Disc Turbine for Energy Harvesting

Abstract

Energy harvesting is part of a current paradigm of distributed production and use of energy. However, we are aware that the size of turbomachinery used to produce the energy can be an advantage, in terms of higher efficiencies when using larger machines. This is one main reason why distributed production and use of energy has not known a very large popularization in the past. Still, with present day fluid dynamics tools and new production technologies it is now becoming possible to expand this concept. A less used turbomachinery is the disc or Tesla turbine or pump. This is based on a series of parallel discs that rotate under the action of a common shaft. These parallel discs impart a movement to the flow by means of viscous effects, due to viscous adherence of the fluid to the rotating discs. Disc turbines offer and inherent advantage to provide a capability of energy harvesting when fluids include living elements, or when the fluid is mostly comprised of slurries. In this paper we present an experimental and numerical analysis of the flow in this special kind of turbomachine. The experimental activities use a direct operating mode to assess the operation of the pump-as-turbine. An experimental set-up provides a set of results that allow to characterize the design conditions of the disc turbomachine under analysis. Further, a numerical simulation is performed for direct and inverse operation modes. After careful validation of the numerical model using the experimental results, the performance of the disc turbine is verified for a range of conditions. Among these are pure water and slurry fluids. The results allow us to provide the set of conditions in which the disc turbine can be used for energy harvesting.