Which is the theoretical cycle on which steam turbine works?

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JKSSB JE Mechanical 02 Nov 2021 Shift 1 Official Paper

Answer 1

Explanation:

Steam power plant:

A steam engine is a heat engine that continuously converts heat (energy released by burning of fuel) into work (shaft work). This conversion is performed in a cycle of processes. In a simple vapour power plant, the working fluid which is water undergoes a change of phase.
Heat is transferred to water in the boiler from an external source to raise steam.
The high-pressure, high-temperature steam leaving the boiler expands in a turbine to produce shaft work.
The steam leaving the turbine condenses into water in the condenser i.e. rejecting heat.
Then again water is pumped back into the boiler with the aid of a pump.
For each process in the vapour power cycle, it is possible to assume a hypothetical or ideal process which represents the basic intended operation and involves no extraneous effects.
When all these four processes are ideal, the cycle is an ideal cycle, called the Rankine cycle which is the most suitable steam power plant.

Rankine cycle:

Rankine cycle is an ideal cycle of heat engine which uses water and steam as a working fluid to generate power with the help of a steam turbine.

These are four processes in the Rankine cycle:

Process 1–2: Isentropic compression: Working fluid is pumped from low to high pressure.
Process 2–3: Isobaric heat addition: The high-pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a dry saturated vapour.
Process 3–4: Isentropic expansion: The dry saturated vapour expands through a turbine, generating power.
Process 4–1: Isobaric heat rejection: The wet vapour then enters a condenser where it is condensed at constant pressure and temperature to become a saturated liquid.

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