(SEM IV) THEORY EXAMINATION 2018-19 APPLIED THERMODYNAMICS

SECTION–A — Short Conceptual Questions Covering Full Thermodynamics Basics (14 Marks)

Section–A contains seven 2-mark questions, each touching a different fundamental area of Applied Thermodynamics. The first question asks for the meaning and significance of air-standard cycles, prompting students to explain why real IC-engine cycles are idealised into Otto, Diesel, and Dual cycles for analysis and comparison.

Next, the paper requires definitions of Brake Power, Indicated Power, Brake Mean Effective Pressure, and Indicated Mean Effective Pressure, all of which are central performance indicators used in analyzing engines. The section then moves toward steam generation, asking for the requirements of a good boiler—efficiency, safety, durability, reliability, ease of inspection, and high steam generation rate.

Further, the paper introduces compressible-flow concepts by asking about supersaturated flow, which occurs when steam expands too rapidly in a nozzle or turbine without attaining thermodynamic equilibrium. Another key theoretical comparison follows: the limitations of Carnot Vapour Cycle and how the Rankine Cycle solves real-world inefficiencies, illustrating how practical constraints (like pump work, irreversibilities, and condensation issues) are handled.

The next question demands differentiating impulse and reaction turbines, requiring explanation of energy conversion, blade profiles, and pressure–velocity variation across stages. The final question touches on choked flow in nozzles, a crucial concept in high-velocity steam/air devices where mass flow becomes maximum regardless of further decrease in downstream pressure.

SECTION–B — Long Analytical Problems & Derivations (21 Marks)

Section–B requires students to attempt any three out of five long questions, each carrying 7 marks. These questions test numerical solving ability, derivations, cycle analysis, and detailed understanding of turbine/boiler operations.

One question asks students to derive the air-standard efficiency of Otto Cycle in terms of compression ratio — a classical derivation showing why efficiency rises sharply with increased compression.

Another question analyses a Rankine Steam Cycle operating between 1.96 MPa, 250°C and 13.7 kPa. Students must compute Rankine cycle efficiency with and without pump work, highlighting the slight improvement when pump work is accounted for.

A third numerical question tests understanding of boiler performance, where boiler generates 7.5 kg steam/kg coal at 11 bar from 70°C feedwater. Students must compute degree of superheat, steam temperature, calorific value of coal, and equivalent evaporation — essential calculations for power plant engineers.

Another question involves a Parson turbine running at 1500 rpm with a given enthalpy drop. Students must determine the number of moving blade rows using stage efficiency, speed ratio, and blade outlet angle.

The fifth option includes Turbojet engine calculations involving enthalpy drop, velocity coefficient, fuel flow rate, TSFC, propulsive power, propulsive efficiency, and overall efficiency. This question brings Aerothermodynamics concepts into practical aircraft propulsion.

 SECTION–C — IC Engine Testing & Thermodynamic Cycle Performance (7 Marks)

Section–C contains two choices. The first asks students to explain the Morse Test, a practical technique used for determining indicated power and mechanical efficiency of multi-cylinder engines by sequentially cutting off cylinders.

The alternate question requires computing thermal efficiency and mean effective pressure (MEP) of a petrol-engine cycle with compression ratio = 7, specified initial state, swept volume, and heat addition at constant volume. This demands application of air-standard cycle equations and ideal-gas properties.

SECTION–D — Steam Turbines: Special Cycles & Advanced Applications (7 Marks)

Section–D asks students to choose one of two advanced steam-power questions.

The first option requires describing pass-out turbines (extraction turbines) and back-pressure turbines, explaining their working, applications, and pressure conditions used in industrial cogeneration.

The alternative option is a numerical problem on Binary Vapour Cycle using mercury and steam. With data provided on enthalpy and entropy for different states, students must compute the thermal efficiency of the combined cycle. Binary cycles improve plant efficiency by using a high-temperature metal vapour (like mercury) in the topping cycle and steam in the bottoming cycle.

 SECTION–E — Boiler Mountings, Accessories & Air Leakage in Condensers (7 Marks)

This section also offers two choices. The first option asks for detailed working of essential boiler mountings: water-level indicator, safety valve, fusible plug, feed-check valve, pressure gauge, stop valve, and blow-off cock. These ensure safety, monitoring, and operational control of boilers.

The alternate question asks students to explain causes of air leakage in a condenser and its effects, such as reduced vacuum, decreased turbine efficiency, increased back pressure, and higher operating costs.

SECTION–F — Nozzle Flow & Turbine Compounding (7 Marks)

Section–F again includes one numerical problem and one theory question.

The first option provides a convergent–divergent nozzle expanding air from 6.89 bar, 427°C to 1 bar. Given throat and exit areas and exit velocity, students must compute mass flow rate, nozzle efficiency, and coefficient of velocity—all essential for high-speed compressible-flow design.

The alternate question requires explaining compounding in steam turbines (velocity compounding, pressure compounding, and pressure–velocity compounding) with diagrams. This ensures students understand how high-speed steam jets are tamed and distributed to maintain efficiency and manageable rotor speeds.

SECTION–G — Jet Propulsion & Gas Turbine Cycle (7 Marks)

The final section presents two advanced thermodynamic power-plant problems.

The first question gives details of a turbojet power plant using aviation kerosene and asks for air–fuel ratio and overall efficiency using thrust, TSFC, velocity, and mass flow of air.

The second option is a thermodynamic problem on a gas turbine cycle with two-stage compression and expansion, each with pressure ratio 3. Students must find back work ratio and thermal efficiency, for cases with and without a regenerator (75% effectiveness).

 FINAL SUMMARY — Full Descriptive Overview of the RME403 Exam Paper

The APPLIED THERMODYNAMICS exam paper is comprehensive and blends theoretical clarity with engineering problem-solving. Section–A confirms foundational definitions across steam turbines, cycles, boilers, and nozzle flow. Section–B tests numerical mastery of Rankine cycle, Otto cycle, boilers, turbojets, and turbine design. Sections C–G explore deeper engineering analysis: Morse test, binary cycles, boiler mountings, nozzle calculations, turbine compounding, jet propulsion, and gas-turbine regeneration.

The paper ensures students demonstrate both conceptual understanding and the ability to solve real thermodynamic engineering problems relevant to power plants, engines, turbines, and propulsion systems.