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Advanced materials for the impeller in an orc radial microturbine
Isaias Hernandez Carrillo, Christopher Wood, Hao Liu
Session: Session 3C: Turbomachinery (1)
Session starts: Wednesday 13 September, 16:30
Presentation starts: 16:30
Room: Building 27 - Lecture room 03

Isaias Hernandez Carrillo (The University)
Christopher Wood (The University of Nottingham)
Hao Liu (The University of Nottingham)

For distributed generation with low-temperature sources, the micro organic Rankine cycle is an exceptional option. However, an abundance of work remains to be done to minimise its high cost; such a problem can be associated to the expander that represents up to 70% of the total capital cost. The design of a lean radial microturbine is proposed, which targets reduction of production costs using simplification strategies e.g. alternative materials for the impeller since low-temperatures allow the possibility of using polymers. The candidate materials are a composite (PEEK-GF30) and a thermoplastic (ABS); aluminium is used as reference. The study is developed in five stages, namely, heat-mass balance (H&MB), mean-line turbine design, 3D blading, fluid-structure interaction (FSI) and prototyping. A gross power and efficiency of 1.5kW and 70% are respectively targeted. R245fa is selected as working fluid. An impeller diameter of 49mm and a rotational speed of 36,000rpm results from the mean-line design. The structural reliability is assessed with an FSI analysis, the fluid modelling delivers consistent results with the mean-line design, except for the turbine efficiency, which is forecasted to be in the range 69-76%. Three situations are evaluated: full load operation, rotor blocked and 27% over-speed. Additionally, three materials are evaluated; therefore, nine scenarios are compared. The factor of safety is used as a unique parameter for comparison. The analysis confirmed that in the worst situation (over-speed), PEEK-GF30 is structurally 11% stronger than Aluminium whereas ABS is 40% weaker than Aluminium and both materials are sufficiently strong to be substitutes. Due to the superior performance of PEEK-GF30 and the fact that ABS is considerably inexpensive; both alternative materials are selected for prototyping using automated machining and additive manufacturing respectively.