PERFORMANCE ANALYSIS AND OPTIMIZATION OF A HELICAL CROSS-FLOW WATER TURBINE

Abstract

In this study, a Computational Fluid Dynamics model is designed to investigate the performance analysis of a helical cross-flow water turbine by using Comsol Multiphysics. In order to predict the main performance characteristics of turbine such as power output and torque, a numerical model is developed which is accurate, fast and quite simple to be used for a simulation. The flow field around turbine is solved with the Rotating Machinery feature in the Comsol CFD Module using a k-ω turbulence model and a steady state formulation. The Navier-Stokes equations are used in the model which are arranged in a rotating frame in the inner domain and in fixed coordinates in the outer domain. The boundary between the inner and the outer domain is a continuity boundary condition that transfers momentum to the fluid in the inner domain. This model also uses the Frozen Rotor study type which speeds up the computation time. Then, to increase the performance of the cross-flow water turbine, a new angular velocity profile is explored with Comsol Optimization Module. Thus, a variable speed turbine control method is developed. Compared to the constant velocity control method, new angular velocity control method yielded a 3% increase in the efficiency of turbine.