“PhD journey from Nepal to Norway”- Nirmal Acharya, PhD candidate,Waterpower Laboratory, NTNU

Nirmal Acharya is a PhD candidate at NTNU, from Nepal, working under a Hydrocen project: FranSed (Francis Turbine for Sediment Laden Waters). He joined team FranSed from October 2018. With Mechanical Engineering as his background, he has master’s degree in Hydropower Engineering from South Korea.

Journey towards NTNU from Kathmandu University

Acharya has a background of working as a research fellow in EnergizeNepal Project (ENEP) at Turbine Testing Lab (TTL), Kathmandu University (KU). ENEP is funded by Royal Norwegian Embassy in Nepal aiming for “Establishment of center for design, operation & maintenance of mechanical equipment for hydropower plants in Himalayan region”. He was also serving as a visiting faculty at Department of Mechanical Engineering (DoME), KU. His association with research, teaching, training, learning and related activities in fluid, hydropower and energy domain for more than 4 years at university level made it easier for him to bridge the gap between his previous works at KU and current PhD program at NTNU.

Investigating erosion problems in Turbine runner at Waterpower laboratory

Nepal is a country with world’s highest mountain ranges yet the youngest one in the planet with weak rock topology. Rivers in Nepal carry abundance of sand and silt which results in severe operational and maintenance challenges for hydropower components.

Currently, Acharya is investigating erosion problems in turbine runner and planning to come up with better design to cope it under the supervision of Prof. Ole Gunnar Dahlhaug and Chirag Trivedi at Waterpower Laboratory, NTNU. His PhD title is “Design of a Francis turbine that accommodates high sediment concentration”.

The FranSed project has identified Bhilangana-III hydroelectric powerplant, located in Uttarakhand- India as one of the case studies. This is a 24 MW (8 MW * 3 units) run-of-river project which has suffered severe operational and maintenance challenges due to sediment erosion. Mineralogical analysis showed presence of particles finer than 150 µm with abundance of quartz in it, that can not be settled in desilting chamber.

Will he come up with a novel Francis turbine design for better sediment handling?

“I have completed numerical analysis of guide vanes and runner blades for the reference case which is quite close to the field observation. I am now involved with runner optimization in MATLAB focusing on the relative velocity which is directly related with sediment rate density.

Previous studies have shown that the erosion is the result of increase in clearance gap during operation, so concept is being developed for either redesign of stay vane or design of system without guide vane. Guide vaneless system is a novel concept and is yet to be explored, which I think is challenging and exciting.

Moreover, studies have also shown the increase in erosion during off- design operations, I will also be exploring the possibility of variable speed operation (VSO) for sediment laden projects for efficiency and performance benefits.”

Acharya's PhD journey at NTNU in his own words

“I feel privileged to be a part of Waterpower Laboratory which is a state-of-the-art laboratory with more than 100 years of experience. I am getting hands-on experience in the lab for calibration, method of measurement and operation procedures on the Francis rig which is completely new and worth knowing for me. It has given me a unique research opportunity from IEC standard test rigs and NTNU’s proud history and extensive knowledge of hydropower development.

I am giving my best to learn, to discover and to achieve. Furthermore, I am planning to perform the model test of my new design at TTL in order to be able to share and implement the knowledge and experiences acquired from Scandinavian system.

Apart from studies, I am travelling quite often in this beautiful country Norway, with such a diverse nature, sublime fjords and lakes, mountains, spectacular aurora borealis, cabin life, fantastic hikes and many more.”