MS Candidate
Dadi Ram Dahal (dadi.dahal@ku.edu.np)
Supervisors / Advisors
Prof. Hari Prasad Neopane
Dr. Biraj Singh Thapa
Objectives
1) To investigate design of Francis Turbine from manufacturing prospective in Himalayan Region.
2) To develop design methods and tool for Francis turbine for micro hydro application.
3) To manufacture Francis turbine using local technology within Nepal and test at laboratory condition.
Summary
This study focus on the design, manufacturing and numerical as well as experimental analysis of 14 kW Francis turbine with simplification in distributor system. Different design methods for Francis turbine are studied and classical Bovet method for obtaining the meridional channel followed by generation of blade profile using energy and beta angle distribution is used. The design obtained from the set of empirical relations given by Bovet was improved by using CFD analysis.
Numerical analysis has been performed in single passage as well as full turbine carried out in ANSYS CFX. Three different spiral casing profile has been compared. After study of pressure as well as velocity distribution with secondary flow at different cross section, the trapezoidal spiral casing is selected. The guide vane system is replaced by the fixed vane system which is the combination of guide and stay vane profile in certain proportion. Comparison of the performance of the turbine with fixed vane and conventional vane system is made.
Manufacturing methods of Francis turbine along with trends and status of manufacturing competency of Nepalese manufacture is studied. Two runner are manufacturing using casting and pressing-welding process; bronze is used for casted runner while mild steel is used for pressing-welding.
A test rig of Francis turbine with simplification in distributor system is manufactured at Thapa Engineering Works Butwal . Experiment analysis carried out at Turbine Testing Laboratory Calibration of the torque transducer is carried out using deadweight load arm system and uncertainty in the system in experiment is carried out. Performance curves of the both turbine at different rpm are obtained and compared with the CFD results of obtained from single passage study. Efficiency up to 94.87 % has been achieved at the 1400 rpm at 5-degree closing position of the vane system. However, the efficiency obtained from experiment is 69.05 % at 1400 for forged runner where as 66.26% at 1350 rpm for . The difference in efficiency between CFD and experiment may be caused by the manufacturing defects of the runner