Experimental Investigation, Modeling and Simulation of a Steam Injected Gas Turbine With Water Recovery

Abstract

Combined heat and power (CHP) plants are faced with alternating heat load caused by different seasonal heating needs of users or alternating heat consumption of industrial processes. To an increasing degree these CHP plants are decentralized generation units of smaller capacity, where combined cycles reach their limits of economy. In these cases, the steam injected gas turbine (STIG) cycle is considered as a promising and efficient technology for more flexible cogeneration of electricity and heat. At decreasing or missing heat load, the process enables to feed excessive steam, generated in the heat recovery steam generator (HRSG), into the gas turbine. Therefore, a flexible response to alternating heat load is possible. At constant electricity output of the gas turbine, steam injection results in a considerable reduction of specific heat consumption. The water losses can be minimized by condensing the steam in the exhaust gas duct of the gas turbine and reconditioning to feed water quality. Process thermodynamic investigations with focus on optimum process scheme have already been conducted for several years by the authors. As a step forward in R&D of the process and its components, a small-capacity STIG plant with water recovery has been commissioned at the Technische Universität Dresden (TUD). It is based on a 600 kW class gas turbine. Investigations are focused both on the process such as performance, process control, water recovery, water reconditioning and on the influence of steam injection on gas turbine and compressor. First experimental results are presented in the paper. Thereby special attention is paid to the measurement instrumentation. In addition, the authors report about thermodynamic simulation of gas turbine operation with and without steam injection.