Article thumbnail

On scaling down turbines to millimeter size

By Rowan Deam, Engida Lemma, Bernard R. Mace and Ralph D. Collins

Abstract

The purpose of this work is to establish the maximum theoretical efficiency that a viscous flow turbine (such as a Tesla turbine) can achieve. This is very much in the spirit of the Betz limit for wind turbines. The scaling down of viscous flow turbines is thought not to alter this result, whereas the scaling down of conventional turbines, whether axial or radial flow, results in an ever lowering of their efficiencies. A semiempirical scaling law is developed for conventional gas turbines using published machine performance data, which is fitted to a simple boundary layer model of turbine efficiency. An analytical model is developed for a viscous flow turbine. This is compared to experimental measurements of the efficiency of a Tesla turbine using compressed air. The semiempirical scaling law predicts that below a rotor diameter of between about 11 mm and 4 mm, a practical Brayton cycle is not possible. Despite that, however, and for rotor diameters less than between about 7 mm and 2 mm, a viscous flow turbine, compressor, or pump will be more efficient than a conventional design. This may have a significant impact on the design of microelectromechanical system devices

Topics: Boundary layers, Brayton cycle, Expansion efficiency, MEMS, Power, Rotors, Scaling law, Turbines, Viscosity, Viscous flow turbine
Publisher: ASME International
Year: 2008
DOI identifier: 10.1115/1.2938516
OAI identifier: oai:vtl.cc.swin.edu.au:swin:9091
Download PDF:
Sorry, we are unable to provide the full text but you may find it at the following location(s):
  • http://purl.org/au-research/gr... (external link)
  • http://dx.doi.org/10.1115/1.29... (external link)
  • http://hdl.handle.net/1959.3/4... (external link)
  • Suggested articles


    To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.