Module 1: An Overview of Engine Emissions and Air Pollution
  Lecture 1: Introduction to IC Engines and Air Pollution
 

Main Events in Four-Stroke CI Engine Cycle

Figure 1.2 shows typical pressure –crank angle (P-θ) history for a four-stroke CI engine cycle. The sequence of main events in the cycle are given in Table 1.3

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Figure 1.2 Main Events in Four-Stroke CI Engine Cycle

 

Table 1.3

Sequence of Events in 4-Stroke CI Engine Cycle


Event

Time of occurrence, Crank angle
Intake valve opens (IO)

5 -20º CA  bTDC at the end of exhaust stroke
Exhaust valve closes (EC)

8 to 20º  CA  aTDC in the beginning of intake stroke
Intake valve closes (IC)

40 -20º  CA aBDC in the beginning of compression stroke
Start of Injection (SOI)

15-5º  CA  bTDC towards the end of compression stroke. Injection duration at full engine load  about 15 to 25º CA
Start of combustion (SOC) 5 -0 º CA bTDC, (considering ignition delay after injection)
 End of combustion (EOC)

20 to 30 CA aTDC in expansion stroke

Exhaust valve opens (EC)

40 to 30º  CA bBDC Shortly before the end of expansion stroke