Design of a high-head Francis turbine for variable speed operation
To drive at a constant speed down the highway a car really only needs one gear. Same goes for turbines. So when the highway changes into more diverse road-system, you need more flexibiliy. Igor Iliev will design a turbine-runner that can «change gears».Ever since the 19th century, hydropower played a key role in the generation of electricity worldwide, which resulted in an unprecedented industrialization and globalization shortly after.
Features like: (i) high efficiency, (ii) low environmental impact, (iii) safety, (iv) robustness etc. have only proved that this technology is here to stay.
More than 100 years later, it is publicly accepted that hydropower has reached its maturity and there is nothing else to be done!?
New need for flexibility
The answer is no. This is actually far from the reality, as hydropower is facing many challenges that have arisen from the modern trends of electricity markets and generation. One of them is the need for enhanced flexibility and increased efficiency for the entire operating range of the turbines.
To put it simply; turbines are designed to operate at fixed parameters and small deviations from those parameters will result in a loss of some portion of the production or will push the mechanical structure beyond its limits. This will result in a poor economic justification of the power plant and, sometimes, even in an unexpected and costly breakdown of the turbine.
Rotating speed of the turbine is one parameter that, in any traditional hydropower plant, is kept constant along the operating range. An analogy to this might be a car with only one gear available and while this might be good for driving on a highway, it will be dangerous and inefficient in urban areas and vice versa.
Therefore, just as cars can be driven at any speed, the present effort is to enable the rotating speed of the hydraulic turbines to be adjusted as well.
This is one measure towards meeting the future requirements for flexibility and efficiency of the hydropower plants and prevention of unplanned major overhauls.
Ilievs research is focused on the hydraulic design of variable-speed turbines under the supervision of professor Ole Gunnar Dahlhaug.
As the traditional/classical design methodology and optimization are based on the fixed-speed operation,he is going to explore the possibility for a variable-speed design methodology in order to maximize the effect from being able to adjust the speed freely.
This method will be applied for the design of a replacement turbine runner and, in order to verify the method, a scaled down model of the turbine will be built and experimentally tested in the Waterpower laboratory at NTNU.