Pumps and Turbines Study Materials
Pump is a device which is used to convert mechanical energy into hydraulic energy. Here hydraulic energy refers to potential and kinetic energy of a liquid Hydraulic pumps are the energy-absorbing machines. Since, it requires mechanical power to run.
Classification of pumps
The reciprocating pump is a positive displacement pump. It operates on a principle of actual displacement or pushing of liquid by a piston or plunger that reciprocates in a closely fitting cylinder. These pumps usually have one or more cylinders which are alternatively filled with liquid to be pumped and then emptied again. In this pump, the mechanical energy is converted into hydraulic energy by sucking the liquid into a cylinder in which a piston is reciprocating and exerts the thrust on the liquid and increases its hydraulic energy. The reciprocating pumps are generally employed for light at pumping, feeding small boiler condensate return and pneumatic pressure systems.
According to the piston being in contact with piston or plunger.
- Single acting pump
- Double acting pump
According to the number of cylinders provided,
- Single cylinder pump
- Double cylinder pump
- Triple cylinder pump
- Duplux double acting pump
- Quantiplex pump
Hydraulic turbines are the machines which convert the energy of flowing water into mechanical energy. The mechanical energy developed by a turbine is used in running an electric generator which directly couples to the shaft of the turbine. Thus the mechanical energy is converted into electrical energy. This electrical power is known as hydroelectric power.
Classification of Turbines:
According to the action of the-water flowing.
- Impulse turbine – Pelton wheel
- Reaction turbine – Francis turbine, Kaplan turbine
According to the main direction of flow of water.
- Tangential flow turbine – Pelton wheel.
- Radial flow turbine – Old Francis turbine.
- Axial flow turbine – Kaplan turbine
- Mixed flow turbine – Modern Francis turbine
According to the head and quantity of water required:
- High head (above 250 m) – Pelton wheel.
- Medium head (60 m – 250 m) – Modern Francis turbine
- Low head turbine (less than 60 m – Kaplan turbine)
According to the specific speed:
- Low specific speed (10 to 35) – Pelton wheel
- Medium specific speed (60 to 400) – Francis turbine
- High specific speed (300 to 1000) – Kaplan turbine
In an impulse turbine, all the energy available by water is converted into kinetic energy by passing it through a nozzle. The high velocity jet coming out of the nozzle then impinges on a series of buckets fixed around the aim of a wheel. Thus, the runner revolves freely in air.
Ex: Pelton wheel
In a reaction turbine, the runner utilizes both potential and kinetic energies. Here only a portion of a potential energy is transformed into kinetic energy before the fluid enters the turbine runner. As the water flows through the runner, remaining part of potential energy goes on changing into kinetic energy.
Ex: Francis turbine and Kaplan turbine.