables under different TITs is consistent with the above results. As the PR increases, the W/A and AE have a more significant effect on HAT cycle efficiency and the effect of RE on the HAT cycle efficiency greatly diminishes. The HAT cycle efficiency, specific work output, and heat recovery achieved 43.9%, 556 kJ/kg, 5505.33 kW, where its corresponding TIT, PR, W/A, AE, RE values are 1280 °C, 8, 1.5,0.75, 0.9, respectively. Overall, a thorough analysis of interactive variables is of great significance to fully understand the effect of heat recovery on the efficiency enhancement and specific work output improvement from the thermodynamic perspective.