Allied & ICAR Exam Bank • ALLIED_1143 MCQ • 1 Mark

Section 3: Farm Power

Farm Power

Subtopic: Diesel Knock

Question Statement:

In a compression ignition (diesel) engine, diesel knock is promoted by:

Options:

  • (A) A long ignition delay period resulting in excessive accumulation of unburned fuel before ignition
  • (B) High cetane number of the diesel fuel
  • (C) High cylinder air temperature and pressure at injection
  • (D) Fine atomization of the injected fuel spray

Answer Key:

A

Step-by-Step Solution & Explanation

A prolonged delay period allows a large mass of fuel to evaporate and mix with air; when ignition finally occurs, this entire mass ignites simultaneously, causing an uncontrolled rate of pressure rise and audible knock.
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