The ratio of the brake power to the indicated power is called
Mechanical efficiency
Overall efficiency
Indicated thermal efficiency
Volumetric efficiency
Correct Answer :
A. Mechanical efficiency
Related Questions
Does the supply of scavenging air at a density greater than that of atmosphere mean engine is supercharged?
Yes
No
To some extent
Unpredictable
In a four stroke cycle, the minimum temperature inside the engine cylinder occurs at the
Beginning of suction stroke
End of suction stroke
Beginning of exhaust stroke
End of exhaust stroke
The working cycle in case of four stroke engine is completed in following number of revolutions of crankshaft
1/2
1
2
4
If one cylinder of a diesel engine receives more fuel than the others, then for that cylinder the
Exhaust will be smoky
Piston rings would stick into piston grooves
Engine starts overheating
Scavenging occurs
The air requirement of a petrol engine during starting compared to theoretical air required for complete combustion is
More
Less
Same
May be more or less depending on engine capacity
The working pressure and temperature inside the cylinder of an internal combustion engine is _________ as compared to a steam engine.
Low
Very low
High
Very high
Theoretically, a four stroke cycle engine should develop _________ power as that of a two stroke cycle engine.
Half
Same
Double
Four times
Pick up the false statement
Thermal efficiency of diesel engine is about 34%
Theoretically correct mixture of air and petrol is approximately 15:1
High speed compression engines operate on dual combustion cycle
S.I. engines are quality governed engines
The thermal efficiency of petrol and gas engines is about
15 %
30 %
50 %
70 %
The thermal efficiency of diesel engines is about
15 %
30 %
50 %
70 %
The ignition quality of petrol is expressed by
Cetane number
Octane number
Calorific value
All of these
The pressure and temperature at the end of compression stroke in a petrol engine are of the order of
4-6 kg/cm² and 200-250°C
6-12 kg/cm² and 250-350°C
12-20 kg/cm² and 350-450°C
20-30 kg/cm² and 450-500°C
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
The actual volume of fresh charge admitted in 4-stroke petrol engine is
Equal to stroke volume
Equal to stroke volume and clearance volume
Less than stroke volume
More than stroke volume
Which of the following does not relate to a compression ignition engine?
Fuel pump
Fuel injector
Governor
Carburettor
Which of the following statement is correct regarding petrol engines?
A fine fuel spray mixed with air is ignited by the heat of compression which is at a high pressure
The fuel supplied to the engine cylinder is mixed with necessary amount of air and the mixture in ignited with the help of a spark plug
The fuel is first evaporated after passing through a carburettor and is mixed with air before ignition
All of the above
If the temperature of intake air in internal combustion engine increases, then its efficiency will
Remain same
Decrease
Increase
None of these
Volatility of diesel 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
It catches fire without external aid
Indicated by 90% distillation temperature, i.e., when 90% of sample oil has distilled off
In a diesel engine, the duration between the time of injection and ignition, is known as
Pre-ignition period
Delay period
Period of ignition
Burning period
The correct sequence of the decreasing order of brake thermal efficiency of the three given basic types of engines is
Four stroke C.I. engine, four stroke S.I. engine, two stroke S.I. engine
Four stroke S.I. engine, four stroke C.I. engine, two stroke S.I. engine
Four stroke C.I. engine, two stroke S.I. engine, four stroke S.I. engine
Two stroke S.I. engine, four stroke S.I. engine, four stroke C.I. engine
The calorific value of gaseous fuels is expressed in terms of
kcal
kcal/kg
kcal/m²
kcal/m3
In a four stroke cycle diesel engine, the exhaust valve
Opens at 30° before bottom dead centre and closes at 10° after top dead centre
Opens at 30° after bottom dead centre and closes at 10° before top dead centre
Opens at bottom dead centre and closes at top dead centre
May open and close anywhere
Supercharging is the process of
Supplying the intake of an engine with air at a density greater than the density of the surrounding atmosphere
Providing forced cooling air
Injecting excess fuel for raising more loads
Supplying compressed air to remove combustion products fully
In a four stroke cycle petrol engine, the charge is ignited at
30° before top dead centre
30° after top dead centre
30° before bottom dead centre
30° after bottom dead centre
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
Which of the following statement is wrong?
A four stroke cycle engine develops twice the power as that of a two stroke cycle engine
For the same power developed, a four stroke cycle engine is lighter, less bulky and occupies less floor area
The petrol engines are costly than diesel engines
All of the above
The higher combustion chamber wall temperature in compression ignition engines will _________ knocking tendency.
Increase
Reduce
Not effect
None of these
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
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
If V₁ is the jet velocity and V₀ is the vehicle velocity, then the propulsive efficiency of a rocket is given by
[2(V₀/V₁)]/ [1 + (V₀/V₁)²]
(V₀/V₁)/ [1 + (V₀/V₁)²]
V₀/(V₀ + V₁)
V₁/(V₀ + V₁)