Internal Combustion Engine MCQ Part-2

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Internal Combustion (IC) Engine MCQ

Internal Combustion (IC) Engine MCQ, IC Engine MCQ, Internal Combustion Engine MCQ, Basic Mechanical Engineering MCQ, BME MCQ, GATE objective questions, Objective Questions on Internal Combustion (IC) Engine, Engineering MCQ

Internal Combustion Engine MCQ Part-1

Multiple choice questions

Q.1. A two stroke engine has a speed of 750 rpm. A four stroke engine having an identical cylinder size runs at 1500 rpm. The theoretical output of the two-stroke engine will

  • be twice that of the four stroke engine
  • be half that of the four stroke engine
  • be the same as that of the four stroke engine
  • depends upon whether it is SI or CI engine.

Answer: be the same as that of the four stroke engine

Q.2. Scavenging air means

  • air used under compression
  • air used for forcing the burnt gases out of the cylinder during the exhaust period
  • forced air for cooling the engine cylinder
  • burnt air containing combustion product

Answer: air used for forcing the burnt gases out of the cylinder during the exhaust period

Q.3. All of the following statements are correct, except

  • For the same power output, a petrol engine is of light construction and low initial cost when compared to a diesel engine.
  • Morse test is used to determine the brake power of a multicylinder engine
  • The thermal efficiency of a well-designed and properly maintained diesel engine usually lies in the range 35-40%
  • A governor is used to adjust the power output from an engine in conformity with the external load.

Answer: Morse test is used to determine the brake power of a multicylinder engine

Q.4. The preference of diesel engines for road transport is due to

  • easy starting
  • low operating cost
  • low specific fuel consumption over a large range of load
  • complete combustion of charge
  • harmless exhaust

Answer: low specific fuel consumption over a large range of load

Q.5. Morse test in multi-cylinder engines is done to determine

  • air-flow to the engine
  • volumetric efficiency
  • indicated power
  • mechanical efficiency

Answer: indicated power

Q.6. Which one of the followings is a wrong statement?

  • valve timing diagram shows the correct crank positions corresponding to opening and closing of the valves
  • valve overlap represents the angle during which both the inlet and exhaust valves remain open
  • closing of inlet valve before bottom dead centre would reduce volumetric efficiency of the engines
  • ignition of charge in a petrol engine takes place very close to top dead centre

Answer: ignition of charge in a petrol engine takes place very close to top dead centre

Q.7. All of the following statements are correct, except

  • a carburetor prepares a homogeneous air-fuel mixture by atomising and vaporising the fuel
  • vacuum at the throat of venturi sucks the fuel through the fuel jet
  • throttle valve controls the supply of air-fuel mixture
  • choke is kept open when cranking a cold engine for starting

Answer: choke is kept open when cranking a cold engine for starting

Q.8. Consider the following statements:

  1. Petrol engines are quality governed
  2. Combustion in spark ignition engines is homogeneous
  3. Lean mixture is required during idling
  4. Choke supplies rich mixture for cold starting.

Which of these are correct statements?

  • 1 and 3
  • 2 and 4
  • 1, 3 and 4
  • 1 and 3

Answer: 2 and 4

Q.9. The purpose of ignition coil in the ignition system of a petrol engine is to

  • increase the voltage
  • reduce sparking in the system
  • distribute high currents to the engine cylinder
  • regulate the, current produced by the dynamo

Answer: increase the voltage

Q.10. What material is used for the insulating body of a spark plug?

  • Silica
  • Dolomite
  • alumina
  • glass

Answer: alumina

Q.11. A particular firing order is necessary in a multi-cylinder engine so as to

  • have better balance of the engine
  • give good distribution of fuel to all the cyclinders
  • obtain uniform toque
  • operate the ignition system smoothly

Answer: obtain uniform toque

Q.12. In diesel engines, the injection pressure is of the order of

  • 5-8 MN/m2
  • 10-15 MN/m2
  • 17.5-25 MN/m2
  • 40-50 MN/m2

Answer: 10-15 MN/m2

Q.13. Supercharging is the process of

  • providing a draft of air for cooling purposes
  • supplying air to remove the spent up gases
  • raising the pressure of charge fed to the cylinder
  • supplying more fuel for getting greater output

Answer: raising the pressure of charge fed to the cylinder

Q.14. Velocity of flame propagation in the SI engine is maximum for air-fuel mixture which is …….  stoichiometric

  • 10% richer than
  • equal to
  • more than 10% richer than
  • 10% leaner than

Answer: 10% richer than

Q.15. Delay period refers to the period that elapses between providing a spark and the commencement of actual combustion of fuel. An increase in which of the following factors increases the delay period?

  • self ignition temperature of fuel
  • intake temperature
  • inlet pressure
  • compression ratio

Answer: self ignition temperature of fuel

Q.16. All of the following factors promote detonation in spark ignition engines, except

  • increase in inlet pressure and temperature of charge
  • higher compression ratio
  • high self ignition temperature of fuel
  • advanced spark timing

Answer: high self ignition temperature of fuel

Q.17. Reference fuels for knock rating of SI engines fuels would include

  • iso-octane and α-methyl napthalene
  • normal octane and anciline
  • iso-octane and n-hexane
  • n-heptane and iso-octane

Answer: n-heptane and iso-octane

Q.18. Which is not the characteristic of diesel knock in a compression ignition engine?

  • instantaneous and rapid burning of the last part of the charge
  • pressure rise in the cylinder occurs at an enormous rate
  • rough running and fatigue failure of engine components
  • drop in engine power and efficiency

Answer: instantaneous and rapid burning of the last part of the charge

Q.19. Consider the following measures:

  1. Increasing the compression ratio
  2. Increasing the intake air temperature
  3. Increasing the length to diameter ratio of the cylinder
  4. Increasing the engine speed

The measures necessary to reduce the tendency to knock in CI engines would include

  • 1, 2 and 3
  • 1, 2 and 4
  • 1, 3 and 4
  • 2, 3 and 4

Answer: 1, 2 and 4

Q.20. All of the following statements are correct, except

  • the detonation follows the spark while pre-ignition precedes it
  • doping refers to the addition of certain additives to petrol to improve its resistance to detonation
  • the two reference fuels used for cetane rating are cetane and n-heptane
  • factors tending to increase detonation in SI engines tend to reduce knocking in CI engines

Answer: the two reference fuels used for cetane rating are cetane and n-heptane

Q.21. All of the following statements are correct, except

  • Petrol engines normally operate in the compression ratio range of 6 – 10
  • A two stroke engine has one inlet port, one exhaust port and one transfer port
  • Two stroke IC engines are less efficient than their four-stroke counterparts due to low compression ratio and shorter stroke length
  • The direction of spray is not critical in indirect combustion chambers

Answer: Two stroke IC engines are less efficient than their four-stroke counterparts due ……

Q.22. Operation of a spark ignition engine at high compression ratios is not desirable as it may

  • lead to incomplete combustion and poor efficiency
  • necessinate robust construction for the engine cylinder
  • promote engine knocking causing damage to the engine
  • cause an excessive temperature rise in the cylinder resulting into back fire

Answer: promote engine knocking causing damage to the engine

Q.23. In spark ignition engines, the flame speed increases with increasing

  1. fuel-air ratio
  2. pressure ratio
  3. turbulence
  4. fuel intake rate

 Which of the statements made above are correct?

  • 1 and 2
  • 2 and 3
  • 1 and 4
  • 3 only

Answer: 3 only

Q.24. Consider the following factors

  1. compression ratio
  2. engine speed
  3. engine output
  4. fuel viscosity

Which of these affect the ignition delay in a CI engine.

  • 1 and 2
  • 2 and 4
  • 1, 2 and 3
  • 1, 2 and 4

Answer: 1, 2 and 3

Q.25. Which of the followings is identified with octane rating of 100?

  • iso-octane
  • n-heptane
  • tetraethyl lead
  • α-methylnapthalene

Answer: iso-octane

Q.26. Identify the aspect an increase in which promotes the tendency of knocking in CI engines

  • compression ratio
  • inlet air temperature
  • coolant water temperature
  • rate of fuel atomisation

Answer: coolant water temperature

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