Differences between Francis and Kaplan turbines

Francis and Kaplan both the turbines come under the category of reaction turbine i.e. both kinetic and pressure energy requirements for the power generation. In both the cases, the hydraulic energy of water gets converted into useful power output. Francis turbine is an old turbine. The invention of the Kaplan turbine is an evolution in the field of hydraulic turbines or we can say that it is the upgrade version of the Francis turbine. Francis turbine had some limitations which were overcome by Kaplan turbine. According to their construction, working and operating conditions following are the major differences between the Francis turbine and Kaplan turbine.

Differences between Francis and Kaplan turbines:

		Francis turbine	Kaplan turbine
According to the type of flow		Francis turbine is a radial flow turbine but in the case of modern Francis turbine water enters radially and leaves the turbine axially which is called as mixed flow turbine.	Kaplan turbine is an axial flow turbine i.e. water enters and leaves the turbine runner both in the axial direction.
Efficiency		of Francis turbine is less as compare to Kaplan turbine	Efficiency of Kaplan turbine is higher than Francis turbine
Losses		Friction losses are higher	Less friction losses as compare to Francis turbine
Size		The size of the Francis turbine is quite large as compare to Kaplan turbine	Kaplan turbine compact in cross sectional area
Vanes		Large number of vanes in a runner, generally the number of vanes are 16 to 24	Kaplan turbine is compact in size so the numbers of vanes are also less; generally, the number of vanes is 4 to 8.
Type of shaft		The direction of the shaft is may be vertical or horizontal as per requirement.	The direction of the shaft is always in the vertical direction because it is an axial flow turbine.
Head available		Francis turbine requires a medium range of water head i.e. it generally varies from 100-600 meters	Kaplan turbine works on the very low head, the requirement of a head is generally 100 meters.
Flow rate		As it is works in medium head therefore it requires a medium flow rate.	Kaplan turbine requires a high flow rate of water.
Specific speed		Francis turbine works on a medium range of specific speed i.e. the specific speed varies from 60 to 300.	Kaplan turbine requires a high value of specific speed because it is works on low head. Generally, the range of specific speed varies from 600-1000.
Governing mechanism		Fancies turbine has a simple governing mechanism.	The governing mechanism of Kaplan turbine is quite complicated in construction and working.
Runner vanes	Francis turbine has fixed runner vanes on the shaft		Kaplan turbines vanes are adjustable i.e. we can easily adjust the runner vanes as per our requirements.

These are all major difference between francis and kaplan turbine. If you have any query regarding this article, ask by commeting. If you like this article, don’t forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.