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Preliminary design optimization of an organic Rankine cycle radial turbine rotor
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.ORCID iD: 0000-0002-8466-356X
Saab AB, Linköping, Sweden.
Federal University of Itajubá, Itajubá, MG, Brazil.
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2017 (English)In: Proceedings of the ASME Turbo Expo, American Society of Mechanical Engineers (ASME) , 2017Conference paper, Published paper (Refereed)
Abstract [en]

The present study describes the application of a preliminary design approach for the optimization of an organic Rankine cycle radial turbine. Losses in the nozzle the rotor have initially been modelled using a mean-line design approach. The work focuses on a typical small-scale application of 50 kW, and two working fluids, R245fa (1,1,1,3,3,-pentafluoropropane) and R236fa (1,1,1,3,3,3-hexafluoropropane) are considered for validation purposes. Real gas formulations have been used based on the NIST REFPROP database. The validation is based on a design from the literature, and the results demonstrate close agreement the reference geometry and thermodynamic parameters. The total-to-total efficiencies of the reference turbine designs were 72% and 79%. Following the validation exercise, an optimization process was performed using a controlled random search algorithm with the turbine efficiency set as the figure of merit. The optimization focuses on the R245fa working fluid since it is more suitable for the operating conditions of the proposed cycle, enables an overpressure in the condenser and allows higher system efficiency levels. The R236fa working fluid was also used for comparison with the literature, and the reason is the positive slope of the saturation curve, somehow is possible to work with lower temperatures. Key preliminary design variables such as flow coefficient, loading coefficient, and length parameter have been considered. While several optimized preliminary designs are available in the literature with efficiency levels of up to 90%, the preliminary design choices made will only hold true for machines operating with ideal gases, i.e. typical exhaust gases from an airbreathing combustion engine. For machines operating with real gases, such as organic working fluids, the design choices need to be rethought and a preliminary design optimization process needs to be introduced. The efficiency achieved in the final radial turbine design operating with R245fa following the optimization process was 82.4%. A three-dimensional analysis of the flow through the blade section using computational fluid dynamics was carried out on the final optimized design to confirm the preliminary design and further analyze its characteristics.

Place, publisher, year, edition, pages
American Society of Mechanical Engineers (ASME) , 2017.
Keyword [en]
Organic ranking cycle, Preliminary design optimization, R245fa, Radial turbine, Alternative fuels, Coal combustion, Computational fluid dynamics, Design, Efficiency, Exhaust gases, Fluids, Gas turbines, Gases, Optimization, Rankine cycle, Turbines, Turbomachinery, Controlled random search, Organic ranking cycles, Preliminary design, Radial turbines, Small-scale applications, Thermodynamic parameter, Three-dimensional analysis, Nozzle design
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-36555DOI: 10.1115/GT2017-64028Scopus ID: 2-s2.0-85029004497ISBN: 9780791850831 OAI: oai:DiVA.org:mdh-36555DiVA: diva2:1147629
Conference
ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition, GT 2017, 26 June 2017 through 30 June 2017
Available from: 2017-10-06 Created: 2017-10-06 Last updated: 2017-10-06Bibliographically approved

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CiteExportLink to record
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Citation style
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