Highest useful compression ratio is the compression ratio at which the engine
Gives maximum power output
Can operate without detonation
Consumes minimum fuel for a particular power output
Maintains operating pressures and temperatures within prescribed limits
An increase in the mean effective pressure of a diesel engine with fixed compression ratio can be obtained with increase in
Speed of engine
Charge density
Cut off ratio
Back pressure
For the same compression ratio and heat supplied, the air standard efficiency of an otto cycle compared to that of a diesel cycle is
Less
More
Equal
Unpredictable
For the same compression ratio and heat input, the cycles in decreasing order of thermal efficiency are
Otto, dual, diesel
Diesel, otto, dual
Dual, diesel, otto
Otto, diesel, dual
Which air standard cycle consists of two isothermals connected by two constant volume processes?
Brayton cycle
Ericsson cycle
Stirling cycle
Atkainson cycle
Identify the motor cycle having more than one cylinder
Rajdoot
Yezdi
Yamah
Bullet
Most of the mopeds in india have a capacity of
50 cc
150 cc
200 cc
250 cc
Which is the true statement in the context of two stroke engines?
Simultaneous suction and compression
Simultaneous suction and exhaust
All operations performed in one revolution of crank
Which aspect does not help to reduce the detonating tendency in a spark ignition engine?
Compact combustion chamber and central location of spark plug
Providing squish recesses in the combustion chamber
Using extreamely rich or lean mixtures
Use of salt or sodium cooled valves
Consider the following statements:
Knock in the SI engine can be reduced by
supercharging
retarding the spark
using a fuel of long straight chain structure
increasing the engine speed
Which of these statements are correct?
1 and 2
2 and 3
1, 3 and 4
2 and 4
Knocking tendency in a SI engine reduces with increasing
Compression ratio
Wall temperature
Supercharging
Engine speed
Which is not the effect of detonation?
High operating temperature
Loss inefficiency and power output
Loud and pulsating noise
High local stresses
The ignition quality of a petrol engine fuel is expressed as
SAE rating
API gravity
Octane number
Cetane number
Which fuel has an octane rating of 100?
iso-octane
Normal heptane
Methyl alocohol
Ethyl fluid
-methyl naphthalene
Reference fuels for knock rating of SI engine fuels would include
Iso-octane and -methyl naphthalene
Normal octane and anciline
Iso-octane and n-hexane
n-heptane and iso-octane
An octane rating of 75 for a particular fuel stipulates that detonation tendency of this fuel is same as that of a fuel blend consisting of
25% iso-octane and 75% normal heptane
75% iso-octane and 25% normal heptane
25% iso-octane and 75% ethyl fluid
75% ethyl-fluid and 25% -methyl naphthalene
The commercially available petrol in India has an octane rating of
20-30
40-50
60-75
85-90
The resistance to detonation of a petrol fuel can be considerably improved by adding ……….in small proportions to it
Ethyl alcohol
Benzol
Tetra ethyl lead
Normal heptane
The use of tetra ethyl lead in gasoline is being gradually discontinued since its presence
Makes the fuel costly
Gives bad odour
Decreases the engine speed
Blocks the catalytic convertor
By higher octane rating of SI fuel, it is meant that the fuel has
Higher heating value
Higher flash point
Lower voltality
Longer ignition delay