Bottoming organic Rankine cycle for a small scale gas turbine: A comparison of different solutions

• Published in: Applied energy Vol. 106; pp. 355 - 364
• Main Authors: Clemente, Stefano, Micheli, Diego, Reini, Mauro, Taccani, Rodolfo
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.06.2013; Elsevier
• Subjects: Applied sciences; Axial flow; combustion; Devices; Energy; Energy. Thermal use of fuels; Engines and turbines; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Expanders; fluids; Gas expanders; Gas turbines; heat; Heat recovery; Organic Rankine cycle; Rankine cycle; Reciprocating; Scroll expander; Small axial turbine; Small gas turbine; Small radial turbine; turbines; Small gas turbine; Small axial turbine; Scroll expander; Small radial turbine; Organic Rankine cycle; Axial turbine; Rankine cycle; Gas turbine
• ISSN: 0306-2619; 1872-9118
• DOI: 10.1016/j.apenergy.2013.02.004

► The ORC bottoming section for a commercial micro gas turbine has been studied. ► Six different organic working fluids have been considered and compared. ► The preliminary designs of both axial and radial turbines have been developed. ► Also scroll and reciprocating expanders have been analyzed for comparison. ► The best suited machine has to be selected after a detailed analysis in each case. Recently, several efforts have been devoted to the improvement of the thermal efficiency of small gas turbines, in order to approach the typical values of the internal combustion engines in the same range of power. One possibility is represented by a combined cycle, obtained coupling the gas turbine to a bottoming organic Rankine cycle (ORC). This paper deals with the definition of the main features of an ORC system aimed to recover heat from a 100kWe commercial gas turbine with internal recuperator. After the optimization of the thermodynamic cycles, involving a comparison between six working fluids, different expanders are analyzed, with the aim of detecting, if possible, the best suited machine. First, single stage turbines, in both radial and axial flow configuration, are designed specifically for each considered fluid, in particular investigating the opportunity of mounting the ORC expander directly on the high-speed shaft of the gas turbine. Then, the performances of these dynamic machines are compared with those of positive displacement expanders, such as scroll devices, obtainable from commercial HVAC compressor with minor revisions, and reciprocating ones, here newly designed.