Modified Rankine Cycle: Theoretical Indicator Diagram

Theoretical indicator diagram for a steam engine is shown in Figure 5.3 without clearance volume and with clearance volume in Figure 5.4. In Figure 5.3, clearance volume is zero. Steam at boiler pressure enters into the cylinder at point 1 and cut-off at point 2. Then the steam expands inside the cylinder isothermally from point 2 to point 3. Point 3 represents atmospheric pressure and the exhaust of the steam occurs at point 4, i.e., below the atmospheric pressure. Point 4 is known as point of release. Exhaust occurs at constant pressure line 4–5. Again steam enters into the cylinder at point 5 but suddenly pressure increases to point 1.

Figure 5.3 Theoretical Indicator Diagram for Steam Engine

Figure 5.4 Theoretical Indicator Diagram with Clearance Volume for Steam Engine

Work done per cycle with clearance volume (Figure 5.4)

Mean effective pressure with clearance volume