If the intake air temperature of I.C. engine increases, its efficiency will
Increase
Decrease
Remain same
None of these
Correct Answer :
B. Decrease
Related Questions
A spark plug gap is kept from
0.3 to 0.7 mm
0.2 to 0.8 mm
0.4 to 0.9 mm
0.6 to 1.0 mm
The operation of forcing additional air under pressure in the engine cylinder is known as
Scavenging
Turbulence
Supercharging
Pre-ignition
Which of the following fuel has little tendency towards detonation?
Benzene
Iso-octane
Normal heptane
Alcohol
Pre-ignition is caused by the spontaneous combustion of the mixture before the end of the compression stroke, and is due to
Cylinder walls being too hot
Overheated spark plug points
Red hot carbon deposits on cylinder walls
Any one of these
Which of the following statements is correct?
All the irreversible engines have same efficiency
All the reversible engines have same efficiency
Both Rankine and Carnot cycles have same efficiency between same temperature limits
All reversible engines working between same temperature limits have same efficiency
It the temperature of intake air in IC engines is lowered, then its efficiency will
Increase
Decrease
Remain same
Increase up to certain limit and then decrease
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 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
Engine pistons are usually made of aluminium alloy because it
Is lighter
Wear is less
Absorbs shocks
Is stronger
The volumetric efficiency of a well designed engine may be
30 to 40 %
40 to 60 %
60 to 70 %
75 to 90 %
The air standard efficiency of an I.C. engine depends on
Fuel used
Speed of engine
Compression ratio
None 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
In a four stroke cycle diesel engine, the inlet valve
Opens at 20° before top dead centre and closes at 40° after bottom dead centre
Opens at 20° after top dead centre and closes at 20° before bottom dead centre
Opens at top dead centre and closes at bottom dead centre
May open and close anywhere
Which of the following statement is wrong?
In compression ignition engines, detonation occurs near the beginning of combustion.
Since the fuel, in compression ignition engines, is injected at the end of compression stroke, therefore, there will be no pre-ignition.
To eliminate knock in compression ignition engines, we want to achieve auto-ignition not early and desire a long delay period.
In compression ignition engines, because of heterogeneous mixture, the rate of pressure rise is comparatively lower.
The ignition quality of diesel oil is expressed by
Cetane number
Octane number
Calorific value
None of these
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
Which of the following medium is compressed in a Diesel engine cylinder?
Air alone
Air and fuel
Air and lub oil
Fuel alone
The thermodynamic cycle on which the petrol engine works, is
Otto cycle
Joule cycle
Rankine cycle
Stirling cycle
A diesel engine has compression ratio from
6 to 10
10 to 15
15 to 25
25 to 40
In a typical medium speed, 4-stroke cycle diesel engine
Fuel injection starts at 10° before to dead center and ends at 20° after tor dead center
Fuel injection starts at top dead center and ends at 20° after top dead center
Fuel injection starts at just before top dead center and ends just after top dead center
May start and end anywhere
Air fuel ratio at which a petrol engine cannot work is
8 : 1
10 : 1
15 : 1
20 : 1 and less
In a four stroke cycle petrol engine, the pressure inside the engine cylinder during the suction stroke is __________ the atmospheric pressure.
Equal to
Below
Above
None of these
In petrol engines, advancing of the spark timing will _________ the knocking tendency.
Not effect
Decrease
Increase
None of these
If the compression ratio of an engine working on Otto cycle is increased from 5 to 7, the percentage increase in efficiency will be
2 %
4 %
8 %
14 %
In a coil ignition system of petrol engines, a condenser is connected across the contact breaker in order to
Prevent sparking across the gap between the points
Cause more rapid break of the primary current, giving a higher voltage in the secondary circuit
Both (A) and (B)
None of the above
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
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
The increase of cooling water temperature in petrol engine will __________ the knocking tendency.
Not effect
Decrease
Increase
None of these
For the same power developed in I.C. engines, the cheaper system is
Naturally aspirated
Supercharged
Centrifugal pump
Turbo charger
The loud pulsating noise heard within the cylinder of an internal combustion engine is known as
Detonation
Turbulence
Pre-ignition
Supercharging