⚙️ Basic Mechanical Engineering Solved Paper 2023
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B.Tech. I-Semester (Main/Back) Exam - 2023
Subject: Basic Mechanical Engineering
Code: 1FY3-07 / 1E3107
PART - A (Short Answer Questions)
Q.1 Describe Law of Thermodynamics?
Thermodynamic laws govern energy transfer:
• Zeroth Law: Defines temperature measurement via thermal equilibrium.
• First Law: Conservation of energy (dQ = dU + dW).
• Second Law: Establishes heat flow direction and entropy constraints.
• Third Law: Entropy approaches zero as absolute zero temperature is reached.
• Zeroth Law: Defines temperature measurement via thermal equilibrium.
• First Law: Conservation of energy (dQ = dU + dW).
• Second Law: Establishes heat flow direction and entropy constraints.
• Third Law: Entropy approaches zero as absolute zero temperature is reached.
Q.2 Describe with figure different type of belt drive.
1. Open Belt Drive: Connects parallel shafts turning in the same direction.
2. Cross Belt Drive: Connects parallel shafts turning in opposite directions.
3. Quarter Turn Belt Drive: Connects non-parallel shafts at right angles.
2. Cross Belt Drive: Connects parallel shafts turning in opposite directions.
3. Quarter Turn Belt Drive: Connects non-parallel shafts at right angles.
Q.3 Define the coefficient of performance of Refrigerator.
The Coefficient of Performance (COP) of a refrigerator is the ratio of heat extracted from the refrigerated space (QL) to the net work input required (Wnet):
COPR = QL / Wnet
Q.4 What is the pattern in casting process?
A pattern is a physical replica model of the object to be cast, slightly enlarged to accommodate metal shrinkage, used to form the mould cavity in foundry sand.
Q.5 What is industrial engineering & its scope?
Industrial Engineering optimizes complex processes, systems, and organizations by integrating personnel, machines, materials, and energy. Its scope includes production planning, quality control, ergonomics, supply chain management, and operations research.
Q.6 Differentiate between water tube and fire tube boiler?
• Water Tube Boiler: Water flows inside tubes surrounded by hot combustion gases; suitable for high-pressure applications.
• Fire Tube Boiler: Hot gases flow inside tubes surrounded by water; limited to low to medium-pressure applications.
• Fire Tube Boiler: Hot gases flow inside tubes surrounded by water; limited to low to medium-pressure applications.
Q.7 Write a short note on different type of power plants.
1. Thermal Power Plant: Burns fossil fuels (coal) to produce steam and drive steam turbines.
2. Hydroelectric Power Plant: Utilizes potential energy of stored water to drive hydraulic turbines.
3. Nuclear Power Plant: Uses heat from atomic fission (Uranium) to generate steam.
4. Renewable Power Plants: Harness solar radiation or wind energy to generate electricity.
2. Hydroelectric Power Plant: Utilizes potential energy of stored water to drive hydraulic turbines.
3. Nuclear Power Plant: Uses heat from atomic fission (Uranium) to generate steam.
4. Renewable Power Plants: Harness solar radiation or wind energy to generate electricity.
Q.8 What is the IP & BP in the Internal Combustion Engine?
• Indicated Power (IP): Total power generated inside the engine cylinder by fuel combustion.
• Brake Power (BP): Net useful power available at the engine crankshaft output shaft (BP = IP - Friction Power).
• Brake Power (BP): Net useful power available at the engine crankshaft output shaft (BP = IP - Friction Power).
Q.9 Describe modern tools used in Mechanical Engineering.
Modern tools include Computer-Aided Design (CAD for 3D modeling), Computer-Aided Manufacturing (CAM for automated machining), Finite Element Analysis (FEA for stress analysis), Computational Fluid Dynamics (CFD), and 3D Printing (Additive Manufacturing).
Q.10 Differentiate between impulse and reaction turbine?
• Impulse Turbine: High-velocity fluid jet strikes moving blades at atmospheric pressure (e.g., Pelton Wheel).
• Reaction Turbine: Fluid expands continuously through nozzle blades and rotor blades under changing pressure (e.g., Francis Turbine).
• Reaction Turbine: Fluid expands continuously through nozzle blades and rotor blades under changing pressure (e.g., Francis Turbine).
PART - B (Analytical / Problem Solving)
Q.1 Explain any one type of water tube boiler with neat sketch.
Babcock & Wilcox Boiler:
It is a horizontal, straight water-tube, high-pressure boiler.
It is a horizontal, straight water-tube, high-pressure boiler.
- Construction: Consists of a longitudinal steam-and-water drum connected to inclined water tubes via uptake and downtake headers.
- Working: Water flows naturally inside inclined tubes due to density differences (thermosyphon action). Hot combustion gases from the grate pass over tubes in baffles, converting water to high-pressure steam stored in the drum.
Q.2 Explain differentiate between 2 stroke & 4 stroke engine.
| Parameter | 2-Stroke Engine | 4-Stroke Engine |
|---|---|---|
| Power Cycle | 1 power stroke every 1 revolution | 1 power stroke every 2 revolutions |
| Mechanism | Uses ports (Inlet, Exhaust, Transfer) | Uses valves operated by camshaft |
| Weight & Compactness | Lighter and compact | Heavier and complex valve gear |
| Efficiency | Lower thermal and fuel efficiency | Higher thermal and fuel efficiency |
Q.3 How Cavitation can be eliminated by Pump?
Cavitation occurs when fluid pressure falls below vapor pressure, forming vapor bubbles that collapse violently on impeller surfaces.
Methods to Eliminate Cavitation:
1. Keep Net Positive Suction Head Available (NPSHA) greater than Required (NPSHR).
2. Lower the suction lift height by placing the pump closer to the liquid source level.
3. Increase suction pipe diameter to reduce flow velocity and frictional pressure loss.
4. Use anti-corrosive, cavitation-resistant impeller materials (e.g., stainless steel).
Methods to Eliminate Cavitation:
1. Keep Net Positive Suction Head Available (NPSHA) greater than Required (NPSHR).
2. Lower the suction lift height by placing the pump closer to the liquid source level.
3. Increase suction pipe diameter to reduce flow velocity and frictional pressure loss.
4. Use anti-corrosive, cavitation-resistant impeller materials (e.g., stainless steel).
Q.4 Describe with figure different types of belt drive?
Types of Belt Drives:
- Flat Belt Drive: Uses rectangular cross-section belts running on smooth flat pulleys; used for moderate power at medium distances.
- V-Belt Drive: Uses trapezoidal cross-section belts fitted into grooved pulleys; wedging action prevents slipping, transmitting high power at short distances.
- Circular/Rope Drive: Uses circular section ropes in deeply grooved pulleys; suited for long center distances and high power transmission.
Q.5 What is air conditioning? Draw and describe different component used in it.
Air Conditioning is the process of conditioning air to control temperature, humidity, purity, and circulation simultaneously to achieve thermal comfort.
Major Components:
1. Compressor: Circulates and compresses refrigerant gas.
2. Condenser: Rejects internal heat to outdoor surroundings, liquefying refrigerant.
3. Expansion Valve: Throttles liquid refrigerant, dropping its pressure and temperature.
4. Evaporator Coil: Absorbs indoor heat, cooling the room air blown across it.
5. Air Filter & Blower: Filters dust particles and distributes conditioned air throughout the space.
Major Components:
1. Compressor: Circulates and compresses refrigerant gas.
2. Condenser: Rejects internal heat to outdoor surroundings, liquefying refrigerant.
3. Expansion Valve: Throttles liquid refrigerant, dropping its pressure and temperature.
4. Evaporator Coil: Absorbs indoor heat, cooling the room air blown across it.
5. Air Filter & Blower: Filters dust particles and distributes conditioned air throughout the space.
Q.6 Explain the various stages of Heat treatment process?
Heat treatment comprises three critical sequential stages:
- Stage 1 (Heating): Slow and uniform heating of metal up to its transformation temperature (above upper/lower critical temperature).
- Stage 2 (Soaking): Holding metal at that elevated temperature for sufficient time to allow homogeneous structural transformation.
- Stage 3 (Cooling): Cooling metal back to room temperature at controlled rates using furnace cooling, air, oil, or water quenching.
Q.7 Write short notes on (i) Forging (ii) Drawing
(i) Forging: Metalworking process where heated metal is shaped using compressive impact forces applied through hammers or presses. Enhances grain structure and mechanical strength.
(ii) Drawing: Cold metal-forming operation where a metal wire, bar, or tube is pulled through a tapered die orifice to reduce cross-sectional area and increase length.
(ii) Drawing: Cold metal-forming operation where a metal wire, bar, or tube is pulled through a tapered die orifice to reduce cross-sectional area and increase length.
PART - C (Descriptive / Analytical / Design)
Q.1 What is meant by refrigeration system? Describe vapor compression refrigeration system?
A refrigeration system extracts thermal energy from a restricted space and rejects it to surroundings to maintain a temperature lower than ambient.
Vapour Compression Refrigeration System (VCRS) Cycle:
Vapour Compression Refrigeration System (VCRS) Cycle:
- Isentropic Compression: Low-pressure dry vapor enters the compressor and gets compressed to high pressure and temperature.
- Isobaric Condensation: High-pressure vapor flows into the condenser, rejecting latent heat to air/water to form high-pressure liquid.
- Throttling Expansion: Liquid refrigerant passes through expansion valve, dropping to low pressure and low temperature.
- Isobaric Evaporation: Low-pressure liquid enters evaporator, absorbing heat from cold storage to vaporize, completing cycle.
Q.2 What is gear transmission? Describe different types of gear.
Gear Transmission: Direct positive mechanical drive using meshed gear teeth on rotating shafts to transmit power and torque at fixed velocity ratios.
Types of Gears:
Types of Gears:
- Spur Gear: Straight teeth parallel to shaft axis; connects parallel shafts.
- Helical Gear: Teeth cut at angle (helix angle); smoother, quieter operation for parallel shafts.
- Bevel Gear: Cone-shaped gears; connects intersecting shafts (usually at 90°).
- Worm & Worm Wheel: Connects non-parallel, non-intersecting shafts at high speed reduction ratios.
- Rack and Pinion: Converts rotational motion to linear motion.
Q.3 Describe rolling process with neat sketches.
Rolling Manufacturing Process:
A compressive deformation process where metal stock (ingots/blooms) passes between two counter-rotating cylindrical rollers.
A compressive deformation process where metal stock (ingots/blooms) passes between two counter-rotating cylindrical rollers.
- Working Principle: Frictional drag between rolls pulls metal forward while compressive force reduces stock thickness and refines internal grain structure.
- Types of Rolling Mills:
- Two-High Rolling Mill (Reversible or Non-reversible)
- Three-High Rolling Mill (Alternative pass directions)
- Four-High & Cluster Rolling Mills (Small diameter work rolls backed up by large support rolls for thin sheet accuracy)
Q.4 With a suitable sketch explain the working of centrifugal pump.
Centrifugal Pump Working:
A rotary dynamic pump converting mechanical motor power into fluid kinetic and pressure energy.
A rotary dynamic pump converting mechanical motor power into fluid kinetic and pressure energy.
- Components: Impeller with backward curved vanes, Spiral Volute Casing, Suction Pipe with Foot Valve, Delivery Pipe with Valve.
- Operation:
1. Pump casing is primed completely with liquid.
2. Electric motor drives impeller at high speed.
3. Centrifugal force flings liquid outward from impeller eye to periphery, increasing kinetic energy.
4. Volute casing gradually expands in area, converting kinetic energy into pressure head, forcing fluid up through delivery pipe.
5. Suction vacuum created at impeller eye continuously draws in fluid from suction pipe.
Q.5 Describe hardening and tempering of steel.
1. Hardening Process:
Heating steel above upper critical temperature (750°C - 900°C) to form fully austenitic phase, followed by rapid quenching in water or oil.
• Microstructure Formed: Extremely hard and brittle Martensite.
• Objective: Maximum surface hardness and wear resistance.
2. Tempering Process:
Reheating previously hardened martensitic steel to a temperature below lower critical limit (150°C - 650°C), holding, then cooling slowly.
• Objective: Relieves internal quenching stresses, reduces excessive brittleness, and restores toughness and ductility without losing hardness.
Heating steel above upper critical temperature (750°C - 900°C) to form fully austenitic phase, followed by rapid quenching in water or oil.
• Microstructure Formed: Extremely hard and brittle Martensite.
• Objective: Maximum surface hardness and wear resistance.
2. Tempering Process:
Reheating previously hardened martensitic steel to a temperature below lower critical limit (150°C - 650°C), holding, then cooling slowly.
• Objective: Relieves internal quenching stresses, reduces excessive brittleness, and restores toughness and ductility without losing hardness.