Pick up the false statement
Thermal efficiency of diesel engine is about 34%
Theoretically correct mixture of air and petrol is approximately 15:1
High speed compression engines operate on dual combustion cycle
S.I. engines are quality governed engines
Correct Answer :
D. S.I. engines are quality governed engines
Related Questions
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 ratio of the work obtained at the crankshaft in a given time to the energy supplied during the same time is called
Mechanical efficiency
Overall efficiency
Indicated thermal efficiency
Volumetric efficiency
The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is
Same
Less
More
More or less depending on power rating
The purpose of testing an internal combustion engine is
To determine the information, which cannot be obtained by calculations
To conform the data used in design, the validity of which may be doubtful
To satisfy the customer regarding the performance of the engine
All of the above
Which of the following is the lightest and most volatile liquid fuel?
Diesel
Kerosene
Fuel oil
Gasoline
The probability of knocking in diesel engines is increased by
High self ignition temperature
Low volatility
Higher viscosity
All of these
The inlet valve of a four stroke cycle internal combustion engine remains open for
130°
180°
230°
270°
A diesel engine has compression ratio from
6 to 10
10 to 15
15 to 25
25 to 40
Fuel consumption of diesel engines is not guaranteed at one quarter load because at such low loads
The friction is high
The friction is unpredictable
The small difference in cooling water temperature or in internal friction has a disproportionate effect
The engine is rarely operated
In the crankcase method of scavenging, the air pressure is produced by
Supercharger
Centrifugal pump
Natural aspirator
Movement of engine piston
A 5 BHP engine running at full load would consume diesel of the order of
0.3 kg/hr
1 kg/hr
3 kg/hr
5 kg/hr
Combustion in compression ignition engines is
Homogeneous
Heterogeneous
Both (A) and (B)
Laminar
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
The firing order in an I.C. engine depends upon
Arrangement of the cylinders
Design of crankshaft
Number of cylinders
All of these
In petrol engine, using a fixed octane rating fuel and fixed compression ratio, supercharging will _________ the knocking tendency.
Not effected
Decrease
Increase
None of these
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 order to mix air and petrol in the required proportion and to supply it to the engine during suction stroke, then _________ is employed.
Fuel pump
Injector
Carburettor
None of these
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
In petrol engines, advancing of the spark timing will _________ the knocking tendency.
Not effect
Decrease
Increase
None of these
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
Compression ratio of I.C. Engines is
The ratio of volumes of air in cylinder before compression stroke and after compression stroke
Volume displaced by piston per stroke and clearance volume in cylinder
Ratio of pressure after compression and before compression
Swept volume/cylinder volume
A fuel of cetane number 40 has the same ignition quality as a mixture of
40% cetane and 60% alpha methyl naphthalene
40% alpha methyl naphthalene and 60% cetane
40% petrol and 60% diesel
40% diesel and 60% petrol
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
Which of the following statement is wrong?
A four stroke cycle engine develops twice the power as that of a two stroke cycle engine
For the same power developed, a four stroke cycle engine is lighter, less bulky and occupies less floor area
The petrol engines are costly than diesel engines
All of the above
In a diesel engine, the fuel is ignited by
Spark
Injected fuel
Heat resulting from compressing air that is supplied for combustion
Ignition
For the same compression ratio
Otto cycle is more efficient than the Diesel
Diesel cycle is more efficient than Otto
Both Otto and Diesel cycles are, equally efficient
Compression ratio has nothing to do with efficiency
Which is more viscous lube oil?
SEA 30
SAE 50
SAE 70
SAE 80
The thermal efficiency of a diesel cycle having fixed compression ratio, with increase in cut-off ratio will
Increase
Decrease
Be independent
May increase or decrease depending on other factors
A supercharged engine as compared to an ordinary engine
Requires smaller foundation
Is lighter
Consumes less lubricating oil
All of these
A gas engine has a swept volume of 300 cm3 and clearance volume of 25 cm3. Its volumetric efficiency is 0.88 and mechanical efficiency is 0.90. The volume of the mixture taken in per stroke is
248 cm3
252 cm3
264 cm3
286 cm3