#Freecad cross section series#

The water is then discharged downwards, out of the base of the runner this type of flow is known as axial flow due to the flow being in a parallel direction to the runner shaft.īecause flow is both radial at entry and axial at discharge, Francis turbines are classified as mixed flow turbines. The water enters the Francis runner radially, flowing from the outside to inside of the runner. The guide vanes convert the water’s potential energy to kinetic energy and can also be used to start, stop and regulate flow to the runner. The water travels along the spiral case and passes through the guide vanes. Water is delivered through a pressurised water conductor known as a penstock.

The below video is an extract from our Introduction to Hydroelectric Power Plants Online Video Course. This conversion increases the overall operating efficiency of the turbine.Įnjoying this article? Then be sure to check out our Hydroelectric Power Plants Video Course! The course has a quiz, handbook, and you will receive a certificate when you finish the course. Enjoy! The purpose of the guide vanes is to convert the potential energy of the water to kinetic energy, and to direct the water into the runner at an optimal angle.Ī draft tube is used to convert some of the kinetic energy of the discharged water back into pressure energy. Guide vanes direct water towards the runner. As the cross-sectional area decreases, the velocity of the water in the case is maintained and an even flow of water is delivered to the runner. Even flow is achieved due to the gradually decreasing cross-sectional area of the casing. Gaps between the blades allow water to flow from the outer periphery of the runner to the inner section of the runner this type of flow is known as radial flow.Ī spiral case -also known as a scroll case- is used to deliver an even flow of water to the entire runner.

#Freecad cross section series#

The Francis turbine consists of a series of blades mounted between a runner crown and runner band. This type of turbine is classified as a reaction turbine, as it operates within a pressure system and relies upon a continuous body of water from the suction to pressure side of the turbine. This efficiency does not decrease until the load is below 40%.įrancis turbines convert potential energy to mechanical energy. The efficiency of Francis turbines often exceeds 90% when the right operating conditions are met. Pumped storage power plants employ Francis runners exclusively, due to this unique feature. The Francis runner can be operated as both a hydraulic pump and hydraulic turbine, this is a unique feature compared to other common hydroelectric runners such as the Kaplanand Peltonrunners.

Due to this wide operating range, the Francis turbine is the most common type of hydroelectric turbine employed today.

As the electrical power industry grew over the past 150 years, the Francis turbine was able to compete with other prime movers in terms of cost, which lead to its widespread use for many applications.ĭue to their versatile design, Francis turbines are suitable for a wide range of pressures and flow rates. James Francis applied mathematical principles when designing the Francis turbine and created a turbine with an efficiency exceeding 90%.Īlthough there are different variations of the Francis turbine now available, the fundamental working principles remain the same as those used over 100 years ago. Waterwheels had been used to complete useful work for over 1,000 years, but they were inefficient. The Francis turbine was invented by James B Francis in the 1850s.