Experimental And CFD Analysis of 0.6m Impulse Turbine With Fixed Guide Vanes

Abstract

This paper presents the comparison of Computational Fluid Dynamics (CFD) analysis with Experimental analysis of 0.6m Impulse Turbine with Fixed Guide Vanes used for wave energy power conversion. A 2D-cascade model was used for CFD analysis while uni-directional steady flow was used for experimental analysis. The blade and guide vane geometry is based on 0.6m rotor diameter, with optimum profile, and a hub to tip ratio of 0.6. The aim of this paper is to report comparison of CFD performance data with experimental results, and to benchmark/validate CFD analysis. KEYWORDS Wave Energy, Impulse Turbine, Computational Fluid Dynamics (CFD) N O M E N C L A T U R E b CT CA lr 8p Q rR Va Z q e V UR 0) : blade height : torque coefficient : input coefficient : chord length of rotor blade : pressure drop : flow rate : mean radius : mean axial flow velocity : number of rotor blades : turbine efficiency under steady flow : setting angle of fixed guide vane : hub-to-tip ratio : flow coefficient : circumferential velocity at rR : angular velocity of turbine rotor INTRODUCTION For the last two decades, Scientists have been investigating and defining different methods for power extraction from wave motion. These devices utilize the principle of an Oscillating Water Column (OWC). OWC based Wave Energy Power Plants convert wave energy into low-pressure pneumatic power in the form of bi-directional airflow. Self-rectifying air turbines (which are capable of operating uni-directionally in bi-directional airflow) are used to extract mechanical shaft power, which is further converted into electrical power by a generator. Two different turbines are currently in use around the world for wave energy power generation, Wells Turbine, introduced by Dr. A. A. Wells in 1976 and Impulse Turbine with guide vanes by Kim et al., (1988). Both these turbines are currently in operation in different power plants in Europe and Asia on experimental as well as commercial basis. Currently, research around the world is focused on improving the performance of both these turbines under different operating conditions. The ultimate purpose of this research is to improve the performance of Impulse turbine with fixed guide vanes for Wave Energy Power conversion by modifying different blade and guide vane geometry parameters, (Khaleeq, 2000). Therefore, as the starting point, it was decided to use a different hub to tip ratio of 0.6 compared to the already published and established optimum value of 0.7 (Setoguchi, 1999). The said turbine was designed, manufactured and tested at unidirectional steady flow testing facilities at University of Limerick, (Thakker, 2000a). This paper presents the work carried out to compare experimental results with 2D CFD analysis. DESIGN AND M A N U F A C T U R E OF IMPULSE TURBINE A 0.6m diameter Impulse turbine rotor with a hub to tip ratio of 0.6 was designed and manufactured at University of Limerick, Ireland for the said performance analysis. Basic blade and guide vane profile parameters were based on the optimum design parameters published by Prof. T. Setoguchi in 1999 (Setoguchi, (1999) and Setoguchi et al., (2001)). Blade chord length is 100mm. A 2D sketch of 0.6m turbine rotor and guide vanes is shown in Figure 1. A 3D model of blades and hub was generated in CAD package ProEngineer v2000i. The blade model was used to manufacture turbine