Radial flow reaction turbine: how to generate electricity from turbine

            Hydraulic machines are defined as those machines, which converts either hydraulic energy into mechanical energy or mechanical energy into hydraulic energy. The hydraulic machine, which convert the hydraulic energy into a mechanical energy is called turbine. The hydraulic machines which convert the mechanical energy into a hydraulic energy is called pumps.
            The basic difference between turbine and compressor is that, Turbine expands the fluids while compressor compress the fluid during process.

Radial flow turbine are those turbine in which the water flow in the radial direction. The water may flow radially from outwards to inwards or from inwards to outwards. If the water flows from outwards to inwards through the runner, The turbine is known as inward radial flow turbine. And if the water flows from inwards to outwards, the turbine is known as outward radial flow turbine.
Turbine


            Reaction turbine means that the water at the inlet of the turbine possesses kinetic energy as well as pressure energy. As the water flows through the runner, a part of pressure energy goes on changing into kinetic energy. Thus the water through the runner is under pressure. The runner is completely enclosed in an air-tight casing and casing and the runner is always full of water.


  • Main parts of a radial flow reaction turbine:-
  1. Casing
  2. Guide mechanism
  3. Runner
  4. Draft-tube
  • Casing:-
          As mentioned above that in case of reaction turbine, casing and runner are always full of water. The water from the penstocks enters the casing which is of spiral shape in which area of cross-section of the casing goes on decreasing gradually. The casing completely surrounded the runner of the turbine. The water may enter the runner at constant velocity throughout the circumference of the runner. The casing is made of concrete, cast steel or plate steel.

  • Guide Mechanism:-
           It consist of a stationary circular wheel all round the runner of the turbine. The stationary guide vanes are fixed on the guide mechanism. The guide vanes allow the water to strike the vanes fixed on the runner without shock at inlet. Also by a suitable arrangement, The width between two adjacent vanes of guide mechanism can be altered so that the amount of water striking the runner can be varied.

  • Runner:-
           It is a circular wheel on which a series of radial curved vanes are fixed. The surface of the vanes are made very smooth. The radial curved vanes are so shaped that the water enters and leaves the runner without shock. The runners are made of cast steel, cast iron or stainless steel. They are keyed to the shaft.

  • Draft tube:-

                 The pressure at the exit of the runner of a reaction turbine is generally less than atmospheric pressure. The water at exit cannot be directly discharged to the tail race. A tube or pipe of gradually increasing area is used for discharging water from the exit of the turbine to the tail race. This tube is increasing area is called draft tube.

No comments