# VIVA-VOICE OF ME LAB

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Mechanical Engineering Department

VIVA OF ME LAB

Q1. What is a boiler?
Ans. Boiler is to generate steam at a desired pressure and temperature.

Q2. What is the difference between fire tube and water tube boiler?
Ans. In fire tube boiler the hot flue gases flow inside the tubes while water
surrounds the tubes and In water tube boiler the water flows inside the tubes
while hot flue gases surrounds the tubes.

Q3. What is the difference between Locomotive and Lancashire boiler?
Ans. Locomotive boiler is a portable boiler and Lancashire boiler is a stationary or
land type boiler.

Q4. How much the thermal efficiency of a boiler?
Ans. It is about 85-88% on fairly efficient working.

Q5. What is draught?
Ans. Draught means a force which is created due to small pressure difference in
stream of flue gas or air, which causes the flow to take place.

Q6.  What is the function of Fusible Plug, Feed Check Valve, Superheater,
superheated steam, Pressure gauge, water level gauge, dampers?
Ans. Fusible Plug: For safety against exposing the flue tube to excessive heat
when the water level falls to low.
Feed Check Valve: Feed water is supplied to the boiler under pressure, feed
check valve stop its escaping back.
Superheater: Its purpose is to increase the temperature of saturated steam
without raising its pressure.
Superheated steam: When the dry steam is further heated at a constant
pressure, thus raising its temperature, it is said to be superheated steam.
Pressure gauge: It is measuring the pressure of steam.
Water level gauge: Its indicate the level of water.
Dampers: Dampers are for controlling the flue of gases.

Q7. What are the advantages of water tube boiler over fire tube boiler?
Ans. i. Ratio of water content to steam capacity is less.
ii. Rate of steam generation is quicker.
iii. It occupies less space for a given power.

Q8. What is the inclined angle of tubes in Babcock & Wilcox Boilers and why?
Ans. The water tubes are inclined 5 to 15 0 to promote water circulation.

Q9.   What is the difference between Boiler Mountings and Accessories?

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Ans. Boiler Mountings are the fittings, which are mounted on the boiler for its
proper and safe functioning Boiler accessories are the devices which are used
as integral parts of a boiler, and help in running efficiently.

Q10. Which are the high pressure steam boilers?
Ans. Loeffler, Benson and Lamont boiler.

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Q11. What is the capacity of steam and pressure in Babcock and Wilcox boiler?
Ans. Steaming capacity is 20000 to 40000 kg/hr and Operating pressure is 40 bar.

Q12. What is the capacity of steam and pressure in Lancashire boiler?
Ans. Steaming capacity is 8000 kg/hr and Operating pressure is 15 bar.

Q13. What is the capacity of steam and pressure in Locomotive boiler?
Ans. Steaming capacity is 4500 to 7000 kg/hr and Operating pressure is 21 bar.

Q14. What is heat Engine?
Ans. Heat engines are the devices that transform chemical energy of fuel into
thermal energy, which is then converted into mechanical energy to perform
useful work.

Q15. What is the difference between Internal Combustion and External Combustion
Engines?
Ans. i. In I.C engine the fuel burnt inside the engine cylinder and in E.C engine the
fuel burnt outside the engine cylinder.
ii. Working pressure and temperature inside the cylinder is very high and E.C
engine working pressure and temperature inside the cylinder is low.

Q16. What is the thermal efficiency of steam engine?

Q17. What are the different advantages of steam turbines over steam engines?
Ans. i. They can operate at high temperatures, and can expand to a lower exhaust
pressure than that in the steam engine. Thus efficiency of steam turbine is
more.
ii. Since the turbine has no reciprocating masses, it has more uniform torque
and less vibration.
iii. Their governing is easier and maintenance is less.

Q18. What is the function of D-Slide valve, Eccentric, Flywheel and Governor,
Ans. D-Slide valve: Its function is to exhaust steam from the cylinder at proper
moment.
Eccentric: Its function is to provide reciprocating motion to the slide valve.

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Flywheel: Its function is to prevent the fluctuation of the engine. Its also
prevents the jerks to the crank shaft.
Governor: It is a device to keep the engine speed, more or less, uniform at
all load conditions. It is done either by controlling the quantity or pressure of
the steam supplied to the engine.
Steam chest: It supplies steam to the cylinder with the movement of D-Slide
valve.
Cross-head: its function is to guide motion of the piston rod and to prevent it
from bending.

Q 19. On which cycle a steam engine works?
Ans. Steam engines works on Rankin cycle.

Q20. What are the internal combustion engines?
Ans. In which the energy of fuel air mixture is released by combustion in the
engine cylinder itself is called I.C Engine.

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Q21. What is the difference between the Diesel Engines and Petrol Engines?
Ans. i. A Petrol engine draws a mixture of petrol and air during suction stroke and
in diesel engine draws only air during suction stroke.
ii. The running cost of petrol engine is high because of the higher cost of
petrol and the running cost of diesel engine is low because of the low cost of
diesel.

Q22. What is the difference between 2-Stroke and 4-Stroke Engines?
Ans. i. In a TWO STROKE engine, the working cycle is completed in two strokes of
the piston or one revolution of crank shaft and in FOUR STROKES engine, the
working cycle is completed in four strokes of the piston or two revolution of
the crankshaft.
ii. The design of two strokes engine is simple and the design of four stroke
engine is complicated.

Q23. How much the thermal efficiency of I.C engine?
Ans. The thermal efficiency of I.C engine is 30 to 35%

Q24. What is the function of Carburetor, spark plug, crank shaft, crank and piston
rings, cam shaft and injection nozzles?

Ans. Carburetor: The carburetor is a device for atomizing and vaporizing the and
mixing it with the air in the varying proportion to suit the charging operations
conditions of the engines. The process of breaking up and mixing the fuel with
the air is called carburetor.
Spark plug: It is used for igniting the charge of petrol engine.

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Crank shaft: The function of the camshaft is to convert the reciprocating
motion of the piston into the rotary motion with the help of connecting rod.
Piston rings: Generally there are two type of rings mounted on the piston.
The function of the upper rings is to provide air tight seal to prevent leakage
of the burnt gases into the lower portion. Similarly, the function of the lower
rings is to provide effective seal to prevent leakage of the oil into the engine
cylinder.
Cam shaft: It is driven from the crank shaft by timing gear on a chain. It
operates the intake valve and the exhaust valve through the cams, cams
followers, push rods and rocker arms.
Injection nozzles: The mechanism by which fuel is introduced into the
combustion space is known as injectors, atomizers, sprayers, nozzles etc.

Q25. How much the air fuel mixture of petrol engine?
Ans. Lower limit- 7 : 1 to 10 : 1
Upper limit- 20 : 1
Theoretically- 15 : 1

Q26. What is the compression ratio of petrol engine?
Ans. Compression ratio of petrol engine is 7 to 10.

Q27. What is the compression ratio of diesel engine?
Ans. Compression ratio of diesel engine is 16to 20.

Q28. How much voltage produces in spark plug?
Ans. Voltage produces in spark plug is 20000 to 25000.

Mechanical Engineering Department

Q29. On which cycle Diesel and Petrol engine works?
Ans. Diesel engine works on diesel cycle and petrol engine work on Otto cycle.

Q30 Which thermal efficiency is higher as compare to diesel and petrol engine?
Ans. Petrol Engine.

Q31. What is Hardness?
Ans. The property of a metal by virtue of which it is able to resist abrasion,
indentation
(or penetration) and scratching by harder bodies.

Q32. What is the difference between Rockwell and Brinell method of hardness
testing?
Ans. In Rockwell test we get quick and direct reading and in Brinell test we get by
calculation.

Q33. What is Impact?
Ans. Suddenly load applied is called impact blows.

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Q34. What is Impact Strength?
Ans. The capacity of a metal to withstand such blows without fracture is known as
impact resistance or impact strength.

Q35. What is the difference between Charpy and Izod test method of impact
testing?
Ans. i. In Charpy test the specimen is placed horizontally as a simply supported
beam and in Izod test the specimen is placed vertically as a cantilever beam.
ii. In charpy test the angle of striking hammer is 1400 and in Izod test the
angle of striking hammer is 900.

Q36. What is the necessity of making a notch in impact test specimen?
Ans. In order to concentrate the stress on the point of V-Notch. Such that it will fail
just like a brittle material.

Q.37. Define Stress?
Ans. When an external load is applied on any body it offers the internal resistance
per unit area is called stress.

38. What is starin?
Ans. Strain is defined as the ratio of change in length v/s original length.

39. What is Hook’s law?
Ans. As per Hook’s law under elastic condition stress is directly proportional to the
strain developed in the body. The constant is called Young’s modulus of elasticity.

40. What is Poisson’s ratio?
Ans. It is the ratio of Lateral strain to longitudinal strain and denoted by μ.

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