Francis Turbines

Noelle Fillo, Kimberly Fridsma, Callen Hecker

History

● Developed by James B. Francis in Lowell, Massachusetts○ Founded ASCE○ Locks and Canals company○ 1848

● The first Francis turbine was housed in the Pawtucket Gatehouse in Lowell, MA.

● He based his designs off of other turbines that were designed around that time.

http://iopscience.iop.org/article/10.1088/1755-1315/22/1/012020/pdf, https://en.wikipedia.org/wiki/Francis_turbine

Pawtucket Gatehouse

History

● Design based off of Benoit Foureyron’s outward-flow turbine and Jean-Victor Poncelet’s inward-flow turbine.

● Can be used in a variety of hydraulic heads and flow levels

● Francis Turbines are a reaction turbine ● First hydraulic turbine with radial inflow

https://en.wikipedia.org/wiki/Francis_turbine, http://turbinegenerator.org/hydro/hydropower-types/francis-turbine, http://www.brighthubengineering.com/fluid-mechanics-hydraulics/27407-hydraulic-turbines-francis-turbine/,

History

● Many different design changes over the years from 1848 to 1920.○ First stock turbine

○ Newer designs included adjustable guide vanes

http://iopscience.iop.org/article/10.1088/1755-1315/22/1/012020/pdf

Elevation and Plan View of a Francis turbine

http://www.bflhydro.com/img/img-modal-francis.jpg

http://hopshop.net/tours/electric-utility/images/francis-turbine.jpg

The Physics of a Francis Turbine

https://www.youtube.com/watch?v=3BCiFeykRzo

Physics Cont.

● Water flows through spiral casing, runners, guide vanes and exits out turbine eye

● Pressure differences caused by blade shape allow for rotation and draws water towards center

● Guide vane angles are manipulated to optimize flow

CFD images showing high velocities near eye and blade edges

http://www.e3k.com/images/CFDfrancis02.pnghttp://www.cfdsupport.com/water-turbine-cfd-manual/francis-turbine-cfd-openfoam-rotor-

results-velocity-1.png

Preventing Cavitation

● Pressure differences caused by flow create vortices that damage surfaces

● Indicated by a popping noise● Static pressure must not go below vapor

pressure● Flow separation at turbine exit must be

avoided to avoid draft tube damage● Must control for:

○ Pressure head○ Flow rate○ Exit Pressure

Advantages of Francis Turbines

● Francis turbines work best for medium to high range heads

● Easily controlled operating head● Francis turbines operate over the largest

range for both flow and head parameters● Large range in size to meet different

power requirements○ Range from 0.25 MW to 1000 MW

● High efficiency○ Generally around 94% Operative ranges of different turbines

http://www.gunt.de/networks/gunt/sites/s1/mmcontent/produktbilder/07036531/Datenblatt/07036531%202.

pdf

Advantages

● Francis turbines are mixed flow designs● Francis turbines have the highest

maximum power for turbines● Francis vs. Pelton

○ Smaller and more economical than a Pelton wheel capable of the same power generation

○ More resistant to wear than the Pelton wheel

○ Francis turbines have higher levels of efficiency http://www.gunt.

de/networks/gunt/sites/s1/mmcontent/produktbilder/07036531/Datenblatt/07036531%202.pdf

Disadvantages

● Unclean water can cause rapid wear in Francis turbines

● Cavitation is always a possibility○ Runner erosion○ Losses in efficiency

● Difficult to maintain and clean● Low acceptance of head variation ● Constant adjustment of guide vanes and

runners● Francis turbines are generally limited to

large hydroelectric systems

Possible cavitation areas on the runnerhttp://www.diva-portal.org/smash/get/diva2:741702/FULLTEXT01.pdf

Effects of cavitation on runnerhttp://authors.library.caltech.edu/25019/1/chap6.htm

Disadvantages

● Francis turbine efficiency significantly decreases with turbine flow rates below 40%○ Decreased flow also greatly increases

cavitation risk● Water hammer effect can cause harmful

effects○ Occurs when runners are forced from high

speed to stopping○ Build up of overpressures can cause

catastrophic results

http://www.plumbingmart.com/water-hammer-information.html

http://www.esru.strath.ac.uk/EandE/Web_sites/01-02/RE_transmission/index.htm

Calculations/Relevant Equations

● Blade Velocity

● Guide vane angle

● Power Generated

● Specific Speed

Example

A Francis turbine is to be operated at a speed of 600 rpm and with a discharge of 4.0 m3/s. If r1 = 0.60 m, β1 = 110⁰, and the blade height B is 10 cm, what should be the guide vane angle α1 for a nonseparating flow condition at the runner entrance?

Case Study I- Itaipu Dam in Brazil/Paraguay

● Located on the Parana River between Brazil and Paraguay

● One of the Seven Wonders of the Modern World

● Second largest hydroelectric power plant● 87.8 TWh generated in 2014● 118m of hydraulic head● 20 Francis turbines

○ 700 MW each○ 16 m diameter

● Average reservoir capacity○ 19x109 m3

http://www.solar.coppe.ufrj.br/itaipu.html

Case Study II- Guri Hydroelectric Power Plant in Orinoco, Venezuela

● On the Caroni River in Necuima Canyon in Orioco, Venezuela

● Installed capacity of 10,200 MW and provides 12,900 GW/h to the country

● Ten 730MW Francis Turbines● Third largest power plant in the

world

http://www.power-technology.com/projects/gurihydroelectric/, http://www.industcards.com/hydro-venezuela.htm,

Case Study III- Vertical Twin Turbines in Australian Irrigation Dams

● Used in Wyangala, Copeton and Burrendong irrigation dams

● Smaller turbines, but useful for privately developed hydro schemes

● Desirable when head is too high for a Kaplan turbine

● Ideal when:○ 13 MW ○ 45 m head

● High efficiency and low priceshttp://www.bryanleyland.co.

nz/uploads/2/9/7/1/29710909/twinfrancisturbines.pdf

Fish-Friendly Francis Turbine Design

● Do not allow cavitation to occur● Direct migratory fish away from

turbines● Low number of blades with thick

edges● Wide wicket gate-runner gaps, ● Wicket gates aligned with stay vanes● Smooth surfaces provided● Use advanced control system and

monitor speeds● Minimize pressure changes

experienced by fishhttp://www1.eere.energy.gov/wind/pdfs/doewater-13741.pdf

http://www.westcoast.fisheries.noaa.gov/images/hydropower/newandoldturbinedesign_102313.gif

Conclusions

● Francis turbines are one of the most widely used turbines of our time

● Extremely high efficiency at specific flows

● Come in many sizes and are very versatile

● Large range of power outputs● Wanted when dealing with

relatively medium head and high flows

https://i.ytimg.com/vi/0-sfeSq1IWs/maxresdefault.jpg