(SEM IV) THEORY EXAMINATION 2023-24 APPLIED THERMODYNAMICS

This document is a B.Tech (Semester IV) Theory Examination Question Paper for the subject BME401 – Applied Thermodynamics, conducted in the academic session 2023–2024.
It is a 3-hour, 70-mark examination designed to assess a student’s knowledge of internal combustion engines, power cycles, boilers, condensers, turbines, gas turbine cycles, combustion, heat transfer in power plants, and steam nozzle/steam turbine calculations.
 

The question paper is divided into three sections—A, B, and C—covering conceptual theory, comparative analysis, numerical problems, and cycle-based calculations.

SECTION A – Short Answer Questions (14 Marks)

Seven short 2-mark questions that test fundamental thermodynamics knowledge:

Difference between S.I. engine and C.I. engine

Limitations of Carnot vapour cycle

Meaning of endothermic & exothermic reactions

Function of air pre-heater in a boiler

Difference between surface condenser and jet condenser

Factors affecting nozzle efficiency

Meaning of stage efficiency

These questions test conceptual understanding of power plants, IC engines, and thermal equipment.

SECTION B – Descriptive / Comparative / Derivation Questions (21 Marks)

Students must attempt any three:

a. Otto Cycle Efficiency Derivation

Derive the expression for air-standard efficiency of the Otto cycle.

b. Regenerative vs Rankine Cycle

Compare performance and efficiency of a Regenerative Rankine cycle with a simple Rankine cycle.

c. Condensers in Power Plants

Discuss different types of condensers and their key features.

d. Maximum Blade Efficiency in Impulse Turbine

Condition for maximum blade efficiency and how it varies with blade speed to steam velocity ratio.

e. Purpose of Reheat in Gas Turbine Cycle

Explain how reheating affects specific work and thermal efficiency.

This section checks derivation skills, analytical reasoning, and knowledge of thermal cycles.

SECTION C – Numerical & Cycle-Based Problems (35 Marks Total)

Each question contains two options, and the student must attempt one part from each.

3. SI Engine Cycle / Turbocharger Principle (7 Marks)

Option 3(a)
A large numerical problem on a 4-stroke SI engine involving:

Compression ratio = 6                                        Swept volume = 0.15 m³

Initial P = 98 kPa, T = 60°C                                 Heat added = 150 kJ/kg

Find P, V, T at all points, entropy change, work done, efficiency, mean effective pressure

Draw T-S diagram

Option 3(b)
Explain operation & performance benefits of a turbocharger.

4. Rankine Cycle / Combustion Analysis (7 Marks)

Option 4(a)
Rankine cycle with steam entering turbine at:

40 bar, 350°C → expands to 0.05 bar

Compute network output per kg steam, cycle efficiency, pump work

Draw T-S diagram

Option 4(b)
Orsat analysis for diesel combustion:

Given CO₂ = 7.2%, O₂ = 10.8%, rest N₂                   Determine air-fuel ratio and excess air %

5. Boiler Draught / Condenser Air Leakage (7 Marks)

Option 5(a)
Artificial draught boiler with:

Gas exit = 150°C                                  Chimney height = 60 m

Gas temp inside = 300°C                     Air temp = 17°C

Air requirement = 19 kg/kg fuel          CV = 32604 kJ/kg
Compute:

Draught in mm of water                       Chimney efficiency

Extra heat lost in flue gases

Option 5(b)
Air leakage into steam condenser:

Steam = 35°C → condensate = 34°C        Air removed at 33°C

Air leak: 3 kg/hr                                        Determine air volumes handled by pumps

6. Impulse Turbine / Nozzle Flow (7 Marks)

Option 6(a)
Single-stage impulse turbine with:

Isentropic drop = 200 kJ/kg                      Nozzle efficiency = 96%

Nozzle angle = 15°                                    Blade velocity coefficient = 0.96

Speed ratio = 0.5                                       Mass flow = 20 kg/s

Inlet steam velocity = 50 m/s

Find:

Blade angles                                               Blade efficiency

Power developed                                       Axial thrust

Option 6(b)
Isentropic nozzle flow:

Inlet: 10 bar, 500°C                                     Exit: 6 bar

Exit area = 20 cm²
Compute mass flow rate and show process on h-s diagram.

7. Gas Turbine / Turbojet Comparison (7 Marks)

Option 7(a)
Gas turbine:

Inlet air = 1 bar, 300 K                                               Compression ratio = 6.2

Compressor efficiency = 88%                                    Fuel CV = 44186 kJ/kg

f/a ratio = 0.017                                                         Turbine internal efficiency = 90%
Compute:

Compressor work                                                       Turbine work

Thermal efficiency

Option 7(b)
Compare turbojet engines with other jet propulsion systems.

📄 Overall Purpose of the Document

This exam paper assesses comprehensive thermodynamic competency, including:

IC engine cycles (Otto, SI engine cycle)

Gas turbine cycles, reheat, turbochargers

Steam power plant cycles (Rankine, regenerative)

Boiler equipment (air pre-heaters, chimneys, draught calculations)

Steam turbines (impulse stage, blade efficiency)

Nozzle flow thermodynamics

Combustion analysis (Orsat method)

Condenser performance and air leakage

Entropy, heat transfer, and cycle efficiencies

This evaluation combines theory, derivations, numerical problems, and thermodynamic cycle diagrams, ensuring a complete assessment of applied thermodynamics.