Static process calculations done by various institutions have shown competitive thermal efficiencies for the evaporative cycle, also known as the HAT-cycle, when compared to the combined gas and steam cycle. The cycle seems also attractive from other standpoints such as lower investment costs and excellent part load performance. With this background several companies and organisations in Sweden have jointly started an evaporative gas turbine project.
The participating organisations agreed to design and erect a pilot plant at the Lund Institute of Technology. In co-operation with the Royal Institute of Technology in Stockholm various tests will be performed with the overall goal to verify efficiency improvements and functional performance. The test schedule started with the gas turbine in dry stand alone operation. From this initial phase the process will be developed, first step is the introduction of a recuperator. The final process includes a water circuit and condensing of water vapour in exhaust gases for recycling to the humidifier.
This paper presents a dynamic model of the gas turbine unit with and without the recuperator. Algebraic models are used for the gas turbine components combined with conservation equations in differential forms for volumes. The approximation used for volumes is the lumped parameter model meaning that properties within the volume are uniform. Heat flow between gas and solid structure is included in the recuperator model but is elsewhere neglected. A comparison between measurements and calculations is presented for the gas turbine without recuperator.