GTU Elements Of Mechanical Engineering Previous Year Question Papers

GTU Elements of Mechanical Engineering Question Paper Winter 2017

Q.1 Objective Question (MCQ)

(A)

1. Biofuels can be produced from

(a) Biomass (b) agricultural waste (c) Municipal garbage (d) all of the above.

2. Which of the following is high-grade energy

(a) work (b) heat (c) chemical energy (d) none of the above

3. In a compressor, the work done is 200kJ and heat rejected to the surrounding is 50kJ. The change in internal energy is

(a) 150kJ (b) 250kJ (c) 4kJ (d) 10000kJ

4. Air is assumed to be

(a) Ideal gas (b) Real gas (c) Condensed gas (d) none of the above.

5. Dryness fraction of fully wet steam is

(a) 0 (b) 1 (c) 0.5 (d) none of the above

6. Air standard Otto cycle is also called

(a) Constant volume cycle (b) constant pressure cycle (c) dual pressure cycle (d) isothermal cycle

7. Which of the following is boiler mounting

(a) Superheater (b) Air preheater (c) Economizer (d) Blow off cock

(B)

1. In a two-stroke engine ports are operated by movement of

(a) Crank (b) Piston (c) Connecting rod (d) Piston Pin

2. The process of filling liquid in casing of pump is

(a) charging (b) pre-starting (c) idling (d) Priming

3. The unit of specific fuel consumption is

(a) Kg/sec (b) kg/kWh (c) kg/kW (d) none of the above

4. The compressor used in aircraft is

(a) Axial flow (b) Roots blower (c) Vane blower (d) Reciprocating compressor

5. Refrigerant used in domestic refrigerators is generally

(a) R134a (b) carbon dioxide (c) oxygen (d) ammonia

6. The size of gear is specified by

(a) Number of teeth (b) pitch circle diameter (c) pressure angle (d) none of the above

7. Mild steel contains % of carbon

(a) 0 to 0.5 (b) 0.5 to 1 (c) 1 to 2 (d) 2 to 4.

Q.2

(a) Explain the following: Global Warming, Ozone depletion.

(b) An engine operating on the ideal diesel cycle has a maximum pressure of 45 bar and a maximum temperature of 1500°C. The pressure and temperature of air at the beginning of compression stroke are 1 bar and 27°C resply. Find the air standard efficiency of the cycle. Assume γ=1.4

(c) What is adiabatic process? Prove with usual notations the law of governing adiabatic process as PVγ = Constant.

Q.3

(a) With usual notations derive an expression for air standard efficiency of Otto cycle.

(b) Draw neat sketches of following: Cochran boiler, bourden pressure gauge.

(c) During a test on a single cylinder four stroke engine having compression ratio of 6, the following data is recorded, Bore=10 cm, stroke =12.5 cm, IMEP =2.6 bar, dead load on dynamometer =60 N spring balance reading =19N, Effective radius of flywheel =40 cm, fuel consumption =1 kg/hr calorific value of fuel is 42000 K J/ Kg speed=2000rpm. Determine indicated power, brake power, mechanical efficiency, overall efficiency, air standard efficiency and relative efficiency.

Q.4

(a) List advantages and disadvantages of two-stroke engines over four stroke engines

(b) Write short note on Gear Pump

(c) With neat sketch explain construction and working of Superheater.

Q.5

(a) Differentiate between the reciprocating pump and centrifugal pump.

(b) Define following terms: swept volume, clearance volume, stroke length, compression ratio.

(c) Calculate mass of 0.2m3 of steam at 10 bar pressure having dryness fraction of 0.7. Also calculate enthalpy, internal energy, and external work during evaporation of 2 m3 of steam.

Q.6

(a) List properties and application of Titanium and its alloys.

(b) Define following terms: Ductility, Resilience, Hardness, and Elasticity.

(c) Compare belt drive, chain drive and gear drive.

Q.7

(a) With neat sketch explain construction and working of cone clutch.

(b) Draw neat and labeled sketches only of following: Protected flange coupling, internal expanding shoe brake, Band brake.

(c) With neat sketch explain construction and working of split air conditioner.

GTU Elements of Mechanical Engineering Question Paper Summer 2017

Q.1 Objective Question (MCQ)

(A)

1. In an isolated system, what transfer?

(a) mass (b) energy (c) both mass and energy (d) neither mass nor energy

2. Which of the following is a path function?

(a) heat (b) temperature (c) pressure (d) volume

3. Which has the highest calorific value?

(a) Petrol (b) Diesel oil (c) Alcohol (d) Benzene

4. Choose the incorrect relationship.

(a) CP + CV = R (b) CP – CV = R (c) γ= CP / CV (d) CV = R/(γ-1)

5. Steam coming out of the whistle of pressure cooker is

(a) Dry and saturated vapour (b) Wet vapour (c) Superheated vapour (d) Ideal gas

6. Superheating of steam is done at constant

(a) pressure (b) volume (c) temperature (d) enthalpy

7. The Otto cycle is also known as

(a) constant pressure cycle (b) constant volume cycle (c) constant temperature cycle (d) constant enthalpy cycle

(B)

1. When heat is added to the water and if its temperature does not change, the heat added is called

(a) latent heat (b) isothermal heat (c) sensible heat (d) constant pressure heat

2. Which one of the following is vertical boiler?

(a) Lancashire (b) Cochran (c) Cornish (d) Locomotive

3. Petrol engine work on ________system.

(a) either spark or compression ignition (b) spark ignition (c) compression ignition (d) all of the above

4. Scroll compressor is a ______________compressor.

(a) reciprocating (b) rotary (c) dynamic (d) radial

5. Pump cannot be driven by

(a) electric motor (b) I.C. Engine (c) steam turbine (d) compressor

6. Performance parameter for refrigeration system is known as

(a) efficiency (b) COP (c) effectiveness (d) energy ratio

7. In VCR cycle, refrigeration effect is produced by

(a) compressor (b) condenser (c) expander (d) evaporator

Q.2

(a) Give the definition of (1) close system (2) open system (3) isolated system

(b) Define the heat and give the comparison of heat and work.

(c) Explain steam formation with figure also draw T-H diagram.

Q.3

(a) Define the terms 1.Melting point 2.Boiling point 3.Critical point

(b) Give the classification of boilers.

(c) Draw the figure of Cochran boiler and explain its construction and working.

Q.4

(a) State Zeroth law of thermodynamics.

(b) Prove that CP – CV= R.

(c) In air compressor, air enters at 1.013 bar and 270C having volume of 5 m3/ kg and it is compressed to 12 bar isothermally.Determine (i) work done (ii) heat transfer, and (iii) change in internal energy.

Q.5

(a) Give comparison between Petrol and Diesel Engine.

(b) What is boiler mountings and accessories? Also give the list of it.

(c) A six-cylinder 4 stroke I.C. engine is to produce 95 kW brake power at 800 rpm. The stroke to bore ratio is 1.25, mean effective pressure is 7 bar. Determine the bore and stroke of the engine. Assume mechanical efficiency as 80%.

Q.6

(a) What is priming? Why it is required in centrifugal pump but not in reciprocating pump.

(b) What is compressor? Give the classification of Rotary Compressors.

(c) Explain Vapor Compression Refrigeration system with neat sketch. Also, draw p-h and T-s diagram for the same.

Q.7

(a) Classify properties of engineering material.

(b) Explain flange coupling with a neat sketch

(c) What is brake? Describe an internal expanding shoe brake with a neat sketch and state its applications.

 

GTU Elements of Question Paper Winter 2016

Q.1 Objective Question (MCQ)

(A) 

 

1. The sum of internal energy (U) and the product of pressure and volume (p.v) is known as
A. workdone
B. entropy
C. enthalpy
D. heat

2.The energy which is not derived from the sun is ______.
A. bio-mass
B. fossil fuels
C. nuclear energy
D. geo-thermal energy

3. An adiabatic process is one in which
A. no heat enters or leaves the gas
B. the temperature of the gas changes
C. the change in internal energy is equal to the mechanical work done
D. all of the above

4. The ratio of specific heat at constant pressure (cp) and specific heat at constant volume (cv) is
A. equal to one
B. less than one
C. greater than one
D. none of these

5. Superheated vapour behaves
A. exactly as gas
B. as steam
C. as ordinary vapour
D. approximately as a gas

6. The behaviour of a perfect gas, undergoing any change in the variables which control physical properties, is governed by
A. Boyle’s law
B. Charles’ law
C. Gay-Lussac law
D. all of these

7. The efficiency of Diesel cycle increases with
A. decrease in cut-off
B. increase in cut-off
C. constant cut-off
D. none of these

(B)

1. Which of the following statement is correct?
A. A fire tube boiler occupies less space than a water tube boiler, for a given power.
B. Steam at a high pressure and in large quantities can be produced with a simple vertical boiler.
C. A simple vertical boiler has one fire tube.
D. all of the above

2.The compression ratio for petrol engine is
A. 3 to 6
B. 5 to 8
C. 15 to 20
D. 20 to 30

3. The impeller of a centrifugal pump may have
A. volute casing
B. volute casing with guide blades
C. vortex casing
D. any one of these

4.The maximum delivery pressure in a rotary air compressor is
A. 10 bar
B. 20 bar
C. 30 bar
D. 50 bar

5. During a refrigeration cycle, heat is rejected by the refrigerant in a
A. compressor
B. condenser
C. evaporator
D. expansion valve

6. A hydraulic coupling belongs to the category of
A. power absorbing machines
B. power developing machines
C. energy transfer machines
D. energy generating machines

7. An open belt drive is used when
A. shafts are arranged parallel and rotate in the opposite directions
B. shafts are arranged parallel and rotate in the same directions
C. shafts are arranged at right angles and rotate in one definite direction
D. driven shaft is to be started or stopped whenever desired without interfering with the driving shaft

Q.2

(a) State Zeroth law, First law and Second law of thermodynamics.

(b) Describe any four form of energy in 100 words.

(c) A balloon of spherical shape 6 m in diameter is filled with hydrogen gas at a pressure of 1 bar absolute and 20°C. At a later time, the pressure of gas is 94 per cent of its original pressure at the same temperature :
1) What mass of original gas must have escaped if the dimension of the balloon is not changed?
2) Find the amount of heat to be removed to cause the same drop in pressure at constant volume.
Take molecular weight for hydrogen, M = 2 and specific heat constant volume for hydrogen, cv = 10400 J/kg.K

Q.3

(a) State Boyle’s, Charle’s and Avogadro law.

(b) Identify the advantages and disadvantages of wind energy.

(c) A rigid tank contains 10 kg of water at 90°C. If 8 kg of the water is in the liquid form and the rest is in the vapor form. Draw p-V diagram and identify the point in p-V diagram. Determine
1) the pressure in the tank
2) the volume of liquid and water vapour
3) quality (dryness fraction) of steam and
4) volume of the tank by using dryness fraction

Q.4

(a) Express the mathematical formula with standard notation/symbol of properties for
1) Wetness fraction of steam
2) Enthalpy of superheated steam
3) Specific volume of wet steam

(b) Explain the construction of Oldham’s coupling with neat sketch in 150 words.

(c) Explain with neat sketch working of any one of the high pressure boiler in 300 words. Tell the two advantages and two disadvantages of it.

Q.5

(a) Define air standard efficiency. State any four assumptions considered for analysis of air standard cycle.

(b) In ideal Rankine cycle, the steam at inlet to turbine is saturated at a pressure of 35 bar and the exhaust pressure is 0.2 bar. Assume flow rate of 9.5 kg/s. Determine :
1) The pump work,
2) The turbine work,
3) The Rankine efficiency,
4) The dryness at the end of expansion.

(c) Compare four stroke engine and two stroke engine based on following point/criteria.
1) Number of piston strokes per cycle
2) Number of crank rotation per cycle
3) Number of power stroke per min
4) Power
5) Flywheel
6) Size for same power output
7) Thermal Efficiency and Mechanical Efficiency

Q.6

(a) Define following terms with respect to compressor.
1) Free air delivery
2) Capacity
3) Volumetric efficiency of an air compressor

(b) A centrifugal pump handles water and drives by motor which consumes 32 kW. The pump running at 2000 rpm. The motor efficiency is 92%. The height of pump axis from sump water surface is 6 m and produces a delivery head of 24 m. The discharge rate of water is 260 m3/hr. Calculate the efficiency of pump.

(c) Sketch fluid flow diagram with component of ideal vapour compression refrigeration system. Sketch p-V, T-s, and p-h chart and show all thermodynamic process of ideal superheated vapour compression refrigeration system

Q.7

(a) Define following terms.
1) Ductility
2) Elasticity
3) Pump

(b) Classify plain carbon steel. Compare their properties and application.

(c) Compare belt drive, chain drive and gear drive based on following criteria :
1) Main elements
2) Application suitability w.r.t to distance and velocity ratio
3) Space requirement
4) Slip
5) Design & Manufacturing complexity
6) Life
7) Maintenance

GTU Elements of Mechanical Engineering Question Paper Summer 2016

Q.1 Objective Question (MCQ)

(A) 

1. The S.I. unit N-m/s is called
(a)Watt (b) Joule (c) Calorie (d) None of the above.

2. The Universal gas Constant is equal to
(a) M/R (b) R/M (c) M*R (d) All of the above

3. The law PV = C is related to this process
(a)Adiabatic (b) Isobaric (c) Isochoric (d) Isothermal

4. Dryness fraction(x) of superheated steam is
(a)equal to 0 (b) greater than 1 (c) less than 1 (d) equal to 1

5. Cut-off ratio is related to
(a)Carnot cycle (b) Otto cycle (c) Diesel cycle (d) Rankine cycle

6. The compression ratio for Diesel engine is in the following range:
(a)12 to 22 (b) 5 to 10 (c) 10 to 12 (d) None of the above

7. Gear pump and Vane pump are types of
(a)Rotary pump (b) Reciprocating pump (c) Centrifugal pump
(d) None of the above.

(B)

1. The work done on compressor is least when the compression is
(a)Isothermal (b) Adiabatic (c) Polytropic (d) None of the above

2. Inter cooling in multi stage compression is used to
(a) cool air (b) Minimize the work done (c) reduce volume of air (d) none of the above.

3. In the domestic refrigerators the bank of tubes at the back of the refrigerator are
(a)Condenser tubes (b) Evaporator tubes (c) Capillary tubes (d) All of the above

4. Heat is absorbed by refrigerant during refrigeration cycle in
(a)Condenser (b) Evaporator (c) Capillary (d) None of the above

5. The unit of pressure is
(a)Pascal (b) N/m2 (c) bar (d) all of the above

6. The sealing ring for pressure cooker is made from
(a)Leather (b) Rubber (c) Plastic (d) Aluminum

7. Plate type, Cone type and Centrifugal type are the types of
(a)Couplings (b) Brakes (c) Clutches (d) Gear drives

Q.2

(a) Classify the engineering materials.

(b) Explain with neat sketch the working of belt drives and gear drives.

(c) What do you understand by the term 1 ton of refrigeration? What are the main components of vapour compression refrigeration system? Write their functions.

Q.3

(a) Differentiate between a Brake and a Clutch.

(b) How the air compressors are classified based on different criteria.

(c) Draw air standard diesel cycle on p-V and T-s diagrams. Derive its efficiency equation with usual notations.

Q.4
(a) With neat sketch explain in brief the working of Vane pump.

(b) Compare: S.I. engines and C.I. engines.

(c) The following readings were recorded during the test on single cylinder four stroke diesel engine.
(1) Cylinder diameter = 250 mm
(2) Stroke length = 350 mm
(3) Mean effective pressure = 6.7 bar
(4) Speed of engine = 250 r.p.m.
(5) Net brake load = 1070 N
(6) Effective brake drum diameter = 1.5 m
(7) Fuel consumption rate = 10 kg per hour.
(8) C.V. of the fuel = 44300 kJ/kg.
Calculate: (1) Indicated Power (2) Brake Power (3) Mechanical efficiency. (4) Brake thermal efficiency.

Q.5

(a) Explain the difference between boiler mountings and accessories.

(b) Calculate the air standard efficiency of the engine working on Otto cycle in which air initially at 1 bar and 20°C is compressed adiabatically to the pressure of 16 bar. Maximum pressure of cycle is 45 bar and adiabatic index γ =1.4.

(c) With neat sketch explain the construction and working of
(i) Fusible plug and (ii) Air pre heater.

Q.6

(a) Prove that Cp – Cv = R with usual notations.

(b) Write a short note on ”Solar Energy”.

(c) A cylinder contains 0.6 m3 of a gas at a pressure of 1 bar and 90 °C. The gas is compressed to a volume of 0.18 m3 by the law PVn = C. The pressure of gas at the end of compression is 5 bar.
Calculate: (1)Mass of gas (2) value of index n (3) The change in internal energy of the gas. (4) Work done (5) The heat received or rejected by the gas during the process. Take γ =1.4 and R= 0.294 kJ/kg K.

Q.7 

(a) Explain in brief Open system and closed system giving examples.

(b) Draw neat and labeled diagram of Cochran Boiler

(c) Calculate the total amount of heat required to produce 6 kg of steam at a pressure of 6 bar and temperature of 258 °C from the water at 30 °C. Take specific heat of steam = 2.1 kJ/kg-K. and the specific heat of water = 4.187 kJ/kg-K.

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