Preliminary Study on Recirculation Vortex and Turbulence Inside Ultra Low Head Pico Hydro Cross-Flow Turbine using Computational Fluid Dynamics Method

Abstract

Cross-flow turbines (CFT) have evolved since the first investigation in 1949. After some use of computational fluid dynamics (CFD) simulations in CFT development, it is known that there might be a recirculation vortex inside the CFT. At the CFT internal flow, some significant turbulent flow occurred, which is indicated by a higher value of turbulence kinetic energy (TKE). However, the effect of the turbulence inside this turbine still evokes many questions. This study ran Several CFD simulations on three CFT blade designs. One of them has already been tested experimentally, and the others are the modifications of the first design. There are two scenarios for the simulations: run in a traditionally two-phase condition or in a submerged state to maximize the usage of the potential head. This study found that the existing configuration has a contra-directional permanent recirculation, dead area, and high turbulency spot, which induce a higher loss. Meanwhile, all those phenomena could be minimized under the modified blade condition. The modification improves multiphase CFT performance by relatively 22.2% efficiency and 16.6% relative escalation for the submerged condition. However, the expected recirculation flow found in the prior study was still not found in this study. Another modification is still needed.