(SEM V) THEORY EXAMINATION 2023-24 I C ENGINE, FUELS & LUBRICATION

Course: B.Tech (Mechanical Engineering)

Semester: V

Subject Code: KME054

Subject Name: I.C. Engine, Fuels & Lubrication

Maximum Marks: 100

Time: 3 Hours

Pattern: Section A (Short), Section B (Medium), Section C (Long)

SECTION A — Short Answer Questions (20 Marks)

Each question carries 2 marks.
Students must answer all questions briefly.

Topics covered:

Difference between two-stroke and four-stroke engines

                                                          Relation between mean effective pressure and mean pressure

Explanation of pre-ignition, auto-ignition, and detonation

                                                          Importance of spark advance and ignition timing

Principle of carburetion

                                                         Fuel injection requirements in CI engines

Advantages and disadvantages of PNG (Piped Natural Gas)

                                                         Hydrocarbon emissions in SI engines

Cooling of engine components through lubrication system

                                                         Why petrol cannot be used in diesel engines (and vice versa)

SECTION B — Descriptive Questions (30 Marks)

Attempt any three questions (10 marks each).
 

Topics include:

Valve timing diagrams — theoretical vs actual (with diagrams)

                                                             Air motion and swirl requirements in CI engines vs SI engines

MPFI System (Multi-Point Fuel Injection) — types and working

                                           Alternative fuels for I.C. engines — biofuels, hydrogen, LPG, CNG, alcohol

Detailed discussion on ignition timing and its affecting factors

SECTION C — Long / Problem-Based Questions (50 Marks)

Attempt one part from each of the given questions (Q3–Q7).

Q3. Thermodynamic Cycles

Compare Otto and Diesel cycles; derive expressions for work done, thermal efficiency, and mean effective pressure

OR

Numerical on Dual cycle involving compression ratio, pressure, temperature, cut-off ratio, and efficiency calculations

Q4. Combustion Process

Explain delay period and its influencing factors

OR

Describe flame propagation and factors affecting flame speed

Q5. Engine Operation

Explain scavenging in a 2-stroke engine

OR

Explain simple carburetor construction and working (with diagram)

Q6. Pollution & Control

Discuss air pollutants from I.C. engines — CO, HC, NOx, and particulate matter

OR

Explain the catalytic converter as an after-treatment device

Q7. Advanced Engine Systems

Explain valve timing control in stratified charge injection engines (with sketch)

OR

Construction and working of battery ignition system (with sketch)

Key Concepts Covered
 

Working and classification of I.C. Engines                    Engine performance parameters

Combustion stages and ignition                                  Air-fuel mixture and carburetion

Alternative fuels and emissions                                    Engine lubrication and cooling

Modern ignition and injection systems

FAQs
 

Q1. What is the full form of MPFI?
MPFI stands for Multi-Point Fuel Injection, where fuel is injected into each cylinder’s intake port for better fuel-air mixing and efficiency.

Q2. What are the major pollutants emitted by IC engines?
Carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and soot are common engine emissions.

Q3. Why can’t diesel fuel be used in a petrol engine?
Because diesel requires compression ignition, whereas petrol engines use spark ignition — their design and combustion methods differ fundamentally.

Q4. What is the delay period in CI engines?
It’s the time gap between the start of fuel injection and the actual start of combustion. Factors like fuel quality, temperature, and injection pressure influence it.

Q5. What is scavenging in a two-stroke engine?
Scavenging is the process of clearing exhaust gases from the cylinder to make room for the next fresh charge.