The Rankine cycle for a steam turbine

Although technological progress is very fast, it is often possible to see situations in which modern installations use principles that were discovered in the past centuries. For example, the Rankine cycle, which was invented in the 19th century, is used in the work of steam turbines today.

The great inventor

Rankin's cycle was discovered by a Scottish physicist and engineer who lived and worked in the century before last. The invention was named after this great scientist, who was also one of the founders of technical thermodynamics.

Rankin William John was born in 1820 in the city of Edinburgh, where he studied for three years at the institute. However, the scientist failed to finish this institution because of a difficult financial situation. But this did not stop the gifted physicist from carrying out a number of useful discoveries. So, in 1849 he received equations in thermodynamics, describing the relationship between mechanical energy and heat. He also constructed the theory of a steam engine and developed the basic principles that underlay the work of this unit. These provisions constitute the process that was given the name in honor of the scientist-the Rankine cycle.

Basic moments

This cycle is a theoretical expression of the work of thermodynamic processes occurring during the operation of steam power plants in the repetition mode. It is possible to single out such basic operations entering into this cycle:

• The liquid evaporates at high pressure;
• The water molecules in the gaseous state expand;
• Wet steam condenses on the walls of the vessel;
• The fluid pressure increases (returns to the original value).

It can be noted that the thermal efficiency for this cycle is in direct proportion to the initial temperature. Also, the efficiency of this process is determined by the pressure values and the heat state index at the starting position and at the outlet.

Steam turbine

This unit is a heat engine, as a result of which electricity is generated. The main nodes of this installation can be presented in the following list:

• Movable part, which consists of a rotor and fixed blades on it;
• A stationary element having such constituent parts as a stator and nozzles.

The work of the plant can be characterized in this way. Water in the gaseous state at high temperature and pressure is fed into the turbine nozzles. Here, at a supersonic velocity, the potential energy of the vapor turns into a kinetic energy, while the particles of the vapor are driven. This, in turn, creates a gaseous flow that acts on the turbine blades. Rotation of these elements causes the rotor to move, resulting in the formation of electricity. Further, condensation of the vapor takes place and it settles in a special chilled water receiver, from where the liquid is again forced into the heat exchanger. Thus, there is a repetition of operations, that is, the Rankine cycle is performed.

This principle is used in installations at nuclear power plants, and it is also used in the operation of autonomous turbine installations for the production of electricity. This scheme is by far the most efficient and economical. Installations working on the principles of Rankin, are distributed throughout the world.