Steady-State Off-Design Thermodynamic Performance Analysis of a Humid Air Turbine Based on a Micro Turbine

This paper presents a steady-state on-design and off-design thermodynamic performance investigation of a Humid Air Turbine (HAT) cycle and other competitive gas turbine cycles based on a simple cycle micro turbine. First of all, several stand-alone softwares and programs were integrated to achieve the computational capability of mass and energy balancing and optimization at on-design and off-design conditions. Later on, this paper shows the simulated on-design performance of a micro turbine in three different modified configurations: 1) recuperated cycle, 2) Recuperated Water Injected (RWI) cycle and 3) HAT cycle. The micro turbine is a 90.10 kW single-shaft simple cycle gas turbine with the electrical efficiency of 12.8%. After transformation, the electrical efficiencies of the recuperated, the RWI and the HAT cycle are 26.21%, 29.26% and 29.92%, respectively; the power outputs are 82.52 kW, 106.22 kW and 109.92 kW, respectively. Finally, the effects of load reduction (part-load at ISO conditions) and ambient temperature on the thermodynamic off-design performance of the simple, the recuperated, the RWI and the HAT cycle were investigated and compared. Simulation results indicate that the HAT cycle and the RWI cycle have similar off-design performance. In addition, the two evaporative cycles have more favorable off-design performance compared with the other two cycles with waste heat utilization of converting to power. It is concluded that the adjustment of the water vapor added to the compressed air has beneficial effect on the stability of the off-design performance. However, because of the absence of intercooler, as well as the limited amount of available waste exergy inside the micro gas turbine cycle, the advantages of the on-design and off-design performance of the transformed HAT cycle on the other competitive cycles are not completely displayed.