SELECTION OF HYDRAULIC TURBINES

Rishabh BoonliaVIT University

On the basis of heads

High heads(350 m and above): Pelton turbine

Reaction turbines not suitable (losses) Medium heads: Francis turbine

(sometimes impulse turbines can also be used)

Low heads(below 60 m): Propeller type of turbine is used.

Selection Criteria

Hydrological Data:

The maximum working head� The design Head� The design discharge � Available discharge Speed and nature of load

DESIGN ANALYSIS

Type of turbine:(for e.g. adjustable blade axial flow turbine or a kaplan turbine) The power generated( in bhp): Diameter of the hydraulic turbine Rotational speed

THE SPECIFIC SPEED

The permissible suction height

In order to achieve no-cavitations in the turbine, the suction height should be limited

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Spiral Casing

Spiral casings are either made of metal for heads ranging from 40 to over 200m or of concrete for low and medium heads, i.e. up to 75m

Draft tube

The role of the draft tube is to convert kinetic energy into pressure energy with a minimum of losses Straight conical draft tube Elbow draft tube

Penstock diameter

Weight of runner

A propeller-type runner rated 28,000 hp (21 MW)

Shaft arrangement

Vertical shaft: (for reaction turbines) Great variations of tail water level Deep foundations, as the weight of the

rotating parts acts in the same direction of the axial hydraulic thrust

Horizontal shaft: (for impulse turbines) Grouping of two or more runners can be

done Foundations are not that deep, but

occupy more surface area