This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Lubrication System, Intake and Exhaust Systems”.
1. Why does a large diesel engine plant require air?
a) To support combustion
b) To remove dust particles
c) To blow out fumes
d) To run the engine
Explanation: A large diesel engine plant requires about 0.076 m3/min to 0.11m3/min of air per KW of power developed inside the engine. Air contains lot of dust; hence it is necessary to remove the dust content in the atmospheric air.
2. What happens if atmospheric temperature is too low?
a) Engine misfires at low loads
b) Engine consumes more amount of fuel
c) Engine gets struck up
d) Exhaust produced comparatively more
Explanation: The air system contains an intake manifold located outside the building with filter to catch dirt which would otherwise cause excessive wear in the engine. If the atmospheric temperature is too low, engine misfires at low loads and hence it is necessary to install a heating element using exhaust gas.
3. What is used in engines to reduce the noise at the exhaust?
a) Noise dampers
d) Composite foam
Explanation: Engine sound during operation may be transmitted back through the air intake systems to the outside air. In such cases a silencer is provided between the engine and the intake. It is a light weight steel pipe.
4. In which type of dust filter used in engine is the air swept over or through the pool of oil??
a) Oil bath type
c) Soot blower
d) Bessel filter
Explanation: in oil bath type of filter the air is swept over or through a pool of oil. The dust particles become coated to the oil. The air is then passed through the filter, which retains the oil coated dust particles.
5. Which type of filter used in engine is made up of cloth, felt and glass wool?
b) Oil-bath type
c) Soot blower
d) Bessel filter
Explanation: Dry type of filter is made up of cloth, felt and glass wool etc. the filters catch dirt by causing it to cling to the surface of filter material. The capacity of such filters drops progressively when they are in use. The cleaning is done by amount of air used by the engines and dust concentrate in it.
6. What is muffling?
a) Reducing vibration
b) Increasing the flow of gas
c) Reducing noise
d) Filtering the exhaust air
Explanation: Muffling is the process of reducing the noise. The exhaust system must carry approximately 0.23m3/min-0.30m3/min of gases per kilowatt developed, at the average exhaust temperature. Muffling of the exhaust noise is done by using silencers located outside building.
7. Exhaust pipe is designed carefully in order to carry toxic gases away from the user machine.
Explanation: An exhaust pipe must be carefully designed to carry toxic and noxious gases away from the users of the machine. It is done so because the gases produced may affect the human being in health wise as well as the environment.
8. Why is lubrication system important in the engine?
a) To improve fuel efficiency
b) To provide cooling
c) To reduce the disturbance
d) To help move the fuel easily
Explanation: Due to the presence of friction, wear and tear of the engine parts takes place reducing the engine life. The lubricant introduced forms a thin film between the rubbing surfaces and prevents metal to metal contact.
9. In which type of lubrication method are splash rods used?
a) Full pressure lubrication
b) Mechanical lubrication
c) Force feed lubrication
d) Spray lubrication
Explanation: In full pressure lubrication splash rods equipped. An oil pump supplies lubricating oil to many parts of the engine through duct system and to the crank shaft through drilled holes. The cylinder walls are lubricated by oil mist that is slung outward by the splash rod connected to flywheel from pool of oil.
10. Why is oil cleaning is necessary in the engine?
a) For continuous reliable operation
b) To cool down the oil
c) To reduce the viscosity of oil
d) To increase thickness of oil
Explanation: For continuous reliable operation attention should be given to oil cleaning. For this purpose filters with centrifuges or chemical action have been employed. Mechanical filters include cloth bags, wool, felt pads, paper discs and cartridge of porous material.
11. Rough cleaning of oil in engine is done through passing the oil through?
a) Paper discs
c) Felt pads
d) High speed centrifuges
Explanation: Rough cleaning of oil is done by passing oil through high speed centrifuges. Centrifuges can be done by periodic centrifuging of the entire lubricating oil or by continuous cleaning of a small fraction of it by splitting the oil from main flow and returning back to main stream.
12. Oil is cooled before passing it to the engine.
Explanation: Oil should be heated before passing it through the centrifuge and then it is cooled before supplying it to the engine. As heat is developed due to friction between the moving parts, the cooling is done by using water from the cooling tower.
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