Difference Between Francis and Kaplan Turbine

Published: 17 Nov 2025

Among all types of turbines, the Francis and Kaplan turbines are among the most common and effective used in hydroelectric plants.

Both belong to the reaction turbine family, meaning they use both pressure and velocity energy of water. However, they differ in design, working principle, and the type of water flow they handle. Understanding the difference between Francis and Kaplan turbines helps engineers and students choose the right turbine for a specific site.

Difference Between Francis and Kaplan Turbine

The Francis turbine and Kaplan turbine may serve the same purpose, but they work best under different conditions. Here’s how they differ from each other:

	Francis Turbine	Kaplan Turbine
Type of Turbine	It is a mixed-flow reaction turbine. Water enters the runner radially and exits axially.	It is an axial-flow reaction turbine where water flows parallel to the turbine shaft.
Water Head	Works best for medium head conditions, usually between 60 and 250 meters.	Designed for low head conditions, generally below 30 meters.
Flow Rate	Needs a medium discharge of water for proper operation.	Handles high discharge or large flow efficiently.
Runner Blades	The blades of the runner stay fixed and do not move.	The runner blades are adjustable, helping it maintain efficiency at different flow rates.
Number of Blades	Usually has 16 to 24 blades.	Has fewer blades, usually 3 to 8.
Direction of Water Flow	Water flows radially inward and then axially downward.	Water flows axially through the runner.
Specific Speed	Has a specific speed range of 50 to 260.	Has a higher specific speed, ranging from 260 to 850.
Energy Loss and Efficiency	Experiences more energy loss because of its many blades. Its efficiency is slightly lower.	Has less frictional loss due to fewer blades and offers up to 90% efficiency.
Shaft Orientation	The shaft can be installed horizontally or vertically.	The shaft is always vertical due to its axial flow design.
Compactness and Speed	Larger in size and runs at a lower speed for the same head and output.	More compact and runs at a higher speed for a given head.
Applications	Used in medium-head hydroelectric plants and dam-based projects.	Suitable for low-head power plants, irrigation systems, and run-of-the-river setups.

Conclusion

Both the Francis turbine and the Kaplan turbine are vital for generating hydroelectric power efficiently. The Francis turbine is perfect for medium head and medium flow conditions, offering steady performance and durability. Meanwhile, the Kaplan turbine is designed for low head and high flow areas, providing flexibility and higher efficiency with adjustable blades.