Water Turbine: Muslims’ landmark achievement
A WATER turbine is known presently as a rotary engine that takes energy from moving water. It was first described in Arabic text as watermill in 9th century.
The first water turbine had wheels and curved blades to flow water as directed axially. The water wheels have been used for thousands of years for industrial power. Their main shortcoming is size, which limits the flow rate and head that can be harnessed.
The migration from water wheels to modern turbines took about one hundred years afterwards significant developments were made in Industrial revolution using scientific principles and methods. They also made extensive use of new materials and manufacturing methods developed at the time.
Today 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. They harness a clean and renewable energy source.
Turbine selection is based mostly on the available water head, and less so on the available flow rate. In general, impulse turbines are used for high head sites, and reaction turbines are used for low head sites.
Kaplan turbines with adjustable blade pitch are well-adapted to wide ranges of flow or head conditions, since their peak efficiency can be achieved over a wide range of flow conditions.Small turbines mostly under capacity of 10 MW may have horizontal shafts. Some have even fairly large bulb-type turbines up to 100 MW or so may be horizontal. Very large Francis and Kaplan machines usually have vertical shafts because this makes best use of the available head, and makes installation of a generator more economical. Pelton wheels may be either vertical or horizontal shaft machines because the size of the machine is so much less than the available head. Some impulse turbines use multiple water jets per runner to increase specific speed and balance shaft thrust.
http://www.technologytimes.pk/mag/2011/jan11/issue02/golden_era.php
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