The knock in diesel engine occurs due to
Instantaneous and rapid burning of the first part of the charge
Instantaneous auto ignition of last part of charge
Delayed burning of the first part of the charge
Reduction of delay period
Correct Answer :
A. Instantaneous and rapid burning of the first part of the charge
Related Questions
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
Polymerisation is a chemical process in which molecules of a compound become
Larger
Slowed down
Smaller
Liquid
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
If petrol is used in a diesel engine, then
Low power will be produced
Efficiency will be low
Higher knocking will occur
Black smoke will be produced
The compensating jet in a carburettor supplies almost constant amount of petrol at all speeds because the
Jet area is automatically varied depending on the suction
The flow from the main jet is diverted to the compensating jet with increase in speed
The diameter of the jet is constant and the discharge coefficient is invariant
Flow is produced due to the static head in the float chamber
The cam shaft of a four stroke I.C. engine running at 1500 rpm will run at
1500 rpm
750 rpm
3000 rpm
Any value independent of engine speed
Antiknock for compression ignition engines is
Napthene
Tetra ethyl lead
Amyl nitrate
Hexadecane
The output of a diesel engine can be increased without increasing the engine revolution or size in following way
Feeding more fuel
Heating incoming air
Scavenging
Supercharging
Scavenging is usually done to increase
Thermal efficiency
Speed
Power output
Fuel consumption
The thermal efficiency of a petrol engine is _________ as compared to diesel engine.
Same
Less
More
None of these
The object of providing masked inlet valve in the air passage of compression ignition engines is to
Enhance flow rate
Control air flow
Induce primary swirl
Induce secondary turbulence
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
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
Fuel oil consumption guarantees for I .C. engine are usually based on
Low heat value of oil
High heat value of oil
Net calorific value of oil
Calorific value of fuel
The magneto in an automobile is basically
Transformer
D.C. generator
Capacitor
Magnetic circuit
The thermal efficiency of diesel engines is about
15 %
30 %
50 %
70 %
Morse test can be conducted for
Petrol engines
Diesel engines
Multi cylinder engines
All of these
Gaseous fuel guarantees are based on
Calorific value of oil
Low heat value of oil
High heat value of oil
Mean heat value of oil
Which of the following is the lightest and most volatile liquid fuel?
Diesel
Kerosene
Fuel oil
Gasoline
If the speed of the engine is increased, the indicated power will
Increase
Decrease
Remain same
None of these
The specific fuel consumption per B.P. hour for a diesel engine is about
0.2 kg
0.25 kg
0.3 kg
0.35 kg
The thermal efficiency of diesel engines on weak mixtures is
Unaffected
Lower
Higher
Dependent on other factors
Most high speed compression engines operate on
Otto cycle
Diesel cycle
Dual cycle
Carnot cycle
A higher compression ratio causes
Pre-ignition
Increase in detonation
Acceleration in the rate of combustion
Any one of these
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
In petrol engines, advancing of the spark timing will _________ the knocking tendency.
Not effect
Decrease
Increase
None of these
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
In petrol engines, the delay period is of the order of
0.001 second
0.002 second
0.003 second
0.004 second
The theoretically correct air fuel ratio for petrol engine is of the order of
6 : 1
9 : 1
12 : 1
15 : 1