🔍 Key Concepts

• Diesel vs Otto vs Dual (combined) cycles and how heat is added in each • What constant pressure and constant volume mean in a pressure‑volume (P‑V) diagram • In a real high‑speed diesel, when does compression ignition start relative to fuel injection and piston position?

💭 Think About

• On a pure Otto cycle, is heat addition modeled at constant pressure or constant volume? How about on a pure Diesel cycle? • A combined or ‘dual’ cycle has part of its heat added one way and the rest another way. Think about which part happens first when fuel begins to burn. • Does ignition usually start when the piston is stopped (TDC) or while it is still moving, and what does that mean for pressure and volume at that instant?

✅ Before You Answer

• Be clear on how heat addition is modeled in a pure Diesel cycle versus a pure Otto cycle before deciding. • Visualize or sketch a simple P‑V diagram for the dual (mixed) cycle and mark where ignition STARTS and where combustion mostly ENDS. • Check which option describes the start of combustion/ignition versus the end of combustion, and match that to the dual‑cycle sequence.