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.
