Mcq Of Internal Combustion Engines-2161902 PDF

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Chapter 1

Introduction of I. C. Engine

1. Advantage of reciprocating IC engines over steam turbine is (a) Mechanical simplicity (b) Improved plant efficiency (e) Lower average temperature (d) all of the above Ans: d 2. The intake charge in a diesel engine consists of (a) air alone (b) air + lubricating oil (c) air + fuel (d) air + fuel + lubricating oil Ans: a 3. Engines of different cylinder dimensions, power and speed can be compared on the basis of (a) Maximum pressure (b) Fuel consumption (c) mean effective pressure (d) unit power Ans: c 4. Disadvantages of reciprocating IC engine are (a) vibration (b) use of fossil fuels

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(c) balancing problems (d) all of the above Ans: d 5. Gudgeon pin forms the link between (a) piston and big end of connecting rod (b) piston and small end of connecting rod (c) connecting rod and crank (d) big end and small end Ans: b 6. An IC engine gives an output of 3 kW when the input is 10,000 J/s. The thermal efficiency of the engine is (a) 33.3% (b) 30% (c) 60% (a) 66.6% Ans: b 7. In a four-stroke IC engine cam shaft rotates at (a) same speed as crankshaft (b) twice the speed of crankshaft (c) halt the speed of crankshaft (d) none of the above Ans: c

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8. Thermal efficiency of CI engine is higher than that of SI engine due (a) light weight (b) higher compression ratio (c) constant pressure heat addition (d) none of the above Ans: b 9. SI engines are of (a) light weight (b) high speed (c) homogeneous change of fuel and oil (d) all of the above Ans: d 10. Compression ratio in diesel engines is of the order of (a)5-7 (b) 7 -10 (c)10 – 12 (d) 14-20 Ans: d 11. In a reciprocating engine with a cylinder diameter of D and stroke of the cylinder volume is

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Ans: c 12. Main advantage of a two-stroke engine over four-stroke engine is (a) more uniform torque on the crankshaft (b) more power output for the cylinder of same dimensions (c) absence of valves (d) all of the above Ans: d 13. Engines used for ships are normally (a) four-stroke Sl engines of very high power (b) two-stroke CI engines of very high power (c) four-stroke Cl engines of high speed (d) two-stroke SI engines of high power Ans: b 14.If L is the stroke and N is the rpm, mean piston speed of two-stroke engine (a) LN (b) LN/2

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(c) 2LN (d) none of the above Ans: c 15. Equivalence ratio is

(d) None of the above the above Ans: d 16. The volumetric efficiency of the SI engine is comparatively (a) lower than CI engine (b) higher than CI engine (c) will be same as CI engine (d) none of the above Ans: a 17. The range of volumetric efficiency of a (a) 65- 75% (b) 75 - 85% (c) 85 - 90% (d) 90 - 95%

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Ans: c 18. Relative efficiency is the ratio of

Ans: b 19. Brake specific fuel consumption is defined as (a) fuel consumption per hour (b) fuel consumption per km (c) fuel consumption per BP (d) fuel consumption per brake power hour Ans: d 20. Engine can be fired with (a) solid fuel (b) liquid fuel (c) gaseous fuel (d) any of the above fuels Ans: d

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21. A two-stroke engine can be identified by (a) cooling system (b) lubrication system (c) absence of valves (d) piston size Ans: c 22. Advantage of two-stroke engine is (a) more uniform torque (b) lighter flywheel (c) no valves (d) all of the above Ans: d 23. Charge pressure at the inlet port of a two-stroke engine is (a) 20 bar (b) vacuum (c) atmospheric (d) higher than atmospheric Ans: d 24. The most perfect method of scavenging is (a) cross scavenging (b) uniflow scavenging (c) loop scavenging

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(d) reverse flow scavenging Ans: b 25. Two-stroke SI engines suffer from (a) fuel loss (b) idling difficulty (c) both (a) and (b) together (d) none of the above Ans: a 26. At the same speed two-stroke engine of the same size as a four-stroke engine will develop (a) same power (b) half the power (c) twice the power (d) four times the power Ans: c 27. Two wheelers without deflector type piston use a) loop scavenging (b) unifow scavenging (c) reverse flow scavenging (d) cross scavenging Ans: d 28. Crankcase scavenged engines have delivery ratio of (a) greater than 1

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(b) less than 1 (c) equal to 1 (d) none of the above Ans: c 29. The working cycle in case of four stroke engine is completed in following number of revolutions of crankshaft (a) 1/2 (b) 1 (c) 2 (d) 4 (e) 8. Ans: c 30. In a diesel engine, the fuel is ignited by (a) spark (b) injected fuel (c) heat resulting from compressing air that is supplied for combustion (d) ignitor (e) combustion chamber. Ans: c 31. Scavenging air in diesel engine means (a) air used for combustion sent under pres-sure (b) forced air for cooling cylinder

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(c) burnt air containing products of com-bastion (d) air used for forcing burnt gases out of engine's cylinder during the exhaust period (e) air fuel mixture. Ans: d 32. Does the supply of scavenging air at a density greater than that of atmosphere mean engine is supercharged? (a) yes (b) no (c) to some extent (d) unpredictable (e) depends on other factors. Ans: b 33. The ratio of indicated thermal efficiency to the corresponding air standard cycle efficiency is called (a) net efficiency (b) efficiency ratio (c) relative efficiency (d) overall efficiency (e) cycle efficiency. Ans: c 34. Compression ratio of LC. Engines is (a) the ratio of volumes of air in cylinder before compression stroke and after compression stroke

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(b) volume displaced by piston per stroke and clearance volume in cylinder (c) ratio of pressure after compression and before compression (d) swept volume/cylinder volume (e) cylinder volume/swept volume. Ans: a

Chapter 2 Fuel Air Cycles and Actual Cycles 1. A perfect engine works on the Carnot cycle between 727 °C and 227°C. The efficiency of the engine is (a) 0.5 (b) 0.75 (c) 1 (d) 0.25 Ans: a 2. The air standard Otto cycle consists of (a) two constant volume and two isentropic processes (b) two constant pressure and two isentropic processes (c) two constant pressure and two constant volume processes (d) none of the above Ans: a 3. In air standard Diesel cycle at fixed r and fixed n (a) ƞthermal increases with increase in heat addition and cut-off ratio (b) ƞthermal decreases with increase in heat addition and cut-off ratio

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(c) ƞthermal Remains the same with increase in heat addition and cut-off ratio (d) none of the above Ans: b 4. Mean effective pressure of Otto cycle is (a) inversely proportional to pressure ratio (b) directly proportional to pressure ratio (c) does not depend on pressure ratio (d) proportional to square root of pressure ratio Ans: b 5. For a given compression ratio the work output of Otto cycle is (a) increases with Increase in r (b) decreases with increase in r (c) is not affected (d) none of the above Ans: a 6. For a given value of r, efficiency of Otto cycle (a) decreases with compression ratio (b) increases with compression ratio (c) is not affected (d) none of the above Ans: b

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7. For dual combustion cycle for fixed value of heat addition and compression ratio (a) mep wil be greater with increase in rp, and decrease in rc (b) mep will be greater with decrease in rp and decrease in rc (c) mep remain the same with increase in rp and decrease in rc (d) none of the above Ans: a 8. The normal range of, compression ratio for Otto cycle is (a) 6 to 10 (b) 2 to 4 (c) >10 (d) none of the above Ans: a 9. The normal range of compression ratio for Diesel cycle is (a) 4 to 6 (b) 6 to 8 (c) 15 to 20 (d) >25 Ans: c 10. For the same compression ratio and heat addition (a) ƞOtto > ƞDiesel > ƞDual (b) ƞDiesel > ƞOtto > ƞDual

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(c) ƞOtto> ƞDual > ƞDiesel (d) ƞDual> ƞDiesel > ƞOtto Ans: c 11. for the same compression ratio and heat rejection, (a) ƞOtto> ƞDual > ƞDiesel (b) ƞDiesel > ƞDual > ƞOtto (c) ƞDual> ƞDiesel > ƞOtto (d) ƞDual> ƞOtto> ƞDiesel Ans: a 12. When the engines are built to withstand the sane thermal and mechanical stresses (a) ƞDiesel > ƞDual > ƞOtto (b) ƞDual> ƞDiesel > ƞOtto (c) ƞOtto> ƞDual > ƞDiesel (d) ƞOtto> ƞDiesel > ƞDual Ans: a 13. For the same peak pressure and heat input (a) ƞOtto > ƞDual > ƞDiesel (b) ƞOtto > ƞDiesel > ƞDual (c) ƞDiesel > ƞDual > ƞOtto

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(d) ƞDiesel > ƞOtto > ƞDual Ans: c 14. For the same peak pressure and work output (a) ƞOtto > ƞDual > ƞDiesel (b) ƞOtto > ƞDiesel > ƞDual (c) ƞDiesel > ƞOtto > ƞDual (d) ƞDiesel > ƞDual > ƞOtto Ans: d 15. Brayton cycle is used in (a) Ramjet engines (b) gas turbines (c) pulse jet engines (d) Cl engines Ans: b 16. The actual efficiency of a good engine is about efficiency. (a) 100% (b) 85% (c) 50% (d) 25% Ans: b

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of the estimated fuel-air cycle

17. With dissociation peak temperature is obtained (a) at the stoichiometric air-fuel ratio (b) when the mixture is slightly lean (c) when the mixture is slightly rich (d) none of the above Ans: c 18. With dissociation the exhaust gas temperature (a) decreases (b) increases (c) no effect (d) increases upto certain air-fuel ratio and then decreases Ans: a 19. Fuel-air ratio affects maximum power output of the engine due to (a) higher specific heats (b) chemical equilibrium losses (c) both (a) and (b) (d) none of the above Ans: c 20. Mean effective pressure at a given compression ratio is maximum when the air-fuel ratio is (a) higher than stoichiometric (b) lower than stoichiometric (c)equal to stoichionetric

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(d) none of the above Ans: b 21. For a compressor process with variable specific heat the peak temperature and pressure are compared to constant specific heat (a)lower (b) higher (c) no effect (d) none of the above

Ans: a 22. Dissociation can be considered as (a) disintegration of combustion products at high temperature (b) reverse process of combustion (c) heat absorption process (d) all of the above Ans: d 23. Time loss factor in actual cycle is due to (a) Progressive combustion (b) heat loss through cylinder walls (c) gas leakage (d) friction Ans: a 24. The major loss in a SI engine is due to

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(a) exhaust blow down (b) pumping (c) incomplete combustion (d) variation in specific heat and chemical equilibrium Ans: d 25. Fuel-air cycle efficiency is less than air-standard cycle efficiency by an amount equal to (a) pumping loss (b) friction loss (c) loss due to specific heat variation and chemical equilibrium (d) exhaust blow down loss Ans: c 26. The major loss in a CI engine is (a) direct heat loss (b) loss due to incomplete combustion (c) rubbing friction loss (d) pumping loss Ans: b 27. The ratio of the actual efficiency and the fuel-air cycle efficiency for CI engines is about (a) 0.2-0.3 (b) 0.5-0.6 (c) 1.0 (d) 0.6-0.8

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Ans: d 28. In an actual SI engine the pumping loss with respect to speed (a) decreases (b) Increases (c) remains constant (d) nothing to do with speed Ans: b 29. The volumetric efficiency is affected by (a) the exhaust gas in the clearance volume (b) the design of intake and exhaust valve (c) valve timing (d) all of the above Ans:d 30. The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is (a) same (b) less (c) more (d) more or less depending on power rating Ans: c 31. The inlet value of a four stroke cycle I.C engine remains open for nearly (a) 180°

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(b) 125° (c) 235° (d) 200° (e) 275°. Ans: c 32. In a typical medium speed, 4-stroke cycle diesel engine (a) fuel injection starts at 10° before to dead center and ends at 20° after tor dead center (b) fuel injection starts at top dead center and ends at 20° after top dead center (c) fuel injection starts at just before top dead center and ends just after top dead center (d) may start and end anywhere Ans: a

Chapter-3 Combustion 1. The amount of heat liberated by complete combustion of unit quantity of fuel is known as (a) Agitation (b) Combustion (c) Calorific value (d) Thermogenesis Ans: c 2. The calorific value of gaseous fuels is expressed in terms of (a) kcal (b) B. kcal/kg (c) C. kcal/m² (d) D. kcal/m3 Ans: D 3. What is the significance of calorific value?

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(a) Helps in deciding which fuel is good (b) Helps in locating fuel (c) Helps in deciding ignition temperature (d) Helps in deciding fire point Ans: a 4. Which gas has the highest calorific value among given option? (a) Oxygen (b) Helium (c) Hydrogen d) Nitrogen Ans: c 5. Which calorimeter is used to find calorific values of solid and liquid fuels? (a) Boy’s calorimeter (b) Bomb calorimeter (c) Junker’s calorimeter (d) Calvet-type calorimeter Ans: b 6. Which calorimeter is used to find calorific values of gaseous fuels? (a) Bomb calorimeter (b) Junker calorimeter (c) Adiabatic calorimeter (d) Isothermal titration calorimeter Ans: b 7. What is the factor on which, difference between the two heating values of fuel depends on? (a) Physical properties (b) Reactants (c) Chemical composition

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(d) Products Ans: c 8. The Bomb calorimeter is used to determine the calorific value of: (a) solids and liquid fuels (b) solid and gaseous fuels (c) liquid fuels that can be easily vaporized (d) solid fuels only Ans: a 9. If the intake air temperature of I.C. engine increases, its efficiency will (a) increase (b) decrease (c) remain same (d) unpredictable (e) depend on other factors. Ans: b 10. All heat engines utilize (a) low heat value of oil (b) high heat value of oil (c) net claorific value of oil (d) calorific value of fuel (e) all of the above. Ans: a 11. An engine indicator is used to determine the following (a) speed (b) temperature (c) volume of cylinder (d) m.e.p. and I.H.P.

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(e) BHP. Ans: d 12. Fuel oil consumption guarantees for I .C. engine are usually based on (a) low heat value of oil (b) high heat value of oil (c) net calorific value of oil (d) calorific value of fuel Ans: b 13.Combustion in compression ignition engines is (a) homogeneous (b) heterogeneous (c) both (a) and (b) (d) laminar (e) turbulent. Ans: b 14.The air requirement of a petrol engine during starting compared to theoretical required for complete combustion is (a) more (b) loss (c) same (d) may be more or less depending on engine capacity (e) unpredictable. Ans: b 15. Diesel fuel, compared to petrol is (a) less difficult to ignite (b) just about the same difficult to ignite (c) more difficult to ignite

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(d) highly ignitable (e) none of the above. Ans: c 16.When crude oil is heated, then which of the following hydrocarbon is given off first. (a) kerosene (b) gasoline (c) paraffin (d) diesel (e) natural gas. Ans: e 17. The rating of a diesel engine, with increase in air-intlet temperature, will (a) increase linearly (b) decrease linearly (c) increase parabolically (d) decrease parabolically (e) first decrease linearly and then increase parabolically. Ans: b 18. A 75 cc engine has following parameter as 75 cc (a) fuel tank capacity (b) lub oil capacity (c) swept volume (d) cylinder volume (e) clearance volume. Ans: c 19.A heat engine utilises the (a) calorific value of oil (b) low heat value of

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(c) high heat value of oil (d) mean heat value of oil (e) all of the above. Ans: c 20. Gaseous-fuel guarantees are based on (a) calorific value of oil (b) low heat value of oil (c) high heat value of oil (d) mean heat value of oil (e) all of the above. Ans: b 21. Fuel consumption of diesel engines is not guaranteed at one quarter load because at such low loads (a) the friction is high (b) the friction is unpredictable (c) the small difference in cooling water temperature or in internal friction has a disproportionate effect (d) the engine is rarely operated (e) none of the above. Ans: c 22. Polymerisation is a chemical process in which molecules of a compound become (a) larger (b) slowed down (c) smaller (d) liquid (e) gaseous. Ans: a

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23. Which of the following is the lightest and most volatile liquid fuel (a) diesel (b) kerosene (c) fuel oil (d) gasoline (e) lub oil. Ans: d 24. The theoretically correct air fuel ratio for petrol engine is of the order of (a) 6 : 1 (b) 9 : 1 (c) 12 : 1 (d) 15 : 1 (e) 20 : 1. Ans: d 25. Air fuel ratio for idling speed of a petrol engine is approximately (a) 1 : 1 (b) 5 : 1 (c) 10:1 (d) 15 : 1 (e) 20 : 1. Ans: c 26. Air fuel ratio at which a petrol engine can not work is (a) 8 : 1 (b) 10 : 1 (c) 15 : 1 (d) 20 : 1 and less (e) will work at all ratios.

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Ans: d 27. For maximum power generation, the air fuel ratio for a petrol engine for vehicles, is of the order of (a) 9 : 1 (b) 12 : 1 (c) 15 : 1 (d) 18 : 1 (e) 20: 1. Ans: b

Chapter-4 Fuels and its supply system for SI and CI engine 1. Advantage of gaseous fuel is that (a) it can be stored easily (b) it can mix easily with air (c) it can displace more air from the engine (d) all of the above Ans: b 2. Paraffins are in general represented by (a) CnHn (b) CnH2n (c) CnH2n+2 (d) CnH2n-6 Ans: c 3. Paraffins have molecular structure of (a) chain saturated (b) chain unsaturated (c) ring saturated

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(d) ring unsaturated Ans: a 4. Olefins are represented by the formula (a) CnH2n (6) CnH2n+2 (c) CnH2n-4 (d) CnH2n-6 Ans: a 5. Hydrocarbons are decomposed into smaller hydrocarbons by (a) reforming (b) refining (c) cracking (d) polymerization Ans: c 6. The molecular structure of the straight-run gasoline is changed by (a) cracking (b) reforming (c) reining (d) boiling Ans: b 7. For SI engines fuels most preferred are (a) aromatics (b) parafins (c) olefins (d) napthenes Ans: a 8. For CI engine fuels most preferred are

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(a) napthenes (b) paraffins (c) olefins (d) aromatics Ans: b 9. Octane number of iso-octane is (a) 0 (b) 30 (c) 60 (d) 100 Ans: d 10. Ignition quality of diesel fuel is indicated by its a) octane number (b) cetane number (c) fash point (d) fire point Ans: b 11. Flash point of fuel oil is (a) minimum temperature to which1 oil is heated in order to give off inflammable vapours in Sufficient quantity to ignite momentarily when brought in contact with a flame (b) temperature at which it solidifies or congeals (c) temperature at which it catches fire without external aid (d) indicated by 90% distillation temperature, i.e. when 90% of sample oil has distilled off (e) none of the above. Ans: a 12. Gasohol is a mixture of (a) 90% ethanol + 10% gasoline

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(b) 10% ethanol +90% gasoline (c) 40% ethanol + 60% gasoline (d) 50% ethanol +50% gasoline Ans: b 13. Stoichiometric air-fuel ratio of petrol is roughly (a) 50:1 (b) 25:1 (c) 15:1 (d) 1:1 Ans: c 14. Venturi in the carburetor results in (a) decrease of air velocity (b) increase of air velocity (c) decrease of fuel flow (d) increase of manifold vacuum Ans: b 15. The choke is closed when the engine is (a) accelerating (b) hot (c) cold (d) idling Ans: c 16. Lean air mixture is required during (a) idling (b) starting (c) accelerating (d) cruising

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Ans: d 17. The limits of air-fuel for SI engine are (a) 8/1 to 18/1 (b) 8/1 to 50/1 (c) 25/1 to 50/1 (d) 50/1 to 100/1 Ans: a 18. For maximum thermal efficiency, the fuel-air mixture in SI engines should be (a) lean (b) rich (c) stoichiometric (d) may be rich or lean An...