Turbine types in hydropower plant

In a power plant, there are different types of equipment can be found whose has its own work to do. Among them turbine is the important equipment in generating electricity. Here we are going to discuss about turbine in hydropower plant and turbine types.

Turbine in hydropower plant

Turbine is a electrical equipment which is used in all types of power plant whose main function is to convert kinetic energy of different medium (such as water, steam / gas) into mechanical rotational energy. For example, when water is passes through penstock to turbine from certain height, kinetic energy is stored in the water. Similarly, when high pressure steam is passes through the turbine, it also contains kinetic energy. When different medium is passes through the turbine, it will cause to rotate the turbine which shaft is connected to generator's shaft and this will generate electricity. There are many types of turbine which should be selected as per requirement on power plant. Here we are going to discuss about hydroelectric turbine. When water is stored in reservoir in the form of potential energy and when it is flow through penstock (from head race to tail race), this stored potential energy will be converted into kinetic energy. When this water with kinetic energy hit or passes through the turbine, it will rotate i.e. kinetic energy is converted to rotational mechanical energy. This rotational energy is further used to rotate generator shaft and generate electricity. 

Hydraulic turbine types

On the basis of pressure

It can be classified on the based on pressure change while water moving through it.

1. Impulse

In impulse turbine, pressure of water doesn't change when the water is flowing through the turbine but the pressure changes only when it flowing through nozzle. At first, hydraulic energy is converted into kinetic energy while moving from high head to nozzle. When the water is flowing from nozzle to turbine, pressure will changes from high pressure to low pressure(atmospheric pressure) and this high pressure water will hit the turbine blade/buckets of turbine which results to rotate the turbine. It also means, the energy available at the turbine is kinetic energy of water and pressure on inlet and outlet side of turbine is constant which is equal to atmospheric pressure. Generally, this is used in high head power plant and its examples are Pelton, crossflow, Turgo-impulse etc.

2. Reaction

It is just opposite to that of the impulse turbine. Here, pressure of water is changed when the water is flowing through it but the pressure doesn't change when water is  flowing through the nozzle. While changing pressure, there is also change in velocity of water and it cause to rotate the turbine. In this type of turbine, the water is flow from inlet, rotate inside the turbine and come out from outlet. The example of this type are Francis, Kaplan etc.

Based on flow path

It can be classified on the based on water flow path.

  1. Axial flow

In this type, water flow parallel to the axis of rotation. For example Kaplan

  

  2. Radial flow

In this type, water flow in a plane perpendicular to the axis of rotation. Example Francis

  

  3. Tangential flow

In this type, water flow in tangential direction to the runner.

  

  4. Mixed flow

In this type, water flow both axial and radial flow. For example Francis turbine where water inlet  in radial direction and outlet in axial direction.

Based on Head

This can be classified on the based on head of the plant.

1. High head :- Example Pelton

2. Medium head :-  Example Francis

3. low head :- Example Kaplan

Based on specific speed

1. High specific speed :- Example Pelton

2. Medium specific speed :- Example Francis

3. Low specific speed :-  Example Kaplan

Some types of hydroelectric turbines are as follows:-

1. Pelton
2. Cross-flow
3. Francis
4. Kaplan and Propeller