Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
273 views
in General by (114k points)
closed by

Consider’ the following factors :

Diesel engine knock can be reduced by

1. Engine speed

2. Compression ratio.

3. Degree of supercharge

4. Injection advance

Which of the statements is/are true?


1. 1, 2 and 3 only
2. 2 and 3 only
3. 1, 3 and 4 only
4. 2 only

1 Answer

0 votes
by (115k points)
selected by
 
Best answer
Correct Answer - Option 1 : 1, 2 and 3 only

Concept:

  • In C.I. engines the injection process takes place over a definite interval of time. Consequently, as the first few droplets injected are passing through the ignition lag period, additional droplets are being injected into the chamber. If the ignition delay is longer, the actual burning of the first few droplets is delayed and a greater quantity of fuel droplets gets accumulated in the chamber.
  • When the actual burning commences, the additional fuel can cause too rapid a rate of pressure rise, resulting in Jamming of forces against the piston (as if struck by a hammer) and rough engine operation. If the ignition delay is quite long, so much fuel can accumulate that the rate of pressure rise is almost instantaneous.
  • Such, a situation produces extreme pressure differentials and violent gas vibration known as knocking (diesel knock), and is evidenced by an audible knock. 
  • The delay period is directly related to the Knocking in CI engine, Less delay period leads to less knicking.
  • Engine speed: Increase in engine speed increases the air motion and turbulence, reduces ID time slightly (in ms)
  • Compression ratio: Increases air temperature and pressure and reduces auto-ignition temperature thus leading to less delay period.
  • Degree of supercharging: Increase in the degree of supercharging increases the intake temperature and pressure leading to less delay period.
  • Injection advance: Cylinder temperature and pressure drop if injection is earlier hence delay period increases.
  • So, first three factors lead to Less knocking.

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...