Steam injected gas turbine (STIG) with water recovery; Stoomgeinjecteerde gasturbine met waterrecuperatie

The steam injected gas turbine (STIG) is a gas turbine with steam injection in or just after the combustion chamber. The steam is produced by evaporation of water followed by superheating in a steam generator using the heat of the gas leaving the turbine. To close the steam cycle, the water contained in the exhaust gas leaving the steam generator has to be partly condensed. Steam injection allows to improve the efficiency and the specific power of a simple cycle gas turbine. The increase in efficiency is due to the recuperation of a part of the heat in the exhaust gas. The increase in specific power is a consequence of the supplementary mass flow through the turbine. In the present study, first, the efficiency of the sTIG has been analysed on the basis of calculations of the thermodynamic cycle. THe calculations have been done for a range of pressure ratios and turbine inlet temparatures, with methane (CH4), hydrogen (H2), propane (C3H6) and natural gas as fuels. Secondly, for the STIG-cycle, the water recuperation in the condensor has been analysed. Due to the combustion of the fuel, water is formed. Calculations show that for hydrogen all the injected steam can be recuperated. For the other fuels full recovery can not be reached. As a third part in the study the practical recuperation of water in the condensor has been studied on a test rig involving a simple gas turbine cycle augmented with a condensor. It is demonstrated that it is possible to cool the combustion gas such that the water corresponding to the injected steam can be recuperated. By bringing together the results of the theoretical analysis and the test a conclusion can be drawn on the realism of using a steam injected gas turbine for electric power applications.