Hydraulic Turbines

Ankit Singh0608ME121019

ME 4th A

Hydraulic Turbine

Introduction Classification Reaction Turbine Impulse Turbine

Introduction The hydraulic machines that

convert hydraulic energy into mechanical energy is called Hydraulic Turbine.

Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids.

Now they are mostly used for electric power generation. Water turbines are mostly found in Embankment dams to generate electric power from water kinetic energy.

ClassificationHydraulicTurbines

ReactionTurbine Impulse Turbine

Reaction Turbine Reaction turbines are acted on by water, which changes

pressure as it moves through the turbine and gives up its energy.

They must be encased to contain the water pressure (or suction), or they must be fully submerged in the water flow.

Most water turbines in use are reaction turbines and are used in low (<30m/98 ft) and medium (30-300m/98–984 ft) head applications. In reaction turbine pressure drop occurs in both fixed and moving blades. It is largely used in dam and large power plants.

E.g. Francis Turbine, Kaplan Turbine.

Reaction Turbine

Figure shows a reaction turbine

Reaction Turbine

(a) Typical radial-flow Francis turbine(b) Typical axial-flow Kaplan turbine.

Points Regarding Reaction Turbine

There is both a pressure drop and a fluid relative speed change across the rotor.

Guide vanes act as nozzle to accelerate the flow and turn it in the appropriate direction as the fluid enters the rotor.

Part of the pressure drop occurs across the guide vanes and part occurs across the rotor.

Impulse Turbine

• Impulse turbines change the velocity of a water jet. The jet pushes on the turbine's curved blades which changes the direction of the flow. The resulting change in momentum (impulse) causes a force on the turbine blades.

• Since the turbine is spinning, the force acts through a distance (work) and the diverted water flow is left with diminished energy.

• An impulse turbine is one which the pressure of the fluid flowing over the rotor blades is constant and all the work output is due to the change in kinetic energy of the fluid.

• E.g. Pelton Wheel

Impulse Turbine

Figure show the Pelton Wheel

Points Regarding Impulse Turbine

The total head of the incoming fluid is converted into a large velocity head at the exit of the supply nozzle.

Both the pressure drop across the bucket (blade) and the change in relative speed of the fluid across the bucket are negligible.

The space surrounding the rotor is not completely filled with fluid.

The individual jets of fluid striking the buckets that generates the torque.

Power Developed

P=η*ρ*g*h*Qwhere,

η= Efficiency of turbineρ= Density of the liquid (kg/m3)g= Acceleration due to gravity (9.81m/s2)h= Head (m)Q= Flow rate (m3/s)

THE END

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