Steam Turbine

In this post, we will discuss the steam turbine use, design features, and its types. This article can help you to better understand the steam turbine and its parts.

steam turbine
steam turbine

Steam Turbine

The steam turbine is the most essential part of a thermal power plant. The turbine is used to produce electricity. This produced electricity can be used as the in-house requirement or can also be transmitted to the power grid.

The steam turbine is a device converts steam energy into mechanical energy. The steam turbine extracts thermal energy from pressurized steam and transforms it into the mechanical work and by this, the rotor rotates. The Steam turbine is designed to produce the maximum amount of mechanical power by using the minimum amount of steam.

The steam turbine is connected to an alternator or generator to produce electricity. Approximately 90% of Electrical generation in the world is through the use of a steam turbine. The steam is piped to a turbine by the use of the steam boiler.

Design features of a turbine

The following features are applied to design the turbine.

  • Single stage & Multistage
  • Multi-blade option
  • Impulse/Impulse-reaction blading
  • Multiple blade option
  • Steam extraction option
  • Nozzle group control option on the larger unit
  • Integrally forged rotor, standard for multistage turbines

Parts of an Electrical generation system

Following are the parts of an electrical generation system by the use of a steam turbine.

  • Steam Turbine
  • Gearbox
  • Lubrication oil system
  • Control oil system
  • AC Generator or Alternator
  • Electrical system
  • Steam Condenser
  • Instrument & Control System

Types of steam turbines

  • Condensing cum extraction turbines

Condensing turbine is commonly and mostly used turbine. This type of turbine is used where we require the extraction pressure or the pressure requirement of the process is more than 1.5-kilogram square centimeter. This type of turbine also works as a full condensing turbine so we can use this type of turbine where no extraction pressure is required and we only want to generate the electricity. This type of turbines is best suited for the electricity production requirement of the power grid.

  • Back pressure or non- condensing turbine

Back pressure or non-condensing turbine is used where pressure requirement is below 1.5 kilograms per square centimeter for example- sugar industry. This type of turbine does not require a condenser hence cooling tower is also not required in back pressure or non- condensing turbines. The exhaust from the back pressure turbine is given to process to fulfill the pressure requirement.

Differences between the condensing cum extraction turbine and the back pressure turbine

The main difference between the condensing cum extraction turbine and the back pressure turbine is that the exhaust from the turbine is given to the condenser in the condensing cum extraction turbine. And the exhaust from the back pressure or noncondensing turbine is given to fulfill the process requirement.

The overall efficiency of the back pressure turbine is more than the extraction cum condensing turbine.

The extraction cum condensing turbine costs higher than back pressure or noncondensing turbine.

The backpressure turbine has only one output and this output steam is used in the process requirement.

The extraction cum condensing turbine has more than one output for example- the extraction steam, the bleed steam.

This difference can easily be understood by the figure below.

condensing steam turbine
condensing steam turbine
back pressure steam turbine
backpressure steam turbine

The steam turbine topic will be discussed more in next topics.

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