š Key Concepts
ā¢ Compare the constant-pressure and constant-volume parts of each ideal cycle (Otto, Diesel, Gas Turbine/Brayton, Rankine) on a PāV diagram.
ā¢ Notice which segments of the diagram are curved (compression/expansion) and which are horizontal or vertical (heat addition/rejection).
ā¢ Think about where, in that cycle, point 1 would be if it is the start of compression, and what the next steps in that specific cycle look like.
š Think About
ā¢ From point 1 to point 2, are you looking at a compression that is mostly a smooth curve (isentropic) or a straight vertical line (constant volume)? Which cycles use which?
ā¢ Between points 2 and 3, the line is nearly horizontal (constant pressure). Which of the listed cycles has heat addition at constant pressure on its ideal PāV diagram?
ā¢ Does this cycle involve a phase change from liquid to vapor (as in Rankine), or is it a pure gas process throughout (as in Otto, Diesel, or Gas Turbine)?
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Before You Answer
ā¢ Verify which cycle has both compression and expansion as smooth, nearly adiabatic curves, with heat addition at constant pressure between 2 and 3.
ā¢ Eliminate any cycle whose ideal PāV diagram shows heat addition at constant volume (a vertical line) where your figure clearly shows a horizontal line.
ā¢ Make sure the cycle you choose is one that is used for a continuous-flow gas engine rather than a reciprocating piston engine with distinct intake and exhaust strokes, if that matches the diagram.