The increase of cooling water temperature in petrol engine will __________ the knocking tendency.
Not effect
Decrease
Increase
None of these
Correct Answer :
C. Increase
Related Questions
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 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
The normal heptane (C7H16) is given a rating of ________ octane number.
0
50
100
120
The exhaust valve in a four stroke cycle petrol engine
Opens at 50° before bottom dead centre and closes at 15° after top dead centre
Opens at bottom dead centre and closes at top dead centre
Opens at 50° after bottom dead centre and closes at 15° before top dead centre
May open and close anywhere
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 ratio of the volume of charge admitted at N.T.P. to the swept volume of the piston is called
Mechanical efficiency
Overall efficiency
Volumetric efficiency
Relative efficiency
Supercharging is essential in
Diesel engines
Gas turbines
Petrol engines
Aircraft engines
The knocking in diesel engines may be prevented by
Reducing the delay period
Raising the compression ratio
Increasing the inlet pressure of air
All of these
Which of the following medium is compressed in a Diesel engine cylinder?
Air alone
Air and fuel
Air and lub oil
Fuel alone
The colour of exhaust from diesel engine is generally
White
Bluish
Black
Violet
In case of gas turbines, the gaseous fuel consumption guarantees are based on
High heat value
Low heat value
Net calorific value
Calorific value
In order to prevent knocking in spark ignition engines, the charge away from the spark plug should have
Low density
Low temperature
Long ignition delay
All of these
The knocking tendency in spark ignition engines may be decreased by
Controlling the air-fuel mixture
Controlling the ignition timing
Controlling the exhaust temperature
Reducing the compression ratio
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
A higher compression ratio causes
Pre-ignition
Increase in detonation
Acceleration in the rate of combustion
Any one of these
The increase of cooling water temperature in petrol engine will __________ the knocking tendency.
Not effect
Decrease
Increase
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.
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)
In a typical medium speed 4-stroke cycle diesel engines
Exhaust valve opens at 35° before bottom dead centre and closes at 20° after top dead centre
Exhaust valve opens at bottom dead centre and closes at top dead centre
Exhaust valve opens just after bottom dead centre and closes just before top dead centre
May open and close anywhere
In an internal combustion engine, the process of removing the burnt gases from the combustion chamber of the engine cylinder is known as
Scavenging
Detonation
Supercharging
Polymerisation
In the crankcase method of scavenging, the air pressure is produced by
Supercharger
Centrifugal pump
Natural aspirator
Movement of engine piston
The air-fuel ratio in petrol engines is controlled by
Controlling valve opening/closing
Governing
Injection
Carburetion
Number of working strokes per min. for a two stroke cycle engine is _________ the speed of the engine in r.p.m.
Equal to
One-half
Twice
Four-times
The pressure inside the cylinder is _________ the atmospheric pressure during the exhaust stroke.
Equal to
Below
Above
None of these
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
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
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
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
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 knocking tendency in compression ignition engines for a given fuel will be
Enhanced by decreasing compression ratio
Enhanced by increasing compression ratio
Dependent on other factors
None of the above