Computational Fluid Dynamics and Structural Finite Element Analysis of a Micro Hydro Turbine

Abstract

Performance characteristics of a micro hydro turbine are determined through the use of computation fluid dynamics (CFD) and finite element analysis (FEA). CFD is used to optimize a portable micro hydro turbine. The runner geometry is designed as a non-uniform Archimedean Spiral. The transient 3D turbulent flow simulation is conducted for various runner designs to determine power generation and the efficiency. The equations governing the fluid motion through the turbine are solved in a frame of reference change between time-steps. A multiphase flow model is employed to study the cavitation for various flow rates and rotation rates to determine the onset of the cavitation. It was determined that the onset of cavitation occurred between inlet flow rates of 0.0625 m3/s and 0.075 m3/s for the 1.5 pitch Archimedean spiral at a rotation rate of 250 RPM. When the rotation rate is increased to 500 RPM, vapor formation within the flow exists between a flow rate of 0.05 m3/s and 0.0625 m3/s. The occurrence of cavitation was predicted using Cavitation number, with the critical number being approximately −10,000. The presence of cavitation caused the efficiency to drop up to 10%. Basic structural analysis of the Archimedean blade yielded a maximum von Mises stress of 143.67 MPa at flow rate of 0.1 m3/s and a rotation rate of 1000 RPM. From the von Mises stress obtained, aluminum alloy is the best material to be used based on the importance of material strength and weight.