Thermodynamic Cycle

A thermodynamic cycle consists of a series of thermodynamic operations (processes), which take place in a certain order, and the initial conditions are restored at the end of the process. When the operations or processes of cycle are plotted on p-v diagram, they form a closed figure, each operation being represented by its own curve. Since the area under each curve gives the work done to some scale, during each operation, therefore, it follows that the net work done during one cycle will be given by the enclosed area of the diagram as shown shaded in Fig 5.6.

Notes:

1. A cycle, which requires four piston strokes and two complete revolutions of the crank is known as four stroke cycle. But a cycle, which requires only two piston strokes and one revolution of the crank, is known as two-stroke cycle.

2. When air is assumed to be the working substance inside the engine cylinder, the cycle is called as an air cycle.