Power Cycle Efficiency

These are ceilings, not predictions — air-standard cycles ignore friction, heat loss, incomplete combustion and pumping, and a real engine reaches roughly 60–75% of the figure shown. What they are genuinely good for is comparison: how much a compression ratio is worth, why Diesel beats petrol, and how far any of it sits below Carnot.

Air-standard analysis assumes a fixed mass of air with constant specific heats, complete combustion modelled as heat addition, and no friction or heat loss. Real efficiencies run roughly 60–75% of these figures. The Rankine case uses dry saturated steam at the boiler, so its exhaust comes out wet — real plant superheats precisely to keep the last turbine stages above about 88% quality. Rankine pressures are absolute bar and must fall inside the saturated steam table (0.006 to 220 bar).