BT-203 Basic Mechanical Engineering - Dec 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aWhat is the necessity of Alloying? What are alloy steels, and how do they differ from carbon steels?
   How to answer

   • Necessity and purposes of alloying metals (corrosion resistance, strength, hardness).
   • Definition of alloy steels.
   • Key differences between alloy steels and plain carbon steels (composition, hardenability, mechanical properties).
2. 7 Marks
   bWhat is the purpose of hardness testing in materials and how it is performed?
   How to answer

   • Definition and purpose of hardness testing (resistance to indentation, wear, abrasion).
   • Overview of common testing methods (Brinell, Rockwell, Vickers).
   • General procedure: applying an indenter under specified load and measuring impression/depth.
3. 7 Marks
   aWrite in detail classification of cast irons along their applications.
   How to answer

   • Definition and carbon content of cast iron.
   • Classification: Gray, White, Malleable, Ductile/Nodular, Compacted Graphite cast irons.
   • Microstructure, properties, and specific engineering applications for each type.
4. 7 Marks
   bExplain the working principles of Drilling machine and different parts of it indicating with line diagram.
   How to answer

   • Working principle of drilling operation (rotational motion + linear feed).
   • Neat labeled line diagram of a drilling machine (bench/upright).
   • Key parts and their functions: base, column, table, spindle head, feed mechanism, motor.
5. 7 Marks
   aGive in detail the flow chart followed in preparation of sand casting.
   How to answer

   • Flow chart diagram showing sequential steps: pattern making, sand preparation, core making, mold making, melting and pouring, cooling, shakeout/fettling, and inspection.
   • Brief explanation of each process in sand casting preparation.
6. 7 Marks
   bWrite short notes on: i) Vernier caliper ii) Micrometer iii) Dial gauge
   How to answer

   • Vernier Caliper: principle, least count calculation, internal/external/depth measurement.
   • Micrometer: screw and nut principle, least count, ratchet stop, parts.
   • Dial Gauge: rack and pinion mechanism, principle of comparative measurement, indicator pointer.
7. 7 Marks
   aExplain how hydraulic turbines convert fluid energy into mechanical energy. Discuss the types of hydraulic turbines and their applications.
   How to answer

   • Working principle of energy conversion (potential/kinetic energy of fluid to mechanical rotation).
   • Classification into Impulse (Pelton wheel) and Reaction turbines (Francis, Kaplan).
   • Head and flow rate requirements and typical applications of each type.
8. 7 Marks
   bDefine and distinguish between: i) Uniform flow and non-uniform flow ii) Laminar and turbulent flow iii) Newtonian and Non-Newtonian flow
   How to answer

   • Uniform vs Non-uniform flow: spatial variation of velocity ($\frac{\partial V}{\partial s} = 0$ vs $\neq 0$).
   • Laminar vs Turbulent flow: fluid particles moving in smooth layers vs chaotic mixing; Reynolds number criteria.
   • Newtonian vs Non-Newtonian flow: linearity between shear stress and rate of shear strain ($\tau = \mu \frac{du}{dy}$).
9. 7 Marks
   aState Newton's law of viscosity and explain its significance. Describe how viscosity is related to shear stress and shear rate in Newtonian fluids.
   How to answer

   • Statement of Newton's Law of Viscosity.
   • Mathematical formula: $\tau = \mu \frac{du}{dy}$.
   • Physical significance of viscosity.
   • Relationship: linear proportionality of shear stress $\tau$ to velocity gradient / shear rate in Newtonian fluids.
10. 7 Marks
    bDifferentiate between boiler mountings and accessories. Discuss the role of boiler accessories in enhancing efficiency and safety in boiler systems.
    How to answer

    • Distinction between mountings (essential for safe operation) and accessories (integral for improving efficiency).
    • Tabular comparison with common examples.
    • Role of key accessories: Economizer, Air Preheater, Superheater, Feed Pump in improving overall plant efficiency and system reliability.
11. 7 Marks
    aDefine thermodynamic system and explain open, close and isolated systems.
    How to answer

    • Definition of thermodynamic system, boundary, and surroundings.
    • Open system: mass and energy cross the boundary (e.g., turbine, nozzle).
    • Closed system: only energy crosses the boundary, mass does not (e.g., piston-cylinder without valves).
    • Isolated system: neither mass nor energy crosses boundary (e.g., insulated thermos flask, universe).
12. 7 Marks
    bWhat does the First Law of Thermodynamics state, and how does it relate to the conservation of energy?
    How to answer

    • Statement of the First Law of Thermodynamics.
    • Mathematical formulation for a closed system undergoing a process: $Q = \Delta U + W$ or $\oint \delta Q = \oint \delta W$ for a cycle.
    • Explanation of First Law as an application of the principle of conservation of energy (energy can neither be created nor destroyed).
13. 7 Marks
    aWith a neat sketch, explain the working of Diesel and derive the expression for thermal efficiency.
    How to answer

    • P-V and T-S diagrams of air-standard Diesel cycle (1-2 isentropic compression, 2-3 constant pressure heat addition, 3-4 isentropic expansion, 4-1 constant volume heat rejection).
    • Formulas for heat added $Q_{in} = m c_p (T_3 - T_2)$ and heat rejected $Q_{out} = m c_v (T_4 - T_1)$.
    • Step-by-step substitution using compression ratio $r = V_1/V_2$ and cut-off ratio $r_c = V_3/V_2$.
    • Final thermal efficiency expression: $\eta = 1 - \frac{1}{r^{\gamma-1}} \left[\frac{r_c^\gamma - 1}{\gamma(r_c - 1)}\right]$.
14. 7 Marks
    bWrite about the various processes involved in Dual cycle with P-V and T-S diagrams.
    How to answer

    • Sketches of P-V and T-S diagrams for the Dual cycle.
    • Step-by-step description of each process:
    • 1-2: Isentropic compression
    • 2-3: Constant volume heat addition
    • 3-4: Constant pressure heat addition
    • 4-5: Isentropic expansion
    • 5-1: Constant volume heat rejection
15. 7 Marks
    aExplain the working of a 4 stroke diesel engine with neat sketch.
    How to answer

    • Neat sketches illustrating the four strokes: Suction, Compression, Power/Expansion, Exhaust.
    • Suction stroke: air drawn into cylinder.
    • Compression stroke: air compressed to high pressure and temperature.
    • Power stroke: fuel injected, auto-ignites, gases expand pushing piston downward.
    • Exhaust stroke: burnt gases discharged through exhaust valve.
16. 7 Marks
    bExplain in detail Classification of engineering material along their applications.
    How to answer

    • Classification hierarchy tree of engineering materials.
    • Metals (Ferrous and Non-ferrous) and their typical applications.
    • Ceramics (traditional and advanced) and applications.
    • Polymers (thermoplastics, thermosets, elastomers) and applications.
    • Composites (FRP, MMC, CMC) and their high-performance applications.