Air-Standard Dual (Mixed) Combustion Cycle – Process Count Check The ideal dual combustion cycle comprises two isentropic processes, two constant-volume processes (heat addition and heat rejection), and one constant-pressure process (part of the heat addition).

Introduction / Context:
The dual (or mixed) combustion cycle bridges Otto and Diesel models by splitting heat addition into constant-volume and constant-pressure phases. Verifying the process count strengthens understanding of ideal cycle layouts used in engine analysis.

Given Data / Assumptions:

• Air-standard cycle with constant specific heats.
• Quasi-equilibrium processes.
• No changes in kinetic or potential energy.

Concept / Approach:

The cycle sequence is: 1–2 isentropic compression; 2–3 constant-volume heat addition; 3–4 constant-pressure heat addition; 4–5 isentropic expansion; 5–1 constant-volume heat rejection. That list totals two isentropic, two constant-volume, and one constant-pressure processes, matching the statement.

Step-by-Step Solution:

Verification / Alternative check:

Setting the constant-pressure segment length to zero reduces the dual cycle to the Otto cycle; setting the constant-volume segment to zero reduces it to the Diesel cycle, confirming the mixed nature.

Why Other Options Are Wrong:

Disagree options conflict with the standard definition. Constraints on gamma or polytropic compression are not part of the ideal dual cycle definition.

Common Pitfalls:

Incorrectly assigning heat rejection to constant pressure; forgetting that only one constant-pressure leg exists in the ideal dual cycle.

Final Answer:

Agree