Real Rankine Cycle (non-ideal)
In a real power plant cycle (the name 'Rankine' cycle used only for the ideal cycle), the compression by the pump and the expansion in the turbine are not isentropic. In other words, these processes are non-reversible and entropy is increased during the two processes. This somewhat increases the power required by the pump and decreases the power generated by the turbine.
In particular the efficiency of the steam turbine will be limited by water droplet formation. As the water condenses, water droplets hit the turbine blades at high speed causing pitting and erosion, gradually decreasing the life of turbine blades and efficiency of the turbine. The easiest way to overcome this problem is by superheating the steam. On the Ts diagram above, state 3 is above a two phase region of steam and water so after expansion the steam will be very wet. By superheating, state 3 will move to the right of the diagram and hence produce a drier steam after expansion.
Read more about this topic: Rankine Cycle
Famous quotes containing the words real and/or cycle:
“Freedom is but the possibility of a various and indefinite activity; while government, or the exercise of dominion, is a single, yet real activity. The longing for freedom, therefore, is at first only too frequently suggested by the deep-felt consciousness of its absence.”
—Karl Wilhelm Von Humboldt (1767–1835)
“The Buddha, the Godhead, resides quite as comfortably in the circuits of a digital computer or the gears of a cycle transmission as he does at the top of a mountain or in the petals of a flower.”
—Robert M. Pirsig (b. 1928)