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.
Correct Answer :
C. To eliminate knock in compression ignition engines, we want to achieve auto-ignition not early and desire a long delay period.
Related Questions
The self ignition temperature of petrol is ________ as compared to diesel oil.
Same
Lower
Higher
None of these
A diesel engine has
One valve
Two valves
Three valves
Four valves
Which of the following fuel detonates readily?
Benzene
Iso-octane
Normal heptane
Alcohol
The air-fuel ratio of the petrol engine is controlled by
Carburettor
Injector
Governor
None of these
Supercharging is essential in
Diesel engines
Gas turbines
Petrol engines
Aircraft engines
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 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
The specific fuel consumption per BH hour for a petrol engine is approximately
0.15 kg
0.2 kg
0.25 kg
0.3 kg
The probability of knocking in diesel engines is increased by
High self ignition temperature
Low volatility
Higher viscosity
All of these
The operation of forcing additional air under pressure in the engine cylinder is known as
Scavenging
Turbulence
Supercharging
Pre-ignition
If the compression ratio in I.C. engine increases, then its thermal efficiency will
Decrease
Increase
Remain same
None of these
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 thermal efficiency of diesel engines on weak mixtures is
Unaffected
Lower
Higher
Dependent on other factors
The mechanical efficiency (ηm) of the engine is given by
ηm = B.P/I.P
ηm = I.P/B.P
ηm = (B.P × I.P)/100
None of these
The colour of exhaust from diesel engine is generally
White
Bluish
Black
Violet
The volumetric efficiency of a well designed engine may be
30 to 40 %
40 to 60 %
60 to 70 %
75 to 90 %
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
Scavenging air in diesel engine means
Air used for combustion sent under pressure
Forced air for cooling cylinder
Burnt air containing products of combustion
Air used for forcing burnt gases out of engine's cylinder during the exhaust period
In a four stroke cycle engine, the sequence of operations is
Suction, compression, expansion and exhaust
Suction, expansion, compression and exhaust
Expansion, compression, suction and exhaust
Compression, expansion, suction and exhaust
The maximum propulsive efficiency of a turbojet engine is at a speed of
1000 km/h
2000 km/h
2400 km/h
3000 km/h
Which of the following is false statement? Some of the methods used to reduce diesel smoke are as follows
Using additives in the fuel
Increasing the compression ratio
Adherence to proper fuel specification
Avoidance of overloading
The air-fuel ratio in petrol engines is controlled by
Controlling valve opening/closing
Governing
Injection
Carburetion
The specific fuel consumption per BHP hour for diesel engine is approximately
0.15 kg
0.2 kg
0.25 kg
0.3 kg
The method of determination of indicated power of a multi cylinder spark ignition engine is by the use of
Morse test
Prony brake test
Motoring test
Heat balance test
The loud pulsating noise heard within the cylinder of an internal combustion engine is known as
Detonation
Turbulence
Pre-ignition
Supercharging
The thermal efficiency of diesel engines is about
15 %
30 %
50 %
70 %
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
The rating of a diesel engine, with increase in air inlet temperature, will
Increase linearly
Decrease linearly
Increase parabolically
Decrease parabolically
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
Alpha-methyl-naphthalene (C₁₁ H₁₀) has a cetane number of
0
50
100
120