Subtopic: Thermodynamic principles of I.C. engines
Question Statement:
Which of the following factors increase the tendency of abnormal knocking / detonation in a Compression Ignition (CI / Diesel) engine?
Options:
(A) Long ignition delay period
(B) Low cetane number of the diesel fuel
(C) Low compression ratio
(D) High inlet air temperature and intake swirl
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
- In CI engines, knocking occurs due to rapid pressure rise from fuel accumulating during a long ignition delay period.
- Low cetane fuel has longer ignition delay, worsening knock.
- Low compression ratio reduces end-of-compression temperature and pressure, increasing ignition delay and knock.
- High intake air temperature and swirl promote rapid auto-ignition, reducing delay and knock.