The ratio of the indicated thermal efficiency to the air standard efficiency is known as
Mechanical efficiency
Overall efficiency
Volumetric efficiency
Relative efficiency
Correct Answer :
D. Relative efficiency
Related Questions
The air-fuel ratio in petrol engines is controlled by
Controlling valve opening/closing
Governing
Injection
Carburetion
The spark ignition engines are governed by
Hit and miss governing
Qualitative governing
Quantitative governing
Combination of (B) and (C)
The expansion of fuel in a four stroke cycle diesel engine
Starts at 15° before top dead centre and ends at 30° after top dead centre
Starts at top dead centre and ends at 30° after top dead centre
Starts at 15° after top dead centre and ends at 30° before bottom dead centre
May start and end anywhere
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
The compression ignition engines are governed by
Hit and miss governing
Qualitative governing
Quantitative governing
Combination of (B) and (C)
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 minimum cranking speed in case of petrol engine is about
Half the operating speed
One fourth of operating speed
250 - 300 rpm
60 - 80 rpm
An hmh flame speed is obtained in diesel engine when air fuel ratio is
Uniform throughout the mixture
Chemically correct mixture
About 35% of rich mixture
About 10% of rich mixture
The maximum temperature in the I.C. engine cylinder is of the order of
500-1000°C
1000-1500°C
1500-2000°C
2000-2500°C
The thermal efficiency of diesel engines is about
15 %
30 %
50 %
70 %
The fuel air ratio in a petrol engine fitted with suction carburettor, operating with dirty air filter as compared to clean filter will be
Higher
Lower
Remain unaffected
None of the above
Alpha-methyl-naphthalene (C₁₁ H₁₀) has a cetane number of
0
50
100
120
In the opposed piston diesel engine, the combustion chamber is located
Above the piston
Below the piston
Between the pistons
There is no such criterion
The process of breaking up or a liquid into fine droplets by spraying is called
Vaporisation
Carburetion
Ionisation
Atomisation
A carburettor is used to supply
Petrol, air and lubricating oil
Air and diesel
Petrol and lubricating oil
Petrol and air
Diesel fuel, compared to petrol is
Less difficult to ignite
Just about the same difficult to ignite
More difficult to ignite
Highly ignitable
The fuel valve in a four stroke cycle diesel engine
Opens at 15° after top dead centre and closes at 20° before bottom dead centre
Opens at 15° before top dead centre and closes at 20° after top dead centre
Opens at top dead centre and closes at bottom dead centre
May open and close anywhere
Theoretically, a four stroke cycle engine should develop _________ power as that of a two stroke cycle engine.
Half
Same
Double
Four times
The advancing of spark timing in spark ignition engines will _________ knocking tendency.
Increase
Reduce
Not effect
None of these
In a petrol engine, the mixture has the lowest pressure at the
Beginning of suction stroke
End of suction stroke
End of compression stroke
None of these
Air fuel ratio at which a petrol engine cannot work is
8 : 1
10 : 1
15 : 1
20 : 1 and less
Does the supply of scavenging air at a density greater than that of atmosphere mean engine is supercharged?
Yes
No
To some extent
Unpredictable
Fuel consumption of diesel engines is not guaranteed at one quarter load because at such low loads
The friction is high
The friction is unpredictable
The small difference in cooling water temperature or in internal friction has a disproportionate effect
The engine is rarely operated
Which of the following is false statement? Excess quantities of sulphur in diesel fuel are Objectionable because it may cause the following
Piston ring and cylinder wear
Formation of hard coating on piston skirts
Oil sludge in the engine crank case
Detonation
Pick up the wrong statement about supercharging
Supercharging reduces knocking in diesel engines
There can be limited supercharging in petrol engines because of detonation
Supercharging at high altitudes is essential
Supercharging results in fuel economy
A supercharged engine as compared to an ordinary engine
Requires smaller foundation
Is lighter
Consumes less lubricating oil
All of these
The effective inhibitor of pre-ignition is
Alcohol
Water
Lead
None of these
The reason for supercharging in any engine is to
Increase efficiency
Increase power
Reduce weight and bulk for a given output
Effect fuel economy
All heat engines utilize
Low heat value of oil
High heat value of oil
Net calorific value of oil
Calorific value of fuel
The increase of efficiency of a compression ignition engine, as the load decreases, is due to
Higher maximum temperature
Qualitative governing
Quantitative governing
Hit and miss governing