The thermal efficiency of diesel engines on weak mixtures is
Unaffected
Lower
Higher
Dependent on other factors
Correct Answer :
C. Higher
Related Questions
The following volume of air is required for consuming 1 litre of fuel by a four stroke engine
1 m3
5 m3
56 m3
910 m3
Which is more viscous lube oil?
SEA 30
SAE 50
SAE 70
SAE 80
A diesel engine has
1 valve
2 valves
3 valves
4 valves
The object of supercharging the engine is
To reduce mass of the engine per brake power
To reduce space occupied by the engine
To increase the power output of an engine when greater power is required
All of the above
The specific fuel consumption per B.P. hour for a petrol engine is about
0.2 kg
0.25 kg
0.3 kg
0.35 kg
A petrol engine has compression ratio from
6 to 10
10 to 15
15 to 25
25 to 40
The frictional power (F.P.) is given by
F.P. = B.P. - I.P.
F.P. = I.P. - B.P.
F.P. = B.P./I.P.
F.P. = I.P./B.P.
Number of working strokes per min. for a two stroke cycle engine is _________ the speed of the engine in r.p.m.
Equal to
One-half
Twice
Four-times
The thermal efficiency of a standard Otto cycle for a compression ratio of 5.5 will be
25 %
50 %
70 %
100 %
The delay period in compression ignition engines depends upon
Temperature and pressure in the cylinder at the time of injection
Nature of the fuel mixture strength
Relative velocity between the fuel injection and air turbulence pressure of residual gases
All of the above
In a typical medium speed 4-stroke cycle diesel engine the inlet valve
Opens at 20° before top dead center and closes at 35° after the bottom dead center
Opens at top dead center and closes at bottom dead center
Opens at 10° after top dead center and closes 20° before the bottom dead center
May open or close anywhere
The operation of forcing additional air under pressure into the engine cylinder is known as
Supercharging
Carburetion
Turbulence
Delay period
The _________ engines can work on very lean mixture of fuel.
Spark ignition
Compression ignition
Both (A) and (B)
None of these
In a four stroke cycle diesel engine, the compression
Starts at 40° after bottom dead centre and ends at 10° before top dead centre
Starts at 40° before top dead centre and ends at 40° after top dead centre
Starts at top dead centre and ends at 40° before bottom dead centre
May start and end anywhere
The brake power of a diesel engine, keeping other parameters constant, can be increased by
Decreasing the density of intake air
Increasing the temperature of intake air
Increasing the pressure of intake air
Decreasing the pressure of intake air
Compression ratio of I.C. Engines is
The ratio of volumes of air in cylinder before compression stroke and after compression stroke
Volume displaced by piston per stroke and clearance volume in cylinder
Ratio of pressure after compression and before compression
Swept volume/cylinder volume
Installation of supercharger on a four cycle diesel engine can result in the following percentage increase in power
Up to 35%
Up to 50%
Up to 75%
Up to 100%
The operation of forcing additional air under pressure in the engine cylinder is known as
Scavenging
Turbulence
Supercharging
Pre-ignition
In a petrol engine, if diesel is used, then the engine will
Not run
Run more efficiently
Run at high speed
Explode
Supercharging is the process of supplying the intake air to the engine cylinder at a density _________ the density of the surrounding atmosphere.
Equal to
Less than
Greater than
None of these
If the temperature of intake air in internal combustion engine increases, then its efficiency will
Remain same
Decrease
Increase
None of these
The self ignition temperature of petrol is ________ as compared to diesel oil.
Same
Lower
Higher
None of these
Which of the following fuel detonates readily?
Benzene
Iso-octane
Normal heptane
Alcohol
The pressure at the end of compression in the case of diesel engine is of the order of
6 kg/cm
12 kg/cm
20 kg/cm
35 kg/cm
The specific fuel consumption per BHP hour for diesel engine is approximately
0.15 kg
0.2 kg
0.25 kg
0.3 kg
Most high speed compression engines operate on
Diesel cycle
Otto cycle
Dual combustion cycle
Special type of air cycle
A diesel engine as compared to petrol engine (both running and rated load) is
More efficient
Less efficient
Equally efficient
Other factors will decide it
Polymerisation is a chemical process in which molecules of a compound become
Larger
Slowed down
Smaller
Liquid
The cetane (C16H34) which is a straight chain paraffin, is assigned a cetane number of
0
50
100
120
Flash point of fuel oil is
Minimum temperature to which oil is heated in order to give off inflammable vapours in sufficient quantity to ignite momentarily when brought in contact with a flame
Temperature at which it solidifies or congeals
Temperature at which it catches fire without external aid
Indicated by 90% distillation temperature, i.e. when 90% of sample oil has distilled off