RRB JE-Mechanical Engineering Solved Paper-2

Test Preparation on RRB JE-Mechanical Engineering Solved Paper-2

1.

The working cycle in the case of the four-stroke engine is completed in the following a number of revolutions of the crankshaft

11/2
21
32
44
58

2.

In a diesel engine, the fuel is ignited by

1spark
2injected fuel
3heat resulting from compressing air that is supplied for combustion
4ignitor
5combustion chamber.

3.

Scavenging air in a diesel engine means

1air used for combustion sent under pres-sure
2forced air for cooling cylinder
3burnt air containing products of com-bastion
4air used for forcing burnt gases out of engine's cylinder during the exhaust period
5air fuel mixture.

4.

Supercharging is the process of

1supplying the intake of an engine with air at a density greater than the density of the surrounding atmosphere
2providing forced cooling air
3injecting excess fuel for raising more load
4supplying compressed air to remove combustion products fully
5raising exhaust pressure.

5.

Does the supply of scavenging air at a density greater than that of atmosphere mean engine is supercharged ?

1yes
2no
3to some extent
4unpredictable
5depends on other factors.

6.

The ratio of indicated thermal efficiency to the corresponding air standard cycle efficiency is called

1net efficiency
2efficiency ratio
3relative efficiency
4overall efficiency
5cycle efficiency.

7.

Compression ratio of LC. engines is

1the ratio of volumes of air in cylinder before compression stroke and after compression stroke
2volume displaced by piston per stroke and clearance volume in cylinder
3ratio of pressure after compression and before compression
4swept volume/cylinder volume
5cylinder volume/swept volume.

8.

The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is

1same
2less
3more
4more or less depending on power rating
5unpredictable.

9.

The calorific value of gaseous fuels is expressed in terms of

1kcal
2kcal/kg
3kcal/m2
4kcal/n?
5all of the above.

10.

If the intake air temperature of I.C. engine increases, its efficiency will

1increase
2decrease
3remain same
4unpredictable
5depend on other factors.

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