If the compression ratio in I.C. engine increases, then its thermal efficiency will
Decrease
Increase
Remain same
None of these
Correct Answer :
B. Increase
Related Questions
The colour of exhaust from diesel engine is generally
White
Bluish
Black
Violet
Which of the following is the lightest and most volatile liquid fuel?
Diesel
Kerosene
Fuel oil
Gasoline
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 higher compression ratio causes
Pre-ignition
Increase in detonation
Acceleration in the rate of combustion
Any one of these
The working cycle in case of four stroke engine is completed in following number of revolutions of crankshaft
1/2
1
2
4
The reason for supercharging in any engine is to
Increase efficiency
Increase power
Reduce weight and bulk for a given output
Effect fuel economy
Which one of the following event would reduce volumetric efficiency of a vertical compression ignition engine?
Inlet valve closing after bottom dead centre
Inlet valve closing before bottom dead centre
Inlet valve opening before top dead centre
Exhaust valve closing after top dead centre
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
Detonation is harmful due to
Increase in the rate of heat transfer, there is a reduction in the power output and efficiency of the engine
Excessive turbulence which removes most of the insulating gas boundary layer from the cylinder walls
High intensity of knock causes crankshaft vibration and the engine runs rough
None of the above
Does the supply of scavenging air at a density greater than that of atmosphere mean engine is supercharged?
Yes
No
To some extent
Unpredictable
By higher octane number of spark ignition fuel, it is meant that the fuel has
Higher heating value
Higher flash point
Lower volatility
Longer ignition delay
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 specific fuel consumption per B.P. hour for a petrol engine is about
0.2 kg
0.25 kg
0.3 kg
0.35 kg
Most high speed compression engines operate on
Diesel cycle
Otto cycle
Dual combustion cycle
Special type of air cycle
A diesel engine, during suction stroke, draws
Air only
Diesel only
A mixture of diesel and air
None of these
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
A stoichiometric air-fuel ratio is
Chemically correct mixture
Lean mixture
Rich mixture for idling
Rich mixture for over loads
The process of breaking up or a liquid into fine droplets by spraying is called
Vaporisation
Carburetion
Ionisation
Atomisation
The turbine of the turboprop engine is __________ that of the turbojet engine.
Same as
Smaller than
Bigger than
None of these
Alpha-methyl-naphthalene (C₁₁ H₁₀) has a cetane number of
0
50
100
120
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
Which of the following medium is compressed in a Diesel engine cylinder?
Air alone
Air and fuel
Air and lub oil
Fuel alone
Combustion in compression ignition engines is
Homogeneous
Heterogeneous
Both (A) and (B)
Laminar
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
The pressure at the end of compression, in diesel engines, is approximately
10 bar
20 bar
25 bar
35 bar
The specific fuel consumption of a petrol engine compared to diesel engine of same H.P. is
Same
More
Less
Less or more depending on operating conditions
The ignition quality of diesel oil is expressed by
Cetane number
Octane number
Calorific value
None of these
The sensing element in the control system of nuclear reactors measures the _________ of the neutron flux in the reactor.
Temperature
Volume
Density
None of these
As a result of detonation in an I.C. engine, following parameter attains very high value
Peak pressure
Rate of rise of pressure
Rate of rise of temperature
Peak temperature
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