Principles of operation of steam turbine
The motive power in a steam turbine is obtained by the rate of change in momentum of a high velocity jet of steam impinging on a curved blade which is free to rotate.
- The steam from the boiler is expanded in a nozzle, resulting in the emission of a high velocity jet. This jet of steam impinges on the moving vanes or blades, mounted on a shaft. Here it undergoes a change of direction of motion which gives rise to a change in momentum and therefore a force.
- Principle of operation is shown below:
- The relationship between work, force and blade velocity can be expressed in the other graph.
- Steam turbines are mostly 'axial flow' types; the steam flows over the blades in a direction parallel to the axis of the wheel. 'Radial flow' types are rarely used.