I.C. Engines - Mechanical Engineering Multiple Choice Questions and Answers for competitive exams

1.    The working cycle in case of four stroke engine is completed in following number of revolutions of crankshaft
(a)     1/2   
(b)     1
(c)     2   
(d)     4
(e)     8.

Ans: c

2.    In a diesel engine, the fuel is ignited by
(a)     spark   
(b)     injected fuel
(c)    heat resulting from compressing air that is supplied for combustion
(d)    ignitor
(e)    combustion chamber.

Ans: c

3.    Scavenging air in diesel engine means
(a)    air used for combustion sent under pres-sure
(b)    forced air for cooling cylinder
(c)    burnt air containing products of com-bastion
(d)    air used for forcing burnt gases out of engine's cylinder during the exhaust period
(e)    air fuel mixture.

Ans: d

4.    Supercharging is the process of
(a)    supplying the intake of an engine with air at a density greater than the density of the surrounding atmosphere
(b)    providing forced cooling air
(c)    injecting excess fuel for raising more load
(d)    supplying compressed air to remove combustion products fully
(e)    raising exhaust pressure.

Ans: a

5.    Does the supply of scavenging air at a density greater than that of atmosphere mean engine is supercharged ?
(a)     yes   
(b)     no
(c)    to some extent
(d)    unpredictable
(e)    depends on other factors.

Ans: b

6.    The ratio of indicated thermal efficiency to the corresponding air standard cycle efficiency is called
(a)    net efficiency
(b)    efficiency ratio
(c)    relative efficiency
(d)    overall efficiency
(e)    cycle efficiency.
Ans: c

7.    Compression ratio of LC. engines is
(a)    the ratio of volumes of air in cylinder before compression stroke and after compression stroke
(b)    volume displaced by piston per stroke and clearance volume in cylinder
(c)    ratio of pressure after compression and before compression
(d)    swept volume/cylinder volume
(e)    cylinder volume/swept volume.
Ans: a

8.    The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is
(a)    same
(b)    less
(c)    more
(d)    more or less depending on power rating
(e)    unpredictable.
Ans: c

9.    The calorific value of gaseous fuels is expressed in terms of
(a)     kcal   
(b)     kcal/kg
(c)     kcal/m2   
(d)     kcal/n?
(e)     all of the above.
Ans: d

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