Design And Computational Fluid Dynamics Modeling Of Ultra-Low Head Dual Axis Cross Flowturbine: Wonji-Shoasugar Factory Irrigation Canalflowin Focus

Abstract

In Ethiopia, the main source of power supply is large scale hydropower plants, which accounts a total generation of 3,822MW in 2019. However, there are a number of problems associated with power transmission schemes for rural electrification. Therefore, this thesis is focused on the design and Computational Fluid Dynamics(CFD) Modelling of Ultra-Low Head (ULH) dual axis cross flow turbine focusing on Wonji-Shoa sugar factory irrigation canal flow. To this end, a design having two measure phases, analytical and CFD analysis, was adopted. The analytical phase includes three sub-components namely, turbine runner, nozzle and speed multiplier mechanism. The analytical design process starts with calculation of initial dimension for the turbine runner based up on various, relevant literatures reviewed. Similarly, the CFD analysis phase focused on developing a methodology used for the CFD analysis, visualization of the results and predicting the performance of ULH turbine. The 3D geometry was also designed on ANSYS design modeler. Subsequently, the model was imported and simulation was performed by using the commercial software ANSYS Fluent 18.0 version. Moreover, a procedure for CFD simulation was followed and physical assumptions were taken based on the literatures reviewed. Finally, the velocity and pressure distribution within the internal surface nozzle, turbine casing, and runner of the cross-flow turbine were analyzed. Accordingly, the simulation results disclosed that the turbine efficiency was improved from 67.5% to 78% (increase by 10.5%) numerically. In other words, when the rotational speed of the turbine is increased from 375 to 650 rpm, the efficiency is increased by 10.5% higher than the design rotational speed of 375rpm. From the results of the simulation, it was also observed that the efficiency will decrease if the rotational speed goes beyond 650 rpm. The overall result depict that the turbine efficiency obtained from the CFD analysis and analytical approaches were found as 78 % and 87.9%, respectively. In line with the findings, future recommendations were also suggested to pave the way for further improvement on the design of thisstudy.