Chapter 9.12, Problem 68P

An air-standard cycle, called the dual cycle, with constant specific heats is executed in a closed piston– cylinder system and is composed of the following five processes:

1-2 Isentropic compression with a compression ratio, r = V₁/V₂

2-3 Constant-volume heat addition with a pressure ratio, rp = P₃/P₂

3-4 Constant-pressure heat addition with a volume ratio, rc V₄/V₃

4-5 Isentropic expansion while work is done until V₅ = V₁

5-1 Constant-volume heat rejection to the initial state

1. (a)   Sketch the P-ν and T-s diagrams for this cycle.
2. (b)   Obtain an expression for the cycle thermal efficiency as a function of k, r, rc, and rp.
3. (c)   Evaluate the limit of the efficiency as rp approaches unity, and compare your answer with the expression for the Diesel cycle efficiency.
4. (d)   Evaluate the limit of the efficiency as rc approaches unity, and compare your answer with the expression for the Otto cycle efficiency.