STEAM FLOW IN TURBINES BASIC INFORMATION AND TUTORIAL

How A Steam Flows In Turbines?

For large turbines, the steam jets are generally designed so the steam fl ow is in a direction approximately parallel to the rotor shaft; these are known as axial-fl ow turbines. Small turbines have their steam flow approximately tangent to the rim of the rotor and are called tangential flow turbines.

The steam flow in smaller units may be radially inward toward or outward from the shaft; these are known as radial-flow turbines.

A turbine in which nearly all the steam that drives the turbine flows through the blades in the same general direction parallel to the rotor axis is known as a single-flow turbine.

A turbine in which the main steam current is divided and the parts fl ow parallel to the rotor axis in opposite directions is known as a double-fl ow turbine.

The latter is used to drive a large generator where the size of a single-flow turbine is so large as to become impractical or uneconomical. Where generation requirements are large, resort is sometimes had to a topping turbine.

This turbine operates at high pressure (1000 to 1200 pounds per square inch) and the entire volume of steam passes through it driving a generator. The steam exhausts at low pressure (500 to 600 pounds per square inch).

This is then passed through one (or more) single-fl ow or double-fl ow turbines, driving a second (or third) generator of smaller capacity than the one driven by the high pressure turbine.

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