Efficiency Boosting and Steam Saving for a Steam-Injected Gas Turbine Engine: Optimization Study of the Running Conditions

Abstract

The increasing demand for gas turbines motivates the need to improve their performance and reduce the associated exhaust pollutants. Steam injection is an effective technique for boosting power because it increases the thermal efficiency, therefore saving fuel. However, in previous studies, the steam-injection process was designed based on a system of prespecified operating parameters without consideration of change. The present work conducted optimization analysis of a steam-injected gas turbine (STIG) engine to determine the optimum amount of steam for injection into the combustion chamber at specific operating conditions, namely pressure ratio and turbine inlet temperature (TIT) to produce maximum efficiency and decrease wasted water. Design point analysis showed that the injection of the optimum steam-to-air (SA) ratio increased engine efficiency by 31%, increased output power by 76.8%, and decreased specific fuel consumption by 23.8% compared with the simple cycle. Off-design analysis changing the operating conditions was conducted to plot the operating curves of efficiency and specific power against the SA ratio in each scenario. The optimum operation locus of the system for which the efficiency was maximum was traced, and an equation for the system’s optimal operation as a function of TIT was formulated. Finally, the optimized and noncontrolled STIG engines were compared to show superior performance of the controlled engine.