🔍 Key Concepts

• Diesel combustion stages: ignition delay, rapid (uncontrolled) combustion, steady (controlled) combustion, and late combustion • Relationship between fuel injection and the steady combustion (controlled) period • How cylinder pressure rise and fuel burn rate change as the piston moves around top dead center (TDC)

💭 Think About

• Think about what defines the start of the steady combustion period in relation to fuel injection and ignition delay. What physically changes in the way fuel is burning at that point? • During the steady combustion period, is fuel being injected, burned, or both? What has to happen to change from a controlled burn to the next phase? • Look at each option and ask: which of these events directly changes the combustion process, rather than just piston or valve position?

✅ Before You Answer

• Identify when ignition delay ends and when rapid (uncontrolled) combustion ends; then consider what marks the end of the controlled or steady combustion stage • Determine whether fuel injection is still occurring throughout the steady combustion period or if it stops right at its end • Verify which event causes a noticeable change in the rate of pressure rise and heat release inside the cylinder