Hydraulic Turbines: Francis Turbine

Written by: naveenagrawal • Edited by: Lamar Stonecypher
Updated Nov 27, 2009

In Francis Turbine water flow is radial into the turbine and exits the Turbine axially. Water pressure decreases as it passes through the turbine imparting reaction on the turbine blades making the turbine rotate. Read more about design and working principle of Francis Turbine in this article.

Francis Turbine is the first hydraulic turbine with radial inflow. It was designed by American scientist James Francis. Francis Turbine is a reaction turbine. Reaction Turbines have some primary features which differentiate them from Impulse Turbines. The major part of pressure drop occurs in the turbine itself, unlike the impulse turbine where complete pressure drop takes place up to the entry point and the turbine passage is completely filled by the water flow during the operation.

Design of Francis Turbine

Francis Turbine has a circular plate fixed to the rotating shaft perpendicular to its surface and passing through its center. This circular plate has curved channels on it; the plate with channels is collectively called as runner. The runner is encircled by a ring of stationary channels called as guide vanes. Guide vanes are housed in a spiral casing called as volute. The exit of the Francis turbine is at the center of the runner plate. There is a draft tube attached to the central exit of the runner. The design parameters such as, radius of the runner, curvature of channel, angle of vanes and the size of the turbine as whole depend on the available head and type of application altogether.

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Working of Francis Turbine

Francis Turbines are generally installed with their axis vertical. Water with high head (pressure) enters the turbine through the spiral casing surrounding the guide vanes. The water looses a part of its pressure in the volute (spiral casing) to maintain its speed. Then water passes through guide vanes where it is directed to strike the blades on the runner at optimum angles. As the water flows through the runner its pressure and angular momentum reduces. This reduction imparts reaction on the runner and power is transferred to the turbine shaft.

If the turbine is operating at the design conditions the water leaves the runner in axial direction. Water exits the turbine through the draft tube, which acts as a diffuser and reduces the exit velocity of the flow to recover maximum energy from the flowing water.

Power Generation using Francis Turbine

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For power generation using Francis Turbine the turbine is supplied with high pressure water which enters the turbine with radial inflow and leaves the turbine axially through the draft tube. The energy from water flow is transferred to the shaft of the turbine in form of torque and rotation. The turbine shaft is coupled with dynamos or alternators for power generation. For quality power generation speed of turbine should be maintained constant despite the changing loads. To maintain the runner speed constant even in reduced load condition the water flow rate is reduced by changing the guide vanes angle.

Laxman Khadka Nov 12, 2011 9:24 PM

RE: Hydraulic Turbines: Francis Turbine

francis turbine isnot reliable as that of pelton in high head available places<br>

naveenagrawal Sep 18, 2011 12:40 PM

Vertical and Horizontal axis Francis Turbines

Generally power generator is directly coupled to the shaft of the turbine. For vertical axis Francis Turbine you can place the turbine at desired height, to obtain maximum power, without changing the height of mounting of the generator. Whereas for horizontal axis Francis turbine position of generator mounting is at the same height as the turbine. Horizontal axis Francis Turbine are more economical for small size and high speed applications.

S B Lalit Sep 16, 2011 6:20 AM

Francis turbine

In what conditions vertical axis francis turbines are better than the horizontal axis francis turbine

nimisha pancholi Sep 11, 2011 6:49 AM

about change in loading conditions

sir,kindly explain that with change in loading conditions,how do we change the guide vane angle?what is the logic behind it?

manoj kumar Apr 22, 2011 1:58 PM

about francis turbine

plz explain me d working procedure wid some more pictures... am not understanding the way of water entering the turbine n how the turbine works here....
we really need some more diagrams to understand

naveenagrawal Apr 12, 2011 10:59 AM

how to choose proper turbine type

Which turbine to use? Answer to this depends upon the source of water you have. The head (H) and the flow rate (Q) of the water determines which turbine should be used. This chart at wikipedia shows water turbine selection very clearly.

http://en.wikipedia.org/wiki/File:Water_Turbine_Chart.png
(copy-paste the address if link doesn't work)

rochhadi Apr 11, 2011 9:21 AM

choose turbin type

please explain to me how to choose proper turbine type

CHANTI Mar 11, 2011 1:36 AM

pelton turbine

1.plz give brief explination of working
2.plz give famulas for velocity,efficiencyes,work,MECHANICALEFFICIENCYES

luis Feb 26, 2011 7:53 AM

carven motor?

have you seen the carven motor? what do you think for this aplication I saw it on carvenmotors.com but I would like to know the opinion of an expert.

ziaee Dec 14, 2010 3:04 AM

minmum water fiow

plz. I need to know speed/waterfiow curve for a fransic turbine .

vimal jha Dec 7, 2010 3:46 AM

draft tube

what is draft tube,where it is used.

martin Nov 17, 2010 12:58 PM

francis turbine

plz give general view of francis turbin in hydro power plant

Read more: http://www.brighthub.com/engineering/mechanical/articles/27407.aspx#ixzz15Z2rWqXm

BADHSHA Nov 9, 2010 10:20 AM

Draft table at different loads

Dear Sir,
1).What is the value of draft at different loads in francis turbine 2.5MW,130 head,horizontal shaft turbine?

2)What is reaction if the shaft ceiling box exit pipe size increasing (increasing out let) for the above turbine?

valmik chaturvedi Nov 7, 2010 11:50 PM

about all video and all topics

please all topics and video are shown in billingual langaage because approxymately all villagers studied in hindi medium so they cannot clearly understandi in hindi language

sumukha Nov 7, 2010 7:09 AM

about francis turbine..

plz explain me d working procedure wid some more pictures... am not understanding the way of water entering the turbine n how the turbine works here....

faisal Oct 26, 2010 12:22 PM

vertical francis turbine

plz give me the working procedure and design details of vertical francis turbine.

umesh gautam Oct 23, 2010 2:57 PM

about fransis turbine

would you please give me an idea of thermodynamics of outlet of fransis turbine with optimization of temperature,cavitation,depth of excavation for placing the turbine.

prince Oct 15, 2010 3:32 PM

hydrolics

hie can you plkiz send me hyrolic diagrams for load haul dumpers especialy the ghh machines and hydrolic layout of bell dump trucks

Si Thu Sep 23, 2010 4:44 AM

Francis Turbine

How energy distribute in a Francis turbine?

I S RAO Sep 23, 2010 3:15 AM

The diagram for the Francis turbine is not very clear especially the parts of the turbine and their functions are not at all clear.A clear and reproducible diagram with lucid explanation will facilitate any student
to follow the turbine. Hence there is a necessity for a new diagram .

I S RAO.

v singh Sep 7, 2010 3:17 AM

plz give general view of francis turbin in hydro power plant

Tashi Dorji Aug 27, 2010 9:55 AM

thanks

i could get all the information that i wanted thanks.

tiwari Aug 12, 2010 12:15 AM

information about francis turbine

Dear sir,
Please give me the francis turbine working principle, efficiency and minimum required head and flow.

Thank you

hari Aug 8, 2010 10:14 AM

velocity triangle for rotor

for an idea impulse turbaine is the axil velocity at inlet ls equal to that of outlet or absolute velocity or whirl velocity or the relative velocity? which is equal at entry and exit and why?

K.K. Sahu Jul 12, 2010 5:00 AM

fluid machines

plz give me the centrifugal pump details, with diagrams

yuhu Jul 6, 2010 8:28 AM

is francis turbine useful in any field????

Sharath Jun 24, 2010 2:21 AM

Dear Naveen,
Thanx for ur information,But in Working of Francis Turbine u ve mention that it generally installed with their axis vertical but there is installed with Horizontal axis also and in comparison its more economical,But i dont know much abt effect on efficiency or other parameters.pls can give me some information abt that

Jhon Smith Jun 11, 2010 12:16 PM

Send me about Francis turbine,please.

Dear naveenagrawal
I'd like to know about Francis turbine because of my thesis . Could you tell me about energy distribution analysis in a low head francis turbine . As you know, my thesis title is "Energy Distribution Analysis In a Low Head Francis Turbine During Thermodynamics Efficiency Measurements". So, May I have a chance to be able to write my thesis. HELP!

dived Jun 2, 2010 3:16 AM

thank you for this informations

maryam rathore May 14, 2010 1:42 AM

i want to know that why we prefer frances reaction turbine?where we use it?

Davinder Singh Apr 12, 2010 1:28 PM

Parameters of francis turbine

wht r diff parameter consider in Francis turbine.....

sweety Mar 25, 2010 5:01 AM

why radial vanes are used in francis turbine?
what is the difference between a curved vane and radial curved vane

naveenagrawal Feb 28, 2010 10:06 PM

Re: DRAFT TUBE

Thanks GURU for this compilation and explanation for draft tube.

It will be a helpful resource for others searching for functions of draft tube and it also tells how a draft tube for francis turbine was developed.

It is really important not only for design of draft tube for francis turbine but also for design of hydraulic machines to avoid cavitation.

Guru Feb 28, 2010 11:50 AM

DRAFT TUBE

Dear Naveen,
After seeing your articles about draft tube, I referred some other texts & I have come out with the following explanation.
1. Turbines can work without draft tubes also. In fact the earlier turbines were essentially without draft tubes.
2. Accidently, it was observed that by introduction of a cylinder at the exit of the turbine, the power output from the turbine increases. Analyses brought out the fact that the weight of the water column below the turbine exit, was responsible for creating a vacuum at the turbine exit and thereby causing more static pressure drop across the turbine. The static pressure drop manifested itself as increased turbine output.
3. With more theoretical insight into the concept brought out the fact that with a conical (diverging shaped passage instead of cylinderical shape at exit) would produce better results. This way the present day draft tues came into picture.
4. With more and more practical experience, the fact came out that since with introduction of a draft tube at the turbine exit, the exit static pressure is below atmospheric, and water temperature is usually (may be 10 deg c to 40 deg c), the water may undergo evaporation at the combination of such static pressures & temperatures. lately tremed as phenomenon of cavitation. So the engineers got to know that it is important to have a limit on the vacuum creation by the draft tube water column keeping the operational water temperatures in view. So the draft tube size is accordingly designed.

naveenagrawal Feb 25, 2010 11:16 AM

RE: Exit point

Your'e welcome! Such discussions help in revising and refining my knowledge. Rather, I should thank you.

In ideal case consideration of exit point will not make any difference as there is no loss of energy in the draft tube. Because Bernoulli's Equation is applicable in ideal case (refer articles on Bernoulli's equation).

Introduction of draft tube reduces the exit energy at the exit of the turbine (or the inlet to the draft tube). Read the last para of my last comment.

Sree Kumar Feb 25, 2010 8:42 AM

Thanks

Really informative..

Guru Feb 25, 2010 4:12 AM

Hydraulic Turbines: Francis Turbine: EXIT POINT

Dear Naveen,
Thanx for the time taken to reply me, but i still have a doubt. In your reply, you hve compared exits which are at different elevations. My idea is that, water can impart energy to the runner only as long as it remains in contact with its blades. So if we have to find out how much energy transfer has taken place from the water to the runner, the exit point in any case should be just after the last contact point between water and the runner blades. In such case, the elevations will remain the same whether it is case with draft tube or without draft tube. Please throw light on it...

naveenagrawal Feb 24, 2010 12:01 PM

RE: Guru

The fall in kinetic energy appears as the increased shaft power output.

To understand the function of draft tube clearly. Consider two cases. One, without the draft tube and other, with draft tube.

Without Draft tube: Exit Velocity = v, Exit Pressure = P(atm), Height at exit = z, Exit Energy = P(atm)/g + v(sqr)/(2g) + z

With Draft tube: Exit Velocity = vd (vd < v), Exit Pressure = P(atm), Height at exit = zd (zd < z), Exit Energy = P(atm)/g + vd(sqr)/(2g) + zd

Power at shaft without considering the efficiency = Inlet Energy - Exit Energy

Exit Energy with draft tube is less than that without draft tube. Hence, the power at shaft is more with the draft tube.

There may be some confusion about the pressure at the exit of turbine and inlet to the draft tube. This is no doubt below atmospheric. Pressure increases and then reach atmospheric pressure so at inlet it must be below atmospheric. But draft tube is designed such that the pressure at inlet remains above the vapour pressure of the water to avoid cavitation.

Guru Feb 24, 2010 3:37 AM

Hello Mr. Naveen,
Thanx for the information on how Draft tube functions but I have a question, if the pressure of the water at exit remains atmospheric and velocity goes down, where does this fall in kinetic energy go.

ashwini,aditya,ajit kiit university Feb 22, 2010 9:31 AM

want to know more

i want to know how this francis turbine work and what is the advantage of this turbine?

amol Feb 16, 2010 9:14 AM

give me fig. of turbine

naveenagrawal Feb 15, 2010 3:34 AM

Function of Draft Tube

Francis turbine can work even if draft tube is not present at the outlet of the turbine. But the efficiency and the power produced will be reduced.

The draft tube helps to extract maximum possible amount of energy from the water and increase the power output at the shaft.

Principle of Draft Tube:

From any hydraulic system, with exit at atmospheric conditions, water exists at atmospheric pressure. The total energy at exit consists of pressure energy, kinetic energy and potential energy. The energy lost by water in turbine is produced as power at the turbine shaft. The more the energy loss more is the power output at the turbine shaft. If we can minimize the energy of water at the exit from the hydraulic turbine we can extract maximum energy from the water and hence power output from the turbine will be maximized.

Functioning of Draft Tube:

Draft tube is like a diffuser (a tube with increasing cross sectional area) place at the exit of the turbine. The water leaves the turbine at atmospheric pressure and some velocity. We can reduce total energy at exit if can reduce the velocity at the exit. This purpose is served by the draft tube, which being a diffuser reduces the velocity of water. Now at the exit pressure is same as the atmospheric but the velocity of water has been reduced.

GUSTAVO A. Feb 11, 2010 10:06 AM

VIBRATION

HOW VIBRATION MONITORING FRANCIS TURBINE?
WHAT ARE THE VALUES OF ACCELERATION CORRECT?

mangal Feb 4, 2010 3:16 AM

function

what is the function of draft tube.
if draft tube is not there,is francis turbine will work?

prakash Feb 3, 2010 12:29 AM

FRANCIS TURBINE

what is minimum head on which francis turbine can work?

umesh Jan 14, 2010 2:50 AM

would u give the complete design

EGBELE ISIMEMEN SOLOMON Dec 28, 2009 10:34 PM

I am Egbele Isimemen Solomon.i am in mechanical Engineering department (final year) in federal university of technology owerri.i am to know eactly how dis turbine works.

julius ogungbayi Oct 16, 2009 6:52 AM

i want to really know more about francis turbine.
am presently doing my industrial training in shiroro hydroelectric.

miki Oct 3, 2009 5:45 AM

desigh

could you inlude the complete design of Francis Turbine

Hydraulic Turbines: Francis Turbine

Design of Francis Turbine

Working of Francis Turbine

Power Generation using Francis Turbine

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