Filed under: Water Power | Tags: Water Power, water powered farm, water wheels
In general, there are two types of water wheels, the _impulse_ wheel
and the _reaction_ wheel. Both are called turbines, although the name
belongs, more properly, to the reaction wheel alone.
Impulse wheels derive their power from the _momentum_ of falling
water. Reaction wheels derive their power from the _momentum and
pressure_ of falling water. The old-fashioned _undershot_, _overshot_,
and _breast_ wheels are familiar to all as examples of impulse
wheels. Water wheels of this class revolve in the air, with the energy
of the water exerted on one face of their buckets. On the other hand,
reaction wheels are enclosed in water-tight cases, either of metal or
of wood, and the buckets are entirely surrounded by water.
The old-fashioned undershot, overshot, and breast wheels were not very
efficient; they wasted about 75 per cent of the power applied to them.
A modern impulse wheel, on the other hand, operates at an efficiency
of 80 per cent and over. The loss is mainly through friction and
leakage, and cannot be eliminated altogether. The modern reaction
wheel, called the _turbine_, attains an equal efficiency. Individual
conditions govern the type of wheel to be selected.
The Topics we will cover in the upcoming days include:
Different types of water wheels–The impulse and reaction
wheels–The impulse wheel adapted to high heads and small amount of
water–Pipe lines–Table of resistance in pipes–Advantages and
disadvantages of the impulse wheel–Other forms of impulse
wheels–The reaction turbine, suited to low heads and large
quantity of water–Its advantages and limitations–Developing a
water-power project: the dam; the race; the flume; the penstock;
and the tailrace–Water rights for the farmer.
