Internal Combustion Engines (i.c. Engines)(Mechanical Engineering ) Questions and Answers

Question 1. The reason for supercharging in any engine is to
  1.    Increase efficiency
  2.    Increase power
  3.    Reduce weight and bulk for a given output
  4.    Effect fuel economy
Explanation:-
Answer: Option C. -> Reduce weight and bulk for a given output
The reason for supercharging in any engine is to Reduce weight and bulk for a given output
-A supercharger is an air compressor that increases the pressure or density of air supplied to an internal combustion engine. This gives each intake cycle of the engine more oxygen, letting it burn more fuel and do more work, thus increasing power.
Question 2. Morse test can be conducted for
  1.    Petrol engines
  2.    Diesel engines
  3.    Multi cylinder engines
  4.    All of these
Explanation:-
Answer: Option C. -> Multi cylinder engines
Morse test can be conducted for Multi cylinder engines
The purpose of Morse test is to obtain the approximate indicated power of a Multi cylinder engine. It consist of running the engine against the dynamo-meter at a particular speed, cutting out the firing of each cylinder in turn and noting the fall in BP each time while maintaining the speed constant.
Question 3. Engine pistons are usually made of aluminium alloy because it
  1.    Is lighter
  2.    Wear is less
  3.    Absorbs shocks
  4.    Is stronger
Explanation:-
Answer: Option A. -> Is lighter
Engine pistons are usually made of aluminium alloy because it Is lighter
Aluminium alloy are used because they are lighter.
Question 4. Alpha-methyl-naphthalene (C11H10) has a cetane number of
  1.    0
  2.    50
  3.    100
  4.    120
Explanation:-
Answer: Option A. -> 0
Alpha-methyl-naphthalene (C11H10) has a cetane number of 0.
Question 5. The cetane (C16H34) which is a straight chain paraffin, is assigned a cetane number of
  1.    0
  2.    50
  3.    100
  4.    120
Explanation:-
Answer: Option C. -> 100
The cetane (C16H34) which is a straight chain paraffin, is assigned a cetane number of 100.
Question 6. The two reference fuels used for cetane rating are
  1.    Cetane and iso-octane
  2.    Cetane and alpha-methyl naphthalene
  3.    Cetane and normal heptane
  4.    Cetane and tetra ethyl lead
Explanation:-
Answer: Option B. -> Cetane and alpha-methyl naphthalene
The two reference fuels used for cetane rating are Cetane and alpha-methyl naphthalene
Question 7. For the same power developed in I.C. engines, the cheaper system is
  1.    Naturally aspirated
  2.    Supercharged
  3.    Centrifugal pump
  4.    Turbo charger
Explanation:-
Answer: Option B. -> Supercharged
For the same power developed in I.C. engines, the cheaper system is Supercharged
Question 8. As compared to air standard cycle, in actual working, the effect of variation in specific heats is to
  1.    Increase maximum pressure and maximum temperature
  2.    Reduce maximum pressure and maximum temperature
  3.    Increase maximum pressure and decrease maximum temperature
  4.    Decrease maximum pressure and increase maximum temperature
Explanation:-
Answer: Option B. -> Reduce maximum pressure and maximum temperature
As compared to air standard cycle, in actual working, the effect of variation in specific heats is to Reduce maximum pressure and maximum temperature
Question 9. The fuel valve in a four stroke cycle diesel engine
  1.    Opens at 15° after top dead center and closes at 20° before bottom dead center
  2.    Opens at 15° before top dead center and closes at 20° after top dead center
  3.    Opens at top dead center and closes at bottom dead center
  4.    May open and close anywhere
Explanation:-
Answer: Option B. -> Opens at 15° before top dead center and closes at 20° after top dead center
The fuel valve in a four stroke cycle diesel engine Opens at 15° before top dead center and closes at 20° after top dead center
Question 10. The expansion of fuel in a four stroke cycle diesel engine
  1.    Starts at 15° before top dead center and ends at 30° after top dead center
  2.    Starts at top dead center and ends at 30° after top dead center
  3.    Starts at 15° after top dead center and ends at 30° before bottom dead center
  4.    May start and end anywhere
Explanation:-
Answer: Option C. -> Starts at 15° after top dead center and ends at 30° before bottom dead center
The expansion of fuel in a four stroke cycle diesel engine Starts at 15° after top dead center and ends at 30° before bottom dead center
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