air standard cycles otto diesel rankine thermal efficiency ic engine performance combustion cooling lubrication - Question Bank

1. Which of the following is a disadvantage of a two-stroke engine compared to a four-stroke engine?
A) Higher thermal efficiency
B) Better fuel economy
C) Higher emissions and poorer lubrication
D) Quieter operation
2. What is the primary role of the camshaft in an IC engine?
A) To control the flow of fuel into the cylinders.
B) To open and close the intake and exhaust valves at the correct times.
C) To ignite the fuel-air mixture.
D) To transfer power from the crankshaft to the drivetrain.
3. In a four-stroke engine, the power stroke occurs during which part of the crankshaft rotation?
A) 0 to 180 degrees
B) 180 to 360 degrees
C) 360 to 540 degrees
D) 540 to 720 degrees
4. Which of the following statements about turbochargers is correct?
A) They are driven by the engine's crankshaft.
B) They use exhaust gases to drive a turbine, which powers a compressor.
C) They reduce the amount of air entering the engine.
D) They are primarily used to cool the engine.
5. The 'Carnot cycle' is often used as a theoretical benchmark for thermal efficiency because it represents:
A) The most efficient cycle possible between two temperature reservoirs.
B) The cycle with the highest power output.
C) The simplest practical thermodynamic cycle.
D) The cycle with the lowest heat rejection.
6. Which emission control device is commonly used in modern gasoline engines to reduce NOx, CO, and UHC?
A) Diesel Particulate Filter (DPF)
B) Selective Catalytic Reduction (SCR)
C) Three-way catalytic converter
D) Exhaust Gas Recirculation (EGR)
7. What is the main pollutant produced by the combustion of fossil fuels that contributes to acid rain?
A) Carbon monoxide (CO)
B) Nitrogen oxides (NOx)
C) Particulate matter (PM)
D) Unburnt hydrocarbons (UHC)
8. The process of 'scavenging' in a two-stroke engine refers to:
A) Igniting the fuel-air mixture
B) Removing exhaust gases and simultaneously introducing fresh charge
C) Compressing the fuel-air mixture
D) Lubricating the moving parts
9. Which type of engine is characterized by external combustion?
A) Diesel engine
B) Gasoline engine
C) Stirling engine
D) Two-stroke engine
10. The ideal Rankine cycle includes reheat and regeneration to:
A) Decrease the thermal efficiency
B) Increase the thermal efficiency and reduce moisture content in the turbine
C) Simplify the cycle operation
D) Reduce the size of the boiler
11. Which component in a steam power plant is responsible for converting thermal energy into mechanical energy?
A) Boiler
B) Pump
C) Turbine
D) Condenser
12. A lower specific fuel consumption indicates:
A) Higher engine efficiency
B) Lower engine efficiency
C) Higher engine temperature
D) Lower engine power output
13. Specific fuel consumption (SFC) is defined as:
A) Mass of fuel consumed per unit time / Power output
B) Power output / Mass of fuel consumed per unit time
C) Heat supplied / Work done
D) Work done / Heat supplied
14. Which of the following is a major source of irreversibility in real IC engine cycles?
A) Isentropic expansion and compression
B) Heat addition and rejection at constant volume
C) Friction and heat transfer
D) Work done by the gas
15. The thermal efficiency of the ideal Brayton cycle is dependent on the:
A) Compression ratio
B) Pressure ratio
C) Cut-off ratio
D) Steam quality
16. In the ideal Brayton cycle, what process represents the compression of air?
A) Isentropic compression
B) Isobaric heat addition
C) Isentropic expansion
D) Isobaric heat rejection
17. The Brayton cycle is the ideal cycle for which type of engine?
A) Reciprocating piston engine
B) Steam turbine
C) Gas turbine
D) Stirling engine
18. Which of the following is a characteristic of a dual combustion cycle (also known as the Seiliger cycle)?
A) Heat addition occurs entirely at constant volume.
B) Heat addition occurs entirely at constant pressure.
C) Heat addition occurs partly at constant volume and partly at constant pressure.
D) Heat rejection occurs at constant volume.
19. What is the main advantage of the Stirling cycle over the Otto or Diesel cycles?
A) Higher peak pressures
B) Ability to use external heat sources
C) Simpler construction
D) Lower operating temperatures
20. The ideal Stirling cycle consists of which processes?
A) Two isothermal and two isochoric processes.
B) Two adiabatic and two isobaric processes.
C) Two isothermal and two isobaric processes.
D) Two adiabatic and two isochoric processes.
21. Brake Mean Effective Pressure (BMEP) is a measure of:
A) The average pressure on the piston during the power stroke.
B) The average pressure acting on the piston throughout the entire cycle, accounting for friction.
C) The theoretical pressure required to produce the indicated work.
D) The pressure in the exhaust manifold.
22. Which of the following is a measure of the power produced by an engine per unit of its displacement volume?
A) Torque
B) Specific power
C) Brake mean effective pressure (BMEP)
D) Indicated mean effective pressure (IMEP)
23. What is the purpose of turbocharging or supercharging an engine?
A) To reduce engine noise
B) To increase the mass of air inducted into the cylinders
C) To improve fuel economy at low speeds
D) To decrease engine temperature
24. Which of the following factors generally improves the volumetric efficiency of an SI engine?
A) Higher engine speed
B) Restricted intake manifold design
C) Higher exhaust back pressure
D) Lower intake air temperature
25. The volumetric efficiency of an IC engine is defined as the ratio of:
A) Actual mass of air inducted to the mass of air that would occupy the swept volume at standard conditions.
B) Mass of fuel inducted to the mass of air inducted.
C) Work done to the heat supplied.
D) Maximum pressure to minimum pressure.
26. Which of the following is a characteristic of dry sump lubrication system?
A) The oil is stored in a large sump pan directly below the crankshaft.
B) An external pump scavenges oil from the sump and returns it to a separate oil tank.
C) It provides less consistent oil pressure than a wet sump system.
D) It is simpler and cheaper to manufacture.
27. What is the most common type of lubricant used in IC engines?
A) Water
B) Grease
C) Mineral oil
D) Synthetic oil
28. The primary function of the lubrication system in an IC engine is to:
A) Cool the engine components
B) Reduce friction and wear between moving parts
C) Clean the engine internals
D) Provide a seal between piston rings and cylinder walls
29. What is the main disadvantage of air cooling systems for IC engines?
A) They are heavier and bulkier.
B) They are less effective at dissipating heat.
C) They require a radiator and coolant.
D) They are more prone to leaks.
30. Which type of cooling system uses a water pump to circulate coolant?
A) Air cooling
B) Thermosiphon cooling
C) Forced circulation cooling
D) Evaporative cooling
31. What is the primary purpose of the cooling system in an IC engine?
A) To increase engine power output
B) To maintain optimal operating temperature and prevent overheating
C) To improve fuel atomization
D) To reduce exhaust emissions
32. Incomplete combustion of fuel in an IC engine results in the formation of:
A) Carbon dioxide and water
B) Carbon monoxide and unburnt hydrocarbons
C) Nitrogen oxides
D) Sulfur dioxide
33. Which of the following factors generally leads to lower combustion efficiency in an IC engine?
A) Rich fuel-air mixture
B) Lean fuel-air mixture
C) High compression ratio
D) Advanced ignition timing
34. Indicated thermal efficiency is defined as:
A) Work done by the gas / Heat supplied
B) Work delivered at the crankshaft / Heat supplied
C) Work done by the gas / Heat rejected
D) Work delivered at the crankshaft / Heat rejected
35. What does brake thermal efficiency consider that indicated thermal efficiency does not?
A) Friction losses
B) Heat losses to the surroundings
C) Work done by the gas
D) Heat added during combustion
36. Which parameter is a measure of how effectively an engine converts the heat energy of the fuel into useful work?
A) Power output
B) Torque
C) Thermal efficiency
D) Specific fuel consumption
37. In a CI engine, the fuel is injected:
A) At the beginning of the intake stroke
B) During the compression stroke
C) At the beginning of the power stroke
D) At the end of the exhaust stroke
38. What is the primary function of a spark plug in an SI engine?
A) To inject fuel into the cylinder
B) To ignite the fuel-air mixture
C) To control the intake valve timing
D) To measure the cylinder pressure
39. Which of the following is NOT a type of internal combustion engine?
A) Spark Ignition (SI) engine
B) Compression Ignition (CI) engine
C) Stirling engine
D) Gas turbine engine
40. The thermal efficiency of the Rankine cycle can be improved by:
A) Increasing the condenser pressure
B) Decreasing the boiler pressure
C) Increasing the boiler pressure and decreasing the condenser pressure
D) Decreasing the pump work
41. What is the primary function of the condenser in the Rankine cycle?
A) To heat the working fluid
B) To increase the pressure of the working fluid
C) To reject heat from the working fluid at constant pressure
D) To expand the working fluid to produce work
42. Which process in the ideal Rankine cycle represents the pumping of water into the boiler?
A) Isentropic expansion in the turbine
B) Constant pressure heat addition in the boiler
C) Isentropic compression in the pump
D) Constant pressure heat rejection in the condenser
43. The Rankine cycle is the ideal cycle for which type of power plant?
A) Gas turbine power plant
B) Internal combustion engine
C) Steam power plant
D) Nuclear reactor
44. The thermal efficiency of an ideal Diesel cycle is generally lower than that of an ideal Otto cycle for the same compression ratio. Why?
A) Higher heat rejection in Diesel cycle.
B) More heat addition in Otto cycle.
C) Inclusion of a constant pressure heat addition process in Diesel cycle.
D) Lower peak temperatures in Diesel cycle.
45. In a Diesel cycle, ignition of fuel occurs due to:
A) Spark plug
B) High temperature of compressed air
C) External ignition source
D) Pre-heating of the cylinder
46. What does the cut-off ratio represent in the Diesel cycle?
A) The ratio of maximum pressure to minimum pressure.
B) The ratio of volume at the end of heat addition to the volume at the beginning of heat addition.
C) The ratio of stroke volume to clearance volume.
D) The ratio of exhaust temperature to intake temperature.
47. The thermal efficiency of an ideal Otto cycle is primarily dependent on which parameter?
A) Fuel type
B) Cut-off ratio
C) Compression ratio
D) Number of cylinders
48. In the ideal Otto cycle, what process represents the heat addition?
A) Isentropic compression
B) Constant volume heat addition
C) Isentropic expansion
D) Constant volume heat rejection
49. Which of the following is a fundamental assumption of the Otto cycle?
A) Combustion occurs at constant pressure.
B) Heat is added and rejected at constant volume.
C) Adiabatic expansion and compression are not considered.
D) There is a presence of valve leakage.
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