(SEM V) THEORY EXAMINATION 2024-25 I C ENGINES, FUELS & LUBRICATION

Subject Code: BME052 / BME052A

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

Course: B.Tech (Semester V)

Maximum Marks: 70

Duration: 3 Hours

Exam Year: 2024–25

Sections: A, B, and C

SECTION A – Short Answer Questions (2 × 7 = 14 Marks)

Attempt all questions briefly.

a. Draw the valve timing diagram.
b. Explain briefly the principle of a Turbocharger.
c. How does carburetion occur in an I.C. engine?
d. Explain the effect of temperature on formation of CO, HC, and NOx.
e. Discuss mixture requirements at different loads and speeds.
f. Why do two-stroke engines have higher mechanical efficiency but lower thermal efficiency?
g. Explain briefly how a GDI (Gasoline Direct Injection) Engine works.
 

SECTION B – Medium-Length Questions (7 × 3 = 21 Marks)

Attempt any three of the following:

Explain the function of a spark plug with a neat diagram.

Explain the effects of CO, HC, NOx, and PM on environment and human health.

Describe the working of an MPFI (Multi-Point Fuel Injection) Engine.

For the same compression ratio and heat addition, which of the following cycles — Otto, Diesel, or Dual — is most and least efficient? Explain.

Explain the effect of air-fuel ratio on pollution generation.
 

SECTION C – Long/Analytical Questions (7 × 5 = 35 Marks)

Attempt one part from each question.

Q3. Air Standard Cycles

a. A petrol engine is supplied with fuel having a calorific value of 42 MJ/kg. The cylinder pressures at 30% and 70% of compression stroke are 1.3 bar and 2.6 bar, respectively.

Assuming pV1.33=constantpV^{1.33} = \text{constant}pV1.33=constant, find the air-standard efficiency of a constant volume cycle.

Also, find the air-standard efficiency of a constant pressure cycle if the cut-off ratio = 1.2.

Compare both efficiencies if the compression ratio is 8.

b. In a diesel cycle, initial pressure and temperature are 1 bar and 170°C, and the pressures at the end of compression and expansion are 40 bar and 2 bar respectively.

Find efficiency, assuming γ=1.4\gamma = 1.4γ=1.4.
 

BME052-I-C-ENGINES-FUELS-LUBRIC…

Q4. Combustion in Engines

a. Discuss stages of combustion in SI (Spark Ignition) engines with a neat diagram.
b. Discuss stages of combustion in CI (Compression Ignition) engines with diagram and explanation.

Q5. Combustion Chambers & Lubrication

a. List different types of combustion chambers in CI engines and explain any one in detail.
b. Describe different types of lubrication systems and explain any one with a neat sketch.

Q6. Fuels and Ignition Systems

a. Explain the working of a Homogeneous Charge Spark Ignition Engine.
b. List and explain different gaseous fuels and their properties in detail.

Q7. Fuel Injection and Emission Control

a. Explain the construction and working of a Jerk Type Fuel Injection Pump with diagram.
b. Describe the Three-Way Catalytic Converter — its construction, working, and purpose in emission control.
 

Key Topics for Preparation

Valve timing diagrams and carburetion process.

Turbocharging principle and GDI engine functioning.

Air standard cycles: Otto, Diesel, and Dual — efficiency comparison.

Stages of combustion in SI and CI engines.

Combustion chamber design and lubrication systems.

Pollutants (CO, HC, NOx, PM) — formation and effects.

Fuel injection systems: Jerk pump, MPFI, and GDI.

Emission control devices: Three-way catalytic converter.

Alternative and gaseous fuels (CNG, LPG, Hydrogen).

Study Tips

Draw neat labeled diagrams for all mechanical components (spark plug, injection pump, valve timing).

Revise thermodynamic relations for Otto, Diesel, and Dual cycles.

Learn numerical problems on efficiency, power output, and air-fuel ratio.

Memorize chemical equations for emission formation and reduction.

Revise differences between 2-stroke vs 4-stroke, SI vs CI, and GDI vs MPFI systems.