HYDRAULIC TURBINES AND ITS CLASSIFICATION

SPONDAN S. BORA

DefinitionHydraulic Turbine is a prime mover that

uses the energy of flowing water and converts it into the mechanical energy in the form of rotation of runner wheel.

Also termed as ‘water turbines’.

Flow sheet of hydroelectric power plant

ClassificationBased on hydraulic action of waterBased on direction of flowBased on head of water and quantity of flowBased on specific speedBased on disposition of turbine shaftBased on name of originator (commonly used

turbines)

Based on hydraulic action of water

Impulse turbine : One in which all the energy of water is converted to kinetic energy before the water strikes the vanes of the runner wheel. This is done by passing the flow through nozzle or some guidelines. The runner is rotated by the force of water and water passes over the wheel at atmospheric pressure.

Ex- Pelton Wheel

Impulse Turbine

Reaction Turbine : Here, water entering the runner wheel of the turbine has both kinetic energy and pressure energy that is total head of water striking the runner wheel ,consist partly of pressure head.

E.g- Francis turbine, Propeller turbine, Kaplan turbine

Reaction Turbine (Kaplan Turbine)

Based on direction of flow Radial flow turbine : A radial flow turbine is a turbine in

which the water as it move along the vane flow towards the axis of rotation or away from it.

Radial flow turbine is of two types:I. Inward flow turbine : If the flow of water is towards the

axis of rotation, its called inward flow turbine.II. Outward flow turbine : If the flow of water is away from

the axis of rotation , its called outward flow turbine.

Radial Flow Turbine

Axial flow turbine : Its the turbine in which water enters the runner wheel parallel to the direction of axis of rotation of runner.

Ex- Kaplan turbine, Propeller turbineTangential flow turbine : Its the turbine in which

water strikes the runner wheel tangentially to the path of rotation.

Ex- Pelton turbine

Axial Flow Turbine

Mixed flow turbine : It’s the turbine in which the direction of flow is partly radial and partly axial. Water enters the blade radially and comes out axially parallel to the turbine shaft.

Based on head of water and quantity of flowHigh head turbine : when head is above 250 mEx- Pelton wheelMedium head turbine : when head is between 60m – 250mEx- Francis turbineLow head turbine : When head is between 15-60 mEx- kaplan turbineVery low head turbine: When is head is less than 15mEx- Propeller turbine

Based on specific speedSpecific speed Types of turbine

10-35 Pelton wheel with one nozzle35-60 Pelton wheel with two or more

nozzle, Multi jet pelton wheel60-300 Francis turbine

300-1000 Kaplan turbine

Based on disposition of turbine shaftTurbine shaft may be either vertical or

horizontal. Pelton turbine usually have horizontal shafts whereas the rest have vertical shafts.

Based on name of originator Pelton wheel : Tangential flow impulse turbine

used for high head of water.Francis turbine : Inward flow reaction turbine used

for medium head of water.Kaplan turbine : Axial flow adjustable blades

reaction turbine used for low head of water.Propeller turbine : Fixed blades axial flow reaction

turbine used for very low head of water.

Francis TurbinePropeller TurbineKaplan Turbine

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