Characterisation of a small viscous flow turbine

The result of experimental and numerical study that was undertaken to determine the performance characteristics of viscous flow turbines is presented. It is anticipated that these devices may find use in applications such as small power sources for electronic appliances and micro-combined heat and power applications. In the numerical work that was carried out to broaden the experimental results, commercial CFD solver Fluent 6.2 was used while accompanying software, Gambit 3.2, was used for performing the necessary pre-processing. The results of the experimental study indicate that the adiabatic efficiency of these machines is around 25%. The main reasons for the low efficiency have been identified to be, parasitic losses in the bearing, viscous losses in the end walls, and other dissipative losses in the plenum chamber that also significantly contribute to the low efficiencies of these devices. If these parasitic losses can be minimised the turbine could potentially operate with an adiabatic expansion efficiency close to the theoretical limit of around 40%.